Risks of Chlorophacinone Use on Black Tailed Prairie 

Dogs to Federally Endangered and Threatened Species 

Pesticide Effects Determinations 

PC Code: 067707 

CAS Number: 3691-35-8 

Environmental Fate and Effects Division 

Office of Pesticide Programs 

Washington, D.C. 20460 

September 29, 2010

Primary Authors: 

Andrew Shelby, Physical Scientist 

Melissa Grable, Biologist

Secondary Review: 

Donna Randall, Senior Scientist 

Acting Branch Chief, Environmental Risk Assessment Branch 2 

Jean Holmes, DVM MPH 

Senior Science Advisor, Environmental Risk Assessment Branch 6 

William P. Eckel, Ph.D. 

1
Acknowledgement 

We would like to acknowledge the contributions of Garland Waleko and Nathan Miller in 

compiling detailed life history information on many of the threatened and endangered 

species. Additionally, the EFED Litigation Steering Committee has provided invaluable 

guidance toward achieving greater consistency in format and content between chemicals 

being assessed. Finally we would like to acknowledge members of the review panel for 

their careful review of this document. The members of the review panel for this 

assessment were Shannon Borges, Bill Jacobs, Alicia Korol, Ed Odenkirchin, and 

Ingrid Sunzenauer. 

2
Table of Contents 

1. EXECUTIVE SUMMARY ............................................................................. 11

1.1. PURPOSE OF ASSESSMENT....................................................................................11 

1.2. SCOPE OF ASSESSMENT........................................................................................11 

1.2.1. Use Assessed..............................................................................................11 

1.2.2. Environmental Fate Properties of Chlorophacinone..................................12 

1.2.3. Evaluation of Degradates and Stressors of Concern..................................12 

1.3. ASSESSMENT PROCEDURES..................................................................................13 

1.3.1. Exposure Assessment.................................................................................13 

1.3.2. Toxicity Assessment ..................................................................................14 

1.3.3. Measures of Risk........................................................................................15 

1.4. SUMMARY OF CONCLUSIONS ...............................................................................15 

2. PROBLEM FORMULATION ....................................................................... 25

2.1. PURPOSE ..............................................................................................................25 

2.2. SCOPE ..................................................................................................................26 

2.2.1. Evaluation of Degradates...........................................................................27 

2.2.2. Evaluation of Mixtures ..............................................................................27 

2.3. PREVIOUS ASSESSMENTS .....................................................................................27 

2.4. ENVIRONMENTAL FATE PROPERTIES ...................................................................28 

2.4.1. Environmental Transport Mechanisms......................................................29 

2.4.2. Mechanism of Action.................................................................................30 

2.4.3. Use Characterization..................................................................................30 

2.5. ASSESSED SPECIES...............................................................................................32 

2.5.1. Consideration of Federally Listed Plants...................................................49 

2.6. DESIGNATED CRITICAL HABITAT.........................................................................50 

2.7. ACTION AREA AND LAA EFFECTS DETERMINATION AREA .................................53 

2.7.1. Action Area................................................................................................53 

2.7.2. MA Effects Determination Area................................................................54 

2.8. ASSESSMENT ENDPOINTS AND MEASURES OF ECOLOGICAL EFFECT....................56 

2.8.1. Assessment Endpoints ...............................................................................56 

2.8.2. Assessment Endpoints for Designated Critical Habitat.............................59 

2.9. CONCEPTUAL MODEL ..........................................................................................59 

2.9.1. Risk Hypotheses.........................................................................................59 

2.9.2. Diagram......................................................................................................60 

2.10. ANALYSIS PLAN...................................................................................................61 

2.10.1. Measures of Exposure................................................................................61 

2.10.2. Measures of Effect .....................................................................................62 

2.10.3. Data Gaps...................................................................................................62 

3. EXPOSURE ASSESSMENT .......................................................................... 63

3.1. LABEL APPLICATION RATES AND INTERVALS ......................................................63 

3.2. AQUATIC EXPOSURE ASSESSMENT ......................................................................64 

3.2.1. Aquatic Exposure in Previous Assessment................................................64 

3
3.3. TERRESTRIAL EXPOSURE ASSESSMENT................................................................64 

3.3.1. Ingestion Rate Determination ....................................................................64 

3.3.2. Food Intake Assumptions Relevant to Terrestrial Exposure .....................65 

4. EFFECTS ASSESSMENT.............................................................................. 68

4.1. ECOTOXICITY STUDY DATA SOURCES .................................................................69 

4.2. TOXICITY OF CHLOROPHACINONE TO TERRESTRIAL ORGANISMS ........................70 

4.2.1. Toxicity to Birds........................................................................................71 

4.2.2. Toxicity to Mammals.................................................................................73 

4.2.3. Toxicity to Terrestrial Invertebrates ..........................................................74 

4.3. INCIDENT DATABASE REVIEW .............................................................................78 

4.3.1. Terrestrial Incidents...................................................................................78 

4.4. USE OF PROBIT SLOPE RESPONSE RELATIONSHIP TO PROVIDE INFORMATION ON 

THE ENDANGERED SPECIES LEVELS OF CONCERN ...............................................78 

5. RISK CHARACTERIZATION...................................................................... 79

5.1. RISK ESTIMATION ................................................................................................79 

5.1.1. Risk to Birds and Herptiles........................................................................80 

5.1.2. Risk to Mammals .......................................................................................82 

5.1.3. Risk to Terrestrial Invertebrates.................................................................84 

5.1.4. Primary Constituent Elements of Designated Critical Habitat ..................84 

5.2. RISK DESCRIPTION...............................................................................................85 

5.2.1. Direct Effects to Listed Species.................................................................98 

5.2.2. Indirect Effects to Listed Species ............................................................107 

5.2.3. Modification of Designated Critical Habitat............................................108 

5.3. EFFECTS DETERMINATIONS SUMMARY..............................................................108 

5.3.1. Addressing the Risk Hypotheses .............................................................109 

6. UNCERTAINTIES ........................................................................................ 109

6.1. EXPOSURE ASSESSMENT UNCERTAINTIES..........................................................109 

6.1.1. Maximum Use Scenario...........................................................................109 

6.1.2. Usage Uncertainties.................................................................................109 

6.2. EFFECTS ASSESSMENT UNCERTAINTIES.............................................................110 

6.2.1. Data Gaps and Uncertainties....................................................................110 

6.2.2. Carcass Residue Concentration................................................................110 

6.2.3. Sublethal Effects......................................................................................110 

7. RISK CONCLUSIONS ................................................................................. 111

8. REFERENCES............................................................................................... 120

4
Appendices 

Appendix A. Maps Showing the Overlap of the Initial Area of Concern and the Species 

Habitat and Occurrence Sections 

Appendix B. Risk Quotient (RQ) Method and Levels of Concern (LOCs) 

Appendix C. Estimation of Upper-bound Aquatic Exposure 

Appendix D. Literature Submitted During the Comment Period for “Receipt of Petition 

Requesting EPA to Suspend the Registration of Rozol Prairie Dog Bait 

and Cancel Certain Application Sites” (EPA-HQ-OPP-2009-0684-0001) 

Appendix E. Summary of Ecotoxicity Data 

Appendix F. Bibliography of ECOTOX Open Literature 

Appendix G. Accepted ECOTOX Data Table (sorted by effect) and Bibliography 

Appendix H. The HED Chapter of the Reregistration Eligibility Decision Document 

(RED) for Rodenticide Cluster 

Appendix I. Summary of Chlorophacinone Incidents 

Appendix J. Calculation of Avian RQs using LD50 data 

Attachments 

Attachment I: Status and Life History for the Threatened and Endangered Species 

for which a May Affect Determination was made 

5
List of Tables

Table 1.1 Effects Determination Summary for Effects of Chlorophacinone to 21 

Endangered Species. ........................................................................................ 17 

Table 1.2. Effects Determination Summary for the Critical Habitat Impact Analysis.... 22 

Table 2.1 Physical-chemical Properties of chlorophacinone........................................... 29 

Table 2.2 Summary of Current Distribution, Habitat Requirements, and Life History 

Information for Listed Species that May be Affected...................................... 33 

Table 2.3 Designated Critical Habitat PCEs.................................................................... 50 

Table 2.4 Taxa Used in the Analyses of Direct Effects from Primary (Bait) and 

Secondary Exposure for the Listed Species that May be Affected.................. 56 

Table 2.5 Taxa Used in the Analyses of Indirect Effects for the Listed Species that May 

be Affected....................................................................................................... 57 

Table 2.6 Taxa and Assessment Endpoints Used to Evaluate the Potential for Use of 

Chlorophacinone to Result in Direct and Indirect Effects to the Listed Species 

or Modification of Critical Habitat that May be Affected ............................... 58 

Table 3.1 Calculation of chlorophacinone intake for birds and herptiles using most 

conservative secondary exposure scenario....................................................... 65 

Table 3.2 Calculation of chlorophacinone intake for mammals using most conservative 

secondary exposure scenario............................................................................ 66 

Table 3.3 Chlorophacinone Residue Levels in Primary Consumers............................... 67 

Table 4.1. Toxicity Profile for Chlorophacinone............................................................. 70 

Table 4.2 Secondary Hazards of Chlorophacinone to Birds in Laboratory Studies........ 71 

Table 4.3 Secondary Hazards of Chlorophacinone to Mammals in Laboratory Studies. 73 

Table 4.4 Evaluation of the Terrestrial Invertebrate Reproduction Study....................... 77 

Table 5.1 Summary of RQ Values for Avian Species. .................................................. 80 

Table 5.2 Calculation of Ingestion Rate and Adjusted LD50 for mammals..................... 82 

Table 5.3 Summary of RQ Values for Mammalian Species. ......................................... 83 

Table 5.4. Risk Estimation Summary for Chlorophacinone ............................................ 86 

Table 5.5. Table 5.5 Risk Estimation Summary for Chlorophacinone - Effects to 

Designated Critical Habitat (PCEs) ................................................................. 91 

Table 7.1 Effects Determination Summary for Effects of Chlorophacinone to 21 

Endangered Species. ...................................................................................... 112 

Table 7.2. Effects Determination Summary for the Critical Habitat Impact Analysis.. 117 

6
List of Figures 

Figure 2.1. Chlorophacinone use area for BTPDs........................................................... 31 

Figure 2.2. Initial area of concern, or “footprint” of potential use, for chlorophacinone 

use to control BTPDs. ...................................................................................... 55 

Figure 2.3 Conceptual model depicting stressors, exposure pathways, and potential 

effects to terrestrial organisms from the use of chlorophacinone on BTPDs. . 60 

7
List of Commonly Used Abbreviations and Nomenclature 

oC Symbol for “degrees Celsius” 

a.i. Active Ingredient 

AIMS Avian Monitoring Information System 

Acc# Accession Number 

Amu Atomic Mass Unit 

BCF Bioconcentration Factor 

BEAD Biological and Economic Analysis Division 

BTPD Black tailed prairie dog 

Bw Body Weight 

CI Confidence Interval 

CL Confidence Limit 

EC50 50% (or Median) Effect Concentration 

ECOTOX EPA managed database of Ecotoxicology data 

EEC Estimated Environmental Concentration 

EFED Environmental Fate and Effects Division 

e.g. Latin exempli gratia (“for example”) 

EIM Environmental Information Management System 

et al. Latin et alii (“and others”) 

etc. Latin et cetera (“and the rest” or “and so forth”) 

FIFRA Federal Insecticide Fungicide and Rodenticide Act 

FQPA Food Quality Protection Act 

Ft Feet 

g/day Grams per day 

GENEEC Generic Estimated Exposure Concentration model 

i.e. Latin for id est (“that is”) 

Kg Kilogram(s) 

Km Kilometer(s) 

Kd Solid-water Distribution Coefficient 

KF Freundlich Solid-Water Distribution Coefficient 

KOC Organic-carbon Partition Coefficient 

KOW Octanol–water Partition Coefficient 

LAA Likely to Adversely Affect 

lb a.i./A Pound(s) of active ingredient per acre 

LC50 50% (or Median) Lethal Concentration 

8
LD50 50% (or Median) Lethal Dose 

LOAEC Lowest Observable Adverse Effect Concentration 

LOAEL Lowest Observable Adverse Effect Level 

LOC Level of Concern 

LOD Level of Detection 

LOQ Level of Quantitation 

M Meter(s) 

MA May Affect 

Mg Milligram(s) 

mg/kg Milligrams per kilogram (equivalent to ppm) 

mg/L Milligrams per liter (equivalent to ppm) 

mL/g Milliliters per gram 

Mi Mile(s) 

mmHg Millimeter of mercury 

MRID Master Record Identification Number 

MW Molecular Weight 

n/a Not applicable 

NAWQA National Water Quality Assessment 

NCOD National Contaminant Occurrence Database 

NE No Effect 

NLAA Not Likely to Adversely Affect 

NOAEC No Observable Adverse Effect Concentration 

NOAEL No Observable Adverse Effect Level 

NOEC No Observable Effect Concentration 

OCSPP Office of Chemical Safety and Pollution Prevention 

OPP Office of Pesticide Programs 

ORD Office of Research and Development 

PCE Primary Constituent Element 

ppb Parts per Billion (equivalent to μg/L or μg/kg) 

ppm Parts per Million (equivalent to mg/L or mg/kg) 

PRD Pesticide Re-Evaluation Division 

RQ Risk Quotient 

SLN Special Local Need 

TGAI Techinical grade active ingredient 

USDA United States Department of Agriculture 

USEPA United States Environmental Protection Agency 

9
USFWS United States Fish and Wildlife Service 

USGS United States Geological Survey 

Wt Weight 

10
1. Executive Summary 

1.1. Purpose of Assessment 

The purpose of this assessment is to evaluate potential direct and indirect effects on federally 

listed threatened and endangered (listed) species and potential effects to designated critical 

habitat, arising from FIFRA regulatory actions regarding use of chlorophacinone to control 

black-tailed prairie dogs (BTPDs). This assessment was completed in accordance with the U.S. 

Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS) Endangered 

Species Consultation Handbook (USFWS/NMFS, 1998), procedures outlined in the Agency’s 

Overview Document (USEPA, 2004a). This ecological risk assessment and effects 

determination is conducted specific to Rozol Prairie Dog Bait (EPA Reg. No. 7173-286) to 

address potential product-specific risks raised in pending litigation1. 

1.2. Scope of Assessment 

1.2.1. Use Assessed 

Chlorophacinone is an anticoagulant rodenticide. Chlorophacinone end-use products include 

tracking powder, bait blocks, pelleted baits, and grain baits. Chlorophacinone is used to control 

house mice, Norway rats, roof rats, pocket gophers, voles, ground squirrels, mountain beavers, 

jack rabbits, wood rats, chipmunks, deer mice and BTPDs. This assessment addresses the one 

chlorophacinone end-use product registered for use to control BTPDs. This use is the federal 

action evaluated in this assessment. This chlorophacinone product, Rozol Prairie Dog Bait (EPA 

registration number 7173-286), is formulated as a loose grain bait with a concentration of 50 mg 

a.i./kg-bait active ingredient (a.i.) chlorophacinone and is only permitted for use on BTPDs in 

Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, 

Texas and Wyoming. The bait is applied by hand at a rate of 1⁄4 cup (53 grams) of bait, at least 6 

inches down into the active BTPD burrows. Based on the assessed label, two carcass searches 

are to occur after application, the first being 5 to 10 days post-application and the second being 

14-21 days post-application. Primary and secondary exposure to non-target animals is possible 

based on this use pattern. If all active BTPD burrows receive the application, the effective 

application rate is 0.00058 lbs a.i./A given a maximum of 100 burrows per acre (King 1959).. 

No bait is to be left on the soil surface at the time of application. The applicator must retrieve 

and dispose of any bait that is spilled above ground or placed less than 6 inches down the burrow 

entrance. A second application may be made if BTPD activity persists several weeks or months 

after the initial bait application. Chlorophacinone uncouples oxidative phosphorylation 

depressing hepatic synthesis of prothrombin and clotting factors VII, IX, and X and it causes 

direct damage to capillary permeability. The ultimate effect is widespread internal hemorrhage. 

In rodents, this type of rodenticide also causes neurologic and cardiopulmonary injuries which 

often lead to death before hemorrhage occurs. 

 

1 Defenders of Wildlife v. U.S. EPA, Case No. 09-1199 (D.C. Cir., 2009); Defenders of Wildlife v. Jackson, Case 

No. 09-cv-1814 (D.D.C., 2009); NRDC v. U.S. EPA, Case No. 10-cv-1063, (D.D.C., 2010). 

11
EPA notes that several changes to the label of Rozol Prairie Dog Bait (EPA reg. no. 7173-286) 

were approved on September 10, 2010. These changes consist of including: (1) a requirement 

that carcass searches start within 4 days, rather than within 5 to 10 days of application; (2) a 

requirement that such searches continue at 1-2 day intervals, for two weeks or potentially longer, 

as opposed to just a second repeat search at the 14-21 day interval; and (3) language that permits 

alternative carcass disposal to burial, where burial is impractical and the alternative disposal will 

ensure no access by scavengers. While EPA expects these label changes will reduce the 

potential for exposure of non-target species to chlorophacinone this potential reduction does not 

quantitatively alter EPA's ecological risk assessment, nor does it alter EPA's effects 

determinations relative to the use of Rozol Prairie Dog Bait (EPA reg. no. 7173-286). 

Adherence to these label changes will reduce the probability that contaminated prairie dogs or 

carcasses will be available to non-target species. However, these changes will not eliminate such 

availability nor will these changes eliminate the potential for non-target species to be directly 

exposed to bait in the burrows or exposed to bait that reaches the surface. While these label 

changes cannot preclude effects likely to adversely affect individuals of a non-target species, the 

reduction in the likelihood of such effects occurring should be considered by the US Fish and 

Wildlife Service when considering whether the potential effects will or will not constitute 

jeopardy to any of the species potentially exposed. 

1.2.2. Environmental Fate Properties of Chlorophacinone 

Chlorophacinone is hardly mobile in soils and other organic matrices (KOC = 15600-95745 

mL/g) and nearly insoluble (34 mg/L). Chlorophacinone is formulated as a grain bait for this use 

and is expected to remain within the bait due to its immobility. Chlorophacinone would also be 

immobile if it were to be soil incorporated. Based on its fate parameters measureable exposure 

to aquatic environments is not expected to occur. It is the operating assumption of this 

assessment that the fate of chlorophacinone in the environment from this use is entirely 

associated with the grain bait formulation. 

1.2.3. Evaluation of Degradates and Stressors of Concern 

Though degradates (i.e. o-phthalic acid and p-chlorophenylphenyl acetic acid) have been 

detected in environmental fate studies, they will not be considered further in this assessment. 

These environmental fate studies were performed using the technical grade active ingredient 

(TGAI) rather than the bait formulation relevant to this assessment. Due to chlorophacinone’s 

immobility in soil, it is also reasonable to conclude it is immobile within bait formulations. 

Chlorophacinone baits retain the parent compound even after exposure to wet weather and 

moisture (Merson and Byers 1985). However, photodegradation occurs in a dry environment 

and the bait is in a dry environment. Degradates were not evaluated in carcass studies and based 

on this lack of data, it is assumed that the degradates are equi-toxic to the parent compound. 

Therefore this risk assessment will be conducted as if the parent is undegraded in the bait. 

12
1.3. Assessment Procedures 

1.3.1. Exposure Assessment 

All listed species within the U.S. were considered in this assessment. Exposures that may occur 

are limited to exposure through consumption of chlorophacinone grain bait (primary exposure) 

or exposure through consumption of animals/prey/carcasses that have consumed 

chlorophacinone grain bait (secondary exposure). Exposure can only occur if: 1) the species 

distribution overlaps or borders the distribution area of BTPDs where Rozol Prairie Dog Bait 

(EPA Reg. No. 7173-286) can be used; and 2) species occur in terrestrial habitats. Twenty one 

species meet these two criteria. Those species are: grizzly bear (Ursus arctos horribilis), 

American burying beetle (Nicrophorus americanus), Salt Creek tiger beetle (Cicindela nevadica 

lincolniana), California condor (Gymnogyps californianus), whooping crane (Grus americana), 

Eskimo curlew (Numenius borealis), northern Aplomado falcon (Falco femoralis 

septentrionalis), black footed ferret (Mustela nigripes), Chiricahua leopard frog (Rana 

chiricahuensis), jaguar (Panthera onca), Gulf Coast jaguarundi (Herpailurus yagouaroundi 

cacomitli), Canada lynx (Lynx Canadensis), Preble’s meadow jumping mouse (Zapus hudsonius 

preblei), ocelot (Leopardus pardalis), Mexican spotted owl (Strix occidentalis lucida), piping 

plover (Charadrius melodus), New Mexican ridge-nosed rattlesnake (Crotalus willardi 

obscurus), Sonora tiger salamander (Ambystoma tigrinum stebbinsi) black-capped vireo (Vireo 

atricapilla), golden-cheek warbler (Dendroica chrysoparia), and gray wolf (Canis lupus). 

Species overlap with BTPD range is demonstrated in Appendix A. Federally-designated critical 

habitat2

 has been established for nine of these 21 species. Primary constituent elements3 (PCEs) 

were used to evaluate whether chlorophacinone has the potential to modify designated critical 

habitat. 

1.3.1.a. Aquatic Exposure 

Based on the physical/chemical properties of Rozol Prairie Dog Bait, chlorophacinone exposure 

to aquatic environments is not expected to occur. Previous assessments are consistent with this 

conclusion and are further discussed and referenced in Section 2.4. 

 

2

 ‘Critical habitat’ is defined in the ESA as the geographic area occupied by the species at the time of the listing 

where the physical and biological features necessary for the conservation of the species exist, and there is a need for 

special management to protect the listed species. It may also include areas outside the occupied area at the time of 

listing if such areas are ‘essential to the conservation of the species.’ Critical habitat receives protection under 

Section 7 of the ESA through prohibition against destruction or adverse modification with regard to actions carried 

out, funded, or authorized by a federal Agency. Section 7 requires consultation on federal actions that are likely to 

result in the destruction or adverse modification of critical habitat. To be included in a critical habitat designation, 

the habitat must be ‘essential to the conservation of the species.’ 

3

 Critical habitat designations identify, to the extent known using the best scientific and commercial data available, 

habitat areas that provide essential life cycle needs of the species or areas that contain certain primary constituent 

elements (PCEs) (as defined in 50 CFR 414.12(b)). PCEs include, but are not limited to, space for individual and 

population growth and for normal behavior; food, water, air, light, minerals, or other nutritional or physiological 

requirements; cover or shelter; sites for breeding, reproduction, rearing (or development) of offspring; and habitats 

that are protected from disturbance or are representative of the historic geographical and ecological distributions of a 

species. Information specific to each species is provided in each ESA. 

13
1.3.1.b. Terrestrial Exposure 

Terrestrial exposure is assessed based on two exposure routes: 1) exposure to chlorophacinone 

grain bait; and 2) exposure to animals/prey/carcasses poisoned by chlorophacinone grain bait. 

The active ingredient concentrations for the two exposure routes are respectively determined 

from: 1) labeled active ingredient concentration of the grain bait; and 2) conservative residue 

concentrations from chlorophacinone poisoned carcass studies. For residue concentrations, 

exposure to BTPDs and non-target granivores exposed to chlorophacinone bait are considered. 

The estimated environmental concentration (EEC) is derived by multiplying the active ingredient 

concentration in the food item by the food ingestion rate for a given species. 

1.3.2. Toxicity Assessment 

Assessment endpoints are limited to direct and indirect effects associated with survival, growth, 

and reproduction. The effects determination assessment endpoints include direct toxic effects on 

survival, as well as indirect effects including reduction of the prey base or modification of 

habitat. Mammalian toxicity data do not characterize growth and reproduction effects because 

mortality effects occur before these effects are seen in mammals. Data informing effects to avian 

reproduction are unavailable for this assessment. These data were requested from the registrant 

but have not been received. As noted in the Overview Document (USEPA, 2004a), the Agency 

relies on acute and chronic effects endpoints that are either direct measures of impairment of 

survival, growth, or reproduction or endpoints for which there is a scientifically robust, peer 

reviewed relationship that can quantify the impact of the measured effect endpoint on the 

assessment endpoints of survival, growth, and reproduction. Data addressing chronic toxicity are 

currently not available for chlorophacinone. For the purposes of this assessment, risk cannot be 

precluded to any assessed bird, mammal or herptile if exposure is expected to occur. 

Direct effects to listed species were determined by multiplying the active ingredient 

concentration in the food item by the ingestion rate for a given species to determine how much of 

the food item would have to be ingested to attain a toxic dose. There are no direct effects caused 

by toxicity to aquatic taxa because exposure does not occur. However, indirect effects based on 

loss of terrestrial prey items and habitat modification based on loss of rodent burrows were 

assessed. 

The Agency evaluated registrant-submitted studies and data from the open literature to 

characterize chlorophacinone toxicity. The most sensitive toxicity value available from 

acceptable or supplemental studies for each taxon relevant for estimating potential risks to the 

listed species and/or their designated critical habitat was used to assess risk. The ecotoxicity data 

used in this assessment, including ECOTOX data and literature submitted to the public docket 

during the comment period for “Receipt of Petition Requesting EPA to Suspend the Registration 

of Rozol Prairie Dog Bait and Cancel Certain Application Sites” (EPA-HQ-OPP-2009-0684-

0001), are summarized in Section 2.8.1. Literature submitted to the docket is cited in Appendix 

D. 

14
1.3.3. Measures of Risk 

Risk quotients (RQs) were compared to the Agency’s Levels of Concern (LOC) for terrestrial 

endangered species to identify instances where chlorophacinone use to control BTPDs has the 

potential to adversely affect threatened and endangered species or modify their designated 

critical habitat, if the species has designated critical habitat. When RQs for a particular type of 

effect are below the LOC, chlorophacinone is considered to have “no effect” (NE) on the species 

or its designated critical habitat. Where RQs exceed the LOC, a potential to cause adverse 

effects or habitat modification is identified, leading to a conclusion of “may affect” (MA). If 

chlorophacinone use to control BTPDs may affect the listed species, and/or may cause effects to 

designated critical habitat, the best available information is considered to refine the potential for 

exposure and effects, and distinguish actions that are Not Likely to Adversely Affect (NLAA) 

from those that are Likely to Adversely Affect (LAA). 

1.4. Summary of Conclusions 

Geospatial analysis indicates that the chlorophacinone action area which corresponds to BTPD 

range either overlaps or borders the range of all 21 threatened and endangered species that may 

be affected by this use. Based on the best available information, the Agency makes a MA 

determination for the use of chlorophacinone to control BTPDs for the following 21 species 

based on direct effects: grizzly bear, American burying beetle, Salt Creek tiger beetle, California 

condor, whooping crane, Eskimo curlew, northern Aplomado falcon, black-footed ferret, 

Chirichaua leopard frog, jaguar, Gulf Coast jaguarundi, Canada lynx, Preble’s meadow jumping 

mouse, ocelot, Mexican spotted owl, piping plover, New Mexican ridge-nosed rattlesnake, 

Sonora tiger salamander, black-capped vireo, golden-cheeked warbler, and the gray wolf. 

Additionally, the Agency has determined that there is the potential for modification of designated 

critical habitat from the use of the chemical. Potential modification of critical habitat occurs for 

the following species: Salt Creek tiger beetle, whooping crane, Canada lynx, Preble’s meadow 

jumping mouse, Mexican spotted owl, piping plover, and the New Mexican ridge-nosed 

rattlesnake. 

Based on the predicted environmental exposures, chlorophacinone is likely to adversely affect 

via direct effects the following species: grizzly bear, American burying beetle, Salt Creek tiger 

beetle, California condor, whooping crane, Eskimo curlew, northern Aplomado falcon, blackfooted ferret, Chirichaua leopard frog, jaguar, Gulf Coast jaguarundi, Canada lynx, Preble’s 

meadow jumping mouse, ocelot, Mexican spotted owl, piping plover, Sonora tiger salamander, 

black-capped vireo, golden-cheeked warbler, and the gray wolf. Based on the predicted 

environmental exposures to prey base species, chlorophacinone is likely to adversely affect via 

indirect effects the following species: grizzly bear, American burying beetle, whooping crane, 

Eskimo curlew, northern Aplomado falcon, black-footed ferret, Chiricahua leopard frog, Preble’s 

meadow jumping mouse, New Mexican ridge-nosed rattlesnake, Sonora tiger salamander, and 

the gray wolf. The black footed ferret is likely to be adversely affected via indirect effects due to 

loss of potential burrow habitat. Preble’s meadow jumping mice do not appear to use the 

burrows of other rodents therefore making it unlikely that this species would be adversely 

affected by loss of burrow habitat. Chlorophacinone use to control BTPDs is expected to result 

in modification of the critical habitat PCEs for the following listed species: Salt Creek tiger 

15
beetle, California condor, whooping crane, Canada lynx, Preble’s meadow jumping mouse, 

Mexican spotted owl, piping plover, New Mexican ridge-nosed rattlesnake, and gray wolf. A 

summary of the risk conclusions and effects determinations for the 21 listed species and the 

critical habitat for the Salt Creek tiger beetle, California condor, whooping crane, Canada lynx, 

Preble’s meadow jumping mouse, Mexican spotted owl, piping plover, New Mexican ridgenosed rattlesnake, and the gray wolf is presented in Table 1.1 and Table 1.2. Further information 

on the results of the effects determination is included as part of the Risk Description in Section 

5.2. 

16
 Table 1.1 Effects Determination Summary for Effects of Chlorophacinone to 21 

Endangered Species. 

Basis for Determination Species Effects 

Determination Direct Effects Indirect Effects 

Grizzly bear LAA1

Direct effects are expected for the grizzly 

bear based on the potential for this species 

to consume the chlorophacinone bait (RQ 

of 75.42 which exceeds the LOC of 0.1) or 

other prey items that may have consumed 

the chlorophacinone bait (RQ of 3.38 for 

exposure to BTPDs and RQ of 8.75 for 

exposure to non-target animals, both 

which exceed the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data; however, growth and reproductive 

effects are not expected because mortality 

typically occurs as a result of acute 

exposure. 

Indirect effects from the loss of the 

prey base are also expected because 

effects to individuals within 

populations have been demonstrated 

in mammals ranging in size from 13 

to 36,363 grams with RQ ranging 

from 19 to 41. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

American 

burying beetle LAA 

Reproductive effects are expected for the 

American burying beetle. The American 

burying beetle uses mammalian and avian 

carcasses as a food resource during their 

reproduction cycle. Dosed carcasses 

negatively affected number of emerged 

beetles (MRID 47383001). 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Salt creek tiger 

beetle LAA 

Reproductive effects are expected for the 

Salt Creek tiger beetle. Salt Creek tiger 

beetle larvae are potentially exposed to 

chlorophacinone residues through 

chlorophacinone exposed terrestrial 

invertebrates. Dosed carcasses in a 

burying beetle study negatively affected 

number of emerged beetles (MRID 

47383001). Similar affects are expected 

for the Salt Creek tiger beetle. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. This species uses 

mud banks of streams and seeps in 

association with saline wetlands and 

exposed mud flats of saline wetlands 

which is distinct from the short grass 

prairie associated with BTPD habitat. 

No indirect effects from habitat loss 

are expected because this species 

does not use BTPD burrows. 

California 

condor LAA 

Direct effects to the California condor are 

expected through their potential exposure 

to prey items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals which 

exceeds the LOC of 0.1). Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data. 

No indirect effects from the loss of 

prey base are expected because this 

species’ range does not overlap with 

the BTPD range. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Whooping crane LAA 

Direct effects to the whooping crane are 

expected to occur based on the potential 

for this species to consume the 

chlorophacinone bait (RQ of 0.89 which 

exceeds the LOC of 0.1) or other prey 

items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

17
exposure to non-target animals which 

exceeds the LOC of 0.1). Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data. 

because this species does not use 

BTPD burrows. 

Eskimo curlew LAA 

Direct effects to the Eskimo curlew are 

expected to occur based on the potential 

for this species to consume prey items that 

have consumed the chlorophacinone bait 

(RQ of 0.104 for exposure to non-target 

animals, which is used as a surrogate for 

invertebrate prey, which exceeds the LOC 

of 0.1). Growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in terrestrial invertebrates. No 

indirect effects from habitat loss are 

expected because this species does 

not use BTPD burrows. 

Northern 

Aplomado 

falcon 

LAA 

Direct effects to the northern Aplomado 

falcon are expected through their potential 

exposure to prey items that may have 

consumed the chlorophacinone bait (RQ 

of 0.104 for exposure to non-target 

animals which exceeds the LOC of 0.1). 

Growth and reproductive effects cannot be 

precluded due to the absence of chronic 

data 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Black-footed 

ferret LAA 

Direct effects are expected for the blackfooted ferret based on the potential for this 

species to consume prey items that may 

have consumed the chlorophacinone bait 

(RQ of 7.45 for exposure to BTPDs and 

RQ of 19.29 for exposure to non-target 

animals, both which exceed the LOC of 

0.1). Significant exposure is expected to 

occur because black-footed ferrets prey 

primarily on BTPDs. Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data; 

however, growth and reproductive effects 

are not expected because mortality 

typically occurs as a result of acute 

exposure. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. In addition, this 

species preys almost exclusively on 

BTPDs. Indirect effects from habitat 

loss are expected because this species 

uses BTPD burrows. 

Chirichaua 

leopard frog LAA 

Direct effects to the Chirichaua leopard 

frog are expected to occur based on the 

potential for this species to consume prey 

items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals, which is 

used as a surrogate for invertebrate prey, 

which exceeds the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in terrestrial invertebrates and birds. 

No indirect effects from habitat loss 

are expected because this species 

does not appear to use BTPD 

burrows. 

Jaguar LAA 

Direct effects are expected for the jaguar 

based on the potential for this species to 

consume prey items that may have 

consumed the chlorophacinone bait (RQ 

of 12.69 for exposure to BTPDs and RQ 

of 32.85 for exposure to non-target 

No indirect effects from the loss of 

the prey base are expected because 

this species’ habitat is distinct from 

the BTPD habitat. Jaguars – 

particularly males of the northern 

reaches – are known to have large 

18
animals, both which exceed the LOC of 

0.1). Growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data; however, growth and 

reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

home ranges that encompass a 

variety of plant communities, 

including: Maderan evergreenwoodland, subalpine conifer forest, 

semidesert shrubland, and Sonoran 

desert scrub. Washes and riparian 

areas with dense vegetative growth 

may also be valuable movement 

corridors. These habitats are distinct 

from the short grass prairie 

associated with BTPD habitat. No 

indirect effects from habitat loss are 

expected because this species does 

not use BTPD burrows. 

