Final Environmental Assessment

Cattle Fever Tick Eradication on Laguna Atascosa and Lower Rio Grande Valley National 

Wildlife Refuges

February 2018

Lead Agency

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Cooperating Agency

U.S. Fish and Wildlife Service

National Wildlife Refuge System

Southwest Region
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Table of Contents

1.0 PURPOSE OF AND NEED FOR PROPOSED ACTION ALTERNATIVE .......................... 1

1.1 Introduction ........................................................................................................................... 1

1.2 Action Area ........................................................................................................................... 1

1.3 Background ........................................................................................................................... 4

1.3.1 USDA-APHIS Efforts to Eradicate Cattle Fever Ticks.................................................. 4

1.3.2 FWS Efforts to Control CFT .......................................................................................... 7

1.4 Purpose and Need for the Proposed Action .......................................................................... 8

1.5 Decision to be Made.............................................................................................................. 8

1.6 Public Comments.................................................................................................................. 9

2.0 ALTERNATIVES..................................................................................................................... 9

2.1 Alternative A – Continue current CFT Treatment Modalities on LANWR and LRGVNWR 

(No Action Alternative) .............................................................................................................. 9

2.2 Alternative B –Implement Additional CFT Eradication Strategies (Proposed Action)........ 9

3.0 AFFECTED ENVIRONMENT.............................................................................................. 14

3.1 Physical Environment ......................................................................................................... 14

3.1.1 Air Quality.................................................................................................................... 14

3.1.2 Soils / Geology ............................................................................................................. 14

3.2 Vegetative Communities/Habitat ........................................................................................ 14

3.2.1 Laguna Atascosa National Wildlife Refuge ................................................................. 14

3.2.2 Bahia Grande Tract of Laguna Atascosa National Wildlife Refuge ............................ 15

3.2.3 Boca Chica Tract of Lower Rio Grande Valley National Wildlife Refuge.................. 15

3.2.4 Willamar Tract of Lower Rio Grande Valley National Wildlife Refuge ..................... 15

3.3 Wildlife................................................................................................................................ 16

3.3.1 Laguna Atascosa National Wildlife Refuge ................................................................. 16

3.3.2 Boca Chica Tract of Lower Rio Grande Valley National Wildlife Refuge.................. 16

3.3.3 Willamar Tract of Lower Rio Grande Valley National Wildlife Refuge ..................... 17

3.4 Threatened & Endangered Species and other Special Status Species................................. 17

3.5 Human Environment ........................................................................................................... 18
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3.5.1 Cultural Resources........................................................................................................ 18

3.5.2 Socioeconomic Resources............................................................................................ 19

4.0 ENVIRONMENTAL CONSEQUENCES ............................................................................. 20

4.1 Resource Impacts associated with Ivermectin and Doramectin.......................................... 20

4.2 Impacts to Air Quality......................................................................................................... 23

4.3 Impacts to Soil and Vegetation ........................................................................................... 23

4.4 Impacts to Threatened and Endangered Species................................................................. 25

4.5 Wildlife Disturbance ........................................................................................................... 27

4.6 Impacts on the Human Environment................................................................................... 28

4.6.1 Impacts on Cultural Resources..................................................................................... 30

4.7 Assessment of Cumulative Impacts .................................................................................... 31

4.8 Environmental Justice ......................................................................................................... 32

5.0 CONSULTATION, COORDINATION AND DOCUMENT PREPARATION ................... 33

5.1 References........................................................................................................................... 34

Appendix A. TAHC Situation Report from December 2017 ....................................................... 39

Appendix B. Summary of and Responses to Comments Received on the Environmental 

Assessment Prepared for Cattle Fever Tick Eradication on Laguna Atascosa and Lower Rio 

Grande Valley National Wildlife Refuges.................................................................................... 41
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1.0 PURPOSE OF AND NEED FOR PROPOSED ACTION ALTERNATIVE

1.1 Introduction

The U.S. Department of Agriculture (USDA), Animal and Plant Health Inspection Service 

(APHIS) and U.S. Department of Interior, U.S. Fish and Wildlife Service (FWS) have prepared 

this environmental assessment (EA) to analyze management options for the eradication of cattle 

fever ticks (CFTs) found on Laguna Atascosa National Wildlife Refuge (LANWR) and Lower 

Rio Grande Valley National Wildlife Refuge (LRGVNWR). The proposed alternatives for

eradication in this EA include: 1) continuation of current refuge management, and 2) conducting 

additional eradication activities on refuge property, which would include the use of ivermectintreated corn in feeders and a study involving cattle grazing. These management actions would 

permit USDA-APHIS and Texas Animal Health Commission (TAHC) via Special Use Permits 

(SUPs) to eradicate CFTs on units of LANWR and LRGVNWR that fall within established

quarantine areas. 

The USDA-APHIS established a Cattle Fever Tick Eradication Program (CFTEP) in 1906 as a 

cooperative State-Federal cattle fever/babesiosis eradication effort. In this EA, USDA-APHIS 

and FWS analyze the potential impacts associated with permitting the treatment of white-tailed 

deer with ivermectin-treated corn and introducing treated cattle through an experimental grazing 

program to control CFTs on FWS lands. The EA has been prepared in accordance with the 

National Environmental Policy Act of 1969 (Public Law [PL] 91 190), regulations of the Council 

on Environmental Quality 40 CFR 1508.9, USDA-APHIS implementing procedures (7 CFR pt. 

372), and the National Wildlife Refuge Improvement Act of 1997, as amended (Public Law 105-

57).

1.2 Action Area

LANWR and LRGVNWR are part of the South Texas Refuge Complex (STRC), which also 

includes Santa Ana National Wildlife Refuge. The scope of this EA includes all FWS lands that 

fall within an established quarantine area (permanent, temporary, or control purpose/buffer) on 

LANWR and LRGVNWR (see Figure 1).

LANWR lies along the Gulf of Mexico at the southern tip of Texas, along the northeastern edge 

of Cameron County and the southeastern edge of Willacy County. The 97,007-acre refuge

consists of four main units: Laguna Atascosa Unit, Bahia Grande Unit, South Padre Island Unit, 

and Coastal Corridor Unit. LANWR is a unique blend of temperate, subtropical, coastal, and 

Chihuahuan desert habitats. Mexican plants and wildlife reach their northernmost limits here 

such as the endangered ocelot and jaguarundi, while migratory birds stop to rest and feed during 

the spring and fall. The refuge topography is typical of the Texas Coastal Plain, which is 

basically flat with a slope toward the Laguna Madre at about 17 inches per mile. The highest 

elevations at Laguna Atascosa occur on “lomas” (natural silty clay mounds), reaching heights 

from 20 to 36 feet, yet the majority of the refuge is less than 10 feet above mean sea level. The 

landscape of the refuge consists of an irregular pattern of meandering resacas, brushy lomas, 

coastal salt prairie (grasslands), tidal flats, sand dunes, freshwater and estuarine wetlands, and 

impoundments.
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The Lower Rio Grande Valley is not actually a “valley” but part of the Rio Grande’s 

international delta. The delta was active roughly between the towns of La Joya and Port 

Mansfield in Texas, and San Fernando in Tamaulipas, Mexico. The LRGVNWR is located 

within the larger South Texas Plains physiographic area, an immense area often generalized as 

being comprised of rolling grasslands and oak or mesquite-dominated woodlands (Gould 1975, 

Scifres 1980, Scifres and Hamilton 1993). The LRGVNWR is located in the southern fourcounty area of Texas that includes Cameron, Hidalgo, Starr, and Willacy Counties. To the north, 

the refuge tracts are bounded by relic prairie and large ranches dominated by brushland in 

various degrees of succession. To the south, refuge tracts, many of which harbor endangered 

species, are adjacent to the Rio Grande. 
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Figure 1. National wildlife refuges in South Texas and their proximity to an established cattle fever tick quarantine area.
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1.3 Background

The CFT, known scientifically as Rhipicephalus (formerly Boophilus) annulatus and R. 

microplus, are uniquely capable of carrying and transmitting the protozoa, or microscopic 

parasites, Babesia bovis or B. bigemina. Without the presence of the CFT, there is no biological 

transmission of the Babesia organisms. Infected CFTs release the protozoa into the bloodstream 

of cattle as they feed. The Babesia organisms invade and destroy red blood cells ultimately 

resulting in an 80-90 percent mortality rate of susceptible naive cattle. The CFTs do not pose a 

human health or safety issue. 

1.3.1 USDA-APHIS Efforts to Eradicate Cattle Fever Ticks

In the 1940s, USDA-APHIS eradicated CFTs in the United States and established a permanent 

quarantine zone that ranges from 200 yards to 10 miles wide along the Rio Grande River. This 

strip of land extends 500 miles, through eight South Texas counties, alongside the Rio Grande 

River from west at Devils River, east to the Gulf of Mexico. The purpose of the permanent 

quarantine zone is to rapidly respond to CFT incursions from Mexican cattle and ungulates that 

cross the Mexico-U.S. border. When these CFT incursions are detected in the permanent 

quarantine zone, they are quickly eliminated by USDA-APHIS to prevent the spread of CFTs to 

the interior of the state and the rest of the United States. There is additional biological 

information and history of the CFTEP in the “Cattle Fever Tick Eradication Program – Tick 

Control Barrier, Maverick, Starr, Webb, and Zapata Counties, Texas, Draft Environmental 

Impact Statement – June 2013”, which is incorporated by reference (USDA-APHIS, 2013) and 

referred to as the CFTEP DEIS.

Despite a permanent quarantine zone on the border, CFTs have occasionally expanded, to 

include the current infestation concern (Figure 2). The current CFT infestation expansion is due 

to the following factors: changes in land use, wet-dry climatic cycles providing favorable 

conditions for CFTs, expansion of native and exotic game species in South Texas (white-tailed 

deer, exotic nilgai antelope, red deer, etc.) that can serve as hosts and reservoirs of CFTs, lack of 

a CFT control program in Mexico, and difficulty tracking CFT populations. In 2014, USDAAPHIS and TAHC placed 223,000 acres in Cameron County, Texas under blanket quarantine 

due to detection of CFTs. This temporary quarantine and control purpose/buffer area extends 

north of the permanent quarantine line and contains the majority of LANWR, as well as portions 

of LRGVNWR (see Figure 1). For the control purpose area, a buffer is used to extend control 

from infested premises and implement eradication strategies. A two-mile buffer is used when 

there are only white-tailed deer present and a three-mile buffer is used when both nilgai and 

white-tailed deer are present. These buffers are developed based on the presumed home range of 

white-tailed deer and nilgai and the likelihood these two wildlife species will carry CFTs to other 

areas. In addition to LANWR, the CFT was also found on many nearby private premises in both 

Cameron and Willacy Counties. Appendix A provides the December 2017 CFT situation report 

from TAHC. Multiple outbreaks are occurring in South Texas including another large outbreak 

near Laredo, Texas. 

USDA-APHIS assessed the use of medicated corn to treat white-tailed deer in the January 2017 

environmental assessment (EA) entitled, "Cattle Fever Tick Eradication Program Use of 

Ivermectin Corn" (USDA-APHIS, 2017) and referred to as the Ivermectin Corn EA. This 

document, and the associated risk assessment, is available online at the following website: 
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https://www.aphis.usda.gov/animal_health/downloads/animal_diseases/ivermectin-corn.pdf. 

The Department issued a Finding of No Significant Impact (FONSI) on January 30, 2017, 

available at https://www.aphis.usda.gov/animal_health/downloads/animal_diseases/fonsiivermectin-corn-ea.pdf, and implemented the preferred alternative off refuges last year. This 

document incorporates the treatments and methods described in that EA by reference. 

USDA-APHIS analyzed population reduction of nilgai in an EA (USDA-APHIS, 2014) using 

aerial and ground-based measures in conjunction with deer capture-release and population 

counts. Based on that analysis and consistent with the FWS Feral Hog and Nilgai Management 

Plan, the FWS allows population reduction of nilgai antelope as part of the efforts to achieve 

elimination of CFTs in the country (USDA-APHIS, 2014, USFWS, 2014). This EA incorporates 

these analyses by reference into the no action alternative, as current management. This process of 

assessing new components and subsequent incorporation of the treatments and methods into the 

overall CFTEP leads to improvements and refinements of the CFTEP over time while ensuring 

the Federal actions do not create significant impacts in the environment.
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Figure 2. Cattle fever tick infestations in the systematic area (permanent tick quarantine zone) and free area (outside of permanent tick 

quarantine zone) areas as of November 30, 2017 in South Texas.
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1.3.2 FWS Efforts to Control CFT

The FWS is committed to management of lands within STRC in a manner that advances the 

purposes for which these refuges were established and is supportive of efforts to eradicate the 

CFT. The FWS has been working with USDA-APHIS and TAHC to control CFTs. Efforts to 

date are outlined below. 

Prescribed Fire

The STRC will continue to use prescribed fire in fire-dependent communities to control CFTs. 

Burning the habitat not only kills CFTs but also removes the vegetation that harbors CFTs,

reducing the likelihood of CFTs attaching to animals in burned areas. In 2016, STRC burned 

approximately 6,000 acres at LANWR and approximately 20,000 acres in 2017 to reduce CFTs

and their habitat. The STRC will continue to maximize the acreage that could be logistically and 

safely burned to address infested areas. All prescribed fire for CFT eradication efforts are

consistent with the STRC Coastal Prairie Prescribed Burn Plan (USFWS 2017). 