Gulf Coast 

jaguarundi LAA 

Direct effects are expected for the Gulf 

Coast jaguarundi based on the potential 

for this species to consume prey items that 

may have consumed the chlorophacinone 

bait (RQ of 9.20 for exposure to BTPDs 

and RQ of 23.82 for exposure to nontarget animals, both which exceed the 

LOC of 0.1). Growth and reproductive 

effects cannot be precluded due to the 

absence of chronic data; however, growth 

and reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

No indirect effects from the loss of 

the prey base are expected because 

this species’ habitat is distinct from 

the BTPD habitat. This species is 

found in chaparral plant communities 

and dense brushy areas near streams 

and rivers which are distinct from the 

short grass prairie associated with 

BTPD habitat. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Canada lynx LAA 

Direct effects to the Canada lynx are 

expected to occur based on the potential 

for this species to consume prey items that 

may have consumed the chlorophacinone 

bait (RQ of 23.30 for exposure to nontarget animals and RQ of 9.00 for 

exposure to BTPDs both of which exceed 

the LOC of 0.1). Growth and reproductive 

effects cannot be precluded due to the 

absence of chronic data; however, growth 

and reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. The Canada lynx is 

associated with the southern, 

transitional reaches of the cool and 

moist boreal forest. Where it occurs 

at these lower latitudes, the boreal 

forest forms a mixed conifer and 

conifer-hardwood landscape. These 

habitat areas are distinct from the 

short grass prairie associated with 

BTPD habitat. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Preble’s 

meadow 

jumping mouse 

LAA 

Direct effects to the Preble’s meadow 

jumping mouse are expected to occur 

based on the potential for this species to 

consume the chlorophacinone bait (RQ of 

41.35 which exceeds the LOC of 0.1). 

Growth and reproductive effects cannot be 

precluded due to the absence of chronic 

data; however, growth and reproductive 

effects are not expected because mortality 

typically occurs as a result of acute 

exposure. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in terrestrial invertebrates. Although 

this species makes nests both above 

and below ground. It does not appear 

to use other species’ burrows. 

Ocelot LAA Direct effects are expected for the ocelot 

based on the potential for this species to 

No indirect effects from loss of prey 

base are expected because this 

19
consume prey items that have may 

consumed the chlorophacinone bait (RQ 

of 10.41 for exposure to BTPDs and RQ 

of 26.96 for exposure to non-target 

animals, both which exceed the LOC of 

0.1). Growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data; however, growth and 

reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

species’ habitat is distinct from 

BTPD habitat. Ocelots appear to use 

areas of dense cover, and in the 

northern part of the range hunt in 

brushy forests and semi-arid deserts. 

In the southern part of its range, 

ocelot habitat includes tropical 

forests, mountain slopes, and pampas 

(grasslands). These habitat areas are 

distinct from the short grass prairie 

associated with BTPD habitat. No 

indirect effects from habitat loss are 

expected because this species does 

not use BTPD burrows. 

Mexican spotted 

owl LAA 

Direct effects to the Mexican spotted owl 

are expected to occur based on the 

potential for this species to consume prey 

items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals which 

exceeds the LOC of 0.1). Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. Mexican spotted owls 

are found in old-growth or mature 

forests with unevenly aged stands of 

trees, high canopy, multi-storied 

levels, and high tree density as well 

as canyons with riparian or conifer 

communities. In Arizona and New 

Mexico they are found in habitats 

associated with mixed conifer, pineoak, Arizona cypress, oak 

woodlands, and associated riparian 

forests. These habitat areas are 

distinct from the short grass prairie 

associated with BTPD habitat. No 

indirect effects from habitat loss are 

expected because this species does 

not use BTPD burrows. 

Piping plover LAA 

Direct effects to the piping plover are 

expected to occur based on the potential 

for this species to consume prey items that 

may have consumed the chlorophacinone 

bait (RQ of 0.104 for exposure to nontarget animals, which is used as a 

surrogate for invertebrate prey, which 

exceeds the LOC of 0.1). Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. The plover’s home 

range within BTPD range is usually 

limited to the wetland, lakeshore, or 

section of beach where its nest is 

located. No indirect effects from 

habitat loss are expected because this 

species does not use BTPD burrows. 

New Mexican 

ridge-nosed 

rattlesnake 

LAA 

No direct effects based on survival to the 

New Mexican ridge-nosed rattlesnake are 

expected to occur (see Section 5.1.1.a. 

RQs of 0.018 for a 50 gram snake and RQ 

of 0.030 for a 500 gram snake. Neither of 

these RQs exceeds the LOC of 0.1). 

However, growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

because this species does not appear 

use BTPD burrows. 

Sonora tiger 

salamander LAA 

Direct effects to the Sonora tiger 

salamander are expected to occur based on 

the potential for this species to consume 

No indirect effects from the loss of 

prey base or loss of habitat (BTPD 

burrow) are expected because this 

20
prey items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals, which is 

used as a surrogate for invertebrate prey, 

which exceeds the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data. 

species’ range does not overlap with 

BTPD range. 

Black-capped 

vireo LAA 

Direct effects to the black-capped vireo 

are expected to occur based on the 

potential for this species to consume prey 

items that have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals, which is 

used as a surrogate for invertebrate prey, 

which exceeds the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. Black-capped vireos 

are found in mixed 

deciduous/evergreen shrub land. 

Breeding vireos use shrubby growth 

of irregular height and distribution 

with spaces the small thickets and 

clumps and with vegetative 

extending to ground level. These 

habitat areas are distinct from the 

short grass prairie associated with 

BTPD habitat. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Golden-cheeked 

warbler LAA 

Direct effects to the golden-cheeked 

warbler are expected to occur based on the 

potential for this species to consume prey 

items that have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals, which is 

used as a surrogate for invertebrate prey, 

which exceeds the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. Golden-cheeked 

warblers are found in mixed Ashejuniper and oak woodlands in ravines 

and canyons. They spend summers 

in open canopy forest and winters in 

closed canopy forests. These habitat 

areas are distinct from the short grass 

prairie associated with BTPD habitat. 

No indirect effects from habitat loss 

are expected because this species 

does not use BTPD burrows. 

Gray wolf LAA 

Direct effects to the gray wolf are 

expected to occur based on the potential 

for this species to consume prey items that 

have consumed the chlorophacinone bait 

(RQ of 24.82 for exposure to non-target 

animals and RQ of 9.59 for exposure to 

BTPDs both of which exceed the LOC of 

0.1). Growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data; however, growth and 

reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

1

 LAA=likely to adversely affect. 

21
Table 1.2. Effects Determination Summary for the Critical Habitat Impact Analysis 

Species with 

Designated Critical 

Habitat 

Effects 

Determination Basis for Determination 

Salt Creek tiger beetle HM1

Reproductive effects are expected for the Salt Creek tiger beetle. Salt Creek tiger 

beetle larvae are potentially exposed to chlorophacinone residues through 

chlorophacinone exposed terrestrial invertebrates. Dosed carcasses in a burying 

beetle study negatively affected number of emerged beetles (MRID 47383001). 

Similar affects are expected for the Salt Creek tiger beetle. No indirect effects 

from loss of prey base are expected because this species’ habitat is distinct from 

BTPD habitat. This species uses mud banks of streams and seeps in association 

with saline wetlands and exposed mud flats of saline wetlands which is distinct 

from the short grass prairie associated with BTPD habitat. No indirect effects 

from habitat loss are expected because this species does not use BTPD burrows. 

California condor No habitat 

modification 

expected 

Direct effects to the California condor are expected through their potential 

exposure to prey items that may have consumed the chlorophacinone bait (RQ of 

0.104 for exposure to non-target animals which exceeds the LOC of 0.1. No 

indirect effects from the loss of prey base are expected because this species’ range 

does not overlap with BTPD range. No indirect effects from habitat loss are 

expected because this species does not use BTPD burrows. No habitat 

modification is expected because the critical habitat for the California condor does 

not overlap with the use area (BTPD habitat). Critical habitat for the California 

condor has only been designated in California. 

Whooping crane HM 

Direct effects to the whooping crane are expected to occur based on the potential 

for this species to consume the chlorophacinone bait (RQ of 0.89 which exceeds 

the LOC of 0.1) or other prey items that have consumed the chlorophacinone bait 

(RQ of 0.104 for exposure to non-target animals which exceeds the LOC of 0.1). 

Indirect effects from the loss of the prey base are also expected because effects to 

individuals within populations have been demonstrated in mammals, birds, and 

terrestrial invertebrates. No indirect effects from habitat loss are expected because 

this species does not use BTPD burrows. Habitat modification for the whooping 

crane is expected because the critical habitat for the whooping crane overlaps with 

the use area (BTPD habitat). 

Canada lynx HM 

Direct effects to the Canada lynx are expected to occur based on the potential for 

this species to consume prey items that have consumed the chlorophacinone bait 

(RQ of 23.30 for exposure to non-target animals and RQ of 9.00 for exposure to 

BTPDs both of which exceed the LOC of 0.1). No indirect effects from loss of 

prey base are expected because this species’ habitat is distinct from BTPD habitat. 

The Canada lynx is associated with the southern, transitional reaches of the cool 

and moist boreal forest. Where it occurs at these lower latitudes, the boreal forest 

forms a mixed conifer and conifer-hardwood landscape. These habitat areas are 

distinct from the short grass prairie associated with BTPD habitat. No indirect 

effects from habitat loss are expected because this species does not use BTPD 

burrows. Habitat modification for the Canada lynx is expected because the critical 

habitat for the Canada lynx overlaps with the use area (BTPD habitat). 

Preble’s meadow 

jumping mouse HM 

Direct effects to the Preble’s meadow jumping mouse are expected to occur based 

on the potential for this species to consume the chlorophacinone bait (RQ of 41.35 

which exceeds the LOC of 0.1). Indirect effects from the loss of the prey base are 

expected because effects to individuals within populations have been demonstrated 

in terrestrial invertebrates. Although this species makes nests both above and 

below ground, it does not appear to use other species’ rodent burrows. Habitat 

modification for the Preble’s meadow jumping mouse is expected because the 

critical habitat for the Preble’s meadow jumping mouse overlaps with the use area 

(BTPD habitat). 

22
Mexican spotted owl HM 

Direct effects to the Mexican spotted owl are expected to occur based on the 

potential for this species to consume prey items that have consumed the 

chlorophacinone bait (RQ of 0.104 for exposure to non-target animals which 

exceeds the LOC of 0.1). No indirect effects from loss of prey base are expected 

because this species’ habitat is distinct from BTPD habitat. Mexican spotted owls 

are found in old-growth or mature forests with unevenly aged stands of trees, high 

canopy, multi-storied levels, and high tree density as well as canyons with riparian 

or conifer communities. In Arizona and New Mexico they are found in habitats 

associated with mixed conifer, pine-oak, Arizona cypress, oak woodlands, and 

associated riparian forests. These habitat areas are distinct from the short grass 

prairie associated with BTPD habitat. No indirect effects from habitat loss are 

expected because this species does not use BTPD burrows. Habitat modification 

for the Mexican spotted owl is expected because the critical habitat for the 

Mexican spotted owl overlaps with the use area (BTPD habitat). 

Piping plover HM 

Direct effects to the piping plover are expected to occur based on the potential for 

this species to consume prey items that have consumed the chlorophacinone bait 

(RQ of 0.104 for exposure to non-target animals, which is used as a surrogate for 

invertebrate prey, which exceeds the LOC of 0.1). No indirect effects from the 

loss of the invertebrate prey base are expected because this species’ habitat is 

distinct from BTPD habitat. The plover’s home range within the BTPD range is 

usually limited to the wetland, lakeshore, or section of beach where its nest is 

located. No indirect effects from habitat loss are expected because this species 

does not use BTPD burrows. Habitat modification for the piping plover is 

expected because the critical habitat for the piping plover overlaps with the use 

area (BTPD habitat). 

New Mexican ridgenosed rattlesnake HM 

No direct effects based on survival to the New Mexican ridge-nosed rattlesnake are 

expected to occur (see Section 5.1.1.a. RQs of 0.018 for a 50 gram snake and RQ 

of 0.030 for a 500 gram snake. Neither of these RQs exceeds the LOC of 0.1). 

However, direct effects based on reproduction cannot be precluded because no 

reproduction data are available. Indirect effects from the loss of the prey base are 

expected because effects to individuals within populations have been demonstrated 

in mammals, birds, and terrestrial invertebrates. No indirect effects from habitat 

loss are expected because this species does not appear to use BTPD burrows. 

Habitat modification for the New Mexican ridge-nosed rattlesnake is expected 

because the critical habitat for the New Mexican ridge-nosed rattlesnake overlaps 

with the use area (BTPD habitat). 

Gray wolf 

No habitat 

modification 

expected 

Direct effects to the gray wolf are expected to occur based on the potential for this 

species to consume prey items that have consumed the chlorophacinone bait (RQ 

of 24.82 for exposure to non-target animals and RQ of 9.59 for exposure to BTPDs 

both of which exceed the LOC of 0.1). Indirect effects from the loss of the prey 

base are also expected because effects to individuals within populations have been 

demonstrated in mammals, birds, and terrestrial invertebrates. No indirect effects 

from habitat loss are expected because this species does not use BTPD burrows. 

No habitat modification is expected because the critical habitat for the gray wolf 

does not overlap with the use area (BTPD habitat). Critical habitat for the gray 

wolf has only been designated in Minnesota and Michigan. 1

Habitat Modification 

The assessment endpoint for each species above is the modification of PCEs. 

Based on the conclusions of this assessment, formal consultation with the U. S. Fish and Wildlife 

Service under Section 7 of the Endangered Species Act should be initiated relative to potential 

effect on the 21 species noted above in Table 1.1, and on the potential for critical habitat 

modification for the 7 species noted above in Table 1.2 

23
When evaluating the significance of this risk assessment’s direct/indirect and adverse habitat 

modification effects determinations, it is important to note that rodenticide exposures and 

predicted risks to the species and its resources (i.e., food and habitat) are not expected to be 

uniform across the action area since BTPDs are not uniformly distributed across action area. 

Evaluation of the implication of this non-uniform distribution of risk to the species would require 

information and assessment techniques that are not currently available. Examples of such 

information and methodology required for this type of analysis would include the following: 

• Enhanced information on the density and distribution of BTPDs within the action 

area and information on the density and distribution of the other 21 listed species 

within the action area and information on the density and distribution within their 

critical habitat of the nine species with critical habitat. This information would 

allow for quantitative extrapolation of the present risk assessment’s predictions of 

individual effects to the proportion of the population extant within geographical 

areas where those effects are predicted. Furthermore, such population 

information would allow for a more comprehensive evaluation of the significance 

of potential resource impairment to individuals of the listed species. 

• Quantitative information on prey base requirements for the listed species. While 

existing information provides a preliminary picture of the types of food sources 

utilized by the listed species, it does not establish minimal requirements to sustain 

healthy individuals at varying life stages. Such information could be used to 

establish biologically relevant thresholds of effects on the prey base, and 

ultimately establish geographical limits to those effects. This information could 

be used together with the density data discussed above to characterize the 

likelihood of adverse effects to individuals. 

• Information on population responses of prey base organisms to chlorophacinone. 

Currently, methodologies are limited to predicting exposures and likely levels of 

direct mortality, growth or reproductive impairment immediately following 

exposure to chlorophacinone. The degree to which repeated exposure events and 

the inherent demographic characteristics of the prey population play into the 

extent to which prey resources may recover is not predictable. An enhanced 

understanding of long-term prey responses to chlorophacinone exposure would 

allow for a more refined determination of the magnitude and duration of resource 

impairment, and together with the information described above, a more complete 

prediction of effects to individual species and potential modification to critical 

habitat. 

• Furthermore, additional information is needed on the types of plants in the BTPD 

range to fully characterize/assess the direct effects on plants that are found within 

the action area as well as to determine the indirect effects on the threatened and 

endangered animal species which are assessed in this document. Although, it is 

known that the BTPD is a keystone species, it is currently unclear what impacts 

the loss of the BTPD would have both on plant communities within the action 

area as well as what effects this would have on listed species. Additional 

information on species occurrence, distribution, life history and species 

associations would be beneficial to determine potential effects to listed plant 

species. 

24
2. Problem Formulation 

Problem formulation provides a strategic framework for the risk assessment. By identifying the 

important components of the problem, it focuses the assessment on the most relevant life history 

stages, habitat components, chemical properties, exposure routes, and endpoints. The structure 

of this risk assessment is based on guidance contained in U.S. EPA’s Guidance for Ecological 

Risk Assessment (USEPA, 1998), the Services’ Endangered Species Consultation Handbook

(USFWS/NMFS, 1998) and is consistent with procedures and methodology outlined in the 

Overview Document (USEPA, 2004a) and reviewed by the U.S. Fish and Wildlife Service and 

National Marine Fisheries Service (USFWS/NMFS/NOAA, 2004). 

2.1. Purpose 

The purpose of this endangered species assessment is to evaluate potential direct and indirect 

effects on all listed species arising from FIFRA regulatory actions regarding use of 

chlorophacinone to control BTPDs. In addition, this assessment evaluates whether use to control 

BTPDs is expected to result in modification of the listed species’ designated critical habitat, for 

those species with designated critical habitat. 

In this assessment, direct and indirect effects to listed species and potential modification to 

designated critical habitat for listed species is evaluated in accordance with the methods 

described in the Agency’s Overview Document (USEPA, 2004a). In accordance with the 

Overview Document, provisions of the Endangered Species Act (ESA), and the Services’ 

Endangered Species Consultation Handbook, the assessment of effects associated with 

registration of chlorophacinone for BTPDs is based on an action area. The action area is the area 

directly or indirectly affected by the federal action. The action area for a FIFRA regulatory

decision associated with a use of chlorophacinone to control BTPDs involves 532 counties in 10 

states (Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South 

Dakota, Texas and Wyoming) based on the range of the BTPD and data regarding listed species 

obtained from NatureServe4

. However, for the purposes of this assessment, attention will be 

focused on relevant sections of the action area including those geographic areas associated with 

locations of listed species that may be affected and their designated critical habitat. As part of 

the “effects determination,” one of the following three conclusions will be reached separately for 

each of the assessed species regarding the potential use of chlorophacinone in accordance with 

the assessed label: 

• “No effect” or “NE”; 

• “May affect, but not likely to adversely affect” or “NLAA”; or 

• “May affect and likely to adversely affect” or “LAA”. 

A risk quotient (RQ) is the ratio of the estimated environmental concentration (EEC) to the 

relevant toxicological endpoint, often the LD50 or LC50. RQs were compared to the Agency’s 

LOC for terrestrial endangered species to identify instances where chlorophacinone use to 

 

4

 NatureServe: NatureServe Explorer [web application]. Updated February 2010. Arlington, Virginia (USA): 

Available: http://www.natureserve.org/explorer. (Accessed: May 12, 2010 ) 

25
control BTPDs has the potential to adversely affect the assessed species or modify their 

designated critical habitat. When RQs for an effect endpoint are below the LOC, 

chlorophacinone is considered to have NE on the species or its designated critical habitat. Where 

RQs exceed the LOC, a potential to cause adverse effects or habitat modification is identified, 

leading to a conclusion of May Affect. If chlorophacinone use may affect the assessed species, 

and/or may cause effects to designated critical habitat, the best available information is 

considered to refine the potential for exposure and effects, and distinguish actions that are NLAA 

from those that are LAA. The best available information relative to this assessment includes 

species life history information which is compiled in Attachment 1. 

2.2. Scope 

The end result of the EPA pesticide registration process (i.e., the FIFRA regulatory action) is an 

approved product label. The label is a legal document that stipulates how and where a given 

pesticide may be used. Product labels (also known as end-use labels) describe the formulation 

type (e.g., liquid or granular), acceptable methods of application, approved use sites, and any 

restrictions on how applications may be conducted. Thus, the use of chlorophacinone in 

accordance with the approved product label for BTPDs is “the action” relevant to this ecological 

risk assessment. 

Chlorophacinone end-use products include tracking powder, bait blocks, pelleted baits, and grain 

baits. The use of chlorophacinone for control of BTPDs only permits use of grain bait 

formulated with 50 mg a.i./kg-bait active ingredient. This bait is permissible for use only 

between October 1 and March 15 or spring green-up, whichever occurs later, in active prairie 

dog burrows. The bait must be placed at least 6 inches into the burrow and below the ground 

surface. Two carcass searches are to occur after application, the first being 5 to 10 days postapplication and the second being 14-21 days post-application. Primary and secondary exposure 

to non-target animals is possible based on this use pattern. Primary exposure takes place when 

the grain bait is consumed by non-target species. This type of exposure can occur on the surface, 

as a result of bioturbation, or while the bait is in the burrow. Secondary exposure takes place 

when chlorophacinone poisoned/contaminated BTPDs or non-target animals or carcasses, are 

consumed by non-target species. Dead and dying animals may be exposed on the surface or may 

be found by predators or scavengers in burrows. 

EPA notes that several changes to the label of Rozol Prairie Dog Bait (EPA reg. no. 7173-286) 

were approved on September 10, 2010. These changes consist of including: (1) a requirement 

that carcass searches start within 4 days, rather than within 5 to 10 days of application; (2) a 

requirement that such searches continue at 1-2 day intervals, for two weeks or potentially longer, 

as opposed to just a second repeat search at the 14-21 day interval; and (3) language that permits 

alternative carcass disposal to burial, where burial is impractical and the alternative disposal will 

ensure no access by scavengers. While EPA expects these label changes will reduce the 

potential for exposure of non-target species to chlorophacinone this potential reduction does not 

quantitatively alter EPA's ecological risk assessment, nor does it alter EPA's effects 

determinations relative to the use of Rozol Prairie Dog Bait (EPA reg. no. 7173-286). 

Adherence to these label changes will reduce the probability that contaminated prairie dogs or 

carcasses will be available to non-target species. However, these changes will not eliminate such 

26
availability nor will these changes eliminate the potential for non-target species to be directly 

exposed to bait in the burrows or exposed to bait that reaches the surface. While these label 

changes cannot preclude effects likely to adversely affect individuals of a non-target species, the 

reduction in the likelihood of such effects occurring should be considered by the US Fish and 

Wildlife Service when considering whether the potential effects will or will not constitute 

jeopardy to any of the species potentially exposed. 

Although current registrations of the active ingredient chlorophacinone allow for use nationwide, 

this ecological risk assessment and effects determination addresses only the registered use of the 

Rozol Prairie Dog Bait ((EPA registration number 7173-286) which is registered only to control 

BTPD on rangeland and noncrop areas in Colorado, Kansas, Montana, Nebraska, New Mexico, 

North Dakota, Oklahoma, South Dakota, Texas and Wyoming. Listed species considered in this 

assessment will occur within and adjacent to counties where BTPDs are known to occur and will 

be reasonably assumed to have potential for chlorophacinone exposure. Further discussion of the 

action area, the listed species and their designated critical habitat is provided in Section 2.7. 

2.2.1. Evaluation of Degradates 

Though degradates (i.e. o-phthalic acid and p-chlorophenylphenyl acetic acid) have been 

detected in environmental fate studies, these degradates will not be considered further in this 

assessment. These environmental fate studies were performed using TGAI rather than the bait 

formulation relevant to this assessment. Due to chlorophacinone’s immobility in soil, it is 

reasonable to conclude it is immobile within bait formulations. Chlorophacinone baits typically 

retain the parent compound even after exposure to wet weather and moisture (Merson and Byers 

1985). However, photodegradation occurs in a dry environment and the bait is in a dry 

environment. Degradates were not evaluated in carcass studies and based on this lack of data, it 

is assumed that the degradates are equi-toxic to the parent compound. Therefore this risk 

assessment will be conducted as if the parent is undegraded on the bait. 

2.2.2. Evaluation of Mixtures 

Product toxicity data for Rozol (2% a.i.) indicates that the formulated product is not more toxic 

than the TGAI compared on a w/w active ingredient basis (MRID 43672005). Rozol Prairie Dog 

Bait is 50 mg a.i./kg-bait but the approximate amount of inert material is equivalent and 

composed of the same materials with the exception of the grain base. The formulation of 

chlorophacinone evaluated in this risk assessment does not contain any other active ingredients. 

2.3. Previous Assessments 

“Potential Risks of Nine Rodenticides to Birds and Nontarget Mammals: a Comparative 

Approach” (USEPA 2004b) evaluated primary and secondary exposure of chlorophacinone, 

among other rodenticides, to birds and mammals. This study determined that the greatest 

risk of chlorophacinone use to non-target animals is via secondary exposure to mammals. 

Risk associated with primary exposure and exposure to birds, however, is also significant. 

These elements provide the general framework for this assessment and are supported 

through the calculation of RQs in this assessment. The study also specified a number of 

27
factors contributing to uncertainty in assessing anticoagulant rodenticides. Those factors 

that contributed the most uncertainty were: (1) missing data, including acute, chronic, and 

secondary toxicity as well as data regarding retention of some active ingredients in the liver, 

blood, and other body tissues; (2) the variable quality and quantity of existing data on 

metabolism and retention times in rodents and nontarget species; (3) specific use 

information by formulation, including typical amounts applied by use site, seasonally, and 

annually; distances applied from buildings; amounts used in rural versus urban areas; use by 

Certified Applicators versus homeowners and other non-certified applicators; and other such 

relevant information; (4) information on the number and species of birds and nontarget 

mammals frequenting baited areas and the likelihood of their finding and consuming bait or 

poisoned primary consumers in the various use areas; (5) methods to determine liver 

concentration(s) and total body burdens of rodenticide that would corroborate death or even 

if such a cause-effect relationship is appropriate (e.g., the “threshold of toxicity” 

concentration); (6) not accounting for the impacts of sublethal effects on reproduction and 

nontarget mortality (e.g., clotting abnormalities, hemorrhaging, stress factors including 

environmental stressors, such as adverse weather conditions, food shortages, and predation); 

(7) not accounting for bioaccumulation of repeated sublethal exposures to bait or poisoned 

rodents utilized as food by predators and scavengers; and (8) lack of incident reporting. All 

of the above issues remain as uncertainties for this assessment. 

In November 2008, an Ecological Risk Assessment evaluating expanded uses of 

chlorophacinone for BTPDs was performed. The assessment offered the following 

recommendations for risk mitigation: (1) requiring carcass searches at 1-to-2 day intervals; (2) 

requiring non-target animal carcasses be provided to proper authorities for identification and 

tissue-residue analysis; (3) requiring a discrete application interval so that full monitoring and 

carcass removal from the initial application may be completed; and (4) taking into consideration 

the black-footed ferret because it is an endangered species, preys on the target species as a 

primary food source and utilizes their burrows. The resulting product label reflected 

recommendations from the assessment in the following ways: (1) requiring an initial carcass 

search 5 to 10 days after application and a second carcass search 14 to 21 days after application; 

(2) allowing reapplication “several weeks” after initial application; and (3) stating: “[d]o not use 

this product within prairie dog towns in the range of the black-footed ferret without first 

contacting endangered species specialists at a U.S. Fish and Wildlife Service office.” 

2.4. Environmental Fate Properties 

Chlorophacinone is hardly mobile with half-lives ranging from 37 minutes (Direct Aqueous 

Photolysis) to 45 days (Aerobic Soil Metabolism, sandy clay loam) and the major environmental 

dissipation processes are photolysis and metabolism. These properties of chlorophacinone are 

summarized in Table 2.1. Chlorophacinone and its degradates are not likely to dissipate from 

the grain bait formulation due to the chemical’s immobility. Chlorophacinone residues can be 

expected to occur in chlorophacinone exposed animal carcasses (Belleville 1981; Dowding 2010; 

MRID 47333603). Further discussion of the implications of chlorophacinone residues in 

carcasses will be limited to Section 2.4.1. For the purposes of discussion of environmental fate, 

discussion will be limited to exposure to the chlorophacinone grain bait formulation only. 

28
Table 2.1 Physical-chemical Properties of chlorophacinone 

Study Value and units Major Degradates 

Minor Degradates

MRID # Study 

Status 

Structure 

Hydrolysis Stable at pH 5, 7, 9 42205501 Acceptable 

Solubility 34 mg/L @ 25oC EPA 1998 

(Rodenticide 

Cluster RED) 

Direct Aqueous 

Photolysis 

T1/2 = 90 minutes 42205502 Acceptable 

Soil Photolysis T1/2 = 4 days o-phthalic acid; 

p-chlorophenylphenyl 

acetic acid

42452301 Acceptable 

Aerobic Soil 

Metabolism 

T1/2 = 45 days; sandy clay loam 

T1/2 = 26 days; sandy loam 

o-phthalic acid; 

p-chlorophenylphenyl 

acetic acid

43159801 Acceptable 

Anaerobic Soil 

Metabolism 

No Data 

Aerobic Aquatic 

Metabolism 

No Data 

Anaerobic Aquatic 

Metabolism 

No Data 

Soil Water Partition 

Coefficient 

 

Kfads 56 to 1000 mL/g 

KOC 15600, 26900, 35400, 95745 

mL/g 

(the Koc model appears valid) 

 

42666001 

 

Acceptable 

Terrestrial Field 

Dissipation 

No Data 

2.4.1. Environmental Transport Mechanisms 

Given chlorophacinone’s physical/chemical properties, grain bait formulation and low 

application rate, it is assumed that negligible amounts of parent chlorophacinone and degradate 

leach from the original bait. Toxicological data on chlorophacinone degradates are not available 

and are therefore assumed to be as toxic as the parent, chlorophacinone. Given this, the exposure 

concentration of 50 mg a.i./kg-bait is assumed to remain constant overtime within the 

formulation. Chlorophacinone has the potential to be available in significant concentrations via 

carcass residues. Ecological incident data, carcass residue data and poisoned carcass feeding 

studies indicate that chlorophacinone poisoned carcasses have the potential to adversely affect 

29
scavengers and predators. Chlorophacinone degradates have not been evaluated in carcass 

studies. 

2.4.2. Mechanism of Action 

Chlorophacinone is an indandione anticoagulant rodenticide. It uncouples oxidative 

phosphorylation depressing hepatic synthesis of prothrombin and clotting factors VII, IX and X 

and, it causes direct damage to capillary permeability. The ultimate effect is widespread internal 

hemorrhage. In rodents, indandiones also cause neurologic and cardiopulmonary injuries which 

often lead to death before hemorrhage occurs (World Health Organization, 2010). 

2.4.3. Use Characterization 

The chlorophacinone product assessed here is registered only as a 50 mg a.i./kg-bait grain bait 

formulation for control of BTPDs. For each active burrow during a single application, 53 grams 

of bait are to be applied no less than 6 inches down the burrow. If prairie dog activity persists, a 

second application at the same use rate can be made “several weeks later”. Neither the National 

Agricultural Statistics Service (NASS) nor the United States Geological Survey (USGS) is able 

to provide geographical data for chloropacinone use to control BTPDs but species distribution 

data, provided by NatureServe at the county level, provides a conservative proxy for the area in 

which chlorophacinone may be used for this purpose. This use area is illustrated in Figure 2.1. 

This species distribution area conservatively represents the use area because it represents the 

historic range for the BTPD. Current and future range relative to historic range is likely to be 

smaller and discontinuous but still within the boundaries of this historic range. 

30
Figure 2.1. Chlorophacinone use area for BTPDs

31
32

2.5. Assessed Species 

This assessment considers all listed species within the U.S. However, the 10 states where 

chlorophacinone use to control BTPDs is permissible (Colorado, Kansas, Montana, Nebraska, 

New Mexico, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming) and the adjacent 

counties (i.e., the action area) are the only areas where exposure is expected to occur. One 

hundred forty two (85 animals and 57 plants) threatened and endangered species are listed within 

the action area according to the USFWS Web site5. Based on species diet, terrestrial habitat and 

the distribution of BTPDs, chlorophacinone will have NE on 87 of the 142 species. The list of 

species for further assessment then is limited to 21 animals (grizzly bear, American burying 

beetle, Salt Creek tiger beetle, California condor, whooping crane, Eskimo curlew, northern 

Aplomado falcon, black footed ferret, Chiricahua leopard frog, jaguar, Gulf Coast jaguarundi, 

Canada lynx, Preble’s meadow jumping mouse, ocelot, Mexican spotted owl, piping plover, New 

Mexican ridge-nosed rattlesnake, Sonora tiger salamander, black-capped vireo, golden-cheek 

warbler, and the gray wolf). A list of the 34 plant species is included in Section 2.5.1 but not 

carried through the assessment because it is unclear what impacts the loss of the BTPD may have 

on these plants. 

 

For the animal species ingestion is the only significant route of exposure and the only exposure 

route assessed in this document and for that, the species’ diet must be that of a granivore or it 

must be attracted to grain baits to have primary exposure to chlorophacinone; it must be a 

carnivore or scavenger to have secondary exposure to chlorophacinone. It was also determined 

that insects may be exposed to the grain bait and may retain residues that are high enough to 

cause direct mortality to invertivores. As a result, direct effects to invertivores will also be 

assessed. Based on the potential for exposure, the list of species for further assessment is limited 

to the 21 terrestrial species noted in Table 1.1. Table 2.2 provides a summary of the current 

distribution, habitat requirements, and relevant life history parameters for these 21 species. More 

detailed life-history and distribution information can be found in Attachment 1. Maps 

indicating listed species location relative to historic range of BTPDs can be found in Appendix 

A.

 

5

 http://www.fws.gov/endangered/ 
Table 2.2 Summary of Current Distribution, Habitat Requirements, and Life History Information for Lis

be Affected. 

Size Current Range Habitat Type Reproductive Cycle 

Grizzly bear (Ursus arctos horribilis) – critical habitat has been proposed Average weight for males: 181-272 kg (400-600 lbs) 

Sections of Washington, Wyoming, Idaho, and Montana. 

Spring: Low elevation riparian sites, wet meadows, and alluvial plains. 

Mating between May and July. Implantation of blastocyst(s) delayeuntil hibernation (4-5 months later). 

Average weight for females: 113-158 kg (250-350 lbs) 

Summer and fall: Higher elevation forests, meadows, and open grassy timber sites. 

Hibernate between October and December. Exits the den between March and May. Implantation of thembryo is delayed and gestation usually lasts about 26 weeks. 

Yellowstone adults: 102-324 kg (225-714 lbs) 

Meadows, shrubfields, and low- and high-elevation riparian communities are also important habitat. 

Length (snout to tail): 170-280 cm (5.5-9.1 ft) Shoulder height: 90-150 cm (3.1-4.8 ft) 

Grizzly bears have been identified in six areas in the Rocky Mountains: 1) the Greater Yellowstone Ecosystem (GYE); 2) the Northern Continental Divide Ecosystem (NCDE); 3) the Bitterroot Ecosystem (BE); 4) the Cabinet-Yaak Ecosystem (CYE); 5) the Selkirks Ecosystem (SE); and 6) the Northern Cascades Ecosystem (NCE) 

33
Size Current Range Reproductive Habitat Type 

Cycle

American burying beetle (Nicrophorus americanus) – no designated critical habitat 2.5-3.5 cm (1.0-1.4 inches) in length 

Occurs in the following states: Arkansas, Kansas, Massachusetts (statewide), Michigan (statewide), Missouri, Nebraska, Ohio, Oklahoma, Rhode Island (statewide), South Dakota, and Texas. 

Eastern deciduous biome. Riparian deciduous forests, grasslands, pastures, and maritime scrub thickets. 

Active from April through Septembbut seen as early as February and as late as October. Breeding in the eas(Block Island) occurs between June and July. Breeding in the west (Oklahoma) occurs between late Apand mid-August. 

Salt Creek tiger beetle (Cicindela nevadica lincolniana) – designated critical habitat1.3 cm (0.5 inches) total length 

Confined to eastern Nebraska saline wetlands and associated streams and tributaries of Salt Creek in the northern third of Lancaster County. 

Mud banks of streams and seeps, and in association with saline wetlands and exposed mud flats of saline wetlands. Larvae have been found only on moist salt flats and saltencrusted banks of Little Salt Creek in northern Lancaster County and saline wetlands associated with Rock Creek in the southern margin of Saunders County. Salt Creek tiger beetles require open, barren salt flat areas for construction of larval burrows, thermoregulation, foraging, and as dispersal corridors. 

Adults are first observed as early as the end of May or as late as mid-JunTheir numbers peak about two weekafter the first individuals appear and begin to feed and mate. Females lay their eggs along sloping banks of creeks in areas where the salt layer iexposed in the soil horizon, on barresalt flats of saline wetlands, or along saline stream edges that are found in close association with water, near a seep or stream. It is believed that, during the night, female Salt Creek tiger beetles lay about 50 eggs. The Salt Creek tiger beetle has a two-yelife cycle. 

34
Size Current Range Reproductive Habitat Type 

Cycle

California condor (Gymnogyps californianus) – designated critical habitat Adults weigh up to 10 kg (22 lbs) Average male weight: 8.8 kg (19.4 lbs) Average female weight: 8.1 kg (17.9 lbs) 

In Arizona, the condor is known to exist in Apache, Coconino, Mohave, Navajo, and Yavapai counties. This species is also found in several counties in California. 

Inhabits a diversity of habitat types. Nesting habitat ranges from scrubby chaparral to forested montane area, mostly on cliffs but also sometimes in cavities in giant sequoia trees. Foraging occurs mostly in open grassland. 

Wild condors court and nest betweeDecember and spring. They lay one egg between late January and early April. The egg hatches after 56 dayThe chick is fed by its parents for 2 months. When the chick is 2-3 months old it leaves the nest but stain the area to continue to be fed, though less frequently. Chicks begito fly at 6-7 months of age. Juvenilmay not be fully independent until uto a year after they begin to fly. 

Whooping crane (Grus americana) – designated critical habitat Males: 1.5 m (5 ft) and average weight is 7.3 kg (16 lbs) for a captive bird. Females: shorter and average weight is 6.4 kg (14 lbs) for a captive bird. 2.3 m (7.5 ft) wingspan 

Three populations of cranes exist in the wild: 1) the Aransas Wood Buffalo Population (AWBP); 2) the Florida Population (FP); and 3) the Eastern Migratory Population (EMP). The AWBP nests in the Wood Buffalo National Park (WBNP) in the Northwest Territories of Canada and in Alberta, Canada. This population migrates south to a stop over location in 

Summer: Marshes and prairie potholes. Winter: Coastal marshes and prairies. 

The crane is a territorial nester and returns to the same area each year. Eggs are laid from April to mid-MaIncubation last for a month. AWBP cranes migrate in the fall during a period beginning in mid-September and ending by mid-November to winter at the Aransas National Wildlife Refuge (ANWR). The EMcranes migrate from late October to early December. In spring, the migration begins between March 25 and April 15. This migration takes less time than the fall migration (2-4 weeks) and there is no known stop over. The EMP cranes leave their wintering grounds between the end 

35
Size Current Range Reproductive Habitat Type 

Cycle

Max. weights observed in December and January and min. weights observed in July and August. Captive whooping crane chicks weigh 100-150 g (0.2-0.3 lbs) when they hatch; 1.75-2.50 kg (3.9-5.5 lbs) at 40 days; 4.30-4.95 kg (9.5-10.9 lbs) at 100 days; and 5.70-6.70 kg (12.6-14.8 lbs) (near adult weight) at 250 days. 

Saskatchewan, before heading south through eastern MT, ND, SD, NE, KS, OK, and TX to the wintering grounds of Aransas National Wildlife Refuge (ANWR) on the Gulf Coast of TX. The FP is non-migratory and located on the Kissimmee Prairie, south of Orlando in Osceola and Polk counties. The EMP was reintroduced to the Necedah National Wildlife Refuge (NWR) in WI with captive birds trained to migrate to Chassahowitzka NWR on the Gulf Coast of FL. The AWBP is the only self sustaining wild population. The FP and EMP are introduced and are designated experimental nonessential by the USFWS. 

February and mid-April. 

36
Size Current Range Reproductive Habitat Type 

Cycle

Eskimo curlew (Numenius borealis) – no designated critical habitat Length:

About 30 cm (11.8 inches) long with a bill about 5 cm (2.0 inches) long. The length ranges from 32 cm (12.6 inches) to 27 cm (10.6 inches). Weight: 

270-454 grams (0.6-1.0 lbs) 

The USFWS lists the Eskimo curlew as statewide in Alaska, Kansas, Montana, and Nebraska, as well as in four counties in Oklahoma, two counties in South Dakota, and one county in Texas. 

Tundra and woodland transition zones, consisting of dwarf shrubgraminoid tundra complex (“barrens”) and grassy meadows for breeding. Coastal and crowberry areas such as those found in Labrador as well as terrestrial habitats were used to feed during the fall migration. Salt marsh, intertidal flats, sand dunes, meadows, pastures, and old fields in Massachusetts. Ericaceous heath habitat in Alaska, the Northwest Territories, northern Ontario, southern Quebec, Newfoundland, Labrador, and the Maritime Provinces. Tallgrass and eastern mixed-grass prairies, usually near a water source, and disturbed by fire or bison or in fields under cultivation during spring migration. Burned prairies and wetlands, plowed fields, clover patches, and beaches. 

Migratory birds. Arrive at breeding grounds in May. Breeding age is noknown, but related species breed at around three years of age. Clutches of eggs are laid from mid to late JunEggs hatch from early to mid July aonly one brood is raised in a seasonChicks feed themselves beginning othe first or second day post-hatch anmigrate at the end of the month. Breeding season is over by July and the adults head south with juveniles follow. Migrate from July to Octoband winter over in South America. Arrive at wintering grounds by early September. The return migration in the spring begins in April or May. However, other sources report that tspring migration begins in late February, with the birds arriving in Texas and Louisiana by early Marchand then heading north through the Midwestern states to eastern South Dakota and then to breeding groundin Canada by the end of May. 

37
Size Current Range Reproductive Habitat Type 

Cycle

Northern Aplomado falcon (Falco femoralis septentrionalis) – no designated critical habitat Length:

35.6-45.7 cm (14-18 inches) in length with a wingspan of 78.7-101.6 cm (31-40 inches) Weight:

410 grams (0.9 lbs)

USFWS lists this species as occurring statewide in Texas. 

Desert grasslands and coastal prairies. Open terrain with scattered trees or shrubs. Specifically in the U.S., this species is found along yucca-covered sand ridges in coastal prairies, riparian woodlands in open grasslands, and in desert grasslands with scattered mesquite and yucca. Essential habitat elements include open terrain with scattered trees, relatively low ground cover, an abundance of insects and small to medium-sized birds, and a supply of nest sites. 

Nesting occurs from March to June. The clutch size is generally 2 to 3 eggs with a brood size of 1 to 3 chicks. Incubation lasts 31 to 33 days. Young birds leave the nest about 4 to 5 weeks after hatching. 

Black-footed ferret (Mustela nigripes) – no designated critical habitat Adult length:

48.3-61.0 cm (19-24 inches), including a 12.7 or 15.2 cm (5 or 6 inch) tail. Adult weight:

0.6-1.1 kg (1.4 to 2.5 lbs) 

All wild populations have been extirpated. Reintroduced into several counties within the following states: Arizona, Kansas, Nebraska, New Mexico, North Dakota, South Dakota, and Wyoming. 

Short midgrass prairie habitat consistent with the North American grassland biome. 

Breeding takes place between Marcand May. Gestation lasts for 41-45 days. 

38
Size Current Range Reproductive Habitat Type 

Cycle

Chirichaua leopard frog (Rana chiricahuensis) – no designated critical habitat10.9 cm (4.3 inches) in length. Snoutto-vent lengths of adults range from approximately 5.4 to 12.0 cm (2.1 to 4.7 inches) 

Central and east-central Arizona into westcentral New Mexico, and also in southeastern Arizona, the bootheel of southwestern New Mexico, and south through western Chihuahua and northeastern Sonora, Mexico 

Highly aquatic. Found in rocky streams with deep rock-bound pools, ponds, earthen stock tanks, and permanent springs. Surrounding upland vegetation includes oak and mixed oak and pine woodlands, and ranges into areas of chaparral, grassland, and desert. It is known from montane and river valley cienegas, springs, pools, cattle tanks, lakes, reservoirs, streams, and rivers. It is a habitat generalist that historically was found in a variety of aquatic habitat types, but is now limited to the comparatively few aquatic systems that support few or no non-native predators. Permanent or semi-permanent pools are required for breeding. Occurs at elevations of 1,000 to 2,709 meters (3,281 to 8,890 feet). 

Breeds primarily from April through October, but egg masses are unusuain June. Populations that are greatethan 1,798 meters (5,900 feet) breed from June-August. Tadpoles take three to nine months to metamorphose, and some overwinteAt low elevations, the frog breeds from mid-February through June, while at higher elevations breeding occurs from May until August. 

39
Size Current Range Reproductive Habitat Type 

Cycle

Jaguar (Panthera onca) – no designated critical habitat Length: 112-

185 cm (44-72 inches), plus a tail length of 45-75 cm (17.5-29 inches). Adult Weight: 

36.39-157.9 kg (80-348 lbs) Birth Weight:

700-900 grams (1.5-2.0 lbs) 

The USFWS lists Arizona (Cochise, Pima, and Santa Cruz counties) and Hidalgo County in New Mexico as jaguar locations in the U.S. 

In the humid tropics of Central America, the jaguar occupies wet, lowland habitat characterized by swampy savannas and tropical rain forests. The northern and southern reaches of current jaguar distribution are marked by far more arid habitat than is found in the areas central to the species’ distribution. Jaguars – particularly males of the northern reaches – are known to have large home ranges that encompass a variety of plant communities, including: Maderan evergreen-woodland, subalpine conifer forest, semidesert shrubland, and Sonoran desert scrub. Washes and riparian areas with dense vegetative growth may also be valuable movement corridors. 

In captivity breeding takes place yearound. However, there may be a spring mating season in the northern and southern limits of the species’ range. Gestation lasts for 93-105 days. In Mexico, most births occur July, August, and September. 

Gulf Coast jaguarundi (Herpailurus yagouaroundi cacomitli) – no designated critical habitatLength: 55-77 

cm (21.7-30.3 inches) (combined head and body) and a tail length of 33-60 cm (13.0-23.6 inches) Adult Weight: 

4.5-9.0 kg (9.9-19.8 lbs) 

26 counties in Texas. Chaparral plant communities and 

dense brushy areas near streams and rivers. 

Kittens are born around March or August. Kittens are weaned after 2 months and within 10 months the young are fully independent. Gestation last between 70 and 75 days. 

40
Size Current Range Reproductive Habitat Type 

Cycle

Canada lynx (Lynx Canadensis) – designated critical habitatLength: 78.7-

99.1 cm (31-39 inches) snout to tail Adult Weight: 

5.1-17.2 kg (11.2-37.9 lbs) Birth Weight:

197-211 g (0.4-0.5 lbs) 

Listed by the USFWS as occurring in 15 states: Alaska, Colorado, Idaho, Maine, Michigan, Minnesota, Montana, New Hampshire, New York, Oregon, Utah, Vermont, Washington, Wisconsin, and Wyoming. 

In the contiguous United States, the lynx is associated with the southern, transitional reaches of the cool and moist boreal forest. Where it occurs at these lower latitudes, the boreal forest forms a mixed conifer and conifer-hardwood landscape. More specific lynx habitat associations vary from state to state. 

Mating takes place in February and March. The gestation period is 9-10 weeks. Kittens are born between Mand June, in litters of 1-8. Kittens aweaned after 5 months, although some meat may be eaten by kittens early as the first month. Sexual maturity is reached prior to two yeaof age. 

41
Size Current Range Reproductive Habitat Type 

Cycle

Preble's meadow jumping mouse (Zapus hudsonius preblei) – designated critical habitatAdult Length:

18.7-25.5 cm (7.4-10.0 inches) with a tail length of 10.8-15.5 cm (4.3-6.1 inches). Juvenile 

Weight: <13 g 

(0.03 lbs) Sub-adult 

Weight: 13-14 g 

(0.03 lbs) Adult Weight:

14-38 g (0.03-0.08 lbs). These mice weigh more in late August to mid-September before hibernation and weigh less in May when they emerge from hibernation. 

Widespread in Wyoming but rare or extirpated in Colorado. 

Well developed riparian vegetation next to undisturbed grassland, with a water source nearby that can range in size from a river to a small drainage of 1-3 meters (3.3-9.8 feet) wide. Seasonal streams, low moist areas, dry gulches, agricultural ditches, wet meadows, and seeps near streams also provide habitat. Trees, tall shrubs, short shrubs, an herbaceous layer, and ground cover are also necessary habitat components. Upper limit of elevation is 2,360 meters (7,742 feet) in Colorado and 2,317 meters (7,601 feet) in Wyoming. Day nests are constructed under debris at the base of shrubs and trees or in open grasslands, made of grasses, forbs, sedges, rushes, and other plant material. The nests are usually above ground but can be underground, are globular shapes or mats of litter, and are abandoned after a week. These mice do not appear to use burrows of other rodents. 

Hibernate from September or Octobuntil May. Adults hibernate by the 

week in August, while the young of the year enter hibernation in September or October. Meadow jumping mice have 2-3 litters per year. Each litter has 2-8 young, with an average of 5 young. The young mature to adult size in 4 weeks. Mice born in June may reproduce at 2 months of age and mice born later in the summer reproduce the following year. 

42
Size Current Range Reproductive Habitat Type 

Cycle

Ocelot (Leopardus pardalis) – no designated critical habitat11.3 - 15.8 kg (24.9-34.8 lbs) 

3 counties in Arizona (Cochise, Pima, and Santa Cruz) and 26 counties in Texas. 

A variety of habitats can be used by ocelots. Ocelots appear to use areas of dense cover, and in the northern part of the range hunt in brushy forests and semi-arid deserts. In the southern part of its range, ocelot habitat includes tropical forests, mountain slopes, and pampas (grasslands). 

Births have been recorded from September to January. Births in Texas have been documented in September and October, and also in late summer, late fall, early winter, and late spring. Typically one or twkittens are born, but litters can range up to four kittens. 

Mexican spotted owl (Strix occidentalis lucida) – designated critical habitatAdult male average weight:

519+32.6 (SD) 

g (1.1 lbs) Adult female 

average weight:

579+31.2 (SD) 

g (1.3 lbs) 

13 counties in Arizona; 33 counties in Colorado; 22 counties in New Mexico; 4 counties in Texas; and 11 counties in Utah. 

Old-growth or mature forests with unevenly aged stands of trees, high canopy, multi-storied levels, and high tree density. Canyons with riparian or conifer communities. In Arizona and New Mexico: mixed conifer, pineoak, Arizona cypress, oak woodlands, and associated riparian forests. Dispersing juveniles move through a variety of habitats before selecting a home range, including: spruce-fir and mixed-conifer forests, pinyon-juniper woodland, mountain shrublands, desert scrubland, and desert grasslands. 

Owls defend their breeding territory during the nesting season (March – August). Clutch size: 1-3 eggs. Eghatch in early May. A second clutch may be produced if the first clutch fails. Owlets fledge at 4-5 weeks ol(early to mid-June). They disperse from the nest in mid-September to early October. Breeding is sporadicNot all birds nest every year. 

43
Size Current Range Reproductive Habitat Type 

Cycle

Piping plover (Charadrius melodus) – designated critical habitatBetween 42 and 64 grams (1.5 to 2 ounces) 17 centimeters from bill to rump, and its wings measure approximately 35 centimeters from tip to tip 

Plover breeding occurs in Montana in Garfield, Sheridan and McCone Counties. In North Dakota, plovers breed in 25 counties located along the Missouri River and in the alkali wetlands located in the center of the state. Plover breeding in South Dakota also occurs on sandbars along the Missouri River, with other isolated nesting sites located in Lake Oahe and saline wetlands in the northeast. In Nebraska, plover breed along the upper Missouri River, the lower Niobrara, and the mid- to lower Platte Rivers, as well as the Middle Loup and Loup Rivers, and Lake McConaughy (USFWS, 1988). 

In north-central North America, Piping Plovers nest on barren sand and gravel Great Lakes shorelines, and along sand and gravel shores of rivers and lakes in the Great Plains. Lake habitat generally consists of wide beaches (>20 m) with less than 5% vegetative cover, with highly clumped vegetation and/or with extensive gravel. Lake habitat may vary from these conditions when unavailable in a given shoreline area. 

Plovers arrive at breeding sites in thGreat Plains between mid-April and mid-May. Egg laying begins the second or third week of May. Incubation lasts for 25-31 days and both adults incubate the egg. Chickfledge between 21 days after hatchinin Manitoba to 30-35 days on Long Island in New York. Adults migrate from breeding grounds beginning in mid-July and ending in early AugusJuveniles often depart as late as late August and breeding males are sometimes reported to depart with their young 

44
Size Current Range Reproductive Habitat Type 

Cycle

New Mexican ridge-nosed rattlesnake (Crotalus willardi obscurus) – designated critical habitatLength:

Maximum length of 60 cm (24 inches). The lengths range from 30-61 cm (11.8-24 inches). Weight:

85-113 grams (0.2-0.3 lbs). 

Exists in fragmented enclaves occupying a combined total of less than two square miles of habitat in the extreme southwest corner of New Mexico. The USFWS lists the species as known to occur in two counties in the U.S.: Hidalgo County, New Mexico and Cochise County, Arizona. 

Narrow mountain canyons at elevations between 1,676 and 2,743 meters (5,500 and 9,000 feet). The snake prefers to hide in leaf litter among cobbles and rocks along canyon floors. Rocks, leaf litter, and mesic conditions are commonalities among all confirmed habitat of this species. The vegetative structure of the habitat is chiefly comprised of open stands of pine-oak forest and associated shrubs and grasses. Specifically, plant species of the typical habitat include Arizona white oak, Alligator juniper, Mexican pinyon, Chihuahua pine, Gambel oak, Arizona Madrone, skunkbush, Manzanita, and birchleaf rhamnus. Bunchgrass is also associated with this species. 

Females are ovoviviparous, and givbirth to live young. This species is biennial species: mating occurs in thsummer and fertilized eggs are retained in the oviducts until ready thatch the following summer. The gestation period averages 13 monthBirths for most species of rattlesnakoccur between August 1st and Octob

15th, however most births of this 

species are in April and May. 

45
Size Current Range Reproductive Habitat Type 

Cycle

Sonora tiger salamander (Ambystoma tigrinum stebbinsi) – no designated critical habitatMetamorphosed Sonora tiger salamanders: 

4.5-15 cm (1.8-5.9 inches) snout to vent length. Branchiate 

adults: 6.5-16.5 

cm (2.6-6.5 inches) snout to vent length. 

This subspecies has been found in 53 ponds in the San Rafael Valley of Arizona. The San Rafael Valley lies between the Hauchuca and Patagonia mountains, is bordered by the Canelo Hills to the north and extends from Santa Cruz County in Arizona south for approximately 30 km (18 miles) into Sonora, Mexico. 

Requires standing water from January through June for breeding and larval growth. Adult, metamorphosed salamanders inhabit adjacent grassland and oak woodland terrestrial habitat when not in ponds. The ecology of the Sonora tiger salamander outside of the pond has not been well studied, but other Ambystoma species spend much of their time in mammal burrows or buried in soft earth to avoid environmental extremes common on land. 

Begin as eggs laid in water. Then hatch and grow as aquatic larvae wigills, and then either mature as gilleaquatic adults (called branchiate adults, neotenes, or paedomorphs), ometamorphose into terrestrial salamanders without gills. Breed as early as January, and eggs can be found in ponds as late as early MayTerrestrial adults, which are often outside of the pond during the rest othe year, return to the ponds to breeand branchiate adults in the pond albreed. Eggs take 2-4 weeks to hatchthe colder the water the longer it takthe eggs to develop. Larvae can develop into the minimum size necessary to metamorphose in as few as two months. However, because many sites hold water all year, larvaoften remain in the water longer before metamorphosing, or instead, develop into branchiate adults. 

46
Size Current Range Reproductive Habitat Type 

Cycle

Black-capped vireo (Vireo atricapilla) – no designated critical habitatLength:

11 to 12 cm (about 4.5 inches) Weight:

9 to 10 grams (0.02 lbs) 

The USFWS website states that the species is known to occur in 8 counties in Oklahoma and 67 counties in TX. However, the USFWS recovery plan states three locations (Blaine, Comanche, and the border of Canadian and Caddo counties) in Oklahoma and 35 counties in Texas. 

Mixed deciduous/evergreen shrub land. Breeding vireos use shrubby growth of irregular height and distribution with spaces the small thickets and clumps and with vegetative extending to ground level. From Oklahoma through most of Texas this type of vegetational configuration occurs most frequently on rocky substrates with shallow soils, in rocky gullies, on edges of ravines, and on eroded slopes. 

Territory size mostly 2-4 acres. Nesting begins when females arrive and continues through August. Nesbuilding requires 2-5 days. Compleclutches have been found as early as April 4th in Texas and April 30th in 

Oklahoma. Latest known nesting start (beginning nest construction) iJuly 21st. Clutches contain 3-4 eggs

Seasonal clutch size is likely betwee12 and 20 eggs allowing up to six nesting attempts per season. One egis laid per day with the first egg beinlaid one day after completion of the nest. Incubation requires 14-19 dayNestling stage is 9-12 days. Fledglistage is 30-45 days. 

Golden-cheeked warbler (Dendroica chrysoparia) – no designated critical habitatLength:

12 cm (4.7 inches) long Weight:

10 grams (0.02 lbs) 

Nests only in central Texas. Edwards Plateau of Texas and locally north to Palo Pinto County 

Mixed Ashe-juniper and oak woodlands in ravines and canyons. Summers in open canopy forest and winters in closed canopy forests. Breeds in juniper-oak woodlands typically in limestone hills and canyons. It is dependent on the bark of the Ashe juniper (Juniperus ashei) for nesting materials. In winter it occurs in pine-oak forests at elevations between 1,500 and 3,000 meters (4,921 and 9,842 feet). 

One brood with incubation of 12 daand 9 days until fledge. Arrives on breeding ground in early March. Nebuilt by female and usually in an Ashe juniper tree. Nests are constructed from strips of juniper bark woven together with spider silk and insect cocoons, and lined with grass, hair, or down. 3-5 eggs are incubated for 10-12 days. Young leave the nest at 9-12 days. Young are independent at about 1 month after fledging. Migration to the wintering grounds occurs from June to August. 

47
48

Size Current Range Habitat Type Reproductive Cycle 

Gray wolf (Canis lupus) – designated critical habitatAdult weight:

18-80 kg (40-175 lbs) 

Found in: Colorado (statewide), Michigan (15 counties), New Mexico (3 counties), North Dakota (53 counties), Oregon (statewide), South Dakota (statewide), Utah (statewide), Washington (statewide), and Wisconsin (32 counties). 

Wide range of habitats including temperate forests, mountains, tundra, taiga, and grasslands. 

Typically only the alpha male and female breed and produce pups. Breeding begins around age 2 and may continue annually until they are 10 years old or older. Pups are born in April. Litter size ranges from 1-1pups with an average of 5 pups per litter. 
2.5.1. Consideration of Federally Listed Plants 

BTPDs may have an effect on the plant communities within their habitat through their feeding 

habits. Eliminating or reducing the numbers of BTPDs may therefore have an effect on the 

composition of plant communities within the range of the BTPD. The impact of this effect to 

listed plants while noted, is not specifically assessed since it is not clear whether such changes 

would have negative or positive effects on individual listed plant species. Further, impacts from 

the use of Rozol Prairie Dog Bait to pollinators and seed dispersers could have effects on the 

viability of listed plants that depend upon those methods of reproduction. Listed plants found 

within the 10 states where Rozol Prairie Dog Bait may be used are enumerated below: 

Penland beardtongue (Penstemon penlandii), Colorado butterfly plant (Gaura neomexicana var. 

coloradensis), Chisos Mountain hedgehog cactus (Echinocereus chisoensis var. chisoensis), 

Knowlton's cactus (Pediocactus knowltonii), Kuenzler hedgehog cactus (Echinocereus fendleri 

var. kuenzleri), Lee pincushion cactus (Coryphantha sneedii var. leei), Lloyd's Mariposa Cactus

(Echinomastus mariposensis), Mesa Verde cactus (Sclerocactus mesae-verdae), Nellie cory 

cactus (Coryphantha minima), Sneed pincushion cactus (Coryphantha sneedii var. sneedii), 

Tobusch fishhook cactus (Ancistrocactus tobuschii), Spalding's catchfly (Silene spaldingii), 

Terlingua Creek cat's-eye (Cryptantha crassipes), bunched cory cactus (Coryphantha ramillosa), 

Zuni fleabane (Erigeron rhizomatus), Holy Ghost Ipomopsis (Ipomopsis sancti-spiritus), Ute 

ladies'-tresses (Spiranthes diluvialis), Mancos milk-vetch (Astragalus humillimus), Osterhout 

milk-vetch (Astragalus osterhoutii), Penland alpine fen mustard (Eutrema penlandii), Hinckley 

oak (Quercus hinckleyi), western prairie fringed orchid (Platanthera praeclara), Todsen's 

pennyroyal (Hedeoma todsenii), blowout penstemon (Penstemon haydenii), North Park phacelia

(Phacelia formosula), Davis' green pitaya (Echinocereus viridiflorus var. davisii), Sacramento 

prickly poppy (Argemone pleiacantha ssp. pinnatisecta), Texas poppy-mallow (Callirhoe 

scabriuscula), slender rush-pea, (Hoffmannseggia tenella), Texas snowbells (Styrax texanus), 

Pecos sunflower (Helianthus paradoxus), Sacramento Mountains thistle (Cirsium vinaceum), 

gypsum wild-buckwheat (Eriogonum gypsophilum), and desert yellowhead (Yermo 

xanthocephalus). 

49
2.6. Designated Critical Habitat 

 

Critical habitat has been designated for the following nine assessed animal species: Salt Creek 

tiger beetle, California condor, whooping crane, Canada lynx, Preble’s meadow jumping mouse, 

Mexican spotted owl, piping plover, New Mexican ridge-nosed rattlesnake, and the gray wolf. 

Critical habitat is defined in the ESA as the geographic area occupied by the species at the time 

of the listing where the physical and biological features necessary for the conservation of the 

species exist, and there is a need for special management to protect the listed species. It may 

also include areas outside the occupied area at the time of listing if such areas are ‘essential to 

the conservation of the species.’ Critical habitat receives protection under Section 7 of the ESA 

through prohibition against destruction or adverse modification with regard to actions carried 

out, funded, or authorized by a federal agency. Section 7 requires consultation on federal actions 

that are likely to result in the destruction or adverse modification of critical habitat. 

To be included in a critical habitat designation, the habitat must be ‘essential to the conservation 

of the species.’ Critical habitat designations identify, to the extent known using best scientific 

and commercial data available, habitat areas that provide essential life cycle needs of the species, 

or areas that contain certain PCEs (as defined in 50 CFR 414.12(b)). PCEs include, but are not 

limited to, space for individual and population growth and for normal behavior; food, water, air, 

light, minerals, or other nutritional or physiological requirements; cover or shelter; sites for 

breeding, reproduction, rearing (or development) of offspring; and habitats that are protected 

from disturbance or are representative of the historic geographical and ecological distributions of 

a species. Table 2.3 describes the PCEs for the critical habitats for the following nine assessed 

species: Salt Creek tiger beetle, California condor, whooping crane, Canada lynx, Preble’s 

meadow jumping mouse, Mexican spotted owl, piping plover, New Mexican ridge-nosed 

rattlesnake, and the gray wolf. 

Table 2.3 Designated Critical Habitat PCEs 

PCEs Reference 

Salt Creek tiger beetle 

(1) Non-vegetated streambanks and mid-channel areas, located adjacent to and between saline 

stream edges and barren salt flats in saline and freshwater wetlands, in assemblages that are 

within 4 mi (6 km) of one another. 

(2) Moist, barren salt flats with: 

(a) Salmo and Saltillo soils or Lamo, Gibbon-Saltine, Obert, and Zoe soils with Salmo and 

Saltillo inclusions: 

(b) Soil electroconductivity ranging from 2,016.0 mS/m to 2,992.2 mS/m; 

(c) Soil moisture ranging from 43.5 percent to 51.7 percent; and 

(d) Differential hydraulic pressures that create evaporation and result in exposed salt on soil 

surfaces. 

(3) A natural hydrologic regime resulting in annual high flows in saline streams in the early 

spring and summer, and natural elevation changes in groundwater levels to hydrate saline 

wetlands located on the floodplain. 

(4) The presence of abundant and diverse flying and non-flying invertebrate prey species 

belonging to the orders Coleoptera, Orthoptera, Hemiptera, Hymenoptera, Odonata, Diptera, or 

Lepidoptera. 

(USFWS, 2010) 

50
California condor 

PCEs were not described for the California condor. However, several factors were considered 

in designating critical habitat: 

The Sespe-Piru, Mantilija, Sisquoc-San Rafael, and the Hi Mountain-Beartrap areas were 

considered critical for nesting and related year-long activities. 

The Mount Pinos and Blue-Ridge areas were considered critical for roosting. 

The Tejon Ranch, Kern County Rangelands, and Tulare County Rangelands were considered 

critical for feeding and other related activities; specifically, the Tejon County Rangelands are 

important because it is the only feeding area close to the Sespe-Piru nesting area. 

Further, areas of open range with limited disturbance that provide food are needed within the 

designated areas to maintain the species, since food availability is directly related to condor 

distribution and reproduction. 

(USFWS, 1976) 

Whooping crane 

Although PCEs were not specifically described for the whooping crane it was stated that each 

of the five factors normally associated with PCEs ((1) Space for individual and population 

growth and for normal behavior; (2) Food, water, air, light, minerals, or other nutritional or 

physiological requirements; (3) Cover or shelter; (4) Sites for breeding, reproduction, or 

rearing of offspring; and generally, (5) Habitats that are protected from disturbances or are 

representative of the geographical distribution of the listed species) pertain to the whooping 

crane and are summarized below: 

Whooping cranes are territorial; pairs require hundreds of acres of undisturbed wetland habitat 

and unmated birds require undefended territory. Refuges in Idaho, Colorado, and New Mexico 

were originally designated as part of the critical habitat to add space for a growing new flock. 

However, these refuges were later removed from the critical habitat designation due to the 

failure of whooping crane reintroduction in these areas. 

(USFWS,1978 

and 1997) 

All of the designated critical habitat areas provide for the nutritional and physiological needs 

of the cranes. This includes the tidal flats and marshes of Aransas that provide crustaceans and 

mollusks, the spring migration marshes that provide frogs, fish, crayfish, and other small 

animals, and the fall migration stopover locations where cranes feed primarily on waste grains 

and insects. 

Whooping cranes require open spaces, primarily sand and gravel bars in rivers and lakes, for 

nightly roosting. These features appear to be one of the major factors in the selection of 

habitat by cranes. 

With regard to breeding, the Grays Lake National Wildlife Refuge in Idaho was previously 

designated as critical habitat in order to provide additional nesting habitat. However, all of the 

designated critical habitat provides areas essential to rearing young. Cranes also require 

undisturbed wetland roosting sites and do not tolerate disturbance to themselves or their 

habitat. 

(USFWS, 1978) 

Canada lynx

Boreal forest of multiple succesional stages. 

Snowshoe hares and their preferred habitat conditions, which include low and dense vegetation 

that protrudes above the snow, and mature multistoried stands with conifer boughs at the snow 

surface. 

Winter snow conditions of deep powder present for extended periods of time. 

Potential den sites characterized by abundant coarse woody debris. 

Matrix habitat (e.g., hardwood forest, dry forest, non-forest, or other habitat types that do not 

support snowshoe hares) which connect patches of boreal forest foraging sites used by the lynx 

within a home range 

(USFWS, 2009) 

51
Preble’s meadow jumping mouse

Riparian corridors formed and maintained by normal, dynamic, geomorphological, and 

hydrologic processes that create and maintain river and stream channels, floodplains, and 

floodplain benches and promote patterns of vegetation favorable to the Preble’s meadow 

jumping mouse, containing dense, riparian vegetation consisting of grasses, forbs, and shrubs, 

or any combination thereof, in areas along rivers and streams, that normally provide open 

water through the mouse’s active season. 