Nilgai reduction

Nilgai are exotic antelope introduced by private ranchers in South Texas and continue to increase 

regionally. Non-native nilgai are already managed on refuges as invasive species because they 

compete with native herbivores and create trails through dense/sensitive habitat that could have 

lasting negative impacts to the ocelot. Due to CFT infestation rates in the area and the lack of an 

effective treatment for CFTs on nilgai, the USDA-APHIS/TAHC recommended that all property 

owners in South Texas reduce nilgai populations to control the spread of CFTs. Nilgai have the 

ability to travel 30–40 miles per day, especially females, and this is one of the main factors for 

the spread of CFTs in Cameron and Willacy Counties. In the last two years alone, over 550

nilgai were harvested from LANWR and LRGVNWR. The FWS will continue to support 

USDA-APHIS/TAHC through harvests of nilgai on STRC lands. 

There is additional background information on nilgai reduction efforts by the CFTEP in the 

“Population Reduction of Nilgai in the Boca Chica Beach, Bahia Grande, and Brownsville 

Navigation District Areas, Cameron County, Texas; Environmental Assessment”, which is 

incorporated by reference (USDA 2014). This document is available online at the following 

website: https://content.govdelivery.com/attachments/USDAAPHIS/2014/07/11/file_attachments

/306647/DraftNilgaiEAComplete.pdf.

White-tailed deer hunting regulations and opportunities

The STRC has over 10 years of spotlight survey data and estimates the average population of 

white-tailed deer at LANWR is approximately 1 deer per 110 acres, with a wide range in 

densities dependent upon habitat. In 2015, the FWS implemented changes to hunter checkstation procedures to include CFT inspection of all harvested animals. In 2016, LANWR 

increased their white-tailed deer bag limit from 2 to 5 deer (the maximum, per State hunting 

regulations). This increase in potential harvest of white-tailed deer was done solely to help 

eradicate the CFT. Implementation of additional emergency white-tailed deer hunts on STRC

tracts may be initiated as soon as State seasons allow. In addition to regular hunts, emergency 

action hunts will focus on LANWR tracts where a hunt program does not currently exist. An 

emergency firearm public hunt is proposed for Unit 7 of LANWR (a previously non-hunted unit) 

and will include white-tailed deer and nilgai. 
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1.4 Purpose and Need for the Proposed Action

The purpose of the proposed action is to conduct certain management activities on refuges in the 

action area to eradicate invasive cattle fever ticks through issuance of SUPs from FWS to 

USDA-APHIS/TAHC. As further described in the USDA-APHIS Ivermectin Corn EA, since 

1968, there has been increasing concern about the role of white-tailed deer in CFT outbreaks. 

Numerous studies have shown that white-tailed deer are suitable hosts and reservoirs for CFTs

(Graham et al. 1972, in Pound et al. 2010, George, 1990). Failure to control ticks on wildlife 

hosts, particularly white-tailed deer and nilgai, compromises efforts to eradicate ticks on 

livestock. 

USDA-APHIS and TAHC find CFT eradication particularly challenging in Cameron and 

Willacy Counties due to their populations of white-tailed deer and nilgai. It has been 

hypothesized that where cattle and deer comingle, regular treatment of cattle may be sufficient to 

eradicate CFTs while negating the need for elimination of deer (George 1990; reviewed in Pérez 

de León et al. 2012). Therefore, grazing cattle under treatment on infested premises has 

historically been employed for ‘mopping’ up ticks (Gray et al. 1979, Kistner and Hayes 1970). 

Studies also show that feeding corn treated with ivermectin to white-tailed deer could be an 

effective tool in minimizing the movement and maintenance of CFTs (Pound et al. 1996, Miller 

et al. 1989). In January 2017, the FWS issued a Biological Opinion (BO) for the use of 

ivermectin-treated corn in deer feeders on private property, and USDA-APHIS published its 

Ivermectin Corn EA and Finding of No Significant Impact. The current proposed action extends 

the use of ivermectin-treated corn to refuge lands. 

The proposed action is needed to support CFTEP goals. Failure to control CFTs on wildlife hosts 

and in pastures greatly compromises efforts to eradicate CFTs on livestock and poses a 

substantial threat of infestation and disease establishment throughout South Texas. These actions 

are consistent with Executive Order 13751 (Safeguarding the Nation for the Impacts of Invasive 

Species), which was established to prevent the introduction of invasive species and provide for 

their control, and to minimize the economic, plant, animal, ecological, and human health impacts 

that invasive species cause. The permitting of USDA-APHIS/TAHC by FWS to conduct these 

eradication strategies (placement of ivermectin-treated corn and grazing cattle under systematic 

treatment) is consistent with invasive species control efforts, CFTEP program goals, and its 

adaptive management strategy to eradicate CFTs within a quarantine area. 

1.5 Decision to be Made

This EA is an evaluation of the environmental impacts of the CFT treatment alternatives on 

LANWR and LRGVNWR. It provides information to help USDA-APHIS and FWS fully 

consider the possible impacts associated with the proposed action (analyzed in Chapter 4 of this 

document) and no action (current management) alternative, which is analyzed in previous NEPA 

documents and incorporated by reference in this EA. Using the analysis in this EA, the agencies 

will decide whether there would be any significant effects on the human environment associated 

with the preferred alternative that may require the preparation of an environmental impact 

statement.
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1.6 Public Comments

USDA-APHIS and FWS made the draft EA available to the public on December 20, 2018, in 

Docket: APHIS-2017-0109, which can be viewed at https://www.regulations.gov/docket?D=

APHIS-2017-0109. USDA-APHIS and FWS asked for comments from the public to be 

submitted by January 22, 2018. The agencies received 187 comments, many of which were form 

letters. These comments were carefully considered during the preparation of the final EA. These 

comments and APHIS’ response to them are detailed in Appendix B.

2.0 ALTERNATIVES 

2.1 Alternative A – Continue current CFT Treatment Modalities on LANWR and 

LRGVNWR (No Action Alternative)

Under the no action alternative, which in this case refers to the continuation of the current 

CFTEP, USDA-APHIS and FWS would continue CFT eradication efforts to date on LANWR 

and LRGVNWR (modifications to/expansions of white-tailed deer/nilgai hunting opportunities, 

nilgai reductions, landowner discussions, prescribed burning) and other USDA-APHIS/TAHC 

CFTEP activities including deployment of ivermectin-treated corn on non-refuge lands. The 

STRC would not issue the SUPs to treat deer with ivermectin-treated corn and experimentally 

graze cattle on STRC lands. 

2.2 Alternative B –Implement Additional CFT Eradication Strategies (Proposed 

Action)

Under this alternative, USDA-APHIS and STRC would continue prescribed fire, nilgai 

reductions, landowner discussions, increased hunting opportunities for white-tailed deer and 

nilgai on the refuges, and other CFTEP activities including the use of ivermectin-treated corn on 

non-refuge lands. Additionally, USDA-APHIS/TAHC would treat white-tailed deer and conduct 

experimental cattle grazing on LANWR and LRGVNWR lands that fall within established 

quarantine areas. These management activities would be administered through SUPs. STRC

would evaluate the SUPs for a 5-year period, on a case-by-case basis. In addition, STRC would 

review the SUPs on an annual basis to determine if any changes are necessary. 

Ivermectin-treated corn for white-tailed deer treatment

Through issuance of a SUP, the FWS will permit USDA-APHIS/TAHC to use ivermectin

(Ivomec® or Ivomax® pour-on) for cattle formulation mixed with whole kernel corn. All mixing 

will be completed off-refuge and any spillage will need to be cleaned up per USDA-APHIS 

standard clean up protocol. Ivomec® pour-on for cattle is sold by Merial, Inc., and Ivomax® 

pour-on for cattle is a generic product (FDA ANADA 200-272). Dosing will be administered as 

outlined in the USDA-APHIS Ivermectin Corn EA, which is 200 milliliters (ml) of the 

formulation containing 5 milligrams (mg) ivermectin/ml pumped into 100 pounds of clean corn 

to produce 10 mg of ivermectin active ingredient per pound of corn. The daily intake dose of the 

deer is approximately 0.22 mg/kilogram (kg) assuming a 100 pound white-tailed deer eats 1 

pound of corn per day. A previous study concluded that a feeding rate of 0.22 mg/kg should 

produce maximum blood serum levels of approximately 30 parts per billion (ppb) (Pound et al. 

1996). The target concentration of 30 ppb assures a high degree of efficacy even in those deer 

that may consume as little as one-third of the targeted dosage. Serum levels of just 10 ppb (one-
10

third of the dosage) should produce 100 percent efficacy against ticks attempting to feed on 

treated animals (Pound et al. 1996, Nolan et al. 1985, Miller et al. 1989). 

The treated corn is placed in gravity flow feeding stations from February through July (removed 

60 days before hunting season to comply with U.S. Food and Drug Administration (FDA)

standards) to control CFTs in deer populations (nilgai are not consistently attracted to the 

feeders, thus, are not treated). The gravity flow feeder is a commercially made plastic bin device 

with three or four feed tubes below the bin, and a lid. Each feed site will include one gravity flow 

feeder that has a holding capacity of approximately 300-350 pounds of corn and serviced 

weekly. There will be a minimum 30-foot diameter fenced perimeter barrier, which is 3 feet tall,

around feeders, and feeders will be enclosed with welded wire panels and silt fencing at ground 

level to exclude non-target animals. Game cameras will be strategically placed and rotated 

annually to observe 50 percent of the feeders on refuges from February-April over the 5-year 

SUP period, prioritizing feeders close to wetland and thornscrub habitat, to monitor and evaluate 

the utilization by white-tailed deer, and the occurrence of non-target animal exposure. A 50-

meter buffer around wetlands and bodies of water bodies will be implemented as an additional 

precaution for refuge lands. 

Figure 3. Photo of ivermectin-treated corn feeder used by USDA-APHIS/TAHC to treat white-tailed 

deer
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The number of feeder sites will be determined based on number and density of deer (1 feeder per 

20–30 deer to minimize excessive competition and social dominance), and density of feeders per 

area (deer do not have to travel more than 1⁄4- to 1⁄2-mile to access feed = 1 per 125 acres to 1 per 

500 acres). Existing deer surveys and remote sensing data will be used to identify placement and 

number of feeders on STRC lands. Selected feeder sites will be relatively flat and level. Feeders 

will be accessible from refuge roads. In the rare case that any off-road feeders are necessary, they

may need to be accessed by utility task vehicle (UTV) or all-terrain vehicle (ATV). In general, 

implementation will be conducted consistent with measures outlined in the BO issued for the 

USDA-APHIS CFTEP ivermectin-treated corn project (USFWS 2017). Locations and placement 

of feeders will be closely coordinated with the refuge manager. 

Experimental Cattle Grazing 

Under this alternative, the STRC will issue SUPs to permit USDA-APHIS/TAHC to conduct an 

experimental grazing program on STRC lands within the quarantine area to test efficacy of CFT

eradication techniques on STRC lands. Eradication techniques on FWS lands will be evaluated 

by observing presence or absence of CFTs. Infestation rates will be recorded by the type of 

eradication treatment strategy to determine trends. These trends will be used to assess the 

effectiveness of any one or combination of CFT treatments on FWS lands. The CFT 

presence/absence data will be collected for areas under the following conditions: 

1. Control (areas where there are not CFT eradication actions) 

2. Nilgai population reduction

3. Cattle grazing under systematic treatment (as defined below)

4. Ivermectin-treated corn feeding

5. Combination of 2 & 3

6. Combination of 2 & 4

7. Combination of 3 & 4

8. Combination of 2, 3, & 4

Laguna Atascosa National Wildlife Refuge

LANWR is comprised of several different ecological sites. These sites vary from clays, clay 

loams up to saline areas. The herbaceous vegetation and production is very diverse and varies 

throughout both refuges. Low producing areas are dominated by bushy sea oxeye while the more 

productive areas are dominated by gulf cordgrass (saline areas) and buffelgrass in some areas. 

Woody vegetation is just as diverse and varies from mesquite/huisache thickets to dense 

communities of blackbrush/cenizo/pricklyash thickets. Grazeable acres (areas where livestock 

have access to the herbaceous vegetation) vary throughout the refuge. Some areas are open with 

little or no brush whereas other areas are extremely dense and access of cattle is non-existent. 

Herbaceous production in these dense areas is limited as well. In February 2017, USDA-Natural 

Resources Conservation Service (NRCS) completed a Grazing/Production Report to determine 

forage production and possible recommended stocking rates for three units on LANWR - Unit 5 

(3,595 acres), Unit 8 (5,600 acres), and Boswell-Jenkins (1,700 acres). Based on the USDANRCS Grazing/Production Report, production on the refuge varies from less than 100 pounds 

per acre up to 4,000 pounds per acre in some areas. Total grazeable area for Unit 5 and Unit 8 is 

approximately 2,337 acres and the recommended stocking rate is 25 animal units for both units 
12

combined. The majority of Boswell-Jenkins is grazeable, but the recommended stocking rate was 

also 25 animal units. The report provides recommendations for fencing, livestock rotation, and 

use of prescribed fire too. 

Lower Rio Grande Valley National Wildlife Refuge

The 2002 Grazing Management Plan for LRGVNWR describes how exotic grasses threaten 

Refuge resources, and how an experimental grazing program can be used to achieve refuge 

objectives by reducing these threats. There are two primary reasons exotic grasses pose a 

management problem at the LRGV: 1) they increase the potential for ignition and spread of fires 

on refuge properties, and 2) they impede the establishment and recovery of native brushland 

vegetation. Permitting USDA-APHIS/TAHC to conduct an experimental grazing program for 

CFT control on LRGVNWR would be in grazeable grasslands, particularly on Willamar and 

Boca Chica tracts. Additional tracts will be evaluated on a case-by-case basis using criteria 

outlined below. 