The riparian areas must also include specific movement corridors that provide connectivity 

between and within populations. 

These could be riparian corridors with less vegetative cover, or include human disturbances 

such as erosion control, travel ways under bridges, along ditches and canals, and through 

culverts. 

Adjacent areas of low disturbance in floodplains and uplands, such as hayed fields, grazed 

pasture, and other unplowed agricultural fields, restored mine lands, recreational trail areas and 

urban-wildland interfaces. 

(USFWS, 2009) 

Mexican spotted owl

A range of tree species, including mixed conifer, pine-oak, and riparian forest types, composed 

of different tree sizes reflecting different stages of trees, 30-45% of which are trees with a 12 

inch or greater trunk diameter when measured 4.5 feet off of the ground. 

A shade canopy created by the tree branches covering 40 percent or more of the ground 

Large dead trees (snags) with a trunk diameter of at least 12 inches (0.3 meters) when 

measured at 4.5 feet (1.4 meters) from the ground. 

High volumes of fallen trees and other woody debris; 

A wide range of tree and plant species, including hardwoods; and 

Adequate levels of residual plant cover to maintain fruits, seeds, and allow plant regeneration. 

Presence of water which typically provides cooler temperatures and higher humidity than the 

nearby areas. 

Clumps of stringers of mixed-conifer, pine-oak, pinyon-juniper, and/or riparian vegetation; 

Canyon wall containing crevices, ledges, or caves; and 

High percent of ground litter and woody debris. 

(USFWS, 2004) 

Piping plover

The PCEs that support foraging, roosting, and sheltering habitat components for the wintering 

piping plover are: 

(1) Intertidal sand beaches (including sand flats) or mud flats (between the MLLW [mean 

lower low water] and annual high tide) with no, or very sparse, emergent vegetation for 

feeding. In some cases, these flats may be covered or partially covered by a mat of blue-green 

algae. 

(2) Unvegetated or sparsely vegetated sand, mud, or algal flats above annual high tide for 

roosting. Such sites may have debris or detritus and may have micro-topographic relief (less 

than 20 in (50 cm) above substrate surface) offering refuge from high winds and cold weather. 

(3) Surf-cast algae for feeding. 

(4) Sparsely vegetated backbeach, which is the beach area above mean high tide seaward of the 

dune line, or in cases where no dunes exist, seaward of a delineating feature such as a 

vegetation line, structure, or road. Backbeach is used by plovers for roosting and refuge during 

storms. 

(5) Spits, especially sand, running into water used for foraging and roosting. 

(6) Salterns, or bare sand flats in the center of mangrove ecosystems that are found above 

mean high water and are only irregularly flushed with seawater. 

(7) Unvegetated washover areas with little or no topographic relief for feeding and roosting. 

Washover areas are formed and maintained by the action of hurricanes, storm surges, or other 

extreme wave actions. 

(8) Natural conditions of sparse vegetation and little or no topographic relief mimicked in 

artificial habitat types (e.g., dredge spoil sites.) 

(USFWS, 2009) 

52
The following PCEs, taken from the critical habitat designation for the northern Great Plains 

breeding population of the piping plover, encompass piping plover habitat outside of the 

designated wintering grounds of the species. 

The one overriding primary constituent element (biological) that must be present at all sites is 

the dynamic ecological processes that create and maintain piping plover habitat. 

The biological primary constituent element, i.e., dynamic ecological processes, creates 

different physical primary constituent elements on the landscape. These habitat types or 

physical primary constituent elements that sustain the northern Great Plains breeding 

population of piping plovers are described as follows: 

On prairie alkali lakes and wetlands, the physical primary constituent elements include – 

(1) Shallow, seasonally to permanently flooded, mixosaline to hypersaline wetlands with sandy 

to gravelly, sparsely vegetated beaches, salt-encrusted mud flats, and/or gravelly salt flats; 

(2) Springs and fens along edges of alkali lakes and wetlands; and 

(3) Adjacent uplands 200 feet (61 m) above the high water mark of the alkali lake or wetland. 

On rivers the physical primary constituent elements include – sparsely vegetated channel 

sandbars, sand and gravel beaches on islands, temporary pools on sandbars and islands, and the 

interface with the river. 

On reservoirs the physical primary constituent elements include – sparsely vegetated shoreline 

beaches, peninsulas, islands composed of sand, gravel, or shale, and their interface with the 

water bodies. 

On inland lakes (Lake of the Woods) the physical primary constituent elements include – 

sparsely vegetated and windswept sandy to gravelly islands, beaches, and peninsulas, and their 

interface with the water body. 

(USFWS, 2002) 

New Mexican ridge-nosed rattlesnake 

PCEs were not described for the New Mexican ridge-nosed rattlesnake by name. However, the 

critical habitat listing notice identified certain attributes and features of the designated critical 

habitat area that are grouped as “constituent elements,” including:

Dens and/or denning habitat that provides shelter during the summer and winter months; 

Vegetation that provides cover for the New Mexican ridge-nosed rattlesnake and habitat for 

prey; 

Abundance of prey (lizards and rodents) 

(USFWS, 1978) 

Gray wolf

PCEs were not described for the gray wolf. However, key habitat components were described 

in the recovery plan: 

A year-round abundance of ungulate prey and alternate prey, 

Secluded and suitable denning and rendezvous sites, and 

Sufficient space with low human disturbance. 

(USFWS, 1987) 

2.7. Action Area and LAA Effects Determination Area 

2.7.1. Action Area 

The action area is defined by the Endangered Species Act as, “all areas to be affected directly or 

indirectly by the Federal action and not merely the immediate area involved in the action” (50 

CFR §402.2). The Federal action is the authorization or registration of pesticide use or uses as 

described on the label(s) of pesticide products containing a particular active ingredient. Based on 

an analysis of the Federal action, the action area is defined by the actual and potential use of the 

pesticide and areas where that use could result in effects. Specific measures of ecological effect 

for the assessed species that define the action area include any direct and indirect toxic effect to 

53
the assessed species and any potential modification of its critical habitat, including reduction in 

survival, growth, and reproduction as well as the full suite of sublethal effects available in the 

effects literature. The overall action area for the national registration of chlorophacinone is 

likely to encompass considerable portions of the United States based on the large array of 

agricultural and non-agricultural uses. However, the scope of this assessment limits 

consideration of the overall action area to reflect the BTPD use pattern and the potential for this 

use to affect listed species. 

For this assessment, BTPD range within the states of Colorado, Kansas, Montana, Nebraska, 

New Mexico, North Dakota, Oklahoma, South Dakota, Texas and Wyoming and counties 

adjacent to this range is considered to be the action area. The action area considered for direct 

effects includes the BTPD range within the 10 states listed above as well as counties adjacent to 

this range. The action area considered for indirect effects includes only the BTPD range with the 

10 states listed above and does not include counties adjacent to this range. This distinction was 

made because indirect effects are not expected to extend beyond the use area. However, direct 

effects may extend beyond the use area due to exposure to individuals or via prey items with 

chlorophacinone residues that could be found outside of their described range. 

It is important to note that the historic range-wide action areas do not imply that direct and/or 

indirect effects and/or critical habitat modification are expected or are likely to occur over the 

full extent of the action area, but rather to identify all areas that may potentially be affected by 

the action. The Agency uses more rigorous analysis including consideration of available land 

cover data, toxicity data, and exposure information to determine areas where listed species and 

their designated critical habitats may be affected or modified via endpoints associated with 

reduced survival, growth, or reproduction. 

2.7.2. MA Effects Determination Area 

A stepwise approach is used to define the May Affect (MA) Effects Determination Area. A MA 

effects determination applies to those areas where chlorophacinone use may directly or indirectly 

affect the species and/or modify its designated critical habitat. As a result, this is the area where 

the BTPD range overlaps with the range and/or designated critical habitat for the listed species. 

If there is no overlap between the BTPD range and the habitat or occurrence areas of the listed 

species and the listed species is not found in a county adjacent to the BTPD range then a no 

effect “NE” determination is made. Counties adjacent to the BTPD range are considered to 

account for potential migration of listed species out of their historic ranges. However, for habitat 

modification effects, adjacent counties will not be considered. The first step in defining the MA 

Effects Determination Area is to understand the federal action. The federal action is defined as 

the use of 50 mg a.i./kg-bait chlorophacinone grain bait to control BTPDs on rangelands and 

noncrop areas within the noted 10 state area. An analysis of this use and review of the product 

label was completed. 

Following a determination of the assessed use, an evaluation of the potential “footprint” of 

chlorophacinone use for BTPDs (i.e., the area where pesticide application may occur) is 

determined. This “footprint” represents the initial area of concern and comes from the range of 

54
the BTPD obtained from NatureServe. The initial area of concern is defined as all land cover 

types within the range of the BTPD. 

Figure 2.2. Initial area of concern, or “footprint” of potential use, for chlorophacinone use 

to control BTPDs.

As previously discussed, the action area is defined by the most sensitive measure of direct and 

indirect ecological toxic effects including reduction in survival, growth, reproduction, and the 

entire suite of sublethal effects from valid, peer-reviewed studies. Once the initial area of 

concern is defined, the next step is to define the boundaries of the potential MA Effects 

55
Determination Area by determining the extent of offsite transport via chlorophacinone exposed 

animals ranging distances from chlorophacinone use sites. The Agency does not have a method 

for modeling this type of off-site transport but will include listed species not just overlapping in 

the range of the BTPD but those species occurring in counties adjacent to counties within the 

historic BTPD range as well. 

2.8. Assessment Endpoints and Measures of Ecological Effect 

2.8.1. Assessment Endpoints 

A complete discussion of all of the toxicity data available for this risk assessment, including 

resulting measures of ecological effect selected for each taxonomic group of concern, is included 

in Section 4 of this document. Registrant submitted data, data from ECOTOX, and data received 

during the comment period for “Receipt of Petition Requesting EPA to Suspend the Registration 

of Rozol Prairie Dog Bait and Cancel Certain Application Sites” (EPA-HQ-OPP-2009-0684-

0001) were all considered. Table 2.4 identifies the taxa relevant to assessing direct effects via 

primary or secondary exposure for each species of concern. The taxa relevant to primary 

exposure are those animals that directly consume the chlorophacinone bait. The taxa relevant to 

secondary exposure are those species of concern that prey upon or scavenge the primary 

consumers of the cholorphacinone bait. 

Table 2.4 Taxa Used in the Analyses of Direct Effects from Primary (Bait) and Secondary 

Exposure for the Listed Species that May be Affected 

Listed Species Terrestrial 

Invertebrates Mammals Birds 

Grizzly bear N/A Primary and Secondary N/A 

American burying beetle Secondary Secondary Secondary 

Salt creek tiger beetle Secondary N/A N/A 

California condor N/A Secondary Secondary 

Whooping crane Secondary Secondary Primary and Secondary 

Eskimo curlew Secondary N/A N/A 

Northern Aplomado falcon Secondary Secondary Secondary 

Black-footed ferret Secondary Secondary Secondary 

Chirichaua leopard frog Secondary N/A Secondary 

Jaguar N/A Secondary Secondary 

Gulf Coast jaguarundi N/A Secondary Secondary 

Canada lynx N/A Secondary Secondary 

Preble’s meadow jumping mouse Secondary Primary N/A 

Ocelot Secondary Secondary Secondary 

Mexican spotted owl Secondary Secondary Secondary 

Piping plover Secondary N/A N/A 

New Mexican ridge-nosed rattlesnake Secondary Secondary Secondary

Sonora tiger salamander Secondary N/A N/A 

Black-capped vireo Secondary N/A N/A 

Golden-cheeked warbler Secondary N/A N/A 

Wolf, Gray Secondary Secondary Secondary 

N/A Not Applicable 

56
The taxa used to assess the potential for indirect effects from the uses of chlorophacinone for 

each listed species are indentified in Table 2.5. Indirect effects consist of modifications to 

critical habitat or loss of prey base. The specific assessment endpoints used to assess the 

potential for direct and indirect effects to each listed species are provided in Section 2.1. 

Table 2.5 Taxa Used in the Analyses of Indirect Effects for the Listed Species that May be 

Affected 

Listed Species Terrestrial 

Invertebrates 

Mammals Birds 

Grizzly bear N/A loss of prey base N/A 

American burying beetle loss of prey base loss of prey base loss of prey base 

Salt creek tiger beetle loss of prey base N/A N/A 

California condor N/A loss of prey base loss of prey base 

Whooping crane loss of prey base loss of prey base loss of prey base 

Eskimo curlew loss of prey base N/A N/A 

Northern Aplomado falcon loss of prey base loss of prey base loss of prey base 

Black-footed ferret loss of prey base loss of prey base and habitat loss of prey base 

Chirichaua leopard frog loss of prey base N/A loss of prey base 

Jaguar N/A loss of prey base loss of prey base 

Gulf Coast jaguarundi N/A loss of prey base loss of prey base 

Canada lynx N/A loss of prey base loss of prey base 

Preble’s meadow jumping 

mouse 

loss of prey base N/A N/A 

Ocelot loss of prey base loss of prey base loss of prey base 

Mexican spotted owl loss of prey base loss of prey base loss of prey base 

Piping plover loss of prey base N/A N/A 

New Mexican ridge-nosed 

rattlesnake 

loss of prey base loss of prey base loss of prey base 

Sonora tiger salamander loss of prey base N/A loss of habitat 

Black-capped vireo loss of prey base N/A N/A 

Golden-cheeked warbler loss of prey base N/A N/A 

Wolf, Gray loss of prey base loss of prey base loss of prey base 

N/A Not Applicable 

1 EFED uses avian toxicity data to assess for exposure to and risks from reptiles and amphibians. 

57
Table 2.6 identifies the most conservative toxic endpoints relevant to each taxa and the most 

conservative residue concentrations. These endpoints and concentrations will be carried through 

the assessment to quantitatively assess risk to the species listed in Table 2.4 and Table 2.5. 

Table 2.6 Taxa and Assessment Endpoints Used to Evaluate the Potential for Use of 

Chlorophacinone to Result in Direct and Indirect Effects to the Listed Species or 

Modification of Critical Habitat that May be Affected 

Taxa Used to Assess 

Direct and Indirect 

Effects to Listed 

Species and/or 

Modification to 

Critical Habitat or 

Habitat

Direct or 

Indirect Effect 

to Listed 

Species

Assessment Endpoints 

Measures of 

Ecological Effects 

Measures of 

Ecological Exposures 

1. Mammals Direct and 

Indirect Effect 

Survival, growth, and 

reproduction of individuals 

or modification of critical 

habitat via direct and 

indirect effects 

Primary Exposure:

Most sensitive mammal 

acute LD50 (5-day)1

: 

Norway rat LD50 = 

0.80 mg a.i./kg-bw2

Secondary Exposure:

Highest whole body 

BTPD average 

concentration (MRID 

47333603): BTPD= 

2.24 mg a.i./kg-bw and 

highest whole body 

non-target average 

concentration 

(Anonymous, 1981): 

Deer Mouse = 5.8 mg 

a.i./kg-bw 

2. Birds and 

Herptiles 

Direct and 

Indirect Effect

Survival, growth, and 

reproduction of individuals 

or modification of critical 

habitat via direct and 

indirect effects 

Primary Exposure: 

Most sensitive bird 

LC50 (MRID 

41513102): Bobwhite 

LC50 = 56 mg a.i./kgdiet2

 

Bobwhite LD50 = 258 

mg a.i./kg-bw 

Secondary Exposure:

Highest whole body 

BTPD average 

concentration (MRID 

47333603): BTPD= 

2.24 mg a.i./kg-bw and 

highest whole body 

non-target average 

concentration 

(Anonymous, 1981): 

Deer Mouse = 5.8 mg 

a.i./kg-bw 

3. Terrestrial 

Invertebrates 

Direct and 

Indirect Effect

Survival, growth, and 

reproduction of individuals 

or modification of critical 

habitat via direct and 

indirect effects 

Secondary Exposure:

Unquantified sublethal 

effects to Nicrophorus 

orbicollis (MRID 

47383001) 

1 Jackson, W.B. and A.D. Ashton. 1992. A review of available anticoagulants and their use in the 

United States. Proc. Vertebr. Pest Conf. 15:156-160.. 2

 The most sensitive endpoint was used in calculations and is displayed in bold font. 

58
2.8.2. Assessment Endpoints for Designated Critical Habitat 

As previously discussed, designated critical habitat is assessed to evaluate actions related to the 

use of chlorophacinone to control BTPDs that may alter the PCEs of the listed species’ 

designated critical habitat. PCEs for the listed species were previously described in Section 2.6. 

Actions that may modify critical habitat are those that alter the PCEs and jeopardize the 

continued existence of the listed species. Therefore, these actions are identified as assessment 

endpoints. It should be noted that evaluation of PCEs as assessment endpoints is limited to those 

of a biological nature (i.e., the biological resource requirements for the listed species associated 

with the critical habitat) and those for which chlorophacinone effects data are available. 

Assessment endpoints used to evaluate potential for direct and indirect effects are equivalent to 

the assessment endpoints used to evaluate potential effects to designated critical habitat. If a 

potential for direct or indirect effects is found, then there is also a potential for effects to 

designated critical habitat. Some components of these PCEs are associated with physical abiotic 

features (e.g., presence of a water body, limits of species ranges or physical geographic features), 

which are not expected to be measurably altered by use of pesticides. 

2.9. Conceptual Model 

2.9.1. Risk Hypotheses 

Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in 

assessment endpoints) and may be based on theory and logic, empirical data, mathematical 

models, or probability models (USEPA, 1998). For this assessment, the risk is stressor-linked, 

where the stressor is chlorophacinone bait placed in BTPD burrows. The following risk 

hypotheses are presumed in this assessment: 

The labeled use of chlorophacinone for control of BTPDs within the action area may: 

• directly affect listed species by causing mortality or by adversely affecting growth or 

reproduction through primary exposure to grain bait; 

• directly affect listed species by causing mortality or by adversely affecting growth or 

reproduction through secondary exposure to chlorophacinone poisoned animals, BTPDs 

or non-target animals, or carcasses. 

• indirectly affect listed species and/or modify their designated critical habitat by reducing 

or changing the composition of their food supply due to a reduction in available BTPDs 

and non-target animals; 

• indirectly affect listed species and/or modify their designated critical habitat by reducing 

populations of BTPDs which provide burrows for shelter 

59
2.9.2. Diagram 

The conceptual model is a graphic representation of the structure of the risk assessment. It 

specifies the chlorophacinone release mechanisms, biological receptor types, and effects 

endpoints of potential concern. The conceptual model for all listed species is shown in Figure 

2.3. Although the conceptual models for direct/indirect effects and modification of designated 

critical habitat PCEs are shown on the same diagram, the potential for direct/indirect effects and 

modification of PCEs will be evaluated separately in this assessment. Not included in the risk 

hypotheses but included in the conceptual diagram is effects to plant communities as a result of 

reduced or loss of BTPD activity. It is uncertain whether this alteration to plant community 

composition would have beneficial and/or detrimental effects to assessed listed species. 

Figure 2.3 Conceptual model depicting stressors, exposure pathways, and potential effects 

to terrestrial organisms from the use of chlorophacinone on BTPDs. 

Stressor 

Transport 

Pathways In Burrow Application 

Consumption by BTPDs 

Incidental Deposition on Surface 

via Bioturbation 

Exposure 

Media 

Exposure 

Route and 

Receptors 

Consumption by non-target 

terrestrial organisms 

Exposed Intact Bait at 

Application Site 

Direct Effect 

Consumption of Tissues by 

Predators/Scavengers/ 

Invertivores 

Reduced Reproduction and 

Survival of BTPDs and 

Terrestrial Non-Target 

Organisms 

Exposed Intact Bait at 

Application Site 

Consumption by BTPDs Consumption by non-target 

terrestrial organisms 

Reduced Reproduction and 

Survival of BTPDs and 

Terrestrial Non-Target 

Organisms 

Reduced prey-base for listed 

species 

Altered plant community 

composition 

Reduced burrows for habitat for 

listed species 

Rozol Bait 

Indirect 

Effect 

60
2.10. Analysis Plan 

In order to address the risk hypotheses, the potential for direct and indirect effects to the assessed 

species, prey items, and loss of burrows is estimated based on a taxon-level approach. In the 

following sections, the use, environmental fate, and ecological effects of chlorophacinone are 

characterized and integrated to assess the risks. This is accomplished using a RQ (ratio of 

exposure concentration to effects concentration) approach. Although risk is often defined as the 

likelihood and magnitude of adverse ecological effects, the RQ-based approach does not provide 

a quantitative estimate of likelihood and/or magnitude of an adverse effect. However, as 

outlined in the Overview Document (USEPA, 2004a), the likelihood of effects to individual 

organisms from the BTPD use of chlorophacinone to control BTPDs is estimated using the probit 

dose-response slope and either the LOC (discussed below) or actual calculated RQ value. 

2.10.1. Measures of Exposure 

Given the environmental fate properties of chlorophacinone and its grain-based bait formulation 

subject to this assessment, only primary exposure to bait and secondary exposure to 

chlorophacinone poisoned carcasses and invertebrates will be considered for measures of 

exposure. 

2.10.1.a. Estimating Primary Exposure 

EFED’s exposure assessment for the rodenticides differs from that for most other pesticides. For 

a rodenticide, the bait itself is the potential food item of concern. Thus, the amount of active 

ingredient in the formulated bait is used as an EEC. This information is used to estimate the 

amount of grain bait that birds and mammals of various sizes need to consume to obtain a dose 

expected to be lethal to 50% of the individuals in the population (i.e., LD50 dose). Estimates of 

food-ingestion rates (g dry matter per day) are determined from established allometric equations 

presented in EPA’s Wildlife Exposure Factors Handbook (EPA 1993). The concentration of 

chlorophacinone in grain bait is also used to estimate initial dietary exposure (mg a.i. per kg in 

bait) which in turn is used to calculate avian and mammalian dietary RQs. 

Acute and chronic LD50 doses are typically used for determining EECs; however, a 

subacute 5-day LD50 will be used in this instance. Due to chlorophacinone’s delayed mode of 

action, subacute LD50 values are lower than calculations from acute LD50 endpoints would 

predict. The acute single-dose LD50 for mammals is 0.49 mg a.i./kg bw/day whereas the 

subacute 5-day LD50 value is 0.16 mg a.i./kg bw/day. Comparisons between acute and subacute 

data for birds are not as straightforward but the subacute data proves more conservative through 

discussions in Section 4.2.1 and calculations performed in Appendix J. Additionally, grain bait 

applications provide temporary but locally abundant new food sources. Consequently, exposure 

over a five day period is highly probable. However, primary exposure can potentially occur over 

a longer period of time than five days. Toxicity resulting from chronic exposure exceeding five 

days cannot be determined based on current data. 

61
2.10.1.b. Estimating Secondary Exposure 

Secondary exposure analysis (from carcass) requires consideration of residues in tissues of target 

and non-target organisms that are commonly consumed by predators and scavengers, as well as 

knowledge of what residue level will result in mortality or adverse chronic effects. Moreover, it 

is important to know how long the residue persists in body tissues. Registrant submitted BTPD 

residue data address these issues, in part, but do not directly determine residues when BTPDs are 

most vulnerable to predation and/or scavenging. Additionally, carcass handling may not have 

allowed a conservative determination of residue concentrations. Residue concentrations for nontarget animals fed chlorophacinone supplement the registrant submitted data. Additionally, a 

number of laboratory tests using avian and mammalian predators and scavengers are available to 

assess mortality from secondary exposure resulting from consumption of prey animals that had 

been exposed to chlorophacinone and related anticoagulant rodenticides. These studies are 

summarized in Table 4.3 and Table 4.4. Design and methodology vary among studies, adding 

unknown variability to the results and analysis. Pending development of standard methods and 

testing requirements for such studies, these tests provide the best data available. A discussion of 

residue levels in tissues of target species is included in the assessment. 

2.10.2. Measures of Effect 

Data identified in Section 2.8 are used as measures of effect for direct and indirect effects. Data 

were obtained from registrant submitted studies or from literature studies identified by 

ECOTOX. 

2.10.2.a. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects characterization to 

determine the potential ecological risk from the use of chlorophacinone to control BTPDs, and 

the likelihood of direct and indirect effects to the assessed species in terrestrial habitats. The 

exposure and toxicity effects data are integrated in order to evaluate the risks of adverse 

ecological effects on non-target species. The RQ method is used to compare exposure and 

measured toxicity values. EECs are divided by acute and chronic toxicity values. The resulting 

RQs are then compared to the Agency’s LOCs (USEPA, 2004a; Appendix B). 

2.10.3. Data Gaps 

An avian reproduction study and a terrestrial field study for the use of chlorophacinone to control 

BTPDs have been required as conditions of registration of Rozol Prairie Dog Bait (7173-286). 

The registrant submitted a study, “Field Efficacy and Hazards of Rozol Bait for Controlling 

Black-Tailed Prairie Dogs (Cynomys ludovicianus)” (MRID 47333602), to support the 

requirement for a terrestrial field study for BTPDs but the component of the study addressing 

field hazards was invalid. The BTPD chlorophacinone residue study (MRID 47333603) is 

supplemental but potentially upgradeable after consideration of carcass handling methods. 

62
3. Exposure Assessment 

Chlorophacinone, for this assessed use to control BTPDs, is formulated as a grain-bait composed 

of 50 mg a.i./kg-bait. The assessed label (EPA 7173-286) permits in-burrow application of bait 

in active BTPD colonies only. 

3.1. Label Application Rates and Intervals 

The label permits hand application of bait in burrows by Certified Applicators or by persons 

under their direct supervision. One quarter cup of 50 mg a.i./kg-bait (53 grams) is to be placed at 

least 6 inches down into active prairie dog burrows. Given a maximum of 100 prairie dog 

burrows per acre, this equals an effective maximum application rate of 0.265 g a.i./A6 (King 

1959). Any bait scattered on the surface or less than 6 inches into the burrow is to be retrieved 

and disposed. 

Fifty-three grams of bait per burrow and 0.265 g a.i./A will be used to generate RQs in this 

assessment. It can also be expected that some bait will be exposed above ground from the 

movement of the target and non-target animals in and out of the burrow (bioturbation). To 

account for this potential, it will be assumed that 1% of applied bait will be exposed above 

ground. This is a conservative estimate considering field trials of Rozol Prairie Dog Bait found 

only one out of 55 samples each containing 50 burrows to have more than 100 grains on the 

surface (MRID 47333602). Because only one sample out of 55 was found to have more than 100 

grains exposed, it is assumed that the number of actual grains is near 100 and therefore 100 

grains is used. Based on a maximum of 100 burrows per acre (King 1959), this means 200 

grains per acre on the surface are possible. Given one grain of bait is 0.2 grams, 0.75% of 

applied grain will be exposed on the ground surface given this conservative scenario7. Because 

the analysis produced an estimate less than 1%, 1% of applied bait on the surface is a 

conservative assumption. 

Following application, the label stipulates that the applicator must return to the site initially 5 to 

10 days post application to collect and properly dispose of bait or dead or dying prairie dogs and 

again 14 to 21 days post-application. Carcass collection and burial are to occur in the late 

afternoon, near sundown, in order to reduce the potential of scavenging animals finding prairie 

dog carcasses. Carcasses buried on site must be in holes dug at least 18 inches deep, or in 

inactive burrows, to avoid scavenging by non-target animals. Burial includes covering and 

packing the hole or burrow with soil. 

If prairie dog activity persists “several weeks or months” after the bait was initially applied, the 

label allows a second application by treating burrows in the same manner as the first application. 

 

6

 100 burrows/A * 53 g bait/burrow * 0.00005 = 0.265 g a.i./A 

7

 100 burrows/acre * 53 g/burrow * 1 grain/0.2 g = 26,500 total grains applied/acre 

(200 exposed grains)/( 26,500 total grains applied/acre) = 0.75 % grains exposed 

63
3.2. Aquatic Exposure Assessment 

3.2.1. Aquatic Exposure in Previous Assessment 

A previous assessment (EPA 2008) modeled aquatic exposure of chlorophacinone for this use 

and found that negligible concentrations of chlorophacinone could occur in the water column 

relative to the toxicity to aquatic organisms. Model results indicated a peak concentration of 

0.92 parts per trillion in surface waters for this use. This result is driven by chlorophacinone’s 

immobility within its grain bait formulation. The most sensitive aquatic endpoint is an LC50 of 

450 parts per billion for the rainbow trout (Oncorhynchus mykiss). This endpoint is more than 

five orders of magnitude greater than the EEC. Given this, risk to aquatic listed species and risk 

to aquatic habitats and PCEs of designated critical habitats will not be further assessed. 

3.3. Terrestrial Exposure Assessment 

Pesticide residues, other than those in poisoned animals and carcasses, are not of environmental 

concern because the active ingredient is not mobile and will remain sorbed to the grain bait. The 

RQ method of assessment is used to make risk determinations. The RQ method is preferred 

because it is quantitative, thus providing concrete justification for risk determinations. However, 

this method is supplemented by data gathered from chlorophacinone-poisoned carcass feeding 

studies. 

3.3.1. Ingestion Rate Determination 

RQs are generated by dividing daily dietary exposure of chlorophacinone for a given species by 

the most conservative toxicity endpoint for the relevant taxa adjusted for body weight of the 

given species. Dietary exposure estimates were derived using allometric equations from Wildlife 

Exposure Factors Handbook (EPA 1993). Allometric equations are distinct by taxon and can be 

refined within a taxon as well. For the purposes of this assessment, generic taxon allometric 

equations will be used. The following equations require input of animal weight (Wt) and 

produce an estimate of daily food intake (FI). 

 FI (g/day) = 0.648 * Wt0.651 all birds 

 FI (g/day) = 0.235 * Wt0.822 all mammals 

The animal weight input is determined using the lowest relevant8 weight for juveniles and adults 

of a given listed species. For species that do not exceed the LOC based on this determination, a 

weight range sensitivity analysis will be performed to account for lower metabolic rates of larger 

animals. Refinements can also be made, as needed, for RQs approaching the LOC based on 

other relevant allometric equations within the Wildlife Exposure Factors Handbook. These 

refinements will be made only if the outcome would change a MA determination from NLAA to 

LAA. 

 

8

 An animal weight is only relevant if it can be expected that exposure to chlorophacinone will occur at the given life 

stage. 

64
3.3.2. Food Intake Assumptions Relevant to Terrestrial Exposure 

For the calculation of RQs, it is assumed the exposed animal consumes chlorophacinone bait or 

chlorophacinone poisoned animals and/or carcasses, depending upon the species diet, exclusively 

for the relevant period of exposure. For assessment of taxa with 5-day LD50 or LC50 values, it is 

assumed that the exposed animal consumes chlorophacinone bait or chlorophacinone poisoned 

animals and/or carcasses exclusively for five consecutive days. The subacute (5-day) LD50s and 

LC50s are both discussed on a single day exposure basis because RQs are calculated based on 

single day ingestion rates. 

3.3.2.a. Chlorophacinone Concentrations in Food Items 

The proportion of chlorophacinone in Rozol bait is 50 mg a.i./kg-bait. Assuming exclusive 

consumption of bait, listed species are exposed to chlorophacinone at the following rate: 

 Chlorophacinone intake (mg/time) = 0.05 mg/g * FI (g/time) 

All inputs for determining the chlorophacinone dose-based EEC are presented in the following 

tables. Only dose-based EECs for mammals are used for calculating RQs. Avian RQs are 

calculated from an LC50 which is dose independent and more conservative than avian LD50 data. 

Appendix J demonstrates this through the calculation of avian RQs using LD50 data. 

Table 3.1 Calculation of chlorophacinone intake for birds and herptiles using most 

conservative secondary exposure scenario. Calculations based on FI (g/day) = 0.648 * Wt 

(dry) 0.651 (EPA 1993); ingestion rate in terms of wet weight is calculated using the following 

equation: Ingestion Rate (wet weight) (invertivores) = Ingestion Rate (dry weight)/(1-0.84) (EPA 

1993) Ingestion Rate (wet weight) (carnivores) = Ingestion Rate (dry weight)/(1-0.68) (EPA 

1993) Dose-based EEC = (Residue*FI)/(Wt/1000) 

Species Weight 

(Wt)(g) 

Food Ingestion (FI) 

(g [ww]/day) 

Residue 

(mg/kg-diet [ww])1

Dose-based EEC 

(mg/kg-bw/day) 

California condor 

(carnivore) 8,100 709.33 5.8 0.508 

Whooping crane (carnivore) 4,300 150.302 50 1.748 

Eskimo curlew (invertivore) 270 155.0 5.8 3.329 

Northern Aplomado falcon 410 101.71 5.8 1.439 

Chirichaua leopard frog 

(invertivore) 100 81.18 5.8 4.709 

Mexican spotted owl 

(carnivore) 519 118.58 5.8 1.325 

Piping plover (invertivore) 42 46.15 5.8 6.373 

New Mexican ridge-nosed 

rattlesnake (carnivore) 85 36.52 5.8 2.492 

Sonora tiger salamander 

(invertivore) 50 51.70 5.8 5.997 

65
Black-capped vireo 

(invertivore) 9 16.93 5.8 10.91 

Golden-cheeked warbler 

(invertivore) 10 18.13 5.8 10.52 

1 The residues for birds and herptiles are either 50 for bait or 5.8 for non-target animals. The residues in mice were 

used as a surrogate for invertebrate residues. 

2 This value was not converted to wet weight because the value is for bait which is in dry weight. 

Table 3.2 Calculation of chlorophacinone intake for mammals using most conservative 

secondary exposure scenario. Calculations based on FI (g/day) = 0.235 * Wt0.822 (EPA 1993);

ingestion rate in terms of wet weight is calculated using the following equation: Ingestion Rate 

(wet weight) = Ingestion Rate (dry weight)/(1-0.68) (EPA 1993); Dose-based EEC = 

(Residue*FI)/(Wt/1000) 

Species Weight 

(Wt) (g) 

Food Ingestion (FI) 

(g [ww]/day) 

Residue 

(mg/kg-diet [ww])1

Dose-based EEC 

(mg/kg-bw/day) 

Grizzly bear 102,000 3077.072 50 1.508 

Black-footed ferret 635 147.84 5.8 1.350 

Jaguar 36,363 4118.89 5.8 0.657 

Gulf Coast jaguarundi 4,500 739.36 5.8 0.953 

Canada lynx 5,100 819.48 5.8 0.932 

Preble’s meadow 

jumping mouse 13 1.942 50 7.443 

Ocelot 11,300 1575.97 5.8 0.809 

Gray wolf 18,000 2310.74 5.8 0.745 1 The highest residue concentration (either bait [50 mg a.i./kg-bait] or non-target animals [5.8 mg a.i./kg-bw]) was 

used.

2 These values were not converted to wet weight because the value is for bait which is in dry weight. 

The determination of chlorophacinone intake for listed species consuming chlorophacinone 

poisoned animals or carcasses is calculated similarly but relies on carcass residue data. BTPD 

carcass residue data is derived from a registrant sponsored study performed by the United States 

Department of Agriculture National Wildlife Research Center (MRID 47333603). This study 

was reviewed and determined to be used as supplemental. This decision was made because the 

study did not describe carcass handling methods. However, the study can be used quantitatively. 

The mean whole body average corrected wet weight concentration of chlorophacinone for prairie 

dogs fed Rozol to mortality is 1.03 mg a.i./kg-bw with a maximum concentration of 2.24 mg 

a.i./kg-bw in a single carcass. To be protective and to account for the supplemental nature of the 

data, a residue concentration of 2.24 mg a.i./kg-bw will be used to assess exposure to 

chlorophacinone poisoned prairie dogs and prairie dog carcasses. Assuming exclusive 

consumption of chlorophacinone poisoned prairie dogs and prairie dog carcasses, listed species 

are exposed to chlorophacinone at the following rate: 

 Chlorophacinone intake (mg/time) = 0.00224 mg/g * FI (g/time) 

66
Other granivores aside from BTPDs (i.e. mice, rabbits, birds, invertebrates etc.) have the 

potential to consume chlorophacinone bait. These non-target granivores also have the potential 

for different mean and maximum chlorophacinone residue concentrations than those determined 

for BTPDs. To characterize these differences, carcass residue concentration data from open 

literature was considered (see Table 3.3). Because formulation concentration can affect carcass 

residue concentration, only studies using bait with chlorophacione concentrations of 50 mg 

a.i./kg-bait were considered. Residue concentrations resulting from other bait formulations are 

also presented in Table 3.3 for context. The highest whole-carcass residue concentration 

reported matching this criterion is 5.8 mg a.i./kg-bw for laboratory mice (Anonymous, 1981). It 

is uncertain whether this residue concentration is presented in wet weight or dry weight. For the 

purposes of this assessment, it is assumed that 5.8 mg a.i./kg-bw represents a wet weight 

concentration. For secondary exposure RQs approaching the listed species LOC and for animals 

likely to prey upon non-target species, this residue concentration can be used to address 

predation and scavenging of non-target primary consumers. Further, food ingestion rates do not 

necessarily reflect actual ingestion patterns as predators and scavengers may engorge themselves 

prior to and following hibernation and during migration. In addition, some species (e.g., 

California condor) may not eat every day. 

Residue concentrations in invertebrates that may be preyed upon by invertivores are not as well 

characterized as residue concentrations in mammals that may be preyed upon by carnivores. 

However, secondary exposure to anticoagulant exposed invertebrates has been attributed to the 

poisoning of birds. Godfrey (1985) cited an incident at an aviary where several birds (avocets, 

pitas, plovers, finches, thrushes, warblers, crakes, honey creepers) died after being exposed to 

brodifacoum. Brodifacoum concentrations of 0.081 to 1.69 mg a.i./kg-bw were reported in 

tissues of dead birds. Because bait was applied in bait stations, it was assumed that the birds 

were exposed by feeding on pavement ants and cockroaches that had eaten bait. One study 

evaluating diphacinone residues in slugs exposed to grain bait similar to Rozol found maximum 

wet weight residue concentrations of 4.0 mg a.i./kg-bw (Primus et al. 2006). Because the body 

of literature is limited and available maximum invertebrate residue concentrations are lower than 

better characterized mammal residue concentrations, the 5.8 mg a.i./kg-bw residue value for 

mice will be used as a surrogate value for invertebrate residue exposure. This surrogate value 

will result in a more conservative assessment. 

Table 3.3 Chlorophacinone Residue Levels in Primary Consumers 

mg 

ai/kg 

bait 

Target 

species Site 

Sample 

size 

Days 

exposed 

Whole-carcass 

residue (mg 

a.i./kg-bw) 

Reference 

100 ground squirrel field 10 unknown 1.27 + 0.56 (sd) Baroch 1996b 

75b mouse laboratory ? 3 6.0 Riedel et al. 1991a

50 ground squirrel field 10 unknown 0.57 + 0.27 (sd) Baroch 1996a 

50 ground squirrel field 10 unknown 0.52 + 0.31(sd) Baroch 1996b 

50 rat laboratory 5 5 0.47 (0.21-0.93) Baroch 1997 

67
mg 

ai/kg 

bait 

Target 

species Site 

Sample 

size 

Days 

exposed 

Whole-carcass 

residue (mg 

a.i./kg-bw) 

Reference 

50 rat laboratory 4 5 0.45 (0.18-0.81) Ahmed et al. 1996 

50 vole laboratory 10 <9 3.2 Askham and Poché 1992 

50 or 

100c

ground squirrel field 62 unknown 0.264 Primus et al. 2001 

50 or 

100c

vole field 3 unknown 1.58 (0.26-4.1) Primus et al. 2001 

50 mouse laboratory ? 3 5.8 Anonymous 1981a

50 or 

100c

pocket gopher field 8 unknown 0.518 Primus et al. 2001 

50 

and 

100d

ground squirrel field 53 unknown 0.93 Goodall et al. 2002 

a

 cited in Joermann 1998 

b

 chlorophacinone baits registered in the U. S. are either 0.005% or 0.01% ai c

 carcasses were collected in the field in CA, where both 50 mg a.i./kg-bait and 100 mg a.i./kg-bw chlorophacinone 

baits are registered 

d

 the study did not distinguish between ground squirrels exposed to 50 mg a.i./kg-bait and 100 mg a.i./kg-bait baits 

3.3.2.b. Adjusting for Snake Food Intake 

Though avian toxicity data are used as a surrogate for assessing toxicity to snakes, dietary 

exposure is distinct and is assessed using methods that reflect snake feeding habits. Avian food 

intake equations may underestimate exposure to snakes when birds are used as a surrogate and 

are assumed to eat similar dietary items because of the large meal size a snake may consume on a 

single day. This equation is modified to estimate exposure to snakes based on the maximum size 

prey item they could consume and is used to refine a risk estimate. The following allometric 

equation developed by King (2002) was used to estimate the maximum size prey items for 

snakes. 

)g(Mass Snake (g) SizePrey 1.015 =

The 95% confidence limits on the coefficient are 0.959 and 1.071 (King, 2002). The upper limit 

is used to estimate exposure to snakes (i.e.. 1.071). 

4. Effects Assessment 

This assessment evaluates the potential for chlorophacinone formulated as Rozol Prairie Dog 

Bait (EPA registration number 7173-286) to directly or indirectly affect listed species or modify 

their designated critical habitat. Assessment endpoints for the effects determination for each 

68
assessed species include direct toxic effects on the survival, reproduction, and growth, as well as 

indirect effects, including reduction of the prey base or modification of its habitat. In addition, 

potential modification of critical habitat is assessed by evaluating effects to the PCEs, which are 

components of the critical habitat areas that provide essential life cycle needs of each assessed 

species. 

As described in the Agency’s Overview Document (USEPA, 2004a), the most sensitive endpoint 

for each taxon is used for risk estimation. For this assessment evaluated taxa include birds, 

mammals and terrestrial invertebrates. Birds are used as the surrogate taxa to assess for 

herptiles. Acute (short-term) toxicity information is characterized based on registrant-submitted 

studies and a comprehensive review of the open literature on chlorophacinone. Chronic toxicity 

information is not available and has not been requested for mammals because mortality occurs at 

low doses in acute tests. Chronic toxicity information is not available for birds either but an 

avian reproduction study has been requested. There is more potential for chronic effects to birds 

because mortality occurs at doses high enough to allow for longer term exposures. In the 

absence of an avian reproduction study, effects to birds and herptiles cannot be precluded. 

4.1. Ecotoxicity Study Data Sources 

Toxicity endpoints are established based on data generated from guideline studies submitted by 

the registrant and from open literature studies that meet the criteria for inclusion into the 

ECOTOX database maintained by EPA/Office of Research and Development (ORD) (USEPA, 

2004a). Open literature data presented in this assessment were obtained from the Comparative 

Assessment (USEPA, 2004b), as well as ECOTOX information obtained on May 14, 2010. In 

order to be included in the ECOTOX database, papers must meet the following minimum 

criteria: 

1. toxic effects are related to single chemical exposure; 

2. toxic effects are on an aquatic or terrestrial plant or animal species; 

3. a biological effect is identified on live, whole organisms; 

4. a concurrent environmental chemical concentration/dose or application rate is reported; 

and 

5. the duration of exposure is explicit. 

Data that pass the ECOTOX screen are evaluated along with the registrant-submitted data, and 

may be incorporated qualitatively or quantitatively into this endangered species assessment. In 

general, effects data in the open literature that are more conservative than the registrantsubmitted data are considered. The degree to which open literature data are quantitatively or 

qualitatively characterized for the effects determination is dependent on whether the information 

is relevant to the assessment endpoints (i.e., survival, reproduction, and growth) identified in 

Section 2.8. For example, endpoints such as behavior modifications are likely to be qualitatively 

evaluated, because quantitative relationships between behavior modifications and reduction in 

species survival, reproduction, and/or growth are not available. Although the effects 

determination relies on endpoints that are relevant to the assessment endpoints of survival, 

growth, or reproduction, it is important to note that the full suite of sublethal endpoints 

69
potentially available in the effects literature (regardless of their significance to the assessment 

endpoints) are considered, as they are relevant to the understanding of potential effects, as 

defined for the action area. Sublethal lethal endpoints of internal bleeding and hemorrhaging are 

considered equivalent to lethality in the consideration of avian secondary exposure data. 

Citations of all open literature not considered as part of this assessment because they were either 

rejected by the ECOTOX screen or accepted by ECOTOX but not used (e.g., the endpoint is less 

sensitive) are included in Appendix F. Appendix F also includes a rationale for rejection of 

those studies that did not pass the ECOTOX screen and those that were not evaluated as part of 

this endangered species risk assessment. 

A detailed spreadsheet of the available ECOTOX open literature data, including the full suite of 

lethal and sublethal endpoints is presented in Appendix G. 

In addition to registrant-submitted and open literature toxicity information, other sources of 

information, including use of the acute probit dose response relationship to establish the 

probability of an individual effect and reviews of ecological incident data, are considered to 

further refine the characterization of potential ecological effects associated with exposure to 

chlorophacinone. A summary of the available terrestrial ecotoxicity information and the incident 

information for chlorophacinone are provided in Sections 4.2 through 4.3. 

4.2. Toxicity of Chlorophacinone to Terrestrial Organisms 

A brief summary of registrant-submitted and open literature data considered relevant to this 

ecological risk assessment is presented in Appendix E. Studies submitted during the comment 

period relevant to “Receipt of Petition Requesting EPA to Suspend the Registration of Rozol 

Prairie Dog Bait and Cancel Certain Application Sites” (EPA-HQ-OPP-2009-0684) are 

discussed in Appendix D. All endpoints are expressed in terms of the active ingredient unless 

otherwise specified. 

Table 4.1 summarizes the most sensitive terrestrial toxicity endpoints, based on an evaluation of 

both the registrant-submitted studies and the open literature, as previously discussed. When 

data are available, it was found that the most conservative 5-day LD50 value is more protective 

than the most conservative single dose LD50 value. 

Table 4.1. Toxicity Profile for Chlorophacinone 

Assessment 

Endpoint 

Acute/ 

Chronic Species Tested 

Toxicity Value Used 

in Risk Assessment 

Citation or 

MRID 

Comment 

Acute Northern bobwhite 

Colinus virginianus 

LD50 = 258 mg a.i./kg 

bw 

Slope = 2.88 

Bird 41513101 

Toxicity to 

listed species 

5-day 

Sub-Acute 

Northern bobwhite 

Colinus virginianus

LC50 = 56 mg a.i./kgdiet 

Slope = 1.49 

41513102 

Mammal Acute Deer mouse 

Peromyscus 

LD50 = 0.49 mg a.i./kgbw Clark 1994 

70
Assessment 

Endpoint 

Acute/ 

Chronic Species Tested 

Toxicity Value Used 

in Risk Assessment 

Citation or Comment 

MRID 

Toxicity to maniculatus 

listed species 5-day 

Sub-Acute 

Norway Rat 

Rattus norvegicus 

5-day LD50 = 0.8 mg 

a.i./kg-bw 

Jackson and 

Ashton 1992 

Doses of 0.16 mg a.i./kg bw 

were administered daily for 

5 consecutive days equal the 

LD50 dose 

Terrestrial 

Invertebrate 

Toxicity to 

listed species 

Chronic Burying beetle 

Nicrophorus 

orbicollis 

Carcasses fed 50 mg 

a.i./kg-bait for 5-10 

days affected number 

of beetles emerged 

47383001 This study was classified as 

supplemental. 

4.2.1. Toxicity to Birds 

Chlorophacinone is moderately toxic to birds with the most sensitive endpoints being an acute 

LD50 of 258 mg a.i./kg bw and a 5-day sub-acute LC50 of 56 mg a.i./kg-diet. Birds are more 

sensitive to sub-acute exposure than single-dose acute exposure. 

An avian reproduction study for chlorophacinone has been required but has yet to be submitted. 

In the absence of this study and any open literature study that may supplement it, risk of adverse 

effects to avian and herptile reproduction cannot be precluded. 

4.2.1.a. Sublethal Effects and Additional Open Literature 

Information 

The effects of chlorophacinone poisoned carcasses on predatory and scavenging birds have been 

evaluated in many studies. This information was previously compiled (USEPA, 2004b) (see 

Table 4.2). The current ECOTOX bibliography (updated May 2010) does not indicate any new 

studies relevant to the effects of chlorophacinone poisoned animals and/or carcasses on predatory 

and scavenging birds. Though no mortalities were reported in these studies, sublethal effects 

including external bleeding, internal hemorrhaging and increased blood coagulation time were 

noted. Previous assessments have considered these effects to be analogous to lethality. Though 

these studies do not allow for quantification of effect, they confirm that secondary exposure can 

result in effect. 

Table 4.2 Secondary Hazards of Chlorophacinone to Birds in Laboratory Studies 

Predator/ 

scavenger 

(p/s) 

Prey offered 

to p/s 

No. prey 

offered 

daily 

per p/s 

No. days 

p/s 

exposed 

No. 

p/s 

exposed 

No. 

p/s 

dead 

No. 

survivors 

with signs 

of 

chlorophaci

none 

toxicitya

Reference 

Barn owl rats fed choice of 0.005% 

bait or untreated bait for 5 

days 

1-2 10 2 0 0 Mendenhall 

and Pank 

1980 

71
Predator/ 

scavenger 

(p/s) 

Prey offered 

to p/s 

No. prey 

offered 

daily 

per p/s 

No. days 

p/s 

exposed 

No. 

p/s 

exposed 

No. 

p/s 

dead 

No. 

survivors 

with signs 

of 

chlorophaci

none 

toxicitya

Reference 

Black-billed 

magpie 

rats fed 0.005% bait for 5 

days 

ad lib. 5 20 0 0 Baroch 

1997 

American 

kestrel 

voles fed 0.01% bait until 

dead 

1 

1 every 3 

days 

21 

61 

10 

10 

0 

0 

10 (eb/ih) 

10 (eb/ih) 

Radvanyi et 

al. 1988 

Red-tailed 

hawk 

voles fed 10 g 0.005% 

bait daily for up to 9 days 

2 6 5 0 0 Askham and 

Poché 1992 

Great 

horned owl 

voles fed 10 g 0.005% 

bait daily for 

 up to 9 days 

2 6 1 0 0 Askham and 

Poché 1992 

Red-tailed 

hawk 

voles fed 0.005% bait for 

up to 

 9 days 

2 6 5 0 0 Askham 

1988 

Great 

horned owl 

voles fed 0.005% bait for 

up to 

 9 days 

2 6 1 0 0 Askham 

1988 

Tawny owl mice fed 0.0075% baitb ad lib. 10 4 0 (ct) Riedel et al. 

1991c

Eurasian 

buzzard 

mice fed 0.0075% baitb ad lib. 7 

10 

5+5+5d

40 

4 

6 

3 

3 

0 

0 

0 

0 

(ct) 

(ct) 

(ct)

(ct) 

Riedel et al. 

1991c

Eurasian 

buzzard 

mice fed 0.0075% baitb 4 7 4 0 0 Anonymous 

1978c

Carrion 

crow 

mice fed 0.0075% baitb ad lib. 10 4 0 (ct) Riedel et al. 

1991c

Carrion 

crow 

mice fed 0.0075% baitb 3-4 3 

5 

12 

12 

0 

0 

0 

0 

Sterner 

1978c

White stork mice fed 0.0075% baitb ad lib. 

(treated 

/untreated 

) 

3 

14 

3 

3 

0 

0 

1 or 2 (ct) 

1 or 2 (ct) 

Sterner 

1981c

a

 eb = external bleeding; ih = internal hematoma; bl = bleeding (unspecified); ct = increased blood coagulation time; 

nr = not reported 

b

 baits registered in the U.S. are either 0.005% or 0.01% ai 

c

 cited in Joermann 1998 

d

 the 3 5-day treatment periods are separated by 3 days when the birds were fed untreated mice

72
Based on the information in Table 4.2, the observed sublethal effects (e.g., external bleeding, 

internal hematoma, and increased blood coagulation time) occurred at levels close to but above 

the % a.i. used for BTPD control. Sublethal effects were seen for 0.0075 and 0.01% a.i. bait 

whereas the bait used for BTPD control is 0.005%. 

4.2.2. Toxicity to Mammals 

Chlorophacinone is very highly toxic to mammals with the most sensitive endpoints being an 

acute LD50 of 0.49 mg a.i./kg bw and a 5-day LD50 of 0.8 mg a.i./kg bw (0.16 mg a.i./kg bw dose 

daily for five days). Mammals are most sensitive to sub-acute exposure due to the chemical’s 

mode of action. A given mammal would need one-third of the single day acute LD50 dose each 

day for five days to achieve a 5-day subacute LD50 dose. A five day exposure is reasonable 

considering the bait application is intended to provide multiple exposures to individual BTPDs. 

4.2.2.a. Sublethal Effects and Additional Open Literature 

Information 

The effects of feeding chlorophacinone poisoned carcasses to predatory and scavenging 

mammals have been evaluated in many studies. This information was compiled (USEPA, 

2004b) (see Table 4.3). The current ECOTOX bibliography (updated May 2010) does not 

indicate any new studies relevant to the effects of feeding chlorophacinone poisoned carcasses to 

predatory and scavenging mammals. Of 55 mammals tested, 32 died before the end of the study 

period. Considering these studies as a whole, secondary exposure of chlorophacinone to 

mammals consistently causes a lethal effect. Sublethal effects of bleeding and increased blood 

coagulation time were also reported. Previous assessments have considered these effects to be 

analogous to lethality. Though these studies do not allow for quantification of effect, they 

confirm that secondary exposure results in effect

Table 4.3 Secondary Hazards of Chlorophacinone to Mammals in Laboratory Studies 

Predator/ 

scavenger 

(p/s) 

Prey offered 

to p/s 

No. prey 

offered 

daily 

per p/s 

No. days 

p/s 

exposed 

No. 

p/s 

exposed 

No. 

p/s 

dead 

No. survivors 

with signs of 

chlorophacin

one toxicitya Reference 

Mongoose rats fed 0.005% 

bait for 5 days 

1 1 

3 

5 

6 

7 

9 

10 

1 

1 

2 

1 

1 

1 

1 

0 

1 

2 

1 

1 

1 

1 

nr 

no survivors 

no survivors 

no survivors 

no survivors 

no survivors 

no survivors 

Pank and 

Hirata 1976 

Coyote ground squirrels 

fed 15 g of 

0.01% bait for 6 

daysb

1 5 7 3 0 Marsh and 

Howard 1986 

73
Predator/ 

scavenger 

(p/s) 

Prey offered 

to p/s 

No. prey 

offered 

daily 

per p/s 

No. days 

p/s 

exposed 

No. 

p/s 

exposed 

No. 

p/s 

dead 

No. survivors 

with signs of 

chlorophacin

one toxicitya Reference 

Red fox mice fed 

0.0075% baitc

20 total 4 1 1d no survivors Bachhuber 

and Beck 

1988e

European 

ferret 

rats fed 0.005% 

bait for 5 days 

ad lib. 5 20 11 nr Ahmed et al. 

1996 

European 

ferret 

prairie dogs fed 

25 g of 0.0025% 

bait daily for 6 

daysc

4 (1 every 

other day) 

8 6 5 nr Fisher and 

Timm 1987 

European 

ferret 

voles/mice fed 

0.0075% baitc

5 total 4 2 1f (ct) Bachhuber 

and Beck 

1988e

European 

ferret 

muskrats fed 

0.005% bait 

ad lib. 4 

8 

2 

1 

0 

1 

1 (bl) 

no survivors 

Jobsen 1978e

European 

ferret 

voles fed 

0.0075% baitc

ad lib. 3 4 0 (ct) Anonymous 

1983e

Weasel mice fed 0.005% 

bait 

ad lib. 90 4 3 0 Anonymous 

1981e

a

 eb = external bleeding; ih = internal hematoma; bl = bleeding (unspecified); ct = increased blood coagulation time; 

nr = not reported 

b

 ground squirrels were fed no-choice for 3 days followed by 3 days in which they had a choice of bait or untreated 

laboratory chow 

c

 baits registered in the U.S. are either 0.005% or 0.01% ai d

 individual was sacrificed but considered ‘dead’ based on coagulation index 

4.2.3. Toxicity to Terrestrial Invertebrates 

The endangered American burying beetle (Nicrophorus americanus), uses mammalian and avian 

carcasses as food resource during their reproduction cycle. A study on a related, abundant 

congeneric species, Nicrophorus orbicollis, was performed to assess the impacts of 

chlorophacinone on the survival and larval growth of burying beetles (MRID 47383001). There 

were two phases to this study. The first phase investigated effects of chlorophacinone on the 

emergence (number of beetles produced), growth, and sex ratio of burying beetles raised on 

chlorophacinone-dosed rat carcasses. The second phase of the study investigated effects on the 

survival and reproductive success of burying beetle adults fed chlorophacinone-dosed meat for 

28 days prior to being provided an undosed quail carcass for brooding of young. 

74
In the first phase of the study each of twenty reproductively mature male-female pairs of fieldcollected N. orbicollis was offered a chlorophacinone-dosed rat carcass. Each of an additional 

twenty reproductively mature male-female pairs was offered an undosed rat carcass as a control. 

In the wild a carcass is usually buried in less than a day, and the female oviposits eggs in the 

surrounding soil within about 48 hours (Wilson and Knollenberg, 1984). Upon emergence of 

offspring (approximately one month later), the total number of young produced per brood was 

counted, sexed, and weighed. The chlorophacinone-dosed carcasses were a group of 20 rats fed 

exclusively 50 mg a.i./kg chlorophacinone bait for a period of 5 to 10 days until death. This is 

same bait concentration which would be used in the environment. A group of 20 undosed rats 

which were fed a standard laboratory rodent diet were used as controls. Upon death all rats 

were frozen and shipped to the study location where they were thawed for 24 hours prior to use. 

While it was indicated in the study that the control rats were selected to be of similar body size 

as the treatment group, reported control carcass weights (mean 102.8 grams) used in the study 

were significantly greater (P<0.001) than those used in the chlorophacinone treatment group 

(mean 89.6 grams). No conclusions about the difference in carcass body weights being 

attributable to the chlorophacinone-bait diet should be drawn from this aspect of the study; rats 

during the pretest period were not from a paired study designed to evaluate effects to rats. 

Number of emerged beetles, the male-female ratio, and individual beetle and total brood weights 

of treatment and control broods were compared using nonpaired t-tests. Significantly (P<0.01) 

fewer beetles emerged from the chlorophacinone-dosed carcasses (mean 12.7 beetles) than from 

control carcasses (mean 22.5 beetles). There was some conjecture that this difference might be 

attributable to the difference in carcass weight rather than the presence of chlorophacinone. 

However, an evaluation of the relationship between brood size and carcass weight in the open 

literature indicates that both the control and chlorophacinone carcass weights are outside the 

range that limits brood size and therefore the reduction observed is attributed to chlorophacinone. 

A significant positive relationship between reproductive success and increasing carcass size has 

been observed in the range of 7 to 35 grams (Wilson and Fudge, 1984; Trumbo, 1990; Trumbo 

and Fernandez, 1995; Creighton, 2005), average brood size in the rat-carcass controls from this 

chlorophacinone study (mean 22.5 beetles) was on par with brood size observed in the upper size 

range of this relationship (average of 14.4 – 22 beetles at 30 – 35 g). A similar pattern has been 

observed with a different burying beetle species wherein at smaller carcass sizes a positive 

relationship between brood size and carcass size were observed but above a given size no further 

gain occurred. Additionally, it has been conjectured that above a given carcass size brood size 

for a single pair of beetles might be reduced due to cost of maintenance, or lack of ability to 

maintain the carcass. Total biomass, which is not independent of brood size, was also found to 

be significantly reduced (P<0.01) on chlorophacinone-dosed carcasses. But growth of 

individuals (total biomass adjusted for brood size) in chlorophacinone-dosed carcasses was not 

significantly different from control weights (P=0.25). Additionally no effect was observed on 

the male-female ratio. Thus, this phase of the study showed that chlorophacinone-dosed 

carcasses have effects on larval survival at concentrations relevant to this assessment. 

The second phase of the study investigated effects on the survival and reproductive success of 

burying beetle adults fed chlorophacinone-dosed meat for 28 days prior to being provided an 

undosed quail carcass for brooding of young. A preliminary study conducted by the National 

Wildlife Research Center found that chlorophacinone residues in whole body prairie dog 

75
76

carcasses ranged from 0.85 mg a.i./kg-bw to 2.25 mg a.i./kg-bw. Based on this information, 

laboratory raised adult N. orbicollis beetles were provided a no-choice test diet consisting of 3.0 

ppm chlorophacinone in ground beef, which exceeded the high end of this range, for 28 days. 

Control adult beetles were fed undosed ground beef. Beetles were segregated by gender during 

this feeding period. 

After the feeding period, surviving male-female paired beetles were offered a thawed non-dosed 

Japanese quail carcass. Upon emergence of offspring (approximately one month later), the total 

number of young produced per brood were counted, sexed, and weighed. Number of emerged 

beetles, male-female ratio, and individual beetle and total brood weights of the treatment and 

control broods were compared using nonpaired t-tests. During the 28 day no-choice feeding 

trial, 12.5% of control adults died compared to 4.7% mortality of adults in the treatment group. 

It appears from these results that chlorophacinone has no direct negative impact on survival of 

adult beetles. No significant differences were found between treatment and control groups in the 

test for evaluating the subsequent ability of adults fed no-choice diets to brood and produce 

normal progeny. The following variables were evaluated: quail carcass weight (in grams), 

number of beetles produced/brood, number of beetles/carcass weight, weight/beetle, estimated 

total brood weight/brood, brood weight/carcass weight, number of females/brood, number of 

males/brood, male-female ratio/brood, and proportion of males/brood. The study authors 

believed that the lower number of broods produced in this experiment, relative to the first which 

used rat carcasses, may be due to either the age of the beetles and/or the use of a different 

type/condition of carcass. 

The results of the study performed on N. orbicollis to assess the impacts of chlorophacinone on 

burying beetles showed that adult burying beetle survival and fecundity is not affected at 

environmentally relevant residue levels but that larvae brooding on chlorophacinone residues 

have reduced survival (MRID 47383001). Therefore, it is expected that any insect with exposure 

to chlorophacinone residues during its developmental early life stage will have significant 

effects. This effect is considered a reproductive effect. However, no other effects to insects are 

expected since chlorophacinone exposure to adults resulted in more of the control beetles dying 

when compared with those in the treatment group who were fed a no-choice diet of 

chlorophacinone dosed ground beef. Furthermore, once these adults, both the control group fed 

non-dosed ground beef and the treatment group fed chlorophacinone dosed ground beef, were 

offered non-dosed quail carcasses no significant effects were seen in the treatment group. 

A 14-day toxicity test on the earthworm (Eisenia foetida) found a LOAEL at soil concentrations 

of 556 mg a.i./kg-soil chlorophacinone (MRID 47383002). This concentration is more than ten 

times the concentration of Rozol Prairie Dog Bait (50 mg a.i./kg-bait). It is outside the realm of 

possibility that concentrations approaching the LOAEL concentration will occur in the 

environment. Additionally, an open literature study in which the Wellington tree weta 

(Hemideina crassidens) was exposed to and consumed diphacinone bait for up to 64 days found 

no effect (Fisher et al. 2007). Diphacinone shares the same mode of action as chlorophacinone 

and is very similar in chemical structure. Based on these studies and the study described above, 

only reproductive effects to terrestrial invertebrates are expected to occur. 
77

Table 4.4 Evaluation of the Terrestrial Invertebrate Reproduction Study. Study Description

A.I. Concentration

Study parameters Test Results 

Phase 1: Poisoned carcasses fed to burying beetles (Nicrophorus orbicollis) 

Rats fed exclusively 50 mg a.i./kg chlorophacinone bait for a period of 5-10 days until death resulting in unknown residue concentrations. 

Each of 20 female-male pairs of field collected N. orbicollis was offered a chlorophacinone-dosed rat carcass and each of another 20 female-male pairs was offered a non-dosed rat carcass. Upon emergence of offspring the total number of young produced per brood was counted, sexed, and weighed. Numbers, male-female ratio, and individual beetle and total brood weights of treatment and control broods were compared. 

Significant differences between control and treatmengroups were found for the following endpoints: carcaweight, number of beetles produced, estimated total bweight (g). Based on open literature the differences carcass weight between the control and treatment groare not expected to have influenced study results. Tobrood weight is not independent of number of beetleproduced, and analysis of individual beetle weight shno significant effect on growth. There was no signifeffect on the male-female ratio. Therefore, the main was larval survival. 

Phase 2: Dosed ground meat feed for 28 days to burying beetles (N. orbicollis) 

followed by brooding of young on a clean carcass 

Adult N. orbicolliswere fed chlorophacinonedosed (3.0 ppm chlorophacinone) ground beef. 

64 adult laboratory reared N. orbicollis (36 females/28 males) were fed a no-choice diet of chlorophacinone-dosed (3.0 ppm chlorophacinone) ground beef. Another 64 adult N. orbicollis (36 females/28 males) were fed a nochoice diet of non-dosed ground beef. After the feeding trial, surviving adult male-female pairs were offered a thawed non-dosed Japanese quail carcass. Upon emergence of offspring the total number of young produced per brood was counted, sexed, and weighed. Numbers, male-female ratio, and individual/total brood weights of the treatment and control broods were compared. 

During the 28 day no-choice feeding trial, 12.5% of tcontrol adults died compared to the 4.7% mortality oadults in the treatment group, demonstrating chlorophacinone has no direct negative impact on suof adult beetles. No significant differences were foubetween the treatment and control groups in the secoof the second phase of the study (subsequent ability oadults fed no-choice diets to brood and produce normprogeny). The following variables were evaluated: qcarcass weight (in grams), number of beetles produced/brood, number of beetles/carcass weight, weight/beetle, estimated total brood weight/brood, brweight/carcass weight, number of females/brood, numof males/brood, male-female ratio/brood, and propormales/brood. The study states that the authors believthe lower number of broods produced in this experimrelative to the first which used rat carcasses, may be either the age of the beetles and/or the use of a differtype/condition of carcass. 
4.3. Incident Database Review 

A review of the Ecological Incident Information System (EIIS, version 2.1), the ‘Aggregate 

Incident Reports’ (v. 1.0) database, and the Avian Monitoring Information System (AIMS) for 

ecological incidents involving chlorophacinone was completed on June 14, 2010. The results of 

this review for terrestrial, plant, and aquatic incidents are discussed below in Section 4.3.1. A 

complete list of the incidents involving chlorophacinone including associated uncertainties is 

included as Appendix I. 

4.3.1. Terrestrial Incidents 

Nine incidents, involving 87 mammals and birds, have been reported that can be reasonably 

attributed to chlorophacinone poisoning as the primary cause of death. Four of these incidents, 

involving five mammals and birds, can be attributed to use of chlorophacinone to control 

BTPDs. The incidents can be found under the reports: I020607-001, I019311-001, I012972-001 

and FWS 2007600155R003. The five animals included two badgers, two turkeys, and a bald 

eagle. Liver concentrations for these incidents range from 0.30 mg a.i./kg-bw for the bald eagle 

to 4.4 mg a.i./kg-bw for one of the badgers. For all five animals, the primary indication of 

anticoagulant poisoning ( i.e., internal hemorrhaging) was reported. 

One additional incident (FWS 2009600498), involving a ferruginous hawk and a great horned 

owl, is not attributed to chlorophacinone use although residues were detected below the level of 

quantitation (LOQ) of 0.25 mg a.i./kg-bw. The ferruginous hawk mortality is attributed to 

interspecific/intraspecific fighting and the great horned owl mortality is attributed to a car 

collision. However, both animals appeared anemic during examination indicating blood loss, 

possibly accelerated by chlorophacinone, as cause of death. Further, hemorrhaging that may 

have occurred may not have been detectable due to the freezing of carcasses prior to 

examination. Some evidence indicates that micro-hemmorhaging can be detected prior to 

carcass freezing but cannot be detected otherwise (personal communication, Scott Larson, 

USFWS, June 25, 2010). 

4.4. Use of Probit Slope Response Relationship to Provide Information on the Endangered 

Species Levels of Concern 

As part of the risk characterization, an interpretation of acute RQs for listed species is discussed. 