Though specific areas have not yet been identified, along with the criteria outlined below, range 

conditions, substrate, feasibility of maintaining fencing, availability of cattle and a cattle 

operator, and presence or absence of reliable water sources on a particular site may all contribute 

to ultimately determining where experimental cattle grazing is deployed. The experimental 

grazing program would be continuously monitored by FWS staff with recommendations from 

USDA-NRCS and adjustments made based on forage and water conditions. Stocking rates and 

grazing schedules will be flexible and adjusted based on an evaluation and recommendation from 

USDA-NRCS. The STRC will use an adaptive management approach for the experimental cattle 

grazing program and retains the right to remove or adjust stocking rates of cattle if there is 

resource damage or conflicts with other operations of the refuge. 

Experimental grazing on quarantined areas within LANWR and LRGVNWR will be evaluated 

and permitted on a case-by-case basis as determined by the refuge manager based on the 

following criteria: 

● Stocking rates have been determined through a USDA-NRCS Grazing/Production Report

● Necessary buffer zones and avoidance measures have been identified to protect areas to 

include thornscrub habitat, wetlands, threatened and endangered species considerations,

cooperative farm fields, thornscrub restoration sites, core ocelot monitoring sites, high 

public use and administrative areas 

● Fencing needs have been identified (wildlife-friendly fencing (safe for mammals and 

ground-nesting birds) for all interior areas; more durable exterior/perimeter fencing may 

be considered to reduce need for frequent maintenance)

● Water sources/needs have been identified (water for cattle operations must be provided 

by using a water line from a private well from an adjacent landowner, having water 

trucked into the refuge, or using an existing irrigation canal)

● Cattle grazed must be gentle steers and/or heifers (the goal is to graze the type of cattle 

that would be the easiest to gather)
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Grazing cattle under systematic treatment, as outlined below, on infested pastures where CFTs

are present is an important tool in an integrated approach in the successful eradication of CFTs. 

The systematic treatment for the experimental grazing program is outlined below.

Cattle Treatment Period: 

A. Cattle will be maintained under direct systematic treatment using doramectin injectable

while grazing for up to 9 months. 

B. Cattle will be gathered every 21–28 days, scratch inspected for CFTs, then injected 

with doramectin.

C. After the first scratch inspection that is free of CFTs, the systematic treatment period 

will continue for up to 9 months assuming no CFTs are found on future cattle or 

wildlife inspections.

D. If CFTs are found during the subsequent scratch inspections, the systematic treatment 

period will start over.

Cattle Sentinel Period:

A. After the completion of the systematic treatment period listed above, cattle will be 

grazed for up to 9 months under no treatment. 

B. The cattle will be scratch inspected at least every 90 days to assess the risk of CFTs on 

the pasture.

C. If during this sentinel period the cattle or wildlife are determined to be infested with 

CFTs, the systematic treatment period will start over.

D. At the conclusion of required sentinel period, USDA-APHIS/TAHC will remove all 

livestock from the property within 30 days.

Additionally, USDA-APHIS/TAHC may provide range cubes (maximum of 4 pounds 

cubes/head/week) as a tool to gather cattle. Range cubes are a supplemental feed that provides 

protein, energy, vitamins and minerals to cattle and are often used to entice cattle to follow, 

especially into corrals or pens. If this method is not successful, then horses may be used to gather 

cattle. If these two methods are unsuccessful, with approval from FWS staff, a helicopter may be 

used. A portable corral system provided by USDA-APHIS/TAHC will be used in the gathering 

and processing of the cattle. If a corral is placed on the refuge, placement must be approved by 

the refuge manager to ensure minimal habitat damage and disturbance.

Refuge units do not have consistent and reliable fresh water sources, especially during drought 

conditions. Water for experimental cattle operations on the refuges must be provided by a 

permittee using any of three methods: 1) a water line from a private well from an adjacent 

landowner; 2) truck water into the property; or 3) an existing irrigation canal. Each cistern must 

be separated by at least one mile (straight-line distance). Placement of all water infrastructures

must be approved by the refuge manager and should be within 100 feet of a designated refuge 

road.

Permethrin will be used to treat any exposed equipment (i.e., panels and trailers that move on 

and off the refuge). Equipment disinfection will take place off-refuge or in a mutually agreeable 

location on the refuge where run-off can be controlled or prevented. Alternative options may be 

evaluated and considered such as pressurized water, steam, or other products that are acceptable 

for cleaning.
14

3.0 AFFECTED ENVIRONMENT

This section describes the environment affected by the alternatives in Section 2. Aspects of the 

affected environment here focus on the major issues. Resources unaffected, or concerns with 

activities outside the refuges, are outside this EA’s scope. 

3.1 Physical Environment

3.1.1 Air Quality 

Air pollution levels in the action area are similar to or lower than other urban and rural areas in 

Texas, including air pollution coming from across the border in Mexico (EPA 1999). Air quality 

data from the Texas Commission on Environmental Quality website show the BrownsvilleHarlingen region as ranging from “good” to “moderate” AQI (Air Quality Index) ratings from 

2010–2017. This is due in large part to the prevailing southeasterly Gulf breeze. The air quality 

at or near the LANWR is therefore not considered to have serious air quality issues due to its 

proximity to the Gulf of Mexico and the Lower Laguna Madre. 

Willamar tract of LRGV is located in Willacy County, which is designated as an attainment area 

for National Ambient Air Quality Standards by the U.S. Environmental Protection Agency. Land 

use over much of the county is agricultural and ranchland. Attainment areas do not exceed any 

threshold for federally designated criteria air pollutants, CO, SO2, O3, NOx, PM10, and Pb. 

3.1.2 Soils / Geology 

The soils within the project area consist of the Laredo-Lomalta association and occur mainly in 

and adjacent to the LANWR (Williams et al. 1977). About 4 percent of Cameron County 

consists of this soil type. The Laredo-Lomalta soil association consists of areas of gently sloping 

to level, saline soils at an elevation of about 1 to 5 feet above the slightly depressional Lomalta 

soils. Lomalta soils are associated with the resascas or old meander channels of the Rio Grande 

that occur within the project area (Williams et al. 1977). More specifically, the project area is 

comprised of Sejita silty clay loam on the lower elevations and Laredo silty clay and Lomalta 

clay that support brush growth on higher elevations. 

3.2 Vegetative Communities/Habitat 

3.2.1 Laguna Atascosa National Wildlife Refuge

The refuge contains 450 documented plant species across a diversity of plant communities, 

including upland Tamaulipan thornscrub brushland, coastal prairie, sand and clay dunes, tidal 

flats, and fresh and saline wetlands. The lands surrounding Bayside Wildlife Drive are generally 

flat, sloping down to the Lower Laguna Madre. Vegetation communities within and near the 

project area include uplands within the road shoulder, brushlands growing on silty clay dunes 

known locally as lomas, coastal prairie dominated by expanses of Gulf Cordgrass or upland 

grasslands, and on lower elevations, salt flats mixed with halophytic vegetation assemblages 

known as “salt prairie.” 

Uplands within the road shoulder itself are typically dominated by the invasive species Kleberg 

bluestem (Dichanthium annulatum) and buffelgrass (Cenchrus ciliaris). However, Tamaulipan 

thornscrub brushlands are dominated by a shrub and tree community with 30 or more species of 

woody plants. These areas have a different plant community than surrounding areas because of 

the higher elevation and lower salinity. Common plant species in these brushlands include 

mesquite (Prosopis glandulosa), Texas ebony (Ebenopsis ebano), huisache (Acacia farnesiana), 
15

Spanish dagger (Yucca treculeana), cenizo (Leucophyllum frutescens), lime prickly ash 

(Zanthoxylum fagara), spiny hackberry (Celtis pallida), Berlandier fiddlewood (Citharexylum 

berlandieri), brasil (Condalia hookeri), tenaza (Harvardia pallens), and many others. The 

vegetation in these areas is often thorny and nearly impenetrable making ideal ocelot habitat. 

Slightly lower elevations may include plants such as tornillo (Prosopisreptans var. cinerascens), 

Christmas tree cactus (Cylindropuntia leptocaulis), and Texas prickly pear (Opuntia engelmannii 

var. lindheimer). 

3.2.2 Bahia Grande Tract of Laguna Atascosa National Wildlife Refuge

The Bahia Grande Unit is approximately 23,000 acres of mostly coastal prairie and estuarine 

wetlands in varying stages of restoration. The wetland restoration is considered one of the largest 

in the United States. The coastal prairie habitat is also in the process of being restored and is one 

of the best examples of near-pristine coastal prairie in South Texas. This Unit is being considered 

for numerous wetland restoration projects and, therefore, human activity could be high on this 

property. In addition, the FWS is currently undergoing the writing of a visitor services plan that 

would allow the public to hike and bike on the Unit. Eventually, the FWS has plans to allow 

hunting and fishing on the property.

3.2.3 Boca Chica Tract of Lower Rio Grande Valley National Wildlife Refuge

The Boca Chica Tract of the LRGVNWR is one of the last undeveloped, pristine coastal areas in 

Texas. About 4,452 ha (11,000 ac) in size, it encompasses wind-tidal flats, mangrove forests, 

oyster beds, bays, beaches, dunes, including more than 3,237 ha (8,000 ac) of highly productive 

wetlands near the mouth of the Rio Grande (Turner 1988). Boca Chica Beach is relatively 

narrow, from as little as 10–100 m wide, and extending for about 12 km from the mouth of the 

Rio Grande to the South Jetties of the Brazos Santiago Pass. Morton et al. (1983) noted this 

segment of beach is under threat of shoreline erosion due to lack of sand deposition from the Rio 

Grande due to construction of dams along its course. More inland from the beach and wind-tidal 

flats are brushy-covered clay “lomas” or hillocks containing dense growths of Tamaulipan 

thornscrub or “chaparral” (Clover 1937). Lomas are surrounded by wind-tidal flats and 

halophytic plant associations known locally as “salt prairie.” Dune hillocks or lomas themselves 

are quite rare (only found elsewhere in Russia, Australia, and Africa) and were formed from silt 

deposited by the Rio Grande shaped by prevailing southeasterly winds over time (Richard 2005).

3.2.4 Willamar Tract of Lower Rio Grande Valley National Wildlife Refuge

The main soil types found on the Willamar tract are Willamar fine sandy loam, Raymondville 

clay loam, and Lyford sandy clay loam. The Willamar Series soils are very high in salinity 

content and retain water very well. This soil often provides prime locations for wetlands. The 

water in these wetlands is high in sodium content and is prime habitat for wading birds and other 

animals that can withstand the salt. This soil is only fair for growing grasses or herbaceous 

plants, again because of the sodium content. The Lyford Series soils are well drained loamy 

soils. This soil is good for growing grasses and herbaceous plants. It also provides prime habitat 

for openland and rangeland wildlife. The Raymondville Series are well drained clayey soils. This 

soil is good for growing grasses, but only fair for growing herbaceous plants. It is also good for 

openland wildlife, but only fair for rangeland.

The Willamar tract is mainly a mesquite (Prosopis qlandulosa)/huisache (Acacia smallii) 

savannah. Much of what grows on the tract must be able to withstand the periodic flooding that 
16

occurs with heavy rainfall. Wetlands occur on the northeast corner and many of the ditches also 

retain water. Many of the wetland areas provide sites for water lilies (Nymphaea odorata) and 

other water loving plants. There are also many open fields towards the northeast corner that are 

covered in Sea Ox-Eye (Borrichia frutescens).

3.3 Wildlife

3.3.1 Laguna Atascosa National Wildlife Refuge

The diverse coastal prairies, brushy lomas, and wetlands at the refuge provide habitat to a high 

diversity of fish and wildlife species, as well as provide important wintering habitat for many 

migratory shorebirds. The refuge provides habitat for approximately 415 species of migratory 

and residential birds, approximately 45 types of mammals, approximately 44 species of reptiles 

and amphibians, and approximately 40 fish species (USFWS 2010). 

Common bird species within the refuge include the northern bobwhite (Colinus virginianus), 

pied-billed grebe (Podilymbus podiceps), double-crested cormorant (Phalacrocorax auritus), 

great blue heron (Ardea herodias), great egret (Ardea alba), snowy egret (Egretta thula), whiteeyed vireo (Vireo griseus), green jay (Cyanocorax yncas), black-crested titmouse (Baeolophus 

atricristatus), eastern meadowlark (Sturnella magna), northern cardinal (Cardinalis cardinalis), 

chachalaca (Ortalis vetula), great kiskadee (Pitangus sulpheratus), and many others (USFWS

2013). At least 95 nesting bird species have been recorded at the refuge. Located on the southern 

end of the Central Flyway, the refuge is a major stopover point on the lower Texas coast for 

migrating waterfowl going to and from Mexico. Peak use occurs in November when more than 

250,000 ducks typically show up on the refuge, with thousands more in the nearby Lower 

Laguna Madre. It is estimated that 80 percent of the North American population of redhead 

ducks winter at LANWR, earning the refuge the title of “Redhead Capital, USA”. The refuge is 

also a vital stopover for migrating neotropical songbirds. Painted buntings (Passerina ciris), 

Bullock’s oriole (Icterus bullockii), and various warbler and hummingbird species all depend on 

the refuge during their migrations. Often, when many of the songbirds are migrating north, an 

occasional cold front moves in and causes the birds to “fallout.” In need of shelter from strong 

winds and cold weather, the birds remain at the refuge until they can regain their strength and 

continue their long journey. 