This interpretation is presented in terms of the chance of an individual event (i.e., mortality or 

immobilization) should exposure at the EEC actually occur for a species with sensitivity to 

chlorophacinone on par with the acute toxicity endpoint selected for RQ calculation. To 

accomplish this interpretation, the Agency uses the slope of the dose response relationship 

available from the toxicity study used to establish the acute toxicity measures of effect for each 

78
taxonomic group that is relevant to this assessment. The individual effects probability associated 

with the acute RQ is based on the mean estimate of the slope and an assumption of a probit dose 

response relationship. In addition to a single effects probability estimate based on the mean, 

upper and lower estimates of the effects probability are also provided to account for variance in 

the slope, if available. 

Individual effect probabilities are calculated based on an Excel spreadsheet tool IECV1.1 

(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental 

Fate and Effects Division (June 22, 2004). The model allows for such calculations by entering 

the mean slope estimate (and the 95% confidence bounds of that estimate) as the slope parameter 

for the spreadsheet. In addition, the acute RQ is entered as the desired threshold. 

5. Risk Characterization 

Risk characterization is the integration of the exposure and effects characterizations. Risk 

characterization is used to determine the potential for direct and/or indirect effects to listed 

species or for modification to designated critical habitat from the use of chlorophacinone to 

control BTPDs. The risk characterization provides an estimation (Section 5.1) and a description 

(Section 5.2) of the likelihood of adverse effects; articulates risk assessment assumptions, 

limitations, and uncertainties; and synthesizes an overall conclusion regarding the likelihood of 

adverse effects to the assessed species or their designated critical habitat (i.e., 

NE; LAA; NLAA). In the risk estimation section, RQs are calculated using standard EFED 

procedures explained in the following section. In the risk description section, additional analyses 

may be conducted to help characterize the potential for risk. 

5.1. Risk Estimation 

Risk is estimated by calculating the ratio of exposure to toxicity. The endpoints in Table 4.1 are 

used to calculate RQs based on conservative terrestrial exposure assumptions. The most 

sensitive species among avian and mammalian species tested are used to calculate RQs and 

characterize the direct risk to listed species. This ratio is the RQ, which is then compared to acute 

LOCs for each category evaluated (USEPA, 2004a). For acute exposure to terrestrial listed 

species the LOC is 0.1. For details regarding the methods, parameter selection and equations for 

this risk estimation, see Section 3.3. 

Exposure to terrestrial animals is considered for two general conditions: 1) primary exposure to 

bait and 2) secondary exposure to carcasses or poisoned animals. In the case of primary 

exposure, the concentration of active ingredient within the bait is considered to be the EEC. 

Therefore, the primary exposure EEC is 50 mg/kg-diet. To determine secondary exposure EECs, 

available literature concerning carcass residue concentrations were considered. In previous 

assessments, open literature sources of chlorophacinone residue concentrations were referenced. 

Erickson and Urban (USEPA, 2004b) compiled this data (see Tables 4.2 and 4.3) and the latest 

ECOTOX bibliography (updated May 2010) did not indicate any additions. Based on the highest 

whole body residue concentrations, the EEC for secondary exposure to chlorophacinone via 

BTPD carcass is 2.24 mg a.i./kg-bw. The EEC for secondary exposure via incidentally exposed 

79
non-target granivores (e.g. mice) is 5.8 mg a.i./kg-bw. For the complete rationale as to why 

these concentrations are used, see Section 3.3. 

5.1.1. Risk to Birds and Herptiles 

Based on an LD50 value of 258 mg a.i./kg bw (calculations explained in Appendix J) and the 

acute listed species LOC of 0.1, no exceedences of the LOC occur for listed avian species based 

on a single acute dose. However, based on an LC50 value of 56 mg a.i./kg-diet exceedences of 

the LOC occur for five-day consumption of the grain bait or chlorophacinone poisoned nontarget animals (Table 5.1). Single dose LD50 calculations are made in Appendix J for two 

species (California condor and New Mexican ridge-nosed rattlesnake) representing the range of 

sizes of species assessed as birds. RQs based on exposure to non-target animals from this 

analysis (0.0003 and 0.0035) are lower than RQs based on exposure to non-target animals for the 

sub-acute LC50 endpoint (0.104). Thus, the LC50 value is the more conservative value. 

Therefore, risk to listed birds and herptiles is evaluated using the most sensitive LC50 value based 

on avian toxicity tests. Exposure to chlorophacinone at concentrations below LOCs based on 

LC50s will be considered a risk based on this uncertainty. 

Because residue concentrations for invertebrates are not as well characterized as residue 

concentrations in rodents and available invertebrate residue data does not exceed rodent residue 

concentrations, the mouse residue concentration is used as a surrogate for invertebrate residues. 

Five-day consumption of chlorophacinone poisoned BTPDs does not exceed the LOC based on 

the LC50. 

An avian reproduction study for chlorophacinone has been required but has yet to be submitted. 

In the absence of this study and any open literature study that may supplement it, risk of adverse 

effects to avian and herptile reproduction cannot be precluded. 

Table 5.1 Summary of RQ Values for Avian Species. RQs were calculated with an LC50 of 

56 mg a.i./kg-diet and RQs are presented for diet as tested. 

Species RQ Bait RQ BTPD RQ mouse1 Probability of Individual Effect at RQ2

California condor * 0.04 0.104 1 in 14 

Whooping crane 0.89 0.04 0.104 1 in 2.13 

Eskimo curlew * ** 0.104 1 in 14 

Northern Aplomado falcon * 0.04 0.104 1 in 14 

Chirichaua leopard frog * ** 0.104 1 in 14 

Mexican spotted owl * 0.04 0.104 1 in 14 

Piping plover * ** 0.104 1 in 14 

80
Sonora tiger salamander * ** 0.104 1 in 14 

Black-capped vireo * ** 0.104 1 in 14 

Golden-cheeked warbler * ** 0.104 1 in 14 

RQ = (Residue Concentration)/(LC50) 1

 The mouse residue concentration of 5.8 mg a.i./kg-bw is used as a surrogate for invertebrate residues.

2

 Highest RQ value was used to calculate the probability of individual effect. The LC50 of 56 ppm was used as well 

as the slope of 1.49 obtained from the study (MRID 41513102). The generic probability of individual effect for 

birds and herpitles calculated using the LC50 of 56 mg a.i./kg-diet, the slope of 1.49, and the LOC of 0.1 was ~1 in 

14.7. Therefore, if any of the probabilities of individual effect are less than 1 in 14.7 there is an exceedance of the 

LOC. The probabilities of individual effect for each species exceeded the LOC. 

Exceedances of LOC are in bold 

* does not eat bait 

** does not eat BTPDs 

5.1.1.a. Risk to New Mexican Ridge-nosed Rattlesnake 

It is not appropriate to assess dietary exposure to a rattlesnake using a 5-day LC50 because based 

on life history information dietary exposure will not occur on a daily basis. Rather, it is more 

appropriate to use a single dose LD50 value because rattlesnakes feed up to a few times per year 

(Howard, 2005). Weight information is not available for this species but for the purposes of this 

analysis, weights for a small rattlesnake will be assumed to be 50 grams and 500 grams. As 

discussed in Section 3.3.2.b, maximum snake prey size can be related to snake mass. From this 

equation, maximum prey sizes are 66 grams and 777 grams for the 50 gram and 500 gram snake, 

respectively9. Because the New Mexican ridge-nosed rattlesnake is a small rattlesnake, it is 

more likely that it would prey upon a small non-target granivore like a mouse rather than a 

BTPD. Therefore, a residue concentration of 5.8 mg a.i./kg-bw will be assumed for the prey 

item. 

50 gram snake: 

Dose of chlorophacinone: 66,000 mg * 0.0000058 = 0.383 mg a.i. 

Weight normalized dose: 0.383 mg a.i. ÷ 0.1 kg bw = 3.83 mg a.i./kg bw 

Adjusted LD50 (Minaeu et al, 1996) (50 g/178 g) * 258 mg a.i./kg bw = 213 mg a.i./kg bw 

Risk Quotient: 3.83 mg a.i./kg bw ÷ 213 mg a.i./kg bw = 0.018 

500 gram snake:

Dose of chlorophacinone: 777,000 mg * 0.0000058 = 4.51 mg a.i. 

Weight normalized dose: 4.51 mg a.i. ÷ 0.5 kg bw = 9.02 mg a.i./kg bw 

Adjusted LD50 (Minaeu et al, 1996) (500 g/178 g) * 258 mg a.i./kg bw = 301 mg a.i./kg bw 

Risk Quotient: 9.02 mg a.i./kg bw ÷ 301 mg a.i./kg bw = 0.030 

 

9

 Prey size (g) = Snake mass1.071 (g) 

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82

5.1.2.

RQs do not vary significantly with a range of body sizes. Both RQs calculated are below the 

LOC for terrestrial endangered species (LOC=0.1). Although the RQs indicate that no effect is 

expected, risk to reproduction cannot be precluded due to lacking avian reproduction data. 

Indirect effects will be discussed separately and a separate determination will be made. 

Risk to Mammals 

Exposure to listed mammals is evaluated using the most sensitive LD50 value based on 

mammalian toxicity tests. Ingestion rates and weight-adjusted LD50s are calculated and 

presented in Table 5.2. Wet weight ingestion rates are used for assessing secondary exposure. 

Grain bait is assumed to be dry and therefore dry weight ingestion rates are used for assessing 

primary exposure. These ingestion rates and LD50s are used, in part, to calculate RQs presented 

in Table 5.3. Exceedences of the LOC are indicated in bold. RQs for all mammals for all 

assessed exposure pathways exceed the Acute Listed Species LOC of 0.1. 

Table 5.2 Calculation of Ingestion Rate and Adjusted LD50 for mammals 

Listed Mammalian 

Species 

Body 

Weight 

Ingestion Rate 

(dry weight) 

(g/day)1 

Ingestion Rate 

(wet weight) 

(g/day)2

Adjusted LD50

(mg a.i./kg bw)3

Mammals with potential to consume grain bait 

Grizzly bear 102000 3077.07 * 0.02 

Preble’s meadow 

jumping mouse 13 1.94 * 0.18 

Carnivores 

Black-footed ferret 635 47.31 147.84 0.07 

Jaguar 36363 1318.04 4118.89 0.02 

Gulf Coast 

jaguarundi 4500 236.60 739.36 0.04 

Canada lynx 5100 262.23 819.48 0.04 

Ocelot 11300 504.31 1575.97 0.03 

Gray wolf 18000 739.44 2310.74 0.03 

* no wet weight to dry weight conversion was calculated because it is assumed that the bait is in dry weight. 1

 Dry weight ingestion rate is calculated using the “all mammals” allometric equation from EPA 1993. 

2

 The ingestion rate in terms of wet weight is calculated using the following equation: 

Ingestion Rate (wet weight) = Ingestion Rate (dry weight)/(1-0.68) 

3

 The Adjusted LD50 is calculated using the following equation: 

Adjusted LD50 = LD50*[(body weight (in grams) of the test animal used in the study)/(body weight of the listed 

mammalian species)]^0.25 

In this case, the LD50 is 0.16 and the body weight (in grams) of the test animal used in the study was 20 grams. 
83

Table 5.3 Summary of RQ Values for Mammalian Species. RQ descriptions are qualified with the associaRQs were calculated with an LD50 of 0.16 mg a.i./kg bw. 

Species 

Ingestion Rate 

(wet weight) 

(g/day) 

Dose-based 

EEC for bait 

(mg/kgbw/day)1 RQ Bait2

Dose-based 

EEC for BTPD 

(mg/kgbw/day) 1 RQ BTPD2

Dose-based 

EEC for mouse

(mg/kgbw/day) 1 

Grizzly bear 3,077.07 1.508 75.42 0.068 3.38 0.175 Black-footed ferret 47.31 * * 0.522 7.45 1.350 Jaguar 1,318.04 * * 0.254 12.69 0.657 Gulf Coast jaguarundi 236.60 * * 0.368 9.20 0.953 Canada lynx 262.23 * * 0.360 9.00 0.932 Preble’s meadow jumping mouse 

1.94 7.443 41.35 ** ** ** 

Ocelot 504.31 * * 0.312 10.41 0.809 Gray wolf 739.44 * * 0.288 9.59 0.745 * does not eat bait ** does not eat BTPDs or non-target animals 1 The Dose-based EEC is calculated using the following equation: 

(Residue (mg/kg-diet [ww])*FI (kg-diet [ww]/day))/(body weight of the listed species (in grams)/1000) Residues are: 50 mg a.i./kg for bait; 2.24 kg-diet [ww]/day for BTPDs; 5.8 kg-diet [ww]/day for non-target animals FI (kg-diet [ww]/day) is calculated by the following equation: Ingestion Rate (wet weight) (g/day)/1000 

2 RQ is calculated using the following equation: 

RQ=Dose-based EEC/Adjusted LD50

3 The highest RQ value was used to calculate the probability of individual effect. The LD50 of 0.16 mg a.i./kg bw was used as well as th

per original Agency assumptions of typical slope cited in Urban and Cook (1986). The generic probability of individual effect for mamLD50 of 0.16 mg a.i./kg bw, the generic slope of 4.5, and the LOC of 0.1 was ~1 in 294,000. Therefore, if any of the probabilities of ind

than 1 in 294,000 there is an exceedance of the LOC. The probabilities of individual effect for each species exceeded the LOC.

Exceedances of LOC are in bold 
5.1.3. Risk to Terrestrial Invertebrates 

Toxicity to listed terrestrial invertebrates (specifically the American burying beetle and the Salt 

Creek tiger beetle) was evaluated qualitatively (as chlorophacinone residues in the dosed rat 

carcasses in the study discussed in Section 4.2.3 (MRID 47383001) were not available). The 

study described in Section 4.2.3 (MRID 47383001) showed larval survival effects to N. 

orbicollis which is supposedly the nearest extant relative to the American burying beetle (MRID 

47383001). Based on this information, it was assumed that the listed American burying beetle 

would also experience larval survival effects if exposed to chlorophacinone residues. Since the 

American burying beetle is found within the action area, it may be exposed to chlorophacinonedosed carcasses. Furthermore, the larvae of the Salt Creek tiger beetle eat insects and may also 

experience survival effects due to chlorophacinone residues. Since the Salt Creek tiger beetle is 

also found within the action area and therefore has the potential to feed on chlorophacinone 

contaminated insects, this species may also experience larval survival effects due to 

chlorophacinone residues. 

5.1.4. Primary Constituent Elements of Designated Critical Habitat 

For chlorophacinone use, the assessment endpoints for designated critical habitat PCEs involve 

the same endpoints as those being assessed for potential direct and indirect effects above. 

Therefore, the preliminary effects determinations for direct and indirect effects are used as the 

basis of the effects determination for potential modification to designated critical habitat. 

All of the assessment endpoints for the PCEs of designated critical habitat for the Salt Creek 

tiger beetle, California condor, whooping crane, Canada lynx, Preble’s meadow jumping mouse, 

Mexican spotted owl, piping plover, New Mexican ridge-nosed rattlesnake, and the gray wolf 

involve potential direct effects to the organism. Through the risk determinations made for listed 

bird, mammal, herptile and invertebrate species, the potential for effects to prey base were 

evaluated. Indirect effects through loss of the prey base or habitat loss (burrows) are seen for the 

Salt Creek tiger beetle, California condor, whooping crane, Canada lynx, Preble’s meadow 

jumping mouse, Mexican spotted owl, piping plover, New Mexican ridge-nosed rattlesnake, and 

the gray wolf. Effects to the prey base are expected because the Acute Risk LOC of 0.5 (the 

LOC used to evaluate risk to non-listed species) is exceeded for mammals, birds and herptiles10

(EPA 2004a). Invertebrate toxicity data indicate that there are direct effects on reproduction for 

invertebrate species whose larvae are exposed to chlorophacinone residues. This exposure is 

possible and therefore direct effects to invertebrates including the Salt Creek tiger beetle are 

expected. Based on these data, effects to the prey base are possible for listed species that prey 

upon birds, mammals, herptiles, or invertebrates. The Agency does not currently have a method 

to analyze effects to populations based on effects to individuals. Because this effect cannot be 

analyzed, risk is presumed and effects to mammal, bird, herptile, and invertebrate prey 

populations is presumed. Therefore prey base effects are presumed for Salt Creek tiger beetle, 

California condor, whooping crane, Canada lynx, Preble’s meadow jumping mouse, Mexican 

spotted owl, piping plover, New Mexican ridge-nosed rattlesnake, and the gray wolf. The only 

 

10 Maximum RQ for mammals = 75.42; Maximum RQ for birds (and herptiles) = 0.89; 

84
85

impact to habitat would be the loss of BTPD burrows. Based on the life history information 

available, none of the species that may be affected with designated critical habitat use BTPD 

burrows therefore this loss of burrows is not expected to have an adverse impact on these species 

(Attachment 1). The preliminary effects determination for all PCEs for all species that may be 

affected is provided in Table 5.5

5.2. Risk Description 

The risk description synthesizes overall conclusions regarding the likelihood of adverse impacts 

leading to a preliminary effects determination (i.e., NE, NLAA, or LAA) for the assessed species 

and the potential for modification of their designated critical habitat based on analysis of RQs 

and a comparison to the LOC. The final determination is made after the spatial analysis is 

completed at the end of the risk description, Section 5.2. In Section 5.2.3, a discussion of any 

potential overlap between areas where potential usage may occur and areas where species are 

expected to occur (including any designated critical habitat) is presented. If there is no overlap 

of the species habitat and occurrence sections with the Potential Area of MA Effects a NE 

determination is made. 

If the RQs presented in the Risk Estimation (Section 5.1) show no direct effects for the assessed 

species and no modification to PCEs of the designated critical habitat, which was already 

described in Section 5.1.4, a NE determination is made, based on the use of chlorophacinone to 

control BTPDs within the action area. However, if the LOC for direct effects is exceeded the 

Agency concludes a preliminary MA determination for the FIFRA regulatory action regarding 

the use of chlorophacinone to control BTPDs. 

A summary of the risk estimation results are provided in Table 5.4 for direct and indirect 

effects to the listed species that may be affected and in Table 5.5 for the PCEs of their 

designated critical habitat. 
Table 5.4. Risk Estimation Summary for Chlorophacinone 

Species LOC Exceedences (Yes/No) Description of Results of Risk Estimat

Direct effects1: 

yes 

Direct effects are expected for the grizzly bear based on the potential for thchlorophacinone bait (RQ of 75.42 which exceeds the LOC of 0.1) or othethe chlorophacinone bait (RQ of 3.38 for exposure to BTPDs and RQ of 8.both which exceed the LOC of 0.1). Growth and reproductive effects cannchronic data; however, growth and reproductive effects are not expected beresult of acute exposure. Grizzly bear 

Indirect effects2: 

yes 

Indirect effects from the loss of the prey base are also expected because effhave been demonstrated in mammals ranging in size from 13 to 36,363 graNo indirect effects from habitat loss are expected because this species does 

Direct effects: 

yes 

Reproductive effects are expected for the American burying beetle. The A

mammalian and avian carcasses as a food resource during their reproductio

affected number of emerged beetles (MRID 47383001). American burying 

beetle 

Indirect effects: 

yes 

Indirect effects from the loss of the prey base are expected because effects 

been demonstrated in mammals, birds, and invertebrates. No indirect effec

because this species does not use BTPD burrows. 

Direct effects: 

yes 

Reproductive effects are expected for the Salt Creek tiger beetle. Salt Creeexposed to chlorophacinone residues through chlorophacinone exposed terin a burying beetle study negatively affected number of emerged beetles (Mexpected for the Salt Creek tiger beetle. Salt creek tiger beetle 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. This species uses mud banks of streams and seeps in association wflats of saline wetlands which is distinct from the short grass prairie associ

effects from habitat loss are expected because this species does not use BT

Direct effects: 

yes 

Direct effects to the California condor are expected through their potential consumed the chlorophacinone bait (RQ of 0.104 for exposure to non-targe0.1). Growth and reproductive effects cannot be precluded due to the abse

California condor 

Indirect effects: 

no 

No indirect effects from the loss of prey base are expected because this speBTPD range. No indirect effects from habitat loss are expected because thburrows. 

Whooping crane Direct effects: Direct effects to the whooping crane are expected to occur based on the po

86
Species LOC Exceedences (Yes/No) Description of Results of Risk Estimat

yes chlorophacinone bait (RQ of 0.89 which exceeds the LOC of 0.1) or other 

the chlorophacinone bait (RQ of 0.104 for exposure to non-target animals Growth and reproductive effects cannot be precluded due to the absence of 

Indirect effects: 

yes 

Indirect effects from the loss of the prey base are also expected because effhave been demonstrated in mammals, birds, and invertebrates. No indirect because this species does not use BTPD burrows. 

Direct effects: 

yes 

Direct effects to the Eskimo curlew are expected to occur based on the potitems that have consumed the chlorophacinone bait (RQ of 0.104 for expoused as a surrogate for invertebrate prey, which exceeds the LOC of 0.1). 

Eskimo curlew cannot be precluded due to the absence of chronic data. 

Indirect effects: 

yes 

Indirect effects from the loss of the prey base are expected because effects 

been demonstrated in terrestrial invertebrates. No indirect effects from hab

species does not use BTPD burrows. 

Direct effects: 

yes 

Direct effects to the northern Aplomado falcon are expected through their may have consumed the chlorophacinone bait (RQ of 0.104 for exposure to 

Northern Aplomado the LOC of 0.1). Growth and reproductive effects cannot be precluded due falcon 

Indirect effects: 

yes 

Indirect effects from the loss of the prey base are also expected because eff

have been demonstrated in mammals, birds, and invertebrates. No indirect because this species does not use BTPD burrows. 

Direct effects: 

yes 

Direct effects are expected for the black-footed ferret based on the potentiaitems that may have consumed the chlorophacinone bait (RQ of 7.45 for exexposure to non-target animals, both which exceed the LOC of 0.1). Signibecause black-footed ferrets prey primarily on BTPDs. Growth and reprod

due to the absence of chronic data; however, growth and reproductive effetypically occurs as a result of acute exposure. 

Black-footed ferret 

Indirect effects: 

yes 

Indirect effects from the loss of the prey base are also expected because eff

have been demonstrated in mammals, birds, and invertebrates. In additionon BTPDs. Indirect effects from habitat loss are expected because this spe

Direct effects: 

yes 

Direct effects to the Chirichaua leopard frog are expected to occur based oconsume prey items that may have consumed the chlorophacinone bait (RQ animals, which is used as a surrogate for invertebrate prey, which exceeds 

Chirichaua leopard frog reproductive effects cannot be precluded due to the absence of chronic dat

Indirect effects: 

yes 

Indirect effects from the loss of the prey base are expected because effects 

been demonstrated in terrestrial invertebrates and birds. No indirect effect

because this species does not appear to use BTPD burrows. 

87
Species LOC Exceedences (Yes/No) Description of Results of Risk Estimat

Direct effects: 

yes 

Direct effects are expected for the jaguar based on the potential for this spehave consumed the chlorophacinone bait (RQ of 12.69 for exposure to BTnon-target animals, both which exceed the LOC of 0.1). Growth and reprodue to the absence of chronic data; however, growth and reproductive effetypically occurs as a result of acute exposure. 

Jaguar 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. Jaguars – particularly males of the northern reaches – are known tencompass a variety of plant communities, including: Maderan evergreen-

semidesert shrubland, and Sonoran desert scrub. Washes and riparian areaalso be valuable movement corridors. These habitats are distinct from the BTPD habitat. No indirect effects from habitat loss are expected because tburrows. 

Direct effects: 

yes 

Direct effects are expected for the Gulf Coast jaguarundi based on the poteitems that may have consumed the chlorophacinone bait (RQ of 9.20 for exexposure to non-target animals, both which exceed the LOC of 0.1). Growprecluded due to the absence of chronic data; however, growth and reprodu

Gulf Coast jaguarundi mortality typically occurs as a result of acute exposure. 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. This species is found in chaparral plant communities and dense br

which are distinct from the short grass prairie associated with BTPD habitaloss are expected because this species does not use BTPD burrows. 

Direct effects: 

yes 

Direct effects to the Canada lynx are expected to occur based on the potentitems that may have consumed the chlorophacinone bait (RQ of 23.30 for eof 9.00 for exposure to BTPDs both of which exceed the LOC of 0.1). Grobe precluded due to the absence of chronic data; however, growth and repr

because mortality typically occurs as a result of acute exposure. Canada lynx 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. The Canada lynx is associated with the southern, transitional reachWhere it occurs at these lower latitudes, the boreal forest forms a mixed co

landscape. These habitat areas are distinct from the short grass prairie asso

indirect effects from habitat loss are expected because this species does no

Preble’s meadow jumping mouse 

Direct effects: 

yes 

Direct effects to the Preble’s meadow jumping mouse are expected to occu

species to consume the chlorophacinone bait (RQ of 41.35 which exceeds reproductive effects cannot be precluded due to the absence of chronic dateffects are not expected because mortality typically occurs as a result of ac

88
Species LOC Exceedences (Yes/No) Description of Results of Risk Estimat

Indirect effects: 

yes 

Indirect effects from the loss of the prey base are expected because effects been demonstrated in terrestrial invertebrates. Although this species makeit does not appear to use other species’ burrows. 

Direct effects: 

yes 

Direct effects are expected for the ocelot based on the potential for this spemay consumed the chlorophacinone bait (RQ of 10.41 for exposure to BTPnon-target animals, both which exceed the LOC of 0.1). Growth and reprodue to the absence of chronic data; however, growth and reproductive effetypically occurs as a result of acute exposure. Ocelot 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. Ocelots appear to use areas of dense cover, and in the northern parand semi-arid deserts. In the southern part of its range, ocelot habitat incluand pampas (grasslands). These habitat areas are distinct from the short grhabitat. No indirect effects from habitat loss are expected because this spe

Direct effects: 

yes 

Direct effects to the Mexican spotted owl are expected to occur based on thconsume prey items that may have consumed the chlorophacinone bait (RQ animals which exceeds the LOC of 0.1). Growth and reproductive effects absence of chronic data. 

Mexican spotted owl 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. Mexican spotted owls are found in old-growth or mature forests wcanopy, multi-storied levels, and high tree density as well as canyons with Arizona and New Mexico they are found in habitats associated with mixed oak woodlands, and associated riparian forests. These habitat areas are disassociated with BTPD habitat. No indirect effects from habitat loss are ex

use BTPD burrows. 

Direct effects: 

yes 

Direct effects to the piping plover are expected to occur based on the potenitems that may have consumed the chlorophacinone bait (RQ of 0.104 for eis used as a surrogate for invertebrate prey, which exceeds the LOC of 0.1)

cannot be precluded due to the absence of chronic data. Piping plover 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. The plover’s home range within BTPD range is usually limited to 

beach where its nest is located. No indirect effects from habitat loss are ex

use BTPD burrows. 

New Mexican ridgenosed rattlesnake Direct effects: yes No direct effects based on survival to the New Mexican ridge-nosed rattles

Section 5.1.1.a. RQs of 0.018 for a 50 gram snake and RQ of 0.030 for a 5exceeds the LOC of 0.1). However, growth and reproductive effects canno

chronic data. 

89
Species LOC Exceedences (Yes/No) Description of Results of Risk Estimat

Indirect effects: 

yes 

Indirect effects from a loss of the prey base are expected because effects to been demonstrated in mammals, birds, and invertebrates. No indirect effecbecause this species does not appear to use BTPD burrows. 

Direct effects: 

yes 

Direct effects to the Sonora tiger salamander are expected to occur based oconsume prey items that may have consumed the chlorophacinone bait (RQ animals, which is used as a surrogate for invertebrate prey, which exceeds reproductive effects cannot be precluded due to the absence of chronic dat

Sonora tiger salamander 

Indirect effects: 

no 

No indirect effects from the loss of prey base or loss of habitat (BTPD burrspecies’ range does not overlap with BTPD range. 

Direct effects: 

yes 

Direct effects to the black-capped vireo are expected to occur based on the prey items that have consumed the chlorophacinone bait (RQ of 0.104 for is used as a surrogate for invertebrate prey, which exceeds the LOC of 0.1)

cannot be precluded due to the absence of chronic data. 

Black-capped vireo 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. Black-capped vireos are found in mixed deciduous/evergreen shrugrowth of irregular height and distribution with spaces the small thickets a

extending to ground level. These habitat areas are distinct from the short g

habitat. No indirect effects from habitat loss are expected because this spe

Direct effects: 

yes 

Direct effects to the golden-cheeked warbler are expected to occur based o

consume prey items that have consumed the chlorophacinone bait (RQ of 0animals, which is used as a surrogate for invertebrate prey, which exceeds reproductive effects cannot be precluded due to the absence of chronic dat

Golden-cheeked warbler 

Indirect effects: 

no 

No indirect effects from loss of prey base are expected because this specie

habitat. Golden-cheeked warblers are found in mixed Ashe-juniper and oaThey spend summers in open canopy forest and winters in closed canopy ffrom the short grass prairie associated with BTPD habitat. No indirect effebecause this species does not use BTPD burrows. 

Direct effects: 

yes 

Direct effects to the gray wolf are expected to occur based on the potential 

that have consumed the chlorophacinone bait (RQ of 24.82 for exposure to for exposure to BTPDs both of which exceed the LOC of 0.1). Growth anprecluded due to the absence of chronic data; however, growth and reprodu

mortality typically occurs as a result of acute exposure. Gray wolf 

Indirect effects: 

yes 

Indirect effects from the loss of the prey base are also expected because eff

have been demonstrated in mammals, birds, and invertebrates. No indirect because this species does not use BTPD burrows. 

90
1 Direct effects are survival, growth, and reproduction effects to the individuals (juveniles and adults) of each listed species (terrestrial phase only if th

aquatic) 

2 Indirect effects are survival, growth, and reproduction effects to the individuals of each listed species via effects on prey or habitat (burrows). Table 5.5. Table 5.5 Risk Estimation Summary for Chlorophacinone - Effects to Designated Critical Habi

Species 

Associated 

with a 

Designated 

Critical Habitat 

PCEs 

LOC 

Exceedances 

(yes/no) 

Description of R

(1) Non-vegetated streambanks and mid-channel areas, located adjacent to and between saline stream edges and barren salt flats in saline and freshwater wetlands, in assemblages that are within 4 mi (6 km) of one another. (2) Moist, barren salt flats with: (a) Salmo and Saltillo soils or Lamo, Gibbon-Saltine, Obert, and Zoe soils with Salmo and Saltillo inclusions: (b) Soil electroconductivity ranging from 2,016.0 mS/m to 2,992.2 mS/m; (c) Soil moisture ranging from 43.5 percent to 51.7 percent; and (d) Differential hydraulic pressures that create evaporation and result in exposed salt on soil surfaces. 

Salt Creek tiger beetle

(3) A natural hydrologic regime resulting in annual high flows in saline streams in the early spring and summer, and natural elevation changes in groundwater levels to hydrate saline wetlands located on the floodplain. 

Yes

Reproductive effecCreek tiger beetle. larvae are potentialchlorophacinone rechlorophacinone exinvertebrates. Dosebeetle study negativemerged beetles (Maffects are expected beetle. No indirect base are expected bis distinct from BTuses mud banks of association with samud flats of saline from the short grasBTPD habitat. No loss are expected buse BTPD burrows

91
(4) The presence of abundant and diverse flying and non-flying invertebrate 

prey species belonging to the orders Coleoptera, Orthoptera, Hemiptera, Hymenoptera, Odonata, Diptera, or Lepidoptera. PCEs were not described for the California condor. However, several factors were considered in designating critical habitat: The Sespe-Piru, Mantilija, Sisquoc-San Rafael, and the Hi Mountain-Beartrap areas were considered critical for nesting and related year-long activities. The Mount Pinos and Blue-Ridge areas were considered critical for roosting. The Tejon Ranch, Kern County Rangelands, and Tulare County Rangelands were considered critical for feeding and other related activities; specifically, the Tejon County Rangelands are important because it is the only feeding area close to the Sespe-Piru nesting area. 

California condor

Further, areas of open range with limited disturbance that provide food are needed within the designated areas to maintain the species, since food availability is directly related to condor distribution and reproduction. 

Yes 

Direct effects to the expected through th

prey items that may chlorophacninone bexposure to non-tarthe LOC of 0.1). Geffects cannot be prof chronic data. No base loss are expeconly occurs in areaNo indirect effects expected because thBTPD burrows. 

Although PCEs were not specifically described for the whooping crane it was stated that each of the five factors normally associated with PCEs ((1) Space for individual and population growth and for normal behavior; (2) Food, water, air, light, minerals, or other nutritional or physiological requirements; (3) Cover or shelter; (4) Sites for breeding, reproduction, or rearing of offspring; and generally, (5) Habitats that are protected from disturbances or are representative of the geographical distribution of the listed species) pertain to the whooping crane and are summarized below: 

Whooping crane

Whooping cranes are territorial; pairs require hundreds of acres of undisturbed wetland habitat and unmated birds require undefended territory. Refuges in Idaho, Colorado, and New Mexico were originally designated as part of the critical habitat to add space for a growing new flock. However, these refuges were later removed from the critical habitat designation due to the failure of whooping crane reintroduction in these areas. 

Yes 

Direct effects to the expected to occur bthis species to consbait (RQ of 0.89 wh0.1) or other prey itthe chlorophacninoexposure to non-tar

the LOC of 0.1). Gdata cannot be precchronic data. Indirthe prey base are alto individuals withidemonstrated in mainvertebrates. No iloss are expected buse BTPD burrows

92
All of the designated critical habitat areas provide for the nutritional and 

physiological needs of the cranes. This includes the tidal flats and marshes of Aransas that provide crustaceans and mollusks, the spring migration marshes that provide frogs, fish, crayfish, and other small animals, and the fall migration stopover locations where cranes feed primarily on waste grains and insects. Whooping cranes require open spaces, primarily sand and gravel bars in rivers and lakes, for nightly roosting. These features appear to be one of the major factors in the selection of habitat by cranes. With regard to breeding, the Grays Lake National Wildlife Refuge in Idaho was previously designated as critical habitat in order to provide additional nesting habitat. However, all of the designated critical habitat provides areas essential to rearing young. Cranes also require undisturbed wetland roosting sites and do not tolerate disturbance to themselves or their habitat. 