Resident mammal species typically found at the refuge include white-tailed deer (Odocoileus 

virginianus), coyote (Canis latrans), bobcat (Lynx rufus), javelina (Pecari tajacu), feral hogs

(Sus scrofa), gray fox (Urocyon cinereoargenteus), long-tailed weasel (Mustela frenata), and 

Mexican free-tailed bats (Tadarida brasiliensis). 

Reptiles occurring on the refuge include the Texas tortoise (Gopherus berlandieri), six-lined 

racerunner lizard (Cnemidophorus sexlineatus), bullsnake (Pituophis catenifer sayi), and redeared slider turtles (Trachemys scripta elegans). The refuge is also home to many species of 

invertebrates, including the blue metalmark (Lasaia sula), a species that reaches its northern 

limits in South Texas. 

3.3.2 Boca Chica Tract of Lower Rio Grande Valley National Wildlife Refuge

Approximately, 344 wildlife species have been documented on or near Boca Chica Tract 

including 184 species of birds, 14 species of mollusks, 23 species of crab and shrimp, 61 species 
17

of fish, 40 species of reptiles and amphibians, and 22 species of mammals (Chaney and Pons 

1987). Wind-tidal flats of the Boca Chica Tract are important migration stopover sites for 

peregrine falcons, Falco peregrinus (Maechtle 1987). The Boca Chica Tract also supports the 

highest concentrations of breeding snowy plovers, Charadrius alexandrinus, and Wilson’s 

plovers, Charadrius wilsonia, in the Lower Laguna Madre Region of Texas (Zdravkovic 2005). 

3.3.3 Willamar Tract of Lower Rio Grande Valley National Wildlife Refuge

The coastal prairie pothole provides food and a dense cover for deer and other mammals. The 

thick brush that also occurs on the tract provides many excellent nesting sites for birds. There are 

many types of birds, several wetland species and other wading birds. The natural wetland areas 

also provide habitat for many reptiles and amphibians. In July 1992, a Mexican milksnake

(Lampropeltis triangulum) was recorded, the first ever recorded in Willacy county. Sheep frogs, 

(Hypopachus variolosus) have also been recorded in the wetlands in the northeast corner.

3.4 Threatened & Endangered Species and other Special Status Species 

Refuges protect, manage for, and provide important habitat for federally-listed, candidate, and 

proposed species. Federally-listed species or other special status species that may occur within 

the project area are the northern aplomado falcon (Falco femoralis septentrionalis), whooping 

crane (Grus americana), Gulf Coast jaguarundi (Herpailurus (=Felis) yagouaroundi cacomitli), 

and ocelot (Leopardus (=Felis) pardalis). 

Northern aplomado falcons are year-round residents of the Lower Rio Grande Valley of Texas 

(Valley) and are known to nest on and near the refuge (USFWS 2013). Large scale 

reintroductions of northern aplomado falcons began on the refuge in 1993 as part of the recovery 

effort. The refuge’s salt prairie, savanna grasslands, and marshes provide some of the best 

aplomado falcon habitat. Generally, this species is found in flat, open habitats containing 

prominent woody vegetation such as yuccas and mesquite trees. 

Cameron County is known to occasionally have a single whooping crane appear within the SUP 

area. A single whooping crane appeared a few miles west of LANWR on November 2015, 

reported by Rio Grande birders and was later confirmed by a bird expert. This is the second 

whooping crane that has appeared in the Rio Grande Valley in the last several years.

Wintering surveys have documented extensive whooping crane use of similar corn feeders on 

private lands throughout wintering whooping crane range. Additionally, whole kernel corn has 

been effectively used to bait and trap whooping cranes at the Aransas National Wildlife Refuge

for research purposes, so the whooping cranes are accustomed to eating corn. Therefore, there is 

some potential for whooping cranes to feed on corn feeders, but the chance of a whooping crane 

appearing in Cameron or Willacy County is low.

The Gulf Coast jaguarundi is thought to be extirpated from South Texas. No reliable sightings 

have been made in recent years. Although jaguarundi habitat is similar to that for ocelot,

jaguarundi are thought to be tolerant of a wider range of habitats. For example, sightings and 

information from Mexico indicate that jaguarundis may frequent open areas such as grasslands 

and pastures more commonly than ocelots (Source: TPWD). This species prefers dense riparian 

habitat along the Rio Grande and the “resaca” systems in the Valley. Although jaguarundis are 
18

more active during the day than ocelots, the last known sighting of one occurred at the Sabal 

Palm Grove Wildlife Sanctuary in southern Cameron County in 1989 (C. Perez pers. obs.). 

The ocelot is a small striped cat that historically ranged from southern Texas to Arkansas and 

Louisiana in the United States, but is now restricted to a few populations in South Texas and 

southern Arizona. Only about 80 or fewer of these small cats are estimated to remain in the 

United States, which includes a population of about 15 at the refuge. In the Valley, typical ocelot 

habitat consists of dense brushlands composed of mixed brush species such as spiny hackberry, 

brasil, lotebush (Zizyphus obtusifolia), amargosa (Castela erecta), whitebrush (Aloysia 

gratissima), catclaw acacia (Acacia greggii), blackbrush (Acacia rigidula), guayacan (Guaiacum 

angustifolium), and cenizo (Leucophyllum frutescens) (Source: TPWD). Interspersed trees such 

as mesquite (Prosopis sp.), live oak (Quercus virginiana), Texas ebony (Ebenopsis ebano), and 

hackberry (Celtis sp.) may also occur in ocelot habitat. Optimal ocelot habitat is described as 

having at least 95 percent canopy cover of shrubs, whereas marginal habitat has 75–95 percent

canopy cover. Ocelots are typically most active at night and rarely leave the cover of dense 

brush. Tewes (1986) found that core areas of ocelot home ranges contained more thornscrub 

habitat than peripheral areas of their home ranges on the refuge. However, ocelots can and do use 

narrow strips of shrubs or forests for travel and dispersal (Ludlow and Sunquist, 1987, Caso,

1994, Tewes et al., 1995). Such corridors provide critical landscape connectivity so they are 

important aspects of ocelot conservation (Tewes et al. 1995, Tewes and Blanton 1998).

Currently, only about 1 percent of the South Texas area supports optimal habitat (Source: 

TPWD). Most of this habitat occurs in scattered patches probably too small to support viable 

populations of ocelots. Although habitat loss is the single greatest long term and ongoing threat 

to ocelots, a conservative estimate attributes 50 percent of known ocelot mortalities to vehicle 

collisions. Ocelots often must travel significant distances and cross dangerous roads in search of 

food, shelter, and mates. 

3.5 Human Environment

3.5.1 Cultural Resources

Section 106 of the National Historic Preservation Act (NHPA) of 1966, as amended (16 USC 

470 et seq.), and its implementing regulations found at 36 CFR 800 require all federal agencies 

to consider the effects of federal actions on cultural properties eligible for or listed in the 

National Register of Historic Places. 

Laguna Atascosa National Wildlife Refuge

Known archaeological, cultural, and historical resources at LANWR are described in the 

Comprehensive Conservation Plan (USFWS 2010). LANWR contains several Coahuiltecan 

archaeological sites, such as the Unland Site, which was discovered in 1976 during the 

construction of a refuge service road. This site contained stone and shell artifacts and human 

skeletal remains. Another site discovered on Horse Island contained the skeletal remains of a 

female buried some 1,200 years ago. 

Lower Rio Grande Valley National Wildlife Refuge

Known archaeological, cultural, and historical resources at LRGVNWR are described in the 

Comprehensive Conservation Plan (USFWS 1997). The Texas Historical Commission initiated 
19

the Los Caminos del Rio Heritage Project in 1989. The purpose of its establishment was to 

promote the linkage of cultural and natural resources of the corridor region. The ultimate desired 

outcome of this endeavor is the preservation of a unique heritage shared by the United States and 

northern Mexico along the Lower Rio Grande. All of the LRGVNWR is included in the heritage 

corridor, and two of the significant historic sites within the heritage corridor are on LRGVNWR. 

As part of the heritage corridor partnership effort the Palmito Ranch Battlefield on LRGVNWR

tracts near Brownsville were nominated to be on the National Register of Historic Places, and the 

Old River Pumphouse on LRGVNWR near Hidalgo was nominated for a National Historic 

Landmark designation. 

3.5.2 Socioeconomic Resources 

Cameron County is the southernmost Texas County with a current population of 415,557 

(Source: U.S. Census Bureau 2011). The County is characterized by agricultural and urban 

development, scattered small farming communities, and the seasonal influx of summer visitors 

and winter residents (i.e., Winter Texans). According to the U.S. Census Bureau, the 2010 

population of Willacy County was 22,134. The nearest cities of Raymondville (11, 284 residents) 

and Harlingen (64,849 residents), Texas are within 9 and 31 miles, respectively. Oil and gas, 

agribusiness, tourism, and fishing are the dominant industries. The nearest metropolitan area to 

the project area is the Harlingen-Brownsville metro area, located about 20-26 miles away. The 

City of Brownsville has a current population of 172,437 and the City of Harlingen has a 

population of 64,202 (Source: 2010 Census). 

The economic area for this project is Cameron, Hidalgo, and Willacy counties (Carver and 

Caudill 2013). The area population increased by 30 percent from 2001–2011 as compared to a 9 

percent increase for the United States as a whole (Carver and Caudill 2013). The median 

household income is calculated at $22,249/year (Carver and Caudill 2013, after U.S. Dept. of 

Commerce – Nov 2012 data). According to Sethi and Arriola (2002), the Valley is one of the top 

30 fastest growing regions in the nation. Area per capita income increased by 15 percent over the 

2001-2011 period (Carver and Caudill 2013). 

Agriculture has always been the staple of the Valley economy. Aside from agriculture, the

service industry represents 36 percent of the total Valley economy, followed by local 

government (20 percent) and trade (17 percent) (Sethi and Arriola 2002). However, one of the 

largest and fastest growing industries is tourism, particularly nature-based or ecotourism (Mathis 

and Matisoff 2004). Ecotourism here generated over $340 million and resulted in the creation of 

4,407 full-time and part time jobs annually (Woosnam et al. 2011). During the winter months, 

retired people (an estimated 125,000–150,000) leave their northern homes to spend the winter in 

the more favorable climate of the Valley. Winter Texans provide an important economic boost in 

the Valley since they provide a substantial seasonal source of revenue for the local economies.

As seen from the high annual visitation, both refuges support ecotourism and provide important 

wildlife-dependent recreational activities for local residents as well as for Winter Texans. The 

refuges also play a role in the local economy as refuge employees typically live in the 

community, own property, and support local businesses through routine purchases of goods and 

services. According to Carver and Caudill (2013), the local economic benefit of LANWR totaled 

$23.4 million providing 205 jobs as of 2011. Or, for every dollar of refuge budget expenditures, 

$37.17 is added to economy of the area. 
20

4.0 ENVIRONMENTAL CONSEQUENCES 

This chapter analyzes and discusses the potential environmental effects or consequences that can 

reasonably be expected by the implementation of the proposed action described in Chapter 2.0 of 

this EA. An analysis of the effects of management activities has been conducted on the physical 

environment (air quality, water quality, and soils); biological environment (vegetation, wildlife, 

and threatened and endangered species); and socioeconomic environment (cultural resources, 

socioeconomic features including public use/recreation, and visual and aesthetic resource). The 

direct, indirect, and cumulative impacts of each alternative are considered. Analysis of actions 

outlined in the no action alternative (current management) were analyzed in previous documents, 

as outlined in the Background Section of this EA and are incorporated by reference in this 

document. USDA-APHIS analyzed the use of ivermectin-treated corn distributed through corn 

feeders in a risk assessment. The risk assessment is appended to the USDA-APHIS Ivermectin 

Corn EA, and that analysis is incorporated by reference. 

4.1 Resource Impacts associated with Ivermectin and Doramectin

Under the proposed action, white-tailed deer will be treated with ivermectin-treated corn, and 

cattle will be treated with doramectin injections and permitted to graze on refuge lands. Both 

ivermectin and doramectin are macrocyclic lactones (part of the avermectin group) commonly 

used to control parasites (Merola and Eubig 2012). Macrocyclic lactones have a systemic mode 

of action, in the case of both injectable doramectin and oral ingestion of ivermectin, the 

treatment gets into the bloodstream of the host (white-tailed deer and cattle), from where they are 

transported throughout the animal to kill the parasite. 

Both ivermectin and doramectin have low volatility and are unlikely to partition into the 

atmosphere (Halley et al. 1993; USDA 2017). Ivermectin and doramectin undergo rapid 

degradation in light and soil, bind tightly to soil and sediment making them unlikely to leach into 

groundwater or runoff to surface water in a dissolved state, will not accumulate, and will not 

undergo translocation in the environment, minimizing impacts to non-target organisms (Halley et 

al. 1993; USDA 2017). Ivermectin breaks down to less bioactive compounds via photo and 

aerobic degradation; degradation in soil varies with the soil type and properties, absorption 

capacity, and temperature (USDA 2017). Doramectin would not be expected to partition into the 

atmosphere because of its high molecular weight, high melting point, and low vapor pressure 

(Pfizer EA 1996). 

Ivermectin half-lives in soil are 7 to 14 days at high temperatures in summer, but can be much 

longer (up to 240 days) at low temperatures (22 degrees or less) in the winter (Halley et al. 

1989). Photolysis in water is less than 0.5 day in summer, and 39 hours in winter. When directly 

exposed to sunlight, its photolytic half-life was approximately 3 hours on a thin, dry film (USDA 

2017). In addition, studies in cotton and food crops (sorghum, lettuce, carrots, and turnips) show 

that plants uptake little ivermectin from direct applications to plants or from soil. Vegetation

uptake of doramectin is not anticipated (EPI Suites, Greg Masson). 

There is the possibility of exposure to some non-target terrestrial wildlife that may consume corn 

spilled onto the ground during feeding by white-tailed deer or when transported from storage 

sites. Transported medicated corn will be in sealed containers/bags and very minimal corn should 

be lost during transportation. The feeders dispense corn from feed ports up from ground level 
21

with a lip intended to minimize spillage and access by animals other than deer. Additionally, the 

use of exclusion barriers (welded wire panels precluding swine, javelina, and livestock, and silt 

fencing to preclude Texas tortoise) combined with weekly monitoring of the feeders greatly 

reduces the likelihood of consumption by non-target species. The exclusion fencing surrounding 

each deer feeder has a height of 34 inches, which is optimum to prevent feral swine from 

accessing the corn feeders (Rattan et al. 2010). Game cameras will be rotated between 50 percent

of the feeders during the study period to evaluate use by deer and the occurrence of non-target 

exposure. USDA-APHIS placed cameras at eight different ivermectin-treated corn feeders in 

Willacy County, Texas in the spring of 2017. These cameras captured images of wildlife at the 

selected feeders from April 2017 until the last week of July 2017. Within the feeder fence, most 

photos contained images of white-tailed deer. Non-target wildlife species that were captured at 

feeders, such as raccoons, grackles, wild turkeys, red winged blackbirds, rose-breasted 

grosbeaks, cardinals, mourning doves, and green jays, are not adversely impacted by ivermectin. 

Images of feral swine were not seen within the perimeter feeder fencing. The perimeter feeder

fencing appears to be sufficient to reduce any adverse impacts associated with the consumption 

of ivermectin-treated corn.

Ivermectin and doramectin are excreted virtually unchanged in the feces of treated animals 

(Lumaret et al. 2012, Suarez et al. 2003). Studies show that up to 90 percent of the ivermectin

dose administered parenterally or orally could be excreted in the feces (USDA 2017, Laffont et 

al. 2001). One study conducted in Canada found that the dung of cattle treated with ivermectin

did not support the insect communities typical of feces from untreated cattle; this continued for 

as many as 12 weeks post drug administration (Floate 1998). Likewise, that same study 

documented the persistence of ivermectin-containing feces on the landscape 4.25 times longer 

than untreated feces. Persistence of ivermectin in soil or feces varies dramatically by season 

(summer 7–14 days; winter 91–217 days) and may depend on temperature or UV exposure 

(reviewed in Lumaret et al. 2012). 

Doramectin has been shown to be toxic to dung fauna; however, excretion of doramectin through 

deer feces into the environment is not expected to have an adverse effect on invertebrates in the 

environment due to the tight binding of doramectin to organic material and resultant reduced 

bioavailability of the medication (Kolar and Erzen 2006). Additionally, the active ingredient in 

this formulation is inactivated by sunlight in approximately 24 hours. Any invertebrates or 

detritivores are expected to be exposed to very limited quantities of doramectin through the 

action area. Doramectin does not bioaccumulate in the environment. Therefore, even if 

bioavailable in dung fauna, doramectin will not amplify up the food chain if consumed (Kolar 

and Erzen 2006). As a result, other animals feeding on these invertebrates are not expected to be 

affected by doramectin. Based on the information above, localized impacts to this group of 

invertebrates depend on site-specific conditions influencing ivermectin and doramectin

degradation and availability, but potentially have moderate adverse impacts that are mediumterm in duration by altering insect communities and nutrient cycling for the duration of the 

treatment and for some days to weeks following its cessation. 

The most sensitive organisms to avermectins (ivermectin and doramectin) are some freshwater 

organisms, such as Daphnia magna, green unicellular algae and bacteria, and fish (e.g., rainbow 

trout, zebrafish) (Halley et al. 1993, Kolar 2006). Both ivermectin and doramectin are highly 
22

toxic to many aquatic invertebrates (reviewed in Lumaret et al. 2012, Schweitzer et al. 2009). 

The labeling of the Ivermax product contains the following warning for topical application in 

cattle: “Free ivermectin may adversely affect fish and certain aquatic organisms. Do not permit 

cattle to enter lakes, streams, or ponds for at least six hours after treatment.” The Safety Data 

Sheet for ivermectin also contains the warning “do not allow any volumes of product to reach 

ground water, water source or sewage system.” The Safety Data Sheet for doramectin contains a 

similar warning “Releases to the environment should be avoided. As with other members of the 

avermectin family, doramectin is highly toxic to fish and certain aquatic organisms.” 

The potential for exposure to aquatic organisms from ivermectin-treated corn is expected to be 

negligible (USDA 2017). Ivermectin is mixed with whole kernel corn and dispensed from a 

closed gravity feeder system to deer (Figure 3). Drift of ivermectin to aquatic areas is not 

anticipated based on the use pattern. Runoff would also not be anticipated because the corn is 

contained within a feeder that is accessed by deer. There is the possibility of some spillage from 

deer feeding at the feeders although the amount of corn would be minor because that corn would 

likely be consumed by deer or other non-target organisms. Previous studies to evaluate 

ivermectin effectiveness in controlling ticks in white-tailed deer populations have shown that 

little to no treated corn is available on the ground (Pound et al. 1996, Rand et al. 2000). Any corn 

left on the ground would not be expected to runoff into aquatic areas due to the size of the 

kernels with a very low probability of movement in a rain event. Ivermectin has low water 

solubility and partitions strongly to soil and organic matter and would not be expected to be in 

solution in detectable levels if there was a rain event that could result in transport of treated corn 

into aquatic habitats. The program will not place feeders within 50 meters of aquatic habitats on 

the refuge, further reducing the probability of any aquatic exposure. Deer droppings containing 

ivermectin may be transported as runoff or deposited directly into aquatic habitats, but this is not 

expected to be a major pathway of exposure for most aquatic organisms, because ivermectin in 

deer droppings would be bound to organic matter and not available to most aquatic organisms

(USDA 2017). Sediment dwelling invertebrates could be exposed due to the preferential binding 

of ivermectin to organic matter. However, the low probability of significant quantities of deer 

droppings being deposited into aquatic habitats, and the degradation of ivermectin would suggest 

that exposure to benthic aquatic invertebrate populations would be very low. Though ivermectin

and doramectin are considered highly toxic to most aquatic species, feeder barriers, fencing, 

buffer zones, and environmental fate of ivermectin and doramectin will minimize exposure to 

aquatic environments, although such measures will not eliminate the risk as treated deer could 

still excrete the drug into those environments. USDA-APHIS and FWS staff will use cameras 

and periodic inspections to ensure that treated corn is contained. Any spillage will be 

immediately cleaned up.

Ivermectin binds strongly to soil particles making it unlikely to leach into groundwater or runoff 

to surface water in a dissolved state (USDA 2017). Ivermectin breaks down to less bioactive 

compounds via photo and aerobic degradation; degradation in soil varies with the soil type and 

properties, sorption capacity, and temperature (USDA 2016). Ivermectin half-lives in soil are 7 

to 14 days at high temperatures in summer, but can be much longer (91 to 217 days) at low 

temperatures in the winter. Photolysis in water is less than 0.5 day in summer, and 39 hours in 

winter. When directly exposed to sunlight, its photolytic half-life was approximately 3 hours on a 

thin, dry film (USDA 2016). In addition, studies in cotton and food crops (sorghum, lettuce, 
23

carrots, and turnips) show that plants uptake little ivermectin from direct applications to plants or 

from soil (USDA 2016).

Ivermectin tolerance for ocelots is likely similar to that of domestic cats. Ivermectin toxicosis in 

domestic cats is not expected until exposure significantly exceeds 750 microgram (μg)/kg in an 

adult cat or 110 μg/kg in a kitten (USDA 2017). This would be equivalent to the consumption of 

approximately 2 kg of medicated corn by a 15 kg cat. Ocelots are not likely to consume 

medicated corn directly but could be exposed indirectly through consumption of exposed prey. 

There is relatively little information available regarding toxic ivermectin thresholds in wild birds. 

The drug is recommended for clinical use at 200 μg/kg in most avian species, but some 

applications recommend up to 1 mg/kg (Carpenter 2005, Plumb 2008). A dosage of 200 μg/kg is 

recommended for most snakes and lizards, but ivermectin is not considered safe for use in 

chelonians, crocodilians, indigo snakes, and skinks (Carpenter 2005, Plumb 2008). Overall, 

ivermectin is a relatively safe veterinary drug for vertebrates. Insectivorous birds would not 

likely ingest ivermectin-treated corn. Small insects that would serve as prey for these birds are 

also not expected to ingest ivermectin-treated corn. The risk assessment provided in the USDAAPHIS Ivermectin Corn EA concluded that direct risk to non-target birds is expected to be low 

based on the method of application for ivermectin-treated corn and low toxicity of ivermectin to 

birds (USDA 2017). Additionally, the use of the closed gravity feeder will reduce risk to most 

terrestrial non-target birds and other animal species. However, if sick or dead animals of any 

species are observed and presumably related to these treatments (ivermectin-treated corn and 

cattle treated with doramectin), an investigation will be conducted and that information provided 

to the refuge to make a determination if these activities need to be reevaluated or discontinued. 

4.2 Impacts to Air Quality

Placement of feeders and conducting an experimental grazing program will increase the number 

of vehicles on refuges by 1–2 vehicles per day. Though greenhouse gas release occurs during the 

routine use of vehicles from implementing the proposed action, the emissions and resulting 

changes in atmospheric CO2 concentration would be virtually undetectable at a global scale. 

Although efforts to reduce emissions are important, implementing the proposed action would not 

affect the climate of LANWR and LRGVNWR to any detectable extent. Driving on unpaved 

gravel roads stirs up dust, which has the potential to negatively impact air quality. Air pollution 

from fugitive dust due to the additional vehicle traffic on the refuge would be negligible to minor

and localized to refuge-wide. These effects would be intermittent and any one effect would be 

short-term (minutes to hours), though the effects would occur as long as the experimental 

grazing and placement of feeders occurs on FWS lands. 

4.3 Impacts to Soil and Vegetation 

Habitats on LANWR and LRGVNWR within the quarantine area are primarily managed for 

dense thornscrub woodlands suitable for ocelot or migratory birds and wetland habitats. 

LANWR has almost 55,000 acres of wetland habitats, ranging from freshwater to mostly 

brackish or salty. LANWR contains about 19,800 acres of coastal prairie and savannah habitat;

prairies are dominated by Gulf cordgrass (Spartina spartinae). Brushland occupies about 11,400 

acres of LANWR, which is generally well drained and not normally flooded. These areas are 

dominated by woody vegetation with 50 percent or more canopy cover. The brushlands on the 
24

lomas are essential to the survival of the endangered ocelot, as well as providing protective 

roosting habitat for aplomado falcons.

Implementing an experimental grazing program may have short-term minor adverse impacts on 

refuge habitats. Overgrazing can cause direct impacts on upland and riparian areas, such as loss 

of vegetation and soil compaction that lead to indirect impacts on the hydrology of an area and 

the ecosystems, both terrestrial and aquatic, that rely on it (EPA 1994). The impacts of livestock 

grazing will depend on timing, intensity, and frequency. Conducting the grazing treatment at 

stocking rates prescribed by USDA-NRCS and developing necessary buffers for sensitive habitat 

areas to including thornscrub, will generally minimize adverse impacts to vegetation. Loss of 

vegetation will occur in some areas of LANWR and LRGVNWR. This could result in both 

beneficial and adverse impacts. Removal of invasive grasses would benefit native habitat and 

wildlife species supporting the purposes for which the refuges were established by reducing 

competition with native grassland and brush species and reducing fire fuel amounts (Davidson 

1996, Bush and Van Auken 1990). Native vegetation removal through grazing would need to be 

closely monitored and the experimental grazing program would need to be adjusted as necessary 

to ensure minimal adverse impacts to native grassland and shrubland species. During heavy 

rainfall or wet conditions, there may be minor impacts to soil and vegetation trampling where 

cattle congregate. Additionally, during dry conditions, cattle will concentrate around watering 

areas causing impacts to the vegetation and soil in that immediate area. When cattle travel as a 

herd, they may create unwanted trails by trampling vegetation in its path. 

Fencing needs will be identified on each area proposed for grazing based on USDA-NRCS 

recommendations for grazeable areas and stocking rates. Fencing will likely be used to keep 

cattle out of sensitive areas to include thornscrub habitat, wetlands, threatened and endangered 

species needs including core ocelot monitoring sites, cooperative farm fields, thornscrub 

restoration sites, core ocelot monitoring sites, high public use, and administrative areas. Fencing 

will cause some fragmentation of habitat. Fencing will be wildlife-friendly on all interior areas. 

A more durable type of fencing may be considered on the perimeter/exterior refuge boundaries to 

reduce vehicle traffic, habitat trampling, and wildlife disturbance from frequent fence 

maintenance. 