93
Boreal forest of multiple succesional stages. 

Snowshoe hares and their preferred habitat conditions, which include low and dense vegetation that protrudes above the snow, and mature multistoried stands with conifer boughs at the snow surface. Winter snow conditions of deep powder present for extended periods of time. Potential den sites characterized by abundant coarse woody debris. 

Canada lynx

Matrix habitat (e.g., hardwood forest, dry forest, non-forest, or other habitat types that do not support snowshoe hares) which connect patches of boreal forest foraging sites used by the lynx within a home range 

Yes 

Direct effects to the to occur based on tto consume prey itechlorophacninone bexposure to non-tarfor exposure to BTthe LOC of 0.1). Geffects cannot be prof chronic data; howreproductive effectmortality typically exposure. No indir

base are expected bis distinct from BTlynx is associated wtransitional reaches boreal forest. Whelatitudes, the boreaconifer and coniferThese habitat areas grass prairie associNo indirect effects expected because thBTPD burrows. 

Riparian corridors formed and maintained by normal, dynamic, geomorphological, and hydrologic processes that create and maintain river and stream channels, floodplains, and floodplain benches and promote patterns of vegetation favorable to the Preble’s meadow jumping mouse, containing dense, riparian vegetation consisting of grasses, forbs, and shrubs, or any combination thereof, in areas along rivers and streams, that normally provide open water through the mouse’s active season. The riparian areas must also include specific movement corridors that provide connectivity between and within populations. These could be riparian corridors with less vegetative cover, or include human disturbances such as erosion control, travel ways under bridges, along ditches and canals, and through culverts. 

Preble’s meadow jumping mouse

Adjacent areas of low disturbance in floodplains and uplands, such as hayed fields, grazed pasture, and other unplowed agricultural fields, restored mine lands, recreational trail areas and urban-wildland interfaces. 

Yes 

Direct effects to the mouse are expected potential for this spchlorophacninone bexceeds the LOC oreproductive effectthe absence of chroand reproductive efbecause mortality tof acute exposure. prey are expected bindividuals within pdemonstrated in terAlthough this speciand below ground, other species’ rode

94
A range of tree species, including mixed conifer, pine-oak, and riparian forest 

types, composed of different tree sizes reflecting different stages of trees, 30-45% of which are trees with a 12 inch or greater trunk diameter when measured 4.5 feet off of the ground. A shade canopy created by the tree branches covering 40 percent or more of the ground Large dead trees (snags) with a trunk diameter of at least 12 inches (0.3 meters) when measured at 4.5 feet (1.4 meters) from the ground. High volumes of fallen trees and other woody debris; A wide range of tree and plant species, including hardwoods; and Adequate levels of residual plant cover to maintain fruits, seeds, and allow plant regeneration. Presence of water which typically provides cooler temperatures and higher humidity than the nearby areas. Clumps of stringers of mixed-conifer, pine-oak, pinyon-juniper, and/or riparian vegetation; Canyon wall containing crevices, ledges, or caves; and 

Mexican spotted owl

High percent of ground litter and woody debris. 

Yes

Direct effects to the expected to occur bthis species to consconsumed the chlor0.104 for exposure exceeds the LOC oreproductive effectthe absence of chroeffects from loss of because this specieBTPD habitat. Mexin old-growth or maged stands of treeslevels, and high trewith riparian or conArizona and New Mhabitats associated oak, Arizona cypreassociated riparian are distinct from thassociated with BTeffects from habitathis species does no

The PCEs that support foraging, roosting, and sheltering habitat components for the wintering piping plover are: (1) Intertidal sand beaches (including sand flats) or mud flats (between the MLLW [mean lower low water] and annual high tide) with no, or very sparse, emergent vegetation for feeding. In some cases, these flats may be covered or partially covered by a mat of blue-green algae. (2) Unvegetated or sparsely vegetated sand, mud, or algal flats above annual high tide for roosting. Such sites may have debris or detritus and may have micro-topographic relief (less than 20 in (50 cm) above substrate surface) offering refuge from high winds and cold weather. (3) Surf-cast algae for feeding. (4) Sparsely vegetated backbeach, which is the beach area above mean high tide seaward of the dune line, or in cases where no dunes exist, seaward of a delineating feature such as a vegetation line, structure, or road. Backbeach is used by plovers for roosting and refuge during storms. 

Piping plover

(5) Spits, especially sand, running into water used for foraging and roosting. 

Yes Direct effects to the 

to occur based on tto consume prey itechlorophacinone baexposure to non-taras a surrogate for inexceeds the LOC oreproductive effectthe absence of chroeffects are expected habitat is distinct frplover’s home rangusually limited to thsection of beach whindirect effects from because this specie

burrows.

95
(6) Salterns, or bare sand flats in the center of mangrove ecosystems that are 

found above mean high water and are only irregularly flushed with seawater. (7) Unvegetated washover areas with little or no topographic relief for feeding and roosting. Washover areas are formed and maintained by the action of hurricanes, storm surges, or other extreme wave actions. (8) Natural conditions of sparse vegetation and little or no topographic relief mimicked in artificial habitat types (e.g., dredge spoil sites.) The following PCEs, taken from the critical habitat designation for the northern Great Plains breeding population of the piping plover, encompass piping plover habitat outside of the designated wintering grounds of the species. The one overriding primary constituent element (biological) that must be present at all sites is the dynamic ecological processes that create and maintain piping plover habitat. The biological primary constituent element, i.e., dynamic ecological 

processes, creates different physical primary constituent elements on the landscape. These habitat types or physical primary constituent elements that sustain the northern Great Plains breeding population of piping plovers are described as follows: 

On prairie alkali lakes and wetlands, the physical primary constituent elements include – (1) Shallow, seasonally to permanently flooded, mixosaline to hypersaline wetlands with sandy to gravelly, sparsely vegetated beaches, salt-encrusted mud flats, and/or gravelly salt flats; (2) Springs and fens along edges of alkali lakes and wetlands; and (3) Adjacent uplands 200 feet (61 m) above the high water mark of the alkali lake or wetland. On rivers the physical primary constituent elements include – sparsely vegetated channel sandbars, sand and gravel beaches on islands, temporary pools on sandbars and islands, and the interface with the river. On reservoirs the physical primary constituent elements include – sparsely vegetated shoreline beaches, peninsulas, islands composed of sand, gravel, or shale, and their interface with the water bodies. On inland lakes (Lake of the Woods) the physical primary constituent elements include – sparsely vegetated and windswept sandy to gravelly islands, beaches, and peninsulas, and their interface with the water body. 

96
PCEs were not described for the New Mexican ridge-nosed rattlesnake by 

name. However, the critical habitat listing notice identified certain attributes and features of the designated critical habitat area that are grouped as “constituent elements,” including:Dens and/or denning habitat that provides shelter during the summer and winter months; Vegetation that provides cover for the New Mexican ridge-nosed rattlesnake and habitat for prey; 

New Mexican ridge-nosed rattlesnake

Abundance of prey (lizards and rodents) 

Yes 

No direct effects baMexican ridge-noseto occur (see Sectioa 50 gram snake angram snake. NeithLOC of 0.1). Howreproductive effectthe absence of chrofrom a loss of the pbecause effects to ipopulations have bmammals, birds, anindirect effects from because this specieBTPD burrows. 

PCEs were not described for the gray wolf. However, key habitat components were described in the recovery plan: A year-round abundance of ungulate prey and alternate prey, Secluded and suitable denning and rendezvous sites, and 

Gray wolf

Sufficient space with low human disturbance. 

Yes 

Direct effects to the occur based on the consume prey itemchlorophacninone bexposure to non-tarfor exposure to BTthe LOC of 0.1). Geffects cannot be prof chronic data; howreproductive effectmortality typically exposure. Indirect prey base are also eindividuals within pdemonstrated in mainvertebrates. No iloss are expected buse BTPD burrows

97
Following a preliminary MA determination, additional information is considered to refine the 

potential for exposure at the predicted levels based on the life history characteristics (i.e., habitat 

range, feeding preferences, etc.) of the assessed species. Based on the best available 

information, the Agency uses the refined evaluation to distinguish those actions that MA - 

NLAA from those actions that are MA - LAA the assessed species and its designated critical 

habitat. 

The criteria used to make determinations that the effects of an action are NLAA the assessed 

species or modify its designated critical habitat include the following: 

• Significance of Effect: Insignificant effects are those that cannot be meaningfully 

measured, detected, or evaluated in the context of a level of effect where “take” occurs 

for even a single individual. “Take” in this context means to harass or harm, defined as 

the following: 

 Harm includes significant habitat modification or degradation that results in 

death or injury to listed species by significantly impairing behavioral patterns 

such as breeding, feeding, or sheltering. 

 Harass is defined as actions that create the likelihood of injury to listed species 

to such an extent as to significantly disrupt normal behavior patterns which 

include, but are not limited to, breeding, feeding, or sheltering. 

• Likelihood of the Effect Occurring: Discountable effects are those that are extremely 

unlikely to occur. 

• Adverse Nature of Effect: Effects that are wholly beneficial without any adverse effects 

are not considered adverse. 

 

A description of the risk and effects determinations for each of the established assessment 

endpoints for the listed species that may be affected and their designated critical habitat is 

provided in Sections 5.2.1 through 5.2.3. The effects determination section will start with a 

discussion of the potential for direct effects, followed by a discussion of the potential for indirect 

effects. These discussions consider the spatial analysis. For those listed species that have 

designated critical habitat, the section will end with a discussion on the potential for modification 

to the critical habitat from the use of chlorophacinone to control BTPDs. Finally, in Section 

5.2.3, a discussion of any potential overlap between the area of concern and the species that may 

be affected (including any designated critical habitat) is presented. If there is no overlap or the 

counties with/containing the species’ habitat are not adjacent to the use area/BTPD habitat a NE 

determination is made. 

5.2.1. Direct Effects to Listed Species 

Those species that may be affected through direct effects are those with RQs that exceed the 

acute listed species LOC of 0.1. All species (i.e. birds and mammals) that have the potential to 

consume chlorophacinone bait or chlorophacinone poisoned animals smaller than a prairie dog 

have RQs that exceed this LOC. Additionally, mammals that have the potential to consume 

chlorophacinone poisoned prairie dogs or larger granivorous prey items have RQs that exceed 

the acute listed species LOC. All of the 21 listed species are expected to have direct effects. The 

New Mexican ridge-nosed rattlesnake is the only species that is not expected to have direct 

98
effects based on survival; however, growth and reproductive effects to this species cannot be 

precluded in the absence of chronic data. Furthermore, direct effects to invertebrates based on 

reproductive effects are expected resulting in direct effects to the American burying beetle and 

the Salt Creek tiger beetle. 

5.2.1.a. Grizzly Bear 

The use of chlorophacinone to control BTPDs is LAA the grizzly bear because the RQ for 

exposure to chlorophacinone bait (75.42) exceeds the LOC (0.1) and significant exposure is 

likely to occur. The range of this species overlaps with the action area (BTPD habitat). Rozol 

Prairie Dog Bait application season for control of BTPDs overlaps periods during which grizzly 

bears are active and not hibernating. Although grizzly bears will be hibernating during most of 

this time. Chlorophacinone can be applied between October 1 and March 15 or spring green-up, 

whichever occurs later. Grizzly bears typically enter hibernation between October and 

December and exit their dens at some point between March and May. A single day exposure to 

chlorophacinone bait or prey items exposed to chlorophacinone bait is likely because grizzly 

bears range over very large areas (1,000 to 1,500 mi2

) that can include prairie dog towns and will 

feed opportunistically on items including chlorophacinone poisoned prey items or 

chlorophacinone bait. A grizzly bear would only need to consume 4 grams of bait to reach the 

LOC11. If a grizzly bear encounters an area where chlorophacinone is applied, it is highly likely 

that at least this amount of bait would be consumed. A grizzly bear is most likely to encounter a 

Rozol application area shortly before or after hibernation at which time the bear is engorging 

itself. This only increases the likelihood that the bait would be consumed. 

5.2.1.b. American Burying Beetle 

The use of chlorophacinone to control BTPDs is LAA the American burying beetle based on 

direct reproductive effects. The reproductive effects are due to lower carcass size in 

chlorophacinone treated carcasses and effects to larvae. An acute toxicity test for the earthworm 

(MRID 47383002) and an open literature study (Fisher et al. 2007) indicate that there is no risk 

to invertebrates at exposure levels relevant to this use. Furthermore, the second phase of the 

burying beetle study (MRID 47383001) that showed reproductive effects to burying beetles 

based on lower carcass weights showed that there were no direct acute effects to adult burying 

beetles fed chlorophacinone treated ground beef. In fact, those exposed to the chlorophacinone 

faired better than the control group. 

Chlorophacinone use is expected to affect reproduction of the American burying beetle through 

effects to emerged beetles. Number of emerged beetles is negatively affected by use of 

chlorophacinone poisoned carcasses in burying beetles (MRID 47383001). This type of effect is 

considered to be a direct effect. 

 

11 RQ for bait consumption = 75.42; dry weight ingestion rate = 3,077 g/day; Acute Listed Species LOC = 0.1. 

(3,077 g/day)/( 75.42)*0.1 = 4 g/day 

99
5.2.1.c. Salt Creek Tiger Beetle 

The use of chlorophacinone to control BTPDs is LAA the Salt Creek tiger beetle based on direct 

reproductive effects. The reproductive effects are due to lower carcass size in chlorophacinone 

treated carcasses and effects to larvae. An acute toxicity test for the earthworm (MRID 

47383002) and an open literature study (Fisher et al. 2007) indicate that there is no risk to 

invertebrates at exposure levels relevant to this use. Furthermore, the second phase of the 

burying beetle study (MRID 47383001) that showed reproductive effects to burying beetles 

based on lower carcass weights showed that there were no direct acute effects to adult burying 

beetles fed chlorophacinone treated ground beef. In fact, those exposed to the chlorophacinone 

faired better than the control group. 

Chlorophacinone use is expected to affect reproduction of the Salt Creek tiger beetle through 

effects to emerged beetles. Number of emerged beetles is negatively affected by use of 

chlorophacinone poisoned carcasses in burying beetles (MRID 47383001). Exposure can 

potentially occur in the larval stage through chlorophacinone insect residues. This type of effect 

is considered to be a direct effect. 

 

5.2.1.d. California Condor 

The use of chlorophacinone to control BTPDs is LAA the California condor. California condors 

are known to occur in four counties in Arizona as well as several counties in California. One of 

the four counties in Arizona where the California condor is known to occur, Apache County, is 

adjacent to a county in New Mexico in which BTPDs are known to occur, Catron County. It is 

conceivable since California condors are wide ranging species that they may prey on animals in 

an adjacent county. Although California condors typically prey on the carcasses of large 

mammals (cattle, sheep, deer, horses) they also have been known to prey on ground squirrels and 

other small to medium sized prey including coyotes, rabbits, foxes, weasels, rats, and pocket 

gophers. The California condor would have to consume 34 poisoned mice or almost two BTPDs 

every day for five days to reach the LOC12. Although consumption of 34 mice by a California 

condor is not likely, consumption of other exposed non-target granivores is more likely and can 

result in similar exposure. Additionally, consumption of two BTPD carcasses is likely if the 

condor finds a Rozol Prairie Dog Bait application site. Furthermore, effects including external 

bleeding, internal hemorrhaging and increased blood coagulation time were seen in secondary 

exposure studies to birds. Previous assessments have considered these effects analogous to 

lethality thereby supporting this LAA determination. Finally, growth and reproductive effects 

cannot be precluded due to the absence of chronic data. 

5.2.1.e. Whooping Crane 

The use of chlorophacinone to control BTPDs is LAA the whooping crane. Rozol Prairie Dog 

Bait application season for the control of BTPDs overlaps, spatially and temporally, with the fall 

 

12 RQ for non-target animal consumption = 0.104; RQ for BTPD consumption = 0.04; wet weight ingestion rate = 

709 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(709 g/day)/( 

RQ)*0.1]/[prey weight] = 34.2 mice or 1.8 BTPDs 

100
migration of the Aransas Wood Buffalo Population. Whooping cranes will eat waste agricultural 

grains during their migration, and therefore it can be expected that the grain-based 

chlorophacinone bait (on or close to the surface) would be consumed as well. The RQ for 

consumption of chlorophacinone grain bait (0.89) exceeds the LOC for endangered species (0.1). 

A whooping crane would need to eat 26 grams of bait to reach the LOC13. This is possible as the 

whooping crane’s ingestion rate (in grams dry weight/day) is 227 g/day. The LC50 on which this 

RQ is based is from a five day feeding study. Whooping cranes are likely to be migrating when 

they are exposed to chlorophacinone bait,. During migration, the cranes engorge themselves 

when they have the opportunity to feed. This only increases the likelihood that the bait will be 

consumed. According to the life history information whooping cranes also consume rodents. It 

was determined that a whooping crane would have to eat 23 poisoned mice or more than one 

poisoned BTPD every day for five days to reach the LOC14. This is possible based on the life 

history information. It is possible that the whooping crane could eat 23 mice per day. However, 

it seems unlikely that the whooping crane would eat more than one BTPD every day. 

Furthermore, effects including external bleeding, internal hemorrhaging and increased blood 

coagulation time were seen in secondary exposure studies to birds. Previous assessments have 

considered these effects analogous to lethality thereby supporting this LAA determination. 

Finally, reproductive effects cannot be precluded based on the absence of chronic data. 

5.2.1.f. Eskimo Curlew 

The use of chlorophacinone to control BTPDs is LAA the Eskimo curlew. The range of this 

species overlaps with BTPD habitat. Eskimo curlews prey on invertebrates which may be 

exposed to chlorophacinone bait. This assessment assumes invertebrates exposed to 

chlorophacinone will have the same maximum residue concentration as the deer mouse (5.8 mg 

a.i./kg-bw). The curlew would have to consume 149 grams of poisoned invertebrates every day 

for five days to reach the LOC15. The curlew’s ingestion rate is 155 g/day. Given this, it is 

possible that the Eskimo curlew would be exposed at levels exceeding the LOC. Furthermore, 

effects including external bleeding, internal hemorrhaging and increased blood coagulation time 

were seen in secondary exposure studies to birds. Previous assessments have considered these 

effects analogous to lethality thereby supporting this LAA determination. Finally, reproductive 

effects cannot be precluded based on the absence of chronic data. 

5.2.1.g. Northern Aplomado Falcon 

The use of chlorophacinone to control BTPDs is LAA the northern Aplomado falcon. The range 

of this species overlaps with BTPD habitat. Northern Aplomado falcons prey on birds and 

rodents which may be exposed to chlorophacinone bait. The falcon would have to consume 5 

 

13 RQ for bait consumption = 0.89; dry weight ingestion rate = 227 g/day; Acute Listed Species LOC = 0.1. (227 

g/day)/( 0.89)*0.1 = 25.5 g/day 

14 RQ for non-target animal consumption = 0.104; RQ for BTPD consumption = 0.04; wet weight ingestion rate = 

470 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(470 g/day)/( 

RQ)*0.1]/[prey weight] = 22.6 mice or 1.2 BTPDs 

15 RQ for invertebrate consumption = 0.104; wet weight ingestion rate = 155 g/day; Acute Listed Species LOC = 

0.1. (155 g/day)/(0.104)*0.1 = 149 g/day 

101
poisoned mice or less than one BTPD to reach the LOC16. According to life history information 

the average weight of their preferred prey (birds) is around 67 grams. The majority of the birds 

weighed less than 100 grams. However, falcons are capable of taking larger prey with weights 

around 300-570 grams. Based on this information it seems unlikely but possible that a falcon 

would prey on a prairie dog but they may consume mice. Given this, it is possible that the 

northern Aplomado falcon would be exposed at levels exceeding the LOC. Furthermore, effects 

including external bleeding, internal hemorrhaging and increased blood coagulation time were 

seen in secondary exposure studies to birds. Previous assessments have considered these effects 

analogous to lethality thereby supporting this LAA determination. Finally, reproductive effects 

cannot be precluded based on the absence of chronic data. 

5.2.1.h. Black Footed Ferret 

The use of chlorophacinone to control BTPDs is LAA black footed ferrets. The black footed 

ferret RQs (7.45 for exposure to BTPDs and 19.29 for exposure to non-target animals) exceed 

the LOC for endangered species (0.1). Exposure is likely considering the black footed ferret 

predominantly preys on prairie dogs. The Rozol Prairie Dog Bait label indicates that the 

“product [is not to be used] within prairie dog towns in the range of the black-footed ferret 

without first contacting endangered species specialists at a U.S. Fish and Wildlife Service.” 

However, if chlorophacinone was used in a BTPD town near black-footed ferrets there would be 

direct effects to the black-footed ferret. The black-footed ferret would need to eat less than one 

poisoned BTPD or one poisoned mouse to reach the LOC17. 

5.2.1.i. Chiricahua Leopard Frog 

The use of chlorophacinone to control BTPDs is LAA the Chiricahua leopard frog. The range of 

this species overlaps with BTPD habitat. Chiricahua leopard frog prey on invertebrates which 

may be exposed to chlorophacinone bait. This assessment assumes many types of insects 

exposed to chlorophacinone will have the same maximum residue concentration as the deer 

mouse (5.8 mg a.i./kg-bw). The Chiricahua leopard frog would have to consume 78 grams of 

poisoned invertebrates every day for five days to reach the LOC18. The Chiricahua leopard 

frog’s ingestion rate is 81 g/day. Given this, it is possible that the Chiricahua leopard frog would 

be exposed at levels exceeding the LOC. Furthermore, effects including external bleeding, 

internal hemorrhaging and increased blood coagulation time were seen in secondary exposure 

studies to birds. Previous assessments have considered these effects analogous to lethality 

thereby supporting this LAA determination. Finally, reproductive effects cannot be precluded 

based on the absence of chronic data. Herptiles are assessed using avian toxicity data; therefore, 

these results are relevant to the Chiricahua leopard frog. 

 

16 RQ for non-target animal consumption = 0.104; RQ for BTPD consumption = 0.04; wet weight ingestion rate = 

102 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(102 g/day)/( 

RQ)*0.1]/[prey weight] = 4.9 mice or 0.3 BTPDs 

17 RQ for non-target animal consumption = 19.29; RQ for BTPD consumption = 7.45; wet weight ingestion rate = 

147.84 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(148 g/day)/( 

RQ)*0.1]/[prey weight] = 0.04 mice or 0.002 BTPDs 

18 RQ for invertebrate consumption = 0.104; wet weight ingestion rate = 81 g/day; Acute Listed Species LOC = 0.1. 

(81 g/day)/(0.104)*0.1 = 78 g/day 

102
5.2.1.j. Jaguar 

The use of chlorophacinone to control BTPDs is LAA the jaguar. Jaguars are known to occur in 

three counties in Arizona as well as one county in New Mexico. The county in New Mexico, 

Hidalgo County, where the jaguar is known to occur is also a county in which BTPDs are known 

to occur. Although jaguars typically prey on javelina (a wild boar), deer, and livestock, they also 

have been known to prey on large rodents including capybaras and paca as well as armadillos 

and caimans. They have also been known to take various species of turtles, birds, and fish. 

Thus, although it is unlikely, it is possible that a jaguar might take a poisoned BTPD. The jaguar 

would have to consume less than one poisoned mouse or less than one poisoned BTPD every day 

for five days to reach the LOC19. Although there is evidence in the life history that they forage 

on rodents, the rodents that they tend to consume are much larger than a BTPD (e.g. capybara 

and paca, both weighing more than 20 pounds). However, it is possible that a jaguar could 

consume poisoned BTPDs. Although, it seems unlikely that a jaguar would feed on a BTPD 

every day for a five day period, if a jaguar encountered a chlorophacinone poisoned BTPD town, 

consumption at this level could possibly occur. 

5.2.1.k. Gulf Coast Jaguarundi 

The use of chlorophacinone to control BTPDs is LAA the Gulf Coast jaguarundi. The Gulf 

Coast jaguarundi occurs in the southern part of Texas but is known to occur in counties as far 

north in Texas as Atascosa County. Atascosa County is adjacent to Bexar County, Texas in 

which BTPDs are known to occur. It is conceivable that the Gulf Coast jaguarundi may prey on 

animals in an adjacent county. Jaguarundis typically prey on small mammals, birds, and reptiles. 

Stomach contents have included: lizards, rodents (mice and rats), small birds, and cottontail 

rabbits, and grass. The Gulf Coast jaguarundi would have to consume less than one poisoned 

mouse or less than one poisoned BTPD every day for five days to reach the LOC20. 

Consumption at this level could reasonably occur. 

5.2.1.l. Canada Lynx 

The use of chlorophacinone to control BTPDs is LAA the Canada lynx. The range of this 

species overlaps with BTPD habitat. Canada lynx typically prey on the snowshow hare but have 

also been known to prey opportunistically on small mammals and birds. Other prey may include 

rodents and fish and lynx may also prey on ungulates. The Canada lynx would have to consume 

less than one poisoned mouse or less than one poisoned BTPD every day for five days to reach 

the LOC21. There is evidence in the life history that the Canada lynx forages on small to 

 

19 RQ for non-target animal consumption = 32.85; RQ for BTPD consumption = 12.69; wet weight ingestion rate = 

4119 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(4119 g/day)/( 

RQ)*0.1]/[prey weight] = 0.6 mice or 0.03 BTPDs 

20 RQ for non-target animal consumption = 23.82; RQ for BTPD consumption = 9.2; wet weight ingestion rate = 

739 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(739 g/day)/( 

RQ)*0.1]/[prey weight] = 0.2 mice or 0.008 BTPDs 

21 RQ for non-target animal consumption = 23.3; RQ for BTPD consumption = 9.0; wet weight ingestion rate = 819 

g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(819 g/day)/( 

RQ)*0.1]/[prey weight] = 0.2 mice or 0.009 BTPDs 

103
medium size prey and further it seems possible that they could consume one BTPD every day 

five da

for 

ys. 

 

5.2.1.m. Preble’s Meadow Jumping Mouse 

The use of chlorophacinone to control BTPDs is LAA the Preble’s meadow jumping mouse. 

The range of this species overlaps with BTPD habitat. Rozol Prairie Dog Bait application season 

for the control for BTPDs overlaps periods during which the Preble’s meadow jumping mouse is 

active and not hibernating. However, Preble’s meadow jumping mice will be hibernating during 

most of this time. Chlorophacinone can be applied between October 1 and March 15 or spring 

green-up, whichever occurs later. Preble’s meadow jumping mice typically enter hibernation 

between late August and October and come out of hibernation in May. Based on the life history 

information it seems reasonable that the Preble’s meadow jumping mouse could be exposed to 

the chlorophacinone bait. A Preble’s meadow jumping mouse would have to eat less than one 

grain of Rozol Prairie Dog Bait per day for five days to reach the LOC22. It is possible that a 

Preble’s meadow jumping mouse could consume this amount of bait. The Preble’s meadow 

jumping mouse is most likely to encounter a Rozol application area shortly before or after 

hibernation at which time the mouse is engorging itself. This only increases the likelihood that 

the bait would be consumed. 

5.2.1.n. Ocelot 

The use of chlorophacinone to control BTPDs is LAA the ocelot. The ocelot occurs in the 

southern part of Texas but is known to occur in counties as far north in Texas as Atascosa 

County. Atascosa County is adjacent to Bexar County, Texas in which BTPDs are known to 

occur. It is conceivable since the ocelot is a wide ranging species that they may prey on animals 

in an adjacent county. Ocelots typically prey on small to medium-sized mammals (rabbits, 

agoutis, and mice), birds, reptiles (snakes and lizards), fish, and invertebrates. Ocelots would 

have to consume less than one poisoned mouse or less than one poisoned BTPD every day for 

five days to reach the LOC23. There is evidence in the life history that they forage on mice and if 

it were intoxicated and easily captured, a BTPD could be a prey item as well. It is possible that 

they would consume a mouse or BTPD every day for five days. 

5.2.1.o. Mexican Spotted Owl 

The use of chlorophacinone to control BTPDs is LAA the Mexican spotted owl. The range of 

this species overlaps with the BTPD habitat. Mexican spotted owls typically prey on small- and 

medium-sized rodents including woodrats, peromyscid mice, and microtine voles. They also eat 

bats, birds, reptiles, and arthropods. The Mexican spotted owl would have to consume almost 

22 RQ for bait consumption = 41.35; dry weight ingestion rate = 1.94 g/day; mass of one grain = 0.2 g; Acute Listed 

Species LOC = 0.1; [(1.94 g/day)/(41.35)*0.1]/(0.2 g) = 0.02 grain 

23 RQ for non-target animal consumption = 26.96; RQ for BTPD consumption = 10.41; wet weight ingestion rate = 

1576 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(1576 g/day)/( 

RQ)*0.1]/[prey weight] = 0.3 mice or 0.02 BTPDs 

104
six poisoned mice or less than one poisoned BTPD every day for five days to reach the LOC24. 

There is evidence in the life history that they forage on small to medium size prey. However, 

based on the Mexican spotted owl’s ingestion rate (41 g/day), it seems unlikely that they would 

consume 20 mice or one BTPD every day for five days. Nonetheless, lacking avian reproduction 

data, risk cannot be precluded at any dose level. Furthermore, effects including external 

bleeding, internal hemorrhaging and increased blood coagulation time were seen in secondary 

exposure studies to birds. Previous assessments have considered these effects analogous to 

lethality thereby supporting this LAA determination. 

5.2.1.p. Piping Plover 

The use of chlorophacinone to control BTPDs is LAA the piping plover. The range of this 

species overlaps with BTPD habitat. Piping plover prey on invertebrates which may be exposed 

to chlorophacinone bait. This assessment assumes invertebrates exposed to chlorophacinone will 

have the same maximum residue concentration as the deer mouse (5.8 mg a.i./kg-bw). The 

piping plover would have to consume 44 grams of poisoned invertebrates every day for five days 

to reach the LOC25. The piping plover’s ingestion rate is 46 g/day. Given this, it is possible that 

the piping plover would be exposed at levels exceeding the LOC. Furthermore, effects including 

external bleeding, internal hemorrhaging and increased blood coagulation time were seen in 

secondary exposure studies to birds. Previous assessments have considered these effects 

analogous to lethality thereby supporting this LAA determination. Finally, reproductive effects 

cannot be precluded at any exposure level in the absence of chronic data. 

5.2.1.q. New Mexican Ridge-nosed Rattlesnake 

The use of chlorophacinone to control BTPDs is LAA the New Mexican ridge-nosed rattlesnake. 

The RQ does not exceed the LOC for the New Mexican ridge-nosed rattlesnake. See Section 

5.1.1.a above for the rationale. However, direct growth and reproductive effects cannot be 

precluded in the absence of avian reproduction data. Furthermore, effects including external 

bleeding, internal hemorrhaging and increased blood coagulation time were seen in secondary 

exposure studies to birds. Previous assessments have considered these effects analogous to 

lethality thereby supporting this LAA determination. Herptiles are assessed using avian toxicity 

data, therefore, these results are relevant to the New Mexican ridge-nosed rattlesnake. 

5.2.1.r. Sonora Tiger Salamander 

The use of chlorophacinone to control BTPDs is LAA the Sonora tiger salamander. The range of 

this species is adjacent to the BTPD habitat. Sonora tiger salamanders are known to occur in two 

counties in Arizona (Cochise and Santa Cruz counties). One of the two counties in Arizona 

where the Sonora tiger salamander is known to occur, Cochise County, is adjacent to a county in 

New Mexico in which BTPDs are known to occur, Hidalgo County. Metamorphosed Sonora 

 

24 RQ for non-target animal consumption = 0.104; RQ for BTPD consumption = 0.04; wet weight ingestion rate = 

118 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(118 g/day)/( 

RQ)*0.1]/[prey weight] = 5.6 mice or 0.4 BTPDs 

25 RQ for invertebrate consumption = 0.104; wet weight ingestion rate = 46 g/day; Acute Listed Species LOC = 0.1. 

(46 g/day)/(0.104)*0.1 = 44 g/day 

105
tiger salamanders prey on terrestrial insects and other macroinvertebrates which may be exposed 

to chlorophacinone bait. This assessment assumes invertebrates exposed to chlorophacinone will 

have the same maximum residue concentration as the deer mouse (5.8 mg a.i./kg-bw). The 

Sonora tiger salamander would have to consume 50 grams of poisoned invertebrates every day 

for five days to reach the LOC26. The Sonora tiger salamander’s ingestion rate is 52 g/day. 

Given this, it is possible that the Sonora tiger salamander would be exposed at levels exceeding 

the LOC. Lacking avian reproduction data, risk cannot be precluded at any dose level. 

Furthermore, effects including external bleeding, internal hemorrhaging and increased blood 

coagulation time were seen in secondary exposure studies to birds. Previous assessments have 

considered these effects analogous to lethality thereby supporting this LAA determination. 

Herptiles are assessed using avian toxicity data; therefore, these results are relevant to the Sonora 

tiger salamander. 

5.2.1.s. Black-capped Vireo 

The use of chlorophacinone to control BTPDs is LAA the black-capped vireo. The range of this 

species overlaps with BTPD habitat. Black-capped vireos prey on invertebrates, primarily 

beetles and caterpillars, which may be exposed to chlorophacinone bait. This assessment 

assumes invertebrates exposed to chlorophacinone will have the same maximum residue 

concentration as the deer mouse (5.8 mg a.i./kg-bw). The black-capped vireo would have to 

consume 16.3 grams of poisoned invertebrates every day for five days to reach the LOC27. The 

black-capped vireo’s ingestion rate is 16.9 g/day. Given this, it is possible that the black-capped 

vireo would be exposed at levels exceeding the LOC. Furthermore, effects including external 

bleeding, internal hemorrhaging and increased blood coagulation time were seen in secondary 

exposure studies to birds. Previous assessments have considered these effects analogous to 

lethality thereby supporting this LAA determination. Finally, reproductive effects cannot be 

precluded at any exposure level in the absence of chronic data. 