Some vegetation loss and trampling will occur through the direct systematic treatment of cattle,

which requires gathering cattle every 21–28 days to inspect for CFTs and retreat with doramectin

injectable. This operation generally requires approximately 12–15 personnel (USDAAPHIS/TAHC ranch staff) for one or two days. To the extent practicable, temporary corrals will 

be set up off-refuge on an adjacent premises. Temporary corrals on refuges will be on the edge of 

the road, previously disturbed sites, or in areas where old corrals still exist from cattle operations 

on these lands prior to establishment as a refuge. These locations will be identified on a case by 

case basis to limit habitat trampling and disturbance. To mitigate potential impacts, the 

experimental grazing program will be continually monitored by FWS based on environmental 

conditions and adjustments to stocking rates as well as the movement of cattle. Additional 

fencing may be used to ensure impacts to refuge habitats are minimized.

There may be some adverse impacts on soil and habitat from placement and service of 

ivermectin-treated corn feeders. Vegetation disturbance and soil compaction will occur in the 
25

immediate vicinity surrounding the feeder and barrier. These impacts are likely to be negligible 

to minor since feeder placement will be prioritized near existing roads. If it becomes necessary to 

place a feeder off an existing road, all travel through refuge habitats will be conducted using a 

UTV or ATV, minimizing vegetation disturbance and soil compaction. 

4.4 Impacts to Threatened and Endangered Species 

Potential effects of the proposed action to listed species and critical habitat include toxicity of 

ivermectin and doramectin to non-target species, runoff of ivermectin and doramectin into 

aquatic areas, trampling of listed plants from cattle operations, species disturbance by feeder set 

up and weekly servicing, and species disturbance from cattle operations (gathering, providing 

water sources, installation of fences). The FWS has determined that implementing the proposed 

action may adversely impact the Gulf Coast jaguarondi, ocelot, northern aplomado falcon, and 

whooping crane due to potential disturbance and minimal habitat loss and subsequently issued a 

Biological Opinion (BO) in January 2018. Adverse impacts will be avoided by surveying 

potential feeder sites for presence of listed plants and nesting birds, placing feeders near existing 

roads and in areas already dominated by nonnative vegetation, avoiding creation or widening of 

trails to access feeders, implementing a 50-meter buffer for feeder placement from aquatic areas, 

avoiding removal of native vegetation and brush, and using a barrier around feeders that prevent 

access to treated corn by non-target species. All experimental grazing units will be identified and 

areas that may impact any listed species will be avoided or fenced off and no thornscrub habitat 

will be removed or cut-through. Additionally, once fencing needs have been identified, FWS 

staff will survey the proposed fence line to ensure there are not any denning ocelots or nesting 

birds in the area. 

Data indicates that ocelot vehicle collision is a significant source of mortality. Approximately 44 

percent (12 of 27) of known ocelot mortalities from 1982 to 1996 were vehicle related (Hewitt et 

al. 1998) and 45 percent of the total ocelot mortality documented in South Texas between 1983 

and 2002 were vehicle related (Haines et al. 2005b). As of April 2016, there were an additional 

seven ocelot road mortalities in South Texas. Implementation of reduced speeds, awareness 

training, and educating USDA-APHIS/TAHC staff will help reduce potential collisions.

A map of existing northern aplomado falcon nesting structures will be provided to USDAAPHIS/TAHC. USDA-APHIS/TAHC would avoid these aplomado nest structures by a 

minimum distance of 1,000 feet at all times of the year. Additionally, if nests are located, refuge 

staff will provide permittees with their locations and are to be avoided by a minimum distance of 

1,000 feet. If access is needed within the 1,000 foot buffer of a falcon nest, USDAAPHIS/TAHC would have to consult with the refuge manager. 

Additional conservation measures for the experimental grazing program are outlined below.

Conservation measures for Gulf Coast jaguarundi and ocelot:

To avoid effects of disturbance and habitat loss:

1. Thornscrub will not be cleared for placement of feeders or for fencing, water sources, or 

corrals associated with the experimental grazing program. Feeders will be placed in open 

areas away from brush habitat.

2. Feeders will be placed in locations that can be accessed by vehicles using existing trails 

and roads. In general, these trails will not be widened and no new trails will be created to 
26

place or access feeders. If necessary, trails may be widened or created to place and 

service feeders that are located in already open and disturbed areas with non-native plant 

species, such as buffelgrass (Cenchrus ciliaris, Pennisetum ciliare), or on bare ground to 

allow UTVs or ATVs to access the feeder.

3. Wildlife-friendly fencing will be required for all interior areas; more durable 

exterior/perimeter fencing may be considered to reduce the need for frequent 

maintenance causing additional disturbance. Cattle will be fenced off and excluded from 

any natural freshwater sources to include arroyos, resacas, wetlands, or rivers. STRC staff 

will survey the proposed fence line to ensure there are not any denning ocelots. All 

placement of fencing will be in consultation with FWS personnel. 

4. Feeders will be placed a minimum of 50 meters from aquatic areas. 

5. Game cameras will be rotated between 50 percent of feeder locations from February to 

April when species are most active to better determine what species may be accessing the 

feeders. Additionally, game camera placement will prioritize feeders near wetland and 

thornscrub habitat. The STRC has developed standard operating procedures to be 

implemented for a five-year period or duration of the SUP, and will coordinate with 

USDA-APHIS/TAHC to make sure the protocol meets the desired objectives. An annual 

report will be provided with the data and summary of ivermectin-treated corn utilization 

by species.

6. Range cubes provided by USDA-APHIS/TAHC (maximum of 4 pounds 

cubes/head/week) will be used as a tool in the gathering of the cattle. If this method is not 

successful, then horses may be used to gather cattle. 

7. Vehicle speed will not exceed 25 miles per hour (mph) unless otherwise posted on refuge

lands.

Conservation measures for aplomado falcons:

To avoid disturbance impacts to nesting falcons:

1. Surveys for nesting falcons will be conducted by a FWS-approved ornithologist on feeder 

locations and proposed fence lines within LANWR and LRGVNWR using approved 

survey protocol.

2. Any newly discovered falcon nests should be reported within one day to FWS staff.

3. Feeders or fences will not be placed within a 1⁄2- mile of an active falcon nest.

4. Feeders will be accessed once a week during the day, limiting disturbance to falcons.

5. Feeders will be placed in locations that can be accessed by vehicles using existing trails 

and roads. In general, these trails will not be widened and no new trails will be created to 

place or access feeders. If necessary and in consultation with refuge staff, trails may be 

widened or created to place and service feeders that are located in already open and 

disturbed areas with non-native plant species, such as buffelgrass, or on bare ground to 

allow UTVs or ATVs to access the feeder.

6. Range cubes provided by USDA-APHIS/TAHC (maximum of 4 pounds 

cubes/head/week) will be used as a tool in the gathering of the cattle. If this method is not 

successful, then horses may be used to gather cattle. Helicopters may be used with FWS 

approval if all other methods prove unsuccessful. 
27

Conservation measures for whooping cranes: 

To avoid feeding impacts and disturbance of whooping cranes:

1. Feeders will be accessed once a week during the day, limiting disturbance to migrating 

whooping cranes.

2. Should a whooping crane be sighted within 1,000 feet of ivermectin-treated corn feeders, 

all work (placing or servicing feeders) will stop until the whooping crane leaves the area.

3. Feeders will be placed in locations that can be accessed by vehicles using existing trails 

and roads. In general, these trails will not be widened and no new trails will be created to 

place or access feeders. If necessary and in consultation with refuge staff, trails may be 

widened or created to place and service feeders that are located in already open and 

disturbed areas with non-native plant species, such as buffelgrass, or on bare ground to 

allow UTVs or ATVs to access the feeder.

4. A 50-meter feeder placement buffer from aquatic areas will deter ivermectin and 

doramectin from adversely affecting the aquatic prey of the whooping crane.

5. Cattle will be fenced off and excluded from any natural freshwater sources to include 

arroyos, resacas, wetlands, or rivers.

6. Remote camera surveillance for the duration of the SUPs will be used if close to 

wetlands, potholes, or other sources of water near whooping crane habitat.

The FWS issued a BO in January 2018indicating that the proposed action as identified in this EA

will not likely jeopardize the continued existence of the ocelot, Gulf coast jaguarundi, northern 

aplomodo falcon, or whooping crane. As outlined in the January 2018BO, USDAAPHIS/TAHC, as the permittees, will provide the following to FWS: 1) information regarding 

take of an ocelot, jaguarundi, northern aplomado falcon, or whooping crane to FWS; and 2) 

annual reports. In addition, USDA-APHIS/TAHC will: 1) provide Endangered Species Act 

training to all CFTEP personnel; 2) follow established standard operating procedures for use of 

game cameras to monitor wildlife visiting the ivermectin corn feeders; and 3) conduct bi-annual 

ivermectin sensitivity testing of ticks.

4.5 Wildlife Disturbance

Implementing an experimental grazing program and placing feeders on both LANWR and 

LRGVNWR will have minor adverse impacts on various wildlife species due to increased 

disturbance. Placement of feeders will not remove brush or native vegetation that migratory birds 

would use as nesting substrate; feeders will be placed in areas dominated by bare ground, 

buffelgrass, or other non-native vegetation. Feeders will also be placed a minimum of 50 meters

from aquatic areas (seasonal and permanent wetlands) to avoid disturbance of nesting shorebirds 

from placement and servicing of feeders. Additionally, from March 15 to August 15, surveys for 

nesting migratory birds will be conducted prior to installing/maintaining fencing, gathering, or 

other operations associated with the cattle grazing program and any areas with nesting migratory 

birds will be avoided to include a 1⁄2-mile buffer from any nesting locations. Therefore, 

disturbance to migratory birds is anticipated to be minor and short-term in duration.

Wildlife disturbance may occur through interruption of normal behavior via flushing when 

placing and servicing feeders and conducting cattle operations, including potential use of 

helicopters to round up cattle. The disturbance is likely to be short term, and minor in intensity 

because once personnel are gone from the area normal behavior should resume. In general, 

typical wildlife responses to human disturbance may be fleeing, increased vigilance, disruption 
28

of feeding, and changes in habitat selection (Larkin 1996, Frid and Dill 2002). Noise can cause 

stress in animals and the responses to noise are varied. Geist (1979 as cited by Larkin 1996) 

believed that there was an energetic cost to animals being disturbed by noise.

For the proposed action, the most severe noise will be from vehicles being used to travel to 

service feeding stations and managing the grazing program through or alongside wildlife habitat

(1–2 vehicles per day). Generally, refuge vehicle use is limited to winter bird tours, wildlife 

monitoring, and general administrative use of these roads by refuge staff. Since these roads are 

travelled regularly, the addition of 1-2 vehicles a day is not likely to result is more than minor 

adverse impacts to wildlife that are short-term in duration. Additionally, vehicles will travel at 

reduced speeds (not to exceed 25 mph, dependent upon conditions) are anticipated to be minor 

and short-term.

Priority for fencing will be along existing roads to reduce disturbance to wildlife and habitat. 

Wildlife-friendly fencing will be used for all interior areas; more durable exterior/perimeter 

fencing may be considered to reduce the need for frequent maintenance. Nilgai can damage 

fencing and more durable exterior/perimeter fencing will reduce the necessary maintenance and 

associated disturbance from installing/fixing fences. The intention is to minimize disruption of 

native plant species destruction as much as possible while also keeping the fence placement in a 

straight line. There would be some loss of native vegetation while clearing area for fence lines, 

but vegetation will likely return on the fence line after installment. 

4.6 Impacts on the Human Environment

Human health risks associated with the use of ivermectin-treated corn in feeding stations are 

determined based on the toxicity of ivermectin and the potential for exposure. Ivermectin is a 

highly lipophilic drug, and as such, it is easily absorbed into the edible tissues of food animals 

(Baynes et al. 2000). As noted in the USDA-APHIS Ivermectin Corn EA, ivermectin has low 

toxicity in mammals because gamma-aminobutyric acid is found only in the central nervous 

system of mammals and is protected by the blood-brain barrier. Therefore, ivermectin is 

sometimes used as a human drug for the treatment of strongyloidiasis and onchocerciasis in the 

United States (FDA 2016), and the treatment of scabies, lice, and ascariasis in other countries 

(NIDDK 2016). A study conducted in 2002 indicated that ivermectin is generally well tolerated 

by healthy adults at levels up to 10 times the highest FDA-approved dose of 200μg/kg and at 

more frequent regimens (Guzzo et al. 2002). Ivermectin can be toxic to humans if accidental 

overdose or significant exposure to veterinary formulations occurs. As further described in the 

USDA-APHIS Ivermectin Corn EA, humans with exposure to ivermectin-treated corn include 

USDA-APHIS/TAHC staff filling feeders, refuge staff working in the area, and potentially the 

general public based on placement of feeders. The corn will be treated with ivermectin off-refuge 

and in well-ventilated areas with proper worker hygiene and properly functioning personal 

protective equipment. Drift from the application of ivermectin will not occur because ivermectin 

has low volatility and corn is loaded directly into the gravity flow feeders. 

For the general public, potential direct exposure to ivermectin-treated corn is unlikely based on 

feeder placement and barriers in place that restrict access to feeders. A sign in both English and 

Spanish will be posted at all feeder locations. Feeders are checked weekly so that damaged 

feeders can be repaired or removed, reducing the potential for exposure to the public from corn 

that may spill onto the ground if the feeder is damaged. Therefore, the potential exposure for the 

general public to ivermectin via inhalation, dermal exposure, or through ingestion of treated corn 
29

is not expected. There is potential for a person to ignore the signage and breach the exclusion 

fencing to access treated corn due to the fence’s height of 34 inches, however, in general, risk to 

the general public from direct contact exposure to ivermectin-treated corn in feeders in restricted 

access feeding stations is expected to be low.

The proposed treatment period is annually from February through July to prevent inadvertent 

human exposure (through human consumption of treated white-tailed deer). All corn will be 

removed from feeders 60 days prior to hunting season. The withdrawal time of 60 days allows 

ivermectin residues to decrease to below the tolerance levels in white-tailed deer (USDA 2017). 

Additionally, hunters will be notified that ivermectin-treated corn feeders are being used on 

refuges. Adverse impacts to hunters or members of the public consuming ivermectin in harvested 

deer meat is expected to be negligible because of the 60-day withdrawal period. Potential 

exposure of the general public from dietary consumption of meat from feral swine that have 

ingested ivermectin-treated corn is unlikely because of the installation of exclusion fencing, the 

design of feed ports, and the time of year associated with hunting swine for food. Feeders will be 

enclosed with welded wire panels to exclude non-target animals, such as hogs, and serviced 

weekly. However, while uncommon, breach of fencing by feral swine could occur (Cooper and 

Ginnett, 2000). When a breach occurs, USDA-APHIS/TAHC staff will repair the fencing and 

report the finding to FWS staff. The feed ports on the feeders are not easily accessible to feral 

swine because they are above ground level with a small opening and ventral lip to minimize 

spillage. The available corn to feral swine if they breach the fencing is minimal—it is estimated 

that there is less than 5 percent of the total treated corn in the feeder that ends up on the ground 

(D. Baca, pers. comm., email dated Oct. 19, 2016). Overall, based on the information above, the 

use of ivermectin-treated corn feeders is not likely to have adverse impacts on human health.

Although the feeders proposed for use on LANWR are constructed to limit consumption by nontarget species, they may not be able to exclude all other species under all circumstances. Feral 

hogs in particular are very common on LANWR and are extremely destructive. Damage to 

feeders by feral hogs could result in their consumption of ivermectin-treated corn. Although feral 

hogs can only be hunted on LANWR during designated hunting seasons, due to its invasive 

status, this species may be harvested on private property year-round without limitation. The 

recommended withdrawal time following oral administration of ivermectin (0.1 mg/kg body 

weight) in swine is 5 days (Baynes et al. 2000). Swine moving between refuge and private 

properties may pose a risk to public health if exposed to ivermectin-treated corn. A similar 

concern for the removal of nilgai is discussed below.

No CFT management activities would be allowed in any unit during a public hunt and/or during 

scout days related to hunting activities. If there is an emergency need related to cattle operations, 

USDA-APHIS/TAHC must get approval from the refuge manager before entering any unit open 

to public hunting to ensure proper coordination with hunters. Additionally, as discussed 

previously, placement/service of feeders is not permitted during public hunting season. The 

quality of hunt provided by the FWS to the paying public may decrease in units where cattle are 

present. Currently, public hunts on both LANWR and LRGVNWR do not have any cattle. Under 

the proposed action potential impacts may include (but are not limited to): safety concerns over 

hunters traversing by foot or on bicycle in close proximity to cattle, particularly those unfamiliar 

with cattle behavior; potential damage to hunter-owned equipment and personal property that 
30

may get damaged by cattle (i.e. hunting ground blinds, tripod stands, game carts, and vehicles 

parked in hunt units); and mistakenly injuring or killing cattle by shooting or hitting them with a 

vehicle. Hunters will be provided with additional safety information during hunter orientation for 

units that have cattle prior to their hunt. The USDA-APHIS/TAHC and FWS will work together 

to minimize impacts to hunting, which is a priority public use as defined by the National Wildlife 

Refuge System Improvement Act of 1997. 

The LANWR welcomes over 300,000 visitors every year. The primary visitation occurs at 

Adolph Thomae Jr. County Park (ATCP) and the area around the LANWR Visitor Center. As 

outlined in the proposed action, when determining locations for implementing experimental 

grazing, the refuges would avoid areas of high public use to minimize any impacts to visitors 

engaging in other priority public uses (fishing, wildlife observation and photography, 

interpretation, and environmental education) on the refuges. Therefore, ATCP and the area 

around the LANWR Visitor Center will be excluded from the cattle grazing based on high public 

use; however, there may be ivermectin corn feeders placed in close proximity to these sites. 

Visitors to these areas of the refuge may feel as though the presence of deer feeders diminishes 

their experience by the placement of an unnatural object.

Additionally, many of the visitors who come to the LANWR Visitor Center are interested in 

taking guided tours onto various refuge units. LANWR offers guided habitat and birding tours, 

which venture into the refuge by traversing the service roads or public tour routes. The most 

popular tour is the open-air habitat tram tour. This tram tour, typically offered from Friday 

through Sundays during the winter months, has been offered as a night tour and a special 

seasonal tour when wildlife are present for viewing. In addition, the tram tour may be offered 

during the spring and fall depending on resource availability. This popular public tour uses what 

staff know as Management Unit 7, on Bayside Wildlife Drive. This wildlife drive is currently 

open to hiking, biking, and the refuge-led tours. Bayside Drive was closed to personal vehicle 

use in September 2013, but current plans are to reconstruct the Drive and reopen it to vehicles 

sometime after March 2018. Additionally, bird tours go to various units within LANWR’s “main 

unit”, but also to other tracts managed by LANWR, including the Bahia Grande Unit. 

Implementing the experimental cattle grazing and placing ivermectin-treated corn feeders have 

the potential to impact visitor experience. Many visitors go to experience the native species and 

habitat on the refuge and do not want to see cattle on the landscape. On the other hand, some 

visitors may appreciate seeing cattle back on the landscape since much of that area was grazed 

by cattle prior to being acquired by FWS. Visitors travelling through the refuge on roadways 

where there are ivermectin-treated corn feeders may feel as though the presence of deer feeders 

diminishes their experience by the placement of an unnatural object, particularly during guided 

tours. The FWS will continue to monitor all refuge programs and make adjustments as needed to 

balance CFT eradication efforts and providing a quality visitor experience for the public. 

4.6.1 Impacts on Cultural Resources

The GPS coordinates for proposed feeder locations and proposed fence lines would be provided 

to the regional archeologist for clearance prior to placement. Any known cultural sites would be 

avoided. 
31

4.7 Assessment of Cumulative Impacts

A cumulative impact is defined as an impact on the environment that results from the 

incremental impact of the proposed action when added to other past, present, and reasonably 

foreseeable future action regardless of what agency (federal or nonfederal) or person undertakes 

such other actions. Cumulative impacts can result from individually minor but collectively 

significant actions taking place over a period of time (40 CFR 1508.7).

Cumulative impacts are the overall, net effects on a resource that arise from multiple actions. 

Impacts can “accumulate” spatially, when different actions affect different areas of the same 

resource. They can also accumulate over the course of time, from actions in the past, the present, 

and the future. Occasionally, different actions counterbalance one another, partially cancelling 

out each other’s effects on a resource. But more typically, multiple effects add up, with each 

additional action contributing an incremental impact on the resource.

As outlined in the USDA-APHIS Ivermectin Corn EA, similar uncertainties are associated with 

this EA primarily from lack of information about the effects of ivermectin, its formulations, 

metabolites, and potential mixtures to non-target organisms that can occur in the environment. 

These uncertainties are not unique to this assessment but are consistent with uncertainties in 

human health and ecological risk assessments with any environmental stressor. In addition, there 

is uncertainty in the number and location of feeding stations, which are based on the number and 

density of deer in the program area. Another area of uncertainty is the potential for cumulative 

impacts to human health and the environment from the proposed use of ivermectin in the 

CFTEP. Areas where cumulative impacts could occur are: 1) repeated worker and environmental 

exposures to ivermectin from program activities; 2) co-exposure to other chemicals with a 

similar mode of action; and 3) exposures to other chemicals in mixtures and how that may affect 

the toxicity of ivermectin. 

Ivermectin is a widely used anti-parasitic drug in humans, livestock, and pets (Crump and 

Omura, 2011). There would be increased environmental loading from the use of ivermectintreated corn for white-tailed deer where there are also ivermectin uses for cattle and other 

domestic animals. Currently, there are about 2,000 feeders in the 13-county area that was 

identified in the USDA-APHIS Ivermectin Corn EA. The impacts to white-tailed deer are 

expected to be incrementally negligible when put in context with other stressors because the dose 

of ivermectin is considered therapeutic and not intended to result in adverse effects. Domestic 

animals that are receiving ivermectin for other purposes are also not expected to have cumulative 

impacts resulting from the proposed use of ivermectin-treated corn because domestic animals 

will not be able to access the feeders. Cumulative impacts to aquatic organisms will be minor 

because of buffer zones that will result in a low probability of exposure to aquatic habitats from 

the proposed use of ivermectin-treated corn.

Additional CFT control efforts include the removal of nilgai. Nilgai are one of the primary 

factors for the spread of CFTs in Willacy and Cameron counties. Nilgai do not eat corn; 

therefore, they are not treated for CFT. Currently, the only mechanism for addressing the spread 

of CFTs by nilgai is population reduction. The STRC is responsible for the majority of the nilgai 

harvests (through public hunting and USDA-APHIS culling) in the temporary quarantine area 

even though significant numbers occur throughout the temporary quarantine area. Some
32

landowners around LANWR are opposed to reducing nilgai numbers due to the potential 

economic loss of the landowner. USDA-APHIS, TAHC, and FWS will continue to explore all 

available options for eradicating CFTs in Texas. 

There is likely going to be increased ongoing disturbance to wildlife and habitat through 

implementation of the CFTEP. In addition to CFT control efforts taking place on the STRC

lands, private landowners are conducting various efforts to battle the CFT infestation. 

Throughout the South Texas landscape, to varying degrees, there are nilgai and white-tailed deer 

harvests, ivermectin-treated corn feeders, and systematic treatment of cattle, which increases the 

amount of vehicle traffic and noise disturbance to native wildlife. Encroachment from urban 

development that brings increased human disturbance; energy exploration and development;

Customs and Border Protection operations that include roads, drag roads, off-road impacts, 

lights, border fence, and road maintenance will also likely result in habitat loss and disturbance 

to wildlife. The FWS will continue to coordinate with Customs and Border Patrol and private 

industry on projects impacting national wildlife refuges and through the Endangered Species Act 

Section 7 process to minimize impacts to trust resources to the extent possible. The wildlife 

disturbance caused by implementing additional CFT eradication actions is likely to be 

temporary, and once personnel have left the area, normal wildlife behavior should resume. 

Therefore, the proposed action is expected to be incrementally negligible when put in context of 

all the other activities occurring on the landscape. 

4.7.1 Other Projects in the Area impacting T&E Species

Wind energy projects have drastically increased in the Rio Grande Valley and have impacted 

habitat used by ocelots, jaguarundi, and falcons by causing fragmentation of the landscape. Oil 

and gas development and the rapid economic expansion of the large metropolitan areas with the 

continuing influx of immigrants, retirees, and increased tourism will likely continue to result in 

the loss of brushlands and coastal grasslands. Road expansions to accommodate the Rio Grande 

Valley development and road network, North American Free Trade Agreement, and border 

crossings will likely increase loss and fragmentation of habitat corridors and increase road 

mortality for ocelots. Encroachment from urban development that brings increased noise, light, 

fencing, and human disturbance; Customs and Border Protection operations that include roads, 

drag roads, off-road impacts, lights, border fence, and road maintenance will also likely result in 

the loss of habitat and avoidance of areas by the endangered ocelot, jaguarundi, and aplomado 

falcon across their listed ranges. The proposed action is expected to be incrementally minor, 

when put in the context of all the other activities occurring in the area. 

4.8 Environmental Justice

Executive Order 12898 (Federal Actions to Address Environmental Justice in Minority and LowIncome Populations; February 11, 1994) was designed to focus the attention of federal agencies 

on the environmental and human health conditions of minority and low-income populations, with 

the goal of achieving environmental protection for all communities. The order directed federal 

agencies to develop environmental justice strategies to aid in identifying and addressing 

disproportionately high and adverse human health and environmental effects of their programs, 

policies, and activities on minority and low-income populations. The order is intended to 

promote nondiscrimination in federal programs substantially affecting human health and the 

environment, to provide minority and low income communities with access to public 

information, and to provide opportunities for participation in matters related to human health and 
33

the environment. Adverse direct or indirect effects on vulnerable populations are not likely to 

occur when there is proper handling of ivermectin-treated corn to minimize exposure combined 

with effective communication about CFTEP with program area residents.

Federal agencies must ensure their programs and activities are accessible to persons with limited 

English proficiency as directed by EO 13166. To meet this need, USDA-APHIS and FWS 

conduct outreach to English-speaking and Spanish-speaking communities through a variety of 

public notices and informational brochures about program activities. USDA-APHIS and FWS

will invite all stakeholders, including Colonia ombudspersons and residents of Colonias, to any 

public meetings. If this EA leads to a FONSI, then USDA-APHIS will provide a Spanish 

translation of the FONSI to all staff for their use when working with the public. In addition, if a 

FONSI is reached, USDA-APHIS will also notify the Director of the Colonia Initiatives Program 

in South Texas about the new CFTEP activities.