5.2.1.t. Golden-Cheeked Warbler 

The use of chlorophacinone to control BTPDs is LAA the golden-cheeked warbler. The range of 

this species overlaps with BTPD habitat. Golden-cheeked warblers prey on invertebrates (e.g. 

insects, spiders and caterpillars) which may be exposed to chlorophacinone bait. This 

assessment assumes invertebrates exposed to chlorophacinone will have the same maximum 

residue concentration as the deer mouse (5.8 mg a.i./kg-bw). The golden-cheeked warbler would 

have to consume 17.4 grams of poisoned invertebrates every day for five days to reach the 

LOC28. The golden-cheeked warbler’s ingestion rate is 18.1 g/day. Given this, it is possible that 

the golden-cheeked warbler would be exposed at levels exceeding the LOC. Lacking avian 

reproduction data, risk cannot be precluded at any dose level. Furthermore, effects including 

external bleeding, internal hemorrhaging and increased blood coagulation time were seen in 

 

26 RQ for invertebrate consumption = 0.104; wet weight ingestion rate = 52 g/day; Acute Listed Species LOC = 0.1. 

(52 g/day)/(0.104)*0.1 = 50 g/day 

27 RQ for invertebrate consumption = 0.104; wet weight ingestion rate = 16.9 g/day; Acute Listed Species LOC = 

0.1. (16.9 g/day)/(0.104)*0.1 = 16.3 g/day 

28 RQ for invertebrate consumption = 0.104; wet weight ingestion rate = 18.1 g/day; Acute Listed Species LOC = 

0.1. (16.9 g/day)/(0.104)*0.1 = 17.4 g/day 

106
secondary exposure studies to birds. Previous assessments have considered these effects 

analogous to lethality thereby supporting this LAA determination. 

5.2.1.u. Gray Wolf 

The use of chlorophacinone to control BTPDs is LAA the gray wolf. The range of this species 

overlaps with the BTPD habitat. Although gray wolves typically prey on white-tailed deer, mule 

deer, moose, elk, caribou, bison, muskox, bighorn sheep, Dall sheep, mountain goat, beaver, and 

snowshoe hare. Small mammals, birds, and large invertebrates are sometimes also taken. The 

gray wolf would have to consume less than one poisoned mouse or less than one poisoned BTPD 

every day for five days to reach the LOC29. There is evidence in the life history that the gray 

wolf forages on small to medium size prey and further it seems possible that they could consume 

mice and/or BTPDs over a five day period. 

5.2.2. Indirect Effects to Listed Species 

The use of chlorophacinone to control BTPDs is LAA the grizzly bear, American burying beetle, 

whooping crane, Eskimo curlew, northern Aplomado falcon, black-footed ferret, Chiricahua 

leopard frog, Preble’s meadow jumping mouse, New Mexican ridge-nosed rattlesnake, and the 

gray wolf with respect to indirect effects. The potential for indirect effects comes from loss of 

prey base (BTPDs or other exposed non-target animal populations) and loss of habitat (BTPD 

burrows). 

Grizzly bears, American burying beetles, whooping cranes, northern Aplomado falcons, blackfooted ferrets, Chiricahua leopard frog, New Mexican ridge-nosed rattlesnakes, and gray wolves 

have potential to prey upon BTPDs and/or other non-target exposed mammals affected by 

chlorophacinone. Effects to individuals have been demonstrated in mammals ranging in size 

from 13 g to 36,363 g with RQs ranging from 19 to 41. The Agency does not currently have a 

method to extrapolate risk from individuals to a prey-base level effect. In the absence of this 

level of analysis, risk cannot be precluded and effects to mammalian prey bases are presumed. 

For this prey-base level effect, use of chlorophacinone to control BTPDs is LAA. 

American burying beetles, whooping cranes, northern Aplomado falcons, black-footed ferrets, 

New Mexican ridge-nosed rattlesnakes, and gray wolves have potential to prey upon birds or 

herptiles affected by chlorophacinone. The diet based RQ for birds consuming chlorophacinone 

bait is 0.89. This RQ exceeds the endangered species Acute Risk LOC and effects to individuals 

are, therefore, expected. The Agency does not currently have a method to extrapolate risk from 

individuals to a prey-base level effect. In the absence of this level of analysis, risk cannot be 

precluded and effects to avian and herptile prey bases are presumed. For this prey-base level 

effect, use of chlorophacinone to control BTPDs is LAA. 

 

29 RQ for non-target animal consumption = 24.82; RQ for BTPD consumption = 9.59; wet weight ingestion rate = 

2311 g/day; BTPD weight = 1000 g; mouse weight = 20 g; Acute Listed Species LOC = 0.1. [(2311 g/day)/( 

RQ)*0.1]/[prey weight] = 0.5 mice or 0.02 BTPDs 

107
Those species that consume invertebrates (i.e. American burying beetle, whooping crane, 

Eskimo curlew, northern Aplomado falcon, black-footed ferret, Chiricahua leopard frog, Preble’s 

meadow jumping mouse, New Mexican ridge-nosed rattlensnake, and the gray wolf) may have 

indirect effects from a loss of their invertebrate prey base because larvae consuming 

chlorophacinone residues have reproductive effects (MRID 47383001). The Agency does not 

currently have a method to extrapolate risk from individuals to a prey-base level effect. In the 

absence of this level of analysis, risk cannot be precluded and effects to invertebrate prey bases 

are presumed. For this prey-base level effect, use of chlorophacinone to control BTPDs is LAA. 

There are indirect effects to the black footed ferret due to habitat (burrow) loss. The blackfooted ferret is a prairie dog obligate species (USFWS, 1988). It has been known to take 

advantage of prairie dog burrows for shelter and travel, and “may modify prairie dog burrows for 

its own use” (Nowak, 1999). 

 

5.2.3. Modification of Designated Critical Habitat 

5.2.3.a. Potential Areas of MA Effect - Overlap or Adjacent BTPD 

Habitat and Occurrence of the Assessed Listed Species 

This assessment analyzes the use of chlorophacinone grain bait to control BTPDs. As a result, 

the action area was identified as the range of the BTPD obtained from NatureServe. The initial 

area of concern is defined as all land cover types within the range of the BTPD. Appendix A

provides an overview of where the action area overlaps with species range as described in 

Section 2.5. Only species with habitat that overlapped or were found in adjacent counties (direct 

effects only) with the BTPD habitat were included in this assessment. For habitat modification 

and prey base effects, adjacent counties were not considered. 

Pesticide exposures and predicted risks to the species and its resources (i.e., food and habitat) are 

not expected to be uniform across the action area since BTPDs are not uniformly distributed 

across action area. 

5.3. Effects Determinations Summary 

The Agency makes a may affect, and likely to adversely affect determination for the grizzly 

bear, American burying beetle, Salt Creek tiger beetle, whooping crane, Eskimo curlew, northern 

Aplomado falcon, black-footed ferret, Chirichaua leopard frog, jaguar, Gulf Coast jaguarundi, 

Canada lynx, Preble’s meadow jumping mouse, ocelot, Mexican spotted owl, piping plover, New 

Mexican ridge-nosed rattlesnake, Sonora tiger salamander, black-capped vireo, golden-cheeked 

warbler, and the gray wolf and a habitat modification determination for the Salt Creek tiger 

beetle, whooping crane, Canada lynx, Preble’s meadow jumping mouse, Mexican spotted owl, 

piping plover, and New Mexican ridge-nosed rattlesnake. The California condor and gray wolf 

are not included in the list of species for which habitat modification was determined because the 

critical habitat for these species do not overlap with the BTPD range. 

108
5.3.1. Addressing the Risk Hypotheses 

In order to conclude this risk assessment, it is necessary to address the risk hypotheses defined in 

Section 2.9.1. Based on the conclusions of this assessment, all four hypotheses represent 

concerns in terms of direct and indirect effects of chlorophacinone on some of the listed assessed 

species and their designated critical habitat. 

The labeled use of chlorophacinone for BTPDs within the action area will: 

• directly affect listed species by causing mortality or by adversely affecting growth or 

reproduction through primary exposure to/consumption of chlorophacinone bait; 

• directly affect listed species by causing mortality or by adversely affecting growth or 

reproduction through secondary exposure to chlorophacinone poisoned animals, BTPDs 

and other non-target animals, and/or carcasses. 

• indirectly affect listed species and/or modify their designated critical habitat by reducing 

or changing the composition of their food supply; 

• indirectly affect listed species and/or modify their designated critical habitat by reducing 

populations of BTPDs which provide burrows for shelter 

6. Uncertainties 

This section describes uncertainties specific to this assessment. 

6.1. Exposure Assessment Uncertainties 

6.1.1. Maximum Use Scenario

The screening-level risk assessment focuses on characterizing potential ecological risks resulting 

from a maximum use scenario, which is determined from labeled statements of maximum 

application rate and number of applications with the shortest time interval between applications. 

The frequency at which actual uses approach this maximum use scenario may be dependant on 

pest resistance, timing of applications, cultural practices, and market forces. 

6.1.2. Usage Uncertainties 

Usage data is unavailable for chlorophacinone though anecdotal evidence and the breadth of the 

registrant’s advertising campaign indicate that use is highly prevalent. Uncertainty regarding 

intensity of chlorophacinone use affects exposure to species of concern with expansive ranges 

(e.g. grizzly bear, California condor, whooping crane, jaguar, Gulf Coast jaguarundi, Canada 

lynx, piping plover, ocelot, black-capped vireo, golden-cheeked warbler, and the gray wolf). 

Whether chlorophacinone is used on one prairie dog town within a given animal’s range or many 

will influence the probability that the animal is affected. To account for this uncertainty, RQs 

109
are based on a food intake of 100% chlorophacinone grain bait and/or chlorophacinone-poisoned 

carcasses. 

6.2. Effects Assessment Uncertainties 

6.2.1. Data Gaps and Uncertainties 

Data gaps include: 

• Avian reproduction study for chlorophacinone (guideline 850.2300). 

• Terrestrial field study for use of chlorophacinone bait to control BTPDs (guideline 

850.2500 in conjunction with protocol discussions). 

Due to these data gaps, risk cannot be precluded to birds and exposure cannot be fully 

characterized. 

6.2.2. Carcass Residue Concentration 

All carcass residue concentration data discussed in this assessment is based on animals that have 

been fed chlorophacinone bait to mortality. Determining residue concentrations at mortality 

does not necessarily capture the highest concentration. Metabolism of toxicants can continue for 

a period of time post-mortem, therefore, residue concentrations are likely highest just prior to or 

concurrent with animal mortality. Poisoned prey items are highly vulnerable to predation before 

succumbing to anticoagulant poisoning. Given this, listed predators and scavengers may be 

exposed to higher residue concentrations than are reflected in carcass residue studies. To 

account for this uncertainty, the highest whole body concentration was used to characterize 

prairie dog chlorophacinone concentrations and the highest relevant concentration was used to 

characterize residue concentrations in non-target granivores. 

6.2.3. Sublethal Effects 

When assessing acute risk, the screening risk assessment relies on the acute mortality endpoint as 

well as a suite of sublethal responses to the pesticide, as determined by the testing of species 

response to chronic exposure conditions and subsequent chronic risk assessment. Consideration 

of additional sublethal data in the effects determination is exercised on a case-by-case basis and 

only after careful consideration of the nature of the sublethal effect measured and the extent and 

quality of available data to support establishing a plausible relationship between the measure of 

effect (sublethal endpoint) and the assessment endpoints. However, the full suite of sublethal 

effects from valid open literature studies is considered for characterization purposes, including 

defining the action area. 

Though no mortalities were reported in the raptor feeding studies, sublethal effects were 

indicated that could affect the likelihood of survival in the wild. These sublethal effects were 

external bleeding, internal hemorrhaging and increased blood coagulation time. Incidents 

involving a bald eagle, a ferruginous hawk, and a great horned owl indicate the potential for 

110
chlorophacinone poisoning to cause mortality or contribute to mortality of predatory birds. 

Sublethal effects are also seen in mammals. 

7. Risk Conclusions 

In fulfilling its obligations under Section 7(a)(2) of the Endangered Species Act, the information 

presented in this endangered species risk assessment represents the best data currently available 

to assess the potential risks of chlorophacinone to the all listed species and their designated 

critical habitat in the action area for registered uses of Rozol Prairie Dog Bait (EPA registration 

number 7173-286). 

Based on the best available information, the Agency makes a Likely to Adversely Affect

determination for the following species: grizzly bear, American burying beetle, Salt Creek tiger 

beetle, California condor, whooping crane, Eskimo curlew, northern Aplomado falcon, blackfooted ferret, Chirichaua leopard frog, jaguar, Gulf Coast jaguarundi, Canada lynx, Preble’s 

meadow jumping mouse, ocelot, Mexican spotted owl, piping plover, New Mexican ridge-nosed 

rattlesnake, Sonora tiger salamander, black-capped vireo, golden-cheeked warbler, and the gray 

wolf from the use of chlorophacinone to control BTPDs. Additionally, the Agency has 

determined that there is the potential for modification of habitat for the following species with 

designated critical habitat: Salt Creek tiger beetle, whooping crane, Canada lynx, Preble’s 

meadow jumping mouse, Mexican spotted owl, piping plover, and the New Mexican ridge-nosed 

rattlesnake. 

A summary of the risk conclusions and effects determinations for the listed species and their 

critical habitat, given the uncertainties discussed in Section 6, is presented in Table 7.1. and 

Table 7.2. 

111
Table 7.1 Effects Determination Summary for Effects of Chlorophacinone to 21 

Endangered Species. 

Basis for Determination Species Effects 

Determination Direct Effects Indirect Effects 

Grizzly bear LAA1

Direct effects are expected for the grizzly 

bear based on the potential for this species 

to consume the chlorophacinone bait (RQ 

of 75.42 which exceeds the LOC of 0.1) or 

other prey items that may have consumed 

the chlorophacinone bait (RQ of 3.38 for 

exposure to BTPDs and RQ of 8.75 for 

exposure to non-target animals, both 

which exceed the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data; however, growth and reproductive 

effects are not expected because mortality 

typically occurs as a result of acute 

exposure. 

Indirect effects from the loss of the 

prey base are also expected because 

effects to individuals within 

populations have been demonstrated 

in mammals ranging in size from 13 

to 36,363 grams with RQ ranging 

from 19 to 41. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

American 

burying beetle LAA 

Reproductive effects are expected for the 

American burying beetle. The American 

burying beetle uses mammalian and avian 

carcasses as a food resource during their 

reproduction cycle. Dosed carcasses 

negatively affected number of emerged 

beetles (MRID 47383001). 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Salt creek tiger 

beetle LAA 

Reproductive effects are expected for the 

Salt Creek tiger beetle. Salt Creek tiger 

beetle larvae are potentially exposed to 

chlorophacinone residues through 

chlorophacinone exposed terrestrial 

invertebrates. Dosed carcasses in a 

burying beetle study negatively affected 

number of emerged beetles (MRID 

47383001). Similar affects are expected 

for the Salt Creek tiger beetle. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. This species uses 

mud banks of streams and seeps in 

association with saline wetlands and 

exposed mud flats of saline wetlands 

which is distinct from the short grass 

prairie associated with BTPD habitat. 

No indirect effects from habitat loss 

are expected because this species 

does not use BTPD burrows. 

California 

condor LAA 

Direct effects to the California condor are 

expected through their potential exposure 

to prey items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals which 

exceeds the LOC of 0.1). Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data. 

No indirect effects from the loss of 

prey base are expected because this 

species’ range does not overlap with 

the BTPD range. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Whooping crane LAA 

Direct effects to the whooping crane are 

expected to occur based on the potential 

for this species to consume the 

chlorophacinone bait (RQ of 0.89 which 

exceeds the LOC of 0.1) or other prey 

items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

112
exposure to non-target animals which 

exceeds the LOC of 0.1). Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data. 

because this species does not use 

BTPD burrows. 

Eskimo curlew LAA 

Direct effects to the Eskimo curlew are 

expected to occur based on the potential 

for this species to consume prey items that 

have consumed the chlorophacinone bait 

(RQ of 0.104 for exposure to non-target 

animals, which is used as a surrogate for 

invertebrate prey, which exceeds the LOC 

of 0.1). Growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in terrestrial invertebrates. No 

indirect effects from habitat loss are 

expected because this species does 

not use BTPD burrows. 

Northern 

Aplomado 

falcon 

LAA 

Direct effects to the northern Aplomado 

falcon are expected through their potential 

exposure to prey items that may have 

consumed the chlorophacinone bait (RQ 

of 0.104 for exposure to non-target 

animals which exceeds the LOC of 0.1). 

Growth and reproductive effects cannot be 

precluded due to the absence of chronic 

data 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Black-footed 

ferret LAA 

Direct effects are expected for the blackfooted ferret based on the potential for this 

species to consume prey items that may 

have consumed the chlorophacinone bait 

(RQ of 7.45 for exposure to BTPDs and 

RQ of 19.29 for exposure to non-target 

animals, both which exceed the LOC of 

0.1). Significant exposure is expected to 

occur because black-footed ferrets prey 

primarily on BTPDs. Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data; 

however, growth and reproductive effects 

are not expected because mortality 

typically occurs as a result of acute 

exposure. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. In addition, this 

species preys almost exclusively on 

BTPDs. Indirect effects from habitat 

loss are expected because this species 

uses BTPD burrows. 

Chirichaua 

leopard frog LAA 

Direct effects to the Chirichaua leopard 

frog are expected to occur based on the 

potential for this species to consume prey 

items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals, which is 

used as a surrogate for invertebrate prey, 

which exceeds the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in terrestrial invertebrates and birds. 

No indirect effects from habitat loss 

are expected because this species 

does not appear to use BTPD 

burrows. 

Jaguar LAA 

Direct effects are expected for the jaguar 

based on the potential for this species to 

consume prey items that may have 

consumed the chlorophacinone bait (RQ 

of 12.69 for exposure to BTPDs and RQ 

of 32.85 for exposure to non-target 

No indirect effects from the loss of 

the prey base are expected because 

this species’ habitat is distinct from 

the BTPD habitat. Jaguars – 

particularly males of the northern 

reaches – are known to have large 

113
animals, both which exceed the LOC of 

0.1). Growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data; however, growth and 

reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

home ranges that encompass a 

variety of plant communities, 

including: Maderan evergreenwoodland, subalpine conifer forest, 

semidesert shrubland, and Sonoran 

desert scrub. Washes and riparian 

areas with dense vegetative growth 

may also be valuable movement 

corridors. These habitats are distinct 

from the short grass prairie 

associated with BTPD habitat. No 

indirect effects from habitat loss are 

expected because this species does 

not use BTPD burrows. 

Gulf Coast 

jaguarundi LAA 

Direct effects are expected for the Gulf 

Coast jaguarundi based on the potential 

for this species to consume prey items that 

may have consumed the chlorophacinone 

bait (RQ of 9.20 for exposure to BTPDs 

and RQ of 23.82 for exposure to nontarget animals, both which exceed the 

LOC of 0.1). Growth and reproductive 

effects cannot be precluded due to the 

absence of chronic data; however, growth 

and reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

No indirect effects from the loss of 

the prey base are expected because 

this species’ habitat is distinct from 

the BTPD habitat. This species is 

found in chaparral plant communities 

and dense brushy areas near streams 

and rivers which are distinct from the 

short grass prairie associated with 

BTPD habitat. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Canada lynx LAA 

Direct effects to the Canada lynx are 

expected to occur based on the potential 

for this species to consume prey items that 

may have consumed the chlorophacinone 

bait (RQ of 23.30 for exposure to nontarget animals and RQ of 9.00 for 

exposure to BTPDs both of which exceed 

the LOC of 0.1). Growth and reproductive 

effects cannot be precluded due to the 

absence of chronic data; however, growth 

and reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. The Canada lynx is 

associated with the southern, 

transitional reaches of the cool and 

moist boreal forest. Where it occurs 

at these lower latitudes, the boreal 

forest forms a mixed conifer and 

conifer-hardwood landscape. These 

habitat areas are distinct from the 

short grass prairie associated with 

BTPD habitat. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Preble’s 

meadow 

jumping mouse 

LAA 

Direct effects to the Preble’s meadow 

jumping mouse are expected to occur 

based on the potential for this species to 

consume the chlorophacinone bait (RQ of 

41.35 which exceeds the LOC of 0.1). 

Growth and reproductive effects cannot be 

precluded due to the absence of chronic 

data; however, growth and reproductive 

effects are not expected because mortality 

typically occurs as a result of acute 

exposure. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in terrestrial invertebrates. Although 

this species makes nests both above 

and below ground. It does not appear 

to use other species’ burrows. 

Ocelot LAA Direct effects are expected for the ocelot 

based on the potential for this species to 

No indirect effects from loss of prey 

base are expected because this 

114
consume prey items that have may 

consumed the chlorophacinone bait (RQ 

of 10.41 for exposure to BTPDs and RQ 

of 26.96 for exposure to non-target 

animals, both which exceed the LOC of 

0.1). Growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data; however, growth and 

reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

species’ habitat is distinct from 

BTPD habitat. Ocelots appear to use 

areas of dense cover, and in the 

northern part of the range hunt in 

brushy forests and semi-arid deserts. 

In the southern part of its range, 

ocelot habitat includes tropical 

forests, mountain slopes, and pampas 

(grasslands). These habitat areas are 

distinct from the short grass prairie 

associated with BTPD habitat. No 

indirect effects from habitat loss are 

expected because this species does 

not use BTPD burrows. 

Mexican spotted 

owl LAA 

Direct effects to the Mexican spotted owl 

are expected to occur based on the 

potential for this species to consume prey 

items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals which 

exceeds the LOC of 0.1). Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. Mexican spotted owls 

are found in old-growth or mature 

forests with unevenly aged stands of 

trees, high canopy, multi-storied 

levels, and high tree density as well 

as canyons with riparian or conifer 

communities. In Arizona and New 

Mexico they are found in habitats 

associated with mixed conifer, pineoak, Arizona cypress, oak 

woodlands, and associated riparian 

forests. These habitat areas are 

distinct from the short grass prairie 

associated with BTPD habitat. No 

indirect effects from habitat loss are 

expected because this species does 

not use BTPD burrows. 

Piping plover LAA 

Direct effects to the piping plover are 

expected to occur based on the potential 

for this species to consume prey items that 

may have consumed the chlorophacinone 

bait (RQ of 0.104 for exposure to nontarget animals, which is used as a 

surrogate for invertebrate prey, which 

exceeds the LOC of 0.1). Growth and 

reproductive effects cannot be precluded 

due to the absence of chronic data. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. The plover’s home 

range within BTPD range is usually 

limited to the wetland, lakeshore, or 

section of beach where its nest is 

located. No indirect effects from 

habitat loss are expected because this 

species does not use BTPD burrows. 

New Mexican 

ridge-nosed 

rattlesnake 

LAA 

No direct effects based on survival to the 

New Mexican ridge-nosed rattlesnake are 

expected to occur (see Section 5.1.1.a. 

RQs of 0.018 for a 50 gram snake and RQ 

of 0.030 for a 500 gram snake. Neither of 

these RQs exceeds the LOC of 0.1). 

However, growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

because this species does not appear 

use BTPD burrows. 

Sonora tiger 

salamander LAA 

Direct effects to the Sonora tiger 

salamander are expected to occur based on 

the potential for this species to consume 

No indirect effects from the loss of 

prey base or loss of habitat (BTPD 

burrow) are expected because this 

115
prey items that may have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals, which is 

used as a surrogate for invertebrate prey, 

which exceeds the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data. 

species’ range does not overlap with 

BTPD range. 

Black-capped 

vireo LAA 

Direct effects to the black-capped vireo 

are expected to occur based on the 

potential for this species to consume prey 

items that have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals, which is 

used as a surrogate for invertebrate prey, 

which exceeds the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. Black-capped vireos 

are found in mixed 

deciduous/evergreen shrub land. 

Breeding vireos use shrubby growth 

of irregular height and distribution 

with spaces the small thickets and 

clumps and with vegetative 

extending to ground level. These 

habitat areas are distinct from the 

short grass prairie associated with 

BTPD habitat. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

Golden-cheeked 

warbler LAA 

Direct effects to the golden-cheeked 

warbler are expected to occur based on the 

potential for this species to consume prey 

items that have consumed the 

chlorophacinone bait (RQ of 0.104 for 

exposure to non-target animals, which is 

used as a surrogate for invertebrate prey, 

which exceeds the LOC of 0.1). Growth 

and reproductive effects cannot be 

precluded due to the absence of chronic 

data. 

No indirect effects from loss of prey 

base are expected because this 

species’ habitat is distinct from 

BTPD habitat. Golden-cheeked 

warblers are found in mixed Ashejuniper and oak woodlands in ravines 

and canyons. They spend summers 

in open canopy forest and winters in 

closed canopy forests. These habitat 

areas are distinct from the short grass 

prairie associated with BTPD habitat. 

No indirect effects from habitat loss 

are expected because this species 

does not use BTPD burrows. 

Gray wolf LAA 

Direct effects to the gray wolf are 

expected to occur based on the potential 

for this species to consume prey items that 

have consumed the chlorophacinone bait 

(RQ of 24.82 for exposure to non-target 

animals and RQ of 9.59 for exposure to 

BTPDs both of which exceed the LOC of 

0.1). Growth and reproductive effects 

cannot be precluded due to the absence of 

chronic data; however, growth and 

reproductive effects are not expected 

because mortality typically occurs as a 

result of acute exposure. 

Indirect effects from the loss of the 

prey base are expected because 

effects to individuals within 

populations have been demonstrated 

in mammals, birds, and terrestrial 

invertebrates. No indirect effects 

from habitat loss are expected 

because this species does not use 

BTPD burrows. 

1

 LAA=likely to adversely affect. 

116
Table 7.2. Effects Determination Summary for the Critical Habitat Impact Analysis 

Species with 

Designated Critical 

Habitat 

Effects 

Determination Basis for Determination 

Salt Creek tiger beetle HM1

Reproductive effects are expected for the Salt Creek tiger beetle. Salt Creek tiger 

beetle larvae are potentially exposed to chlorophacinone residues through 

chlorophacinone exposed terrestrial invertebrates. Dosed carcasses in a burying 

beetle study negatively affected number of emerged beetles (MRID 47383001). 

Similar affects are expected for the Salt Creek tiger beetle. No indirect effects 

from loss of prey base are expected because this species’ habitat is distinct from 

BTPD habitat. This species uses mud banks of streams and seeps in association 

with saline wetlands and exposed mud flats of saline wetlands which is distinct 

from the short grass prairie associated with BTPD habitat. No indirect effects 

from habitat loss are expected because this species does not use BTPD burrows. 

California condor No habitat 

modification 

expected 

Direct effects to the California condor are expected through their potential 

exposure to prey items that may have consumed the chlorophacinone bait (RQ of 

0.104 for exposure to non-target animals which exceeds the LOC of 0.1. No 

indirect effects from the loss of prey base are expected because this species’ range 

does not overlap with BTPD range. No indirect effects from habitat loss are 

expected because this species does not use BTPD burrows. No habitat 

modification is expected because the critical habitat for the California condor does 

not overlap with the use area (BTPD habitat). Critical habitat for the California 

condor has only been designated in California. 

Whooping crane HM 

Direct effects to the whooping crane are expected to occur based on the potential 

for this species to consume the chlorophacinone bait (RQ of 0.89 which exceeds 

the LOC of 0.1) or other prey items that have consumed the chlorophacinone bait 

(RQ of 0.104 for exposure to non-target animals which exceeds the LOC of 0.1). 

Indirect effects from the loss of the prey base are also expected because effects to 

individuals within populations have been demonstrated in mammals, birds, and 

terrestrial invertebrates. No indirect effects from habitat loss are expected because 

this species does not use BTPD burrows. Habitat modification for the whooping 

crane is expected because the critical habitat for the whooping crane overlaps with 

the use area (BTPD habitat). 

Canada lynx HM 

Direct effects to the Canada lynx are expected to occur based on the potential for 

this species to consume prey items that have consumed the chlorophacinone bait 

(RQ of 23.30 for exposure to non-target animals and RQ of 9.00 for exposure to 

BTPDs both of which exceed the LOC of 0.1). No indirect effects from loss of 

prey base are expected because this species’ habitat is distinct from BTPD habitat. 

The Canada lynx is associated with the southern, transitional reaches of the cool 

and moist boreal forest. Where it occurs at these lower latitudes, the boreal forest 

forms a mixed conifer and conifer-hardwood landscape. These habitat areas are 

distinct from the short grass prairie associated with BTPD habitat. No indirect 

effects from habitat loss are expected because this species does not use BTPD 

burrows. Habitat modification for the Canada lynx is expected because the critical 

habitat for the Canada lynx overlaps with the use area (BTPD habitat). 

117
Preble’s meadow 

jumping mouse HM 

Direct effects to the Preble’s meadow jumping mouse are expected to occur based 

on the potential for this species to consume the chlorophacinone bait (RQ of 41.35 

which exceeds the LOC of 0.1). Indirect effects from the loss of the prey base are 

expected because effects to individuals within populations have been demonstrated 

in terrestrial invertebrates. Although this species makes nests both above and 

below ground, it does not appear to use other species’ rodent burrows. Habitat 

modification for the Preble’s meadow jumping mouse is expected because the 

critical habitat for the Preble’s meadow jumping mouse overlaps with the use area 

(BTPD habitat). 

Mexican spotted owl HM 

Direct effects to the Mexican spotted owl are expected to occur based on the 

potential for this species to consume prey items that have consumed the 

chlorophacinone bait (RQ of 0.104 for exposure to non-target animals which 

exceeds the LOC of 0.1). No indirect effects from loss of prey base are expected 

because this species’ habitat is distinct from BTPD habitat. Mexican spotted owls 

are found in old-growth or mature forests with unevenly aged stands of trees, high 

canopy, multi-storied levels, and high tree density as well as canyons with riparian 

or conifer communities. In Arizona and New Mexico they are found in habitats 

associated with mixed conifer, pine-oak, Arizona cypress, oak woodlands, and 

associated riparian forests. These habitat areas are distinct from the short grass 

prairie associated with BTPD habitat. No indirect effects from habitat loss are 

expected because this species does not use BTPD burrows. Habitat modification 

for the Mexican spotted owl is expected because the critical habitat for the 

Mexican spotted owl overlaps with the use area (BTPD habitat). 

Piping plover HM 

Direct effects to the piping plover are expected to occur based on the potential for 

this species to consume prey items that have consumed the chlorophacinone bait 

(RQ of 0.104 for exposure to non-target animals, which is used as a surrogate for 

invertebrate prey, which exceeds the LOC of 0.1). No indirect effects from the 

loss of the invertebrate prey base are expected because this species’ habitat is 

distinct from BTPD habitat. The plover’s home range within the BTPD range is 

usually limited to the wetland, lakeshore, or section of beach where its nest is 

located. No indirect effects from habitat loss are expected because this species 

does not use BTPD burrows. Habitat modification for the piping plover is 

expected because the critical habitat for the piping plover overlaps with the use 

area (BTPD habitat). 

New Mexican ridgenosed rattlesnake HM 

No direct effects based on survival to the New Mexican ridge-nosed rattlesnake are 

expected to occur (see Section 5.1.1.a. RQs of 0.018 for a 50 gram snake and RQ 

of 0.030 for a 500 gram snake. Neither of these RQs exceeds the LOC of 0.1). 

However, direct effects based on reproduction cannot be precluded because no 

reproduction data are available. Indirect effects from the loss of the prey base are 

expected because effects to individuals within populations have been demonstrated 

in mammals, birds, and terrestrial invertebrates. No indirect effects from habitat 

loss are expected because this species does not appear to use BTPD burrows. 

Habitat modification for the New Mexican ridge-nosed rattlesnake is expected 

because the critical habitat for the New Mexican ridge-nosed rattlesnake overlaps 

with the use area (BTPD habitat). 

Gray wolf 

No habitat 

modification 

expected 

Direct effects to the gray wolf are expected to occur based on the potential for this 

species to consume prey items that have consumed the chlorophacinone bait (RQ 

of 24.82 for exposure to non-target animals and RQ of 9.59 for exposure to BTPDs 

both of which exceed the LOC of 0.1). Indirect effects from the loss of the prey 

base are also expected because effects to individuals within populations have been 

demonstrated in mammals, birds, and terrestrial invertebrates. No indirect effects 

from habitat loss are expected because this species does not use BTPD burrows. 

No habitat modification is expected because the critical habitat for the gray wolf 

does not overlap with the use area (BTPD habitat). Critical habitat for the gray 

wolf has only been designated in Minnesota and Michigan. 1

Habitat Modification 

118
The assessment endpoint for each species above is the modification of PCEs. 

Based on the conclusions of this assessment, a formal consultation with the U. S. Fish and 

Wildlife Service under Section 7 of the Endangered Species Act should be initiated. 

When evaluating the significance of this risk assessment’s direct/indirect and adverse habitat 

modification effects determinations, it is important to note that pesticide exposures and predicted 

risks to the listed species and its resources (i.e., food and habitat) are not expected to be uniform 

across the action area since BTPDs are not uniformly distributed across action area. Evaluation 

of the implication of this non-uniform distribution of risk to the species would require 

information and assessment techniques that are not currently available. Examples of such 

information and methodology required for this type of analysis would include the following: 

• Enhanced information on the density and distribution of BTPDs within the action 

area and information on the density and distribution of the other 21 listed species 

within the action area and information on the density and distribution within their 

critical habitat of the nine species with critical habitat. This information would 

allow for quantitative extrapolation of the present risk assessment’s predictions of 

individual effects to the proportion of the population extant within geographical 

areas where those effects are predicted. Furthermore, such population 

information would allow for a more comprehensive evaluation of the significance 

of potential resource impairment to individuals of the listed species. 

• Quantitative information on prey base requirements for the listed species. While 

existing information provides a preliminary picture of the types of food sources 

utilized by the listed species, it does not establish minimal requirements to sustain 

healthy individuals at varying life stages. Such information could be used to 

establish biologically relevant thresholds of effects on the prey base, and 

ultimately establish geographical limits to those effects. This information could 

be used together with the density data discussed above to characterize the 

likelihood of adverse effects to individuals. 

• Information on population responses of prey base organisms to chlorophacinone. 

Currently, methodologies are limited to predicting exposures and likely levels of 

direct mortality, growth or reproductive impairment immediately following 

exposure to chlorophacinone. The degree to which repeated exposure events and 

the inherent demographic characteristics of the prey population play into the 

extent to which prey resources may recover is not predictable. An enhanced 

understanding of long-term prey responses to chlorophacinone exposure would 

allow for a more refined determination of the magnitude and duration of resource 

impairment, and together with the information described above, a more complete 

prediction of effects to individual species and potential modification to critical 

habitat. 

119
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July 23, 2010 

List of MRIDs: 

47383002 

43672005 

 

122