5.0 CONSULTATION, COORDINATION AND DOCUMENT PREPARATION

Preparers: 

Michelle Gray, U.S. Department of Agriculture, Animal and Plant Health Inspection Service

Monica Kimbrough, U.S. Fish and Wildlife Service, National Wildlife Refuge System, 

Southwest Region

List of Agencies, Organizations, and Persons Contacted:

USDA Cattle Fever Tick Eradication Program, Hallie Hasel, DVM 

USDA Cattle Fever Tick Eradication Program, Roberta Duhaime, DVM

U.S. Fish and Wildlife Service, Wildlife Health office, Samantha E. J. Gibbs, DVM PhD

U.S. Fish and Wildlife Service, Southwest Region, Kelly McDowell

U.S. Fish and Wildlife Service, South Texas National Wildlife Refuge Complex, Robert Jess

U.S. Fish and Wildlife Service, South Texas National Wildlife Refuge Complex, Sonny Perez

U.S. Fish and Wildlife Service Laguna Atascosa National Wildlife Refuge, Boyd Blihovde 

U.S. Fish and Wildlife Service, Lower Rio Grande Valley National Wildlife Refuge, Bryan 

Winton

U.S. Fish and Wildlife Service, Texas Coastal Ecological Services Field Office, Dawn Gardiner

U.S. Fish and Wildlife Service, Alamo Ecological Services Field Office, Ernesto Reyes

Texas Animal Health Commission, Roger Parker, DVM PhD

Texas Animal Health Commission, Chelsea Pike, DVM
34

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39

Appendix A. TAHC Situation Report from December 2017
40
41

Appendix B. Summary of and Responses to Comments Received on the 

Environmental Assessment Prepared for Cattle Fever Tick Eradication 

on Laguna Atascosa and Lower Rio Grande Valley National Wildlife 

Refuges

Issue: Several commenters expressed a concern about non-target vertebrates and invertebrates 

consuming ivermectin-treated corn. They also expressed a concern about hunting and consuming 

game animals.

Response: The risk of ivermectin to non-target vertebrates and invertebrates has been 

evaluated previously in risk assessments by the U.S. Food and Drug Administration 

(FDA) and USDA-APHIS (Bloom and Matheson 1993, USDA 2017). The available data 

and the proposed use pattern in the Cattle Fever Tick Eradication Program (CFTEP) 

suggest that the risk is low to most non-target vertebrate and invertebrate species and 

would be localized to areas in proximity to the feeders. Deer may range over larger areas; 

however, they would be expected to congregate near feeders resulting in more deer 

droppings that could contain ivermectin in a smaller area. Deer that forage farther away 

from the feeders after receiving a dose of ivermectin could impact sensitive invertebrates 

but the risk would be lower due to the wider distribution and lack of fecal accumulation 

in one location.

As mentioned in the EA, the group of non-target organisms that are at greatest risk would 

be terrestrial invertebrates that would use dung from animals that ingested ivermectintreated corn. These potential impacts would be mostly to flies and beetles that use dung 

and would only occur during the dosing period which lasts from February to July, with 

potential impacts to diversity but with no changes in overall abundance (Wall and 

Beynon 2012, Jochman et al. 2015). The risks to sensitive invertebrates would be 

expected to last for approximately one to two weeks after the treated corn is removed 

based on a summary of studies that evaluated oral dosing of ivermectin and effects to 

certain dung dependent species (Floate et al. 2005). After reviewing the literature and 

assessing the proposed program use, we expect the risk to terrestrial invertebrates to be 

low.

Indirect effects to non-target vertebrates that rely on terrestrial invertebrates as prey are 

also expected to be low because available studies show that impacts may occur for some 

sensitive invertebrate species, but not all. Only those invertebrates sensitive to 

ivermectin, and that use dung from treated white-tailed deer, would be at risk. The lack of 

impacts to other invertebrates, including some that are dung dependent, suggests that 

terrestrial invertebrate abundance would not be affected and, therefore, would not be 

anticipated to result in indirect effects to vertebrates that feed on invertebrate prey items. 

APHIS evaluated the potential for risks to the ocelot in a previous EA (“Cattle Fever Tick 

Eradication Program Use of Ivermectin Corn Final Environmental Assessment”) 

regarding the dosing of deer with ivermectin (USDA 2017). This type of secondary risk 

where animals feed on prey items that may contain residues of ivermectin showed that an 

animal such as an ocelot would have to consume many times its daily consumption rate 
42

to exceed a median lethality value. Sublethal effects would also not be anticipated 

because the exposure estimates in the previous EA assumed that ocelots would consume 

only mice containing residues and that the residues in the mice would not include any 

metabolism and depuration. In the wild, ocelots feed on a variety of items such as rabbits, 

snakes, lizards, and frogs, many of which would not have residues of ivermectin. 

Available data for upland game birds such as quail show low toxicity from ivermectin in 

oral dosing and dietary studies (USDA 2017). Ivermectin has been used in other birds, 

such as wild pigeons, to treat various parasites without negative impacts. In an 

environmental review of ivermectin, the FDA reported that mallards exposed for 18 

months to ivermectin showed no effects on reproduction at concentrations ranging from 3 

to 12 parts per million (Bloom and Matheson 1993). Ivermectin has also been used to 

treat internal and external parasites in various vertebrates in zoo settings including 

various bird species without reported adverse effects (Panayotova-Pencheva 2016). The 

risk to birds in South Texas is expected to be low based on the lack of impacts to other 

bird species. The potential for exposure to wild turkeys, for example, will be low because 

they will not be able to directly access the feeders because they are above ground level 

with a small opening and ventral lip to minimize spillage. Exposure would only be to any 

spilled corn during white-tailed deer feeding, which is expected to be minimal. USDAAPHIS and FWS staff will use cameras and periodic inspections to reduce exposure from 

spilled corn. If found, it will be immediately cleaned up.

Exposure of feral swine to ivermectin-treated corn will be minimized because the feeders 

will be enclosed with welded wire panels to exclude non-target animals, such as hogs, 

and will be serviced frequently. However, while uncommon, breach of fencing by feral 

swine could occur. When a breach occurs, Program staff will repair the fencing and 

report the finding to U.S. Fish and Wildlife Service (FWS) staff. The feed ports on the 

feeders are not easily accessible to feral swine due to their height.

Other game animals would not be exposed to ivermectin-treated corn based on the design 

of the feeders, which is above ground level with a small opening and ventral lip to 

minimize spillage. While the incidence of spilled corn is low based on field observations 

(<5 percent), there is the potential for some exposure to non-target game animals that 

would access spilled feed. If excessive spillage does occur, the feeder will be modified to 

minimize spilled corn. The low quantities of spilled feed would reduce the potential for 

exposure for most game animals, other than white-tailed deer, the target species. In 

addition, the time frame for placing feeders with ivermectin-treated corn (February 

through July) would be outside of the hunting season for most game animals in Texas. 

Game cameras also will be used to monitor non-target use and, if needed, feeders will be 

moved to minimize non-target exposure. 

Ivermectin is registered for human use. Its low potential to result in residues in tissue of 

harvested game animals would not be expected to result in impacts to human health based 

on available mammalian data used to support its registration (USDA 2017) 

Issue: Several commenters wondered what would happen if deer eat too much or too little 

ivermectin-treated corn. One commenter also wanted to know why there is a waiting period 

before deer can be hunted and consumed if ivermectin was safe for a deer to eat.
43

Response: The number of feed sites, quantity of corn, and ivermectin dosing levels are 

designed to ensure that white-tailed deer receive the appropriate dose to treat for ticks. 

The number of feed sites will be determined based on the number and density of deer (1 

feeder per 20–30 deer to minimize excessive competition and social dominance), and 

density of feeders per area (deer do not have to travel more than 1⁄4- to 1⁄2-mile to access 

feed = 1 per 125 acres to 1 per 500 acres), minimizing the potential for over or under 

consumption of ivermectin-treated corn. The proposed concentrations in the CFTEP are 

based on published studies that document effectiveness against tick species on whitetailed deer when fed ivermectin-treated corn (USDA 2017). Ivermectin has been used 

successfully for treatment of parasites in a variety of mammals, including deer species. 

The density of feed sites and dose of ivermectin are designed to maximize effectiveness 

of the treatments. A deer would have to consume more than its daily food consumption 

rate to ingest enough ivermectin to result in an adverse effect, which is unlikely based on 

how the feed sites are established and monitored.

The FDA has set tolerance levels for treating various mammals, including domestic 

livestock and animals such as the American Bison, with ivermectin to control parasites 

(USDA 2017). The waiting period between treatment of white-tailed deer with 

ivermectin-treated corn and hunting is a conservative estimate to ensure that any 

ivermectin residues would be below detection in meat that would be harvested and 

consumed by the public. The 60-day period between allowing deer to feed on ivermectintreated corn and hunting is based on various studies that document the half-life of 

ivermectin in tissues and organs of various mammal species, including deer (Pound et al. 

2004, USDA 2017). 

Ivermectin levels in corn are such that white-tailed deer receive an effective dose for 

treating ticks but would not receive a dose that could result in adverse effects to the deer 

themselves. Pound (1996) determined that the current dosing rate will result in maximum 

blood serum levels in deer of 30 parts per billion (ppb). The target concentration of 30 

ppb assures a high degree of efficacy even in those deer that may consume as little as 

one-third of the targeted dosage. Serum levels of 10 ppb (one-third of the proposed 

dosage) should produce 100 percent efficacy against ticks attempting to feed on treated 

animals (Pound et al. 1996, Nolan et al. 1985, Miller et al. 1989). The levels of 

ivermectin in blood serum will be approximately three times higher than that needed for 

achieving efficacy, ensuring an effective dose of ivermectin in situations where a deer 

does not consume a comparable amount of ivermectin-treated corn to other deer that visit 

the feeders. 

Issue: One commenter asked why the proposed concentrations of ivermectin are lower than what 

is used in commercial applications and expressed concern about increasing pest resistance.

Response: The proposed concentrations of ivermectin may differ from commercial 

applications to livestock for reasons such as differences in the method of dosing, time 

interval of dosing, and the parasite being controlled. The proposed concentrations in the 

CFTEP are based on published studies that document effectiveness against tick species 

on white-tailed deer when fed ivermectin-treated corn (Rand et al. 2000, USDA 2017. 

Pound (1996) determined that the current dosing rate will result in maximum blood 

serum levels in deer of 30 ppb. The target concentration of 30 ppb assures a high degree 
44

of efficacy even in those deer that may consume as little as one-third of the targeted 

dosage. Serum levels of just 10 ppb (one-third of the dosage) should produce 100 percent 

efficacy against ticks attempting to feed on treated animals (Pound et al. 1996, Nolan et 

al. 1985, Miller et al. 1989). Subsequently, the risk for increased pest resistance is 

minimal. Additionally, USDA-APHIS will conduct bi-annual ivermectin sensitivity 

testing of ticks. 

Issue: Multiple commenters raised concerns about negative impacts of cattle grazing on native 

vegetation, which is important for the endangered ocelot, and important to the entire ecosystem.

Response: The FWS agrees with the importance of protecting sensitive habitat on the 

refuge. Prior to permitting experimental grazing, the FWS will evaluate any proposed 

area by USDA/(Texas Animal Health Commission (TAHC) and will ensure there are 

necessary buffer zones and avoidance measures identified to protect areas including 

thornscrub habitat, wetlands, threatened and endangered species considerations, 

thornscrub restoration sites, and core ocelot monitoring sites. Permitting experimental 

grazing on various refuge units will be evaluated on a case-by-case basis. Additionally, 

wildlife-friendly fencing (safe for mammals and ground-nesting birds) will be used for all 

interior areas. The USDA-Natural Resources Conservation Service (NRCS) production 

report provides information for stocking rates, and cattle will be stocked at that level or 

below. The CFTEP has proposed cattle grazing as an experimental use and it will be 

continuously monitored. The refuge will carefully monitor all impacts, particularly to

native vegetation, and adjust the experimental grazing program as needed including 

removing cattle from an area.

Issue: Multiple commenters had concerns about cattle introducing non-native grasses on the 

refuge and the impact cattle would have to native plant communities. 

Response: Invasive grasses in this area are common, both on and off-refuge. Cattle 

grazing could provide a benefit by removing some non-native grasses. Grazing is a 

successful management tool in reducing invasive grasses on national wildlife refuges. If 

it is determined that cattle would be introduced to a unit that has predominately native 

grasses, cattle will be required to be on weed-free feed prior to being placed on the 

refuge. Although some seeds can take a long time to work their way through the 

gastrointestinal tract of cattle, this requirement would reduce the risk of spreading nonnative grasses. The FWS will use an adaptive management approach for the experimental 

cattle grazing program and retains the right to remove or adjust stocking rates of cattle, as 

needed, to minimize impacts to native vegetation.

Issue: One commenter questioned the scale used to discuss greenhouse gas emissions relating to 

the routine use of vehicles. 

Response: We intended for the comparison to indicate the negligible level of changes in 

atmospheric CO2 concentration from the proposed program as being indistinguishable 

from current background ambient levels, including those that naturally occur. We agree 

that local actions cumulatively impact overall global levels. However, when an action’s 

impacts already are at undetectable levels, there is a point of diminishing returns 
45

associated with implementation of mitigation measures because their effectiveness also 

would be undetectable. 

Issue: One commenter expressed concern about the global effect that chemicals have on the 

planet and its inhabitants.

Response: This EA discusses the specific chemicals proposed for use in the program. 

This EA also discusses the potentially impacted ecosystems, and has built mitigation 

measures into the proposed action to ensure any impacts do not rise to the level of being 

significant. These measures minimize the amount of chemical released into the 

environment, and then natural chemical degradation occurs until presence of the chemical 

cannot be detected. There is an inherent balancing of competing interests that occurs 

when determining what promotes a healthy environment: a tick-free environment 

improves animal health and the U.S. economy, whereas a tick-filled environment may be 

associated with a reduced presence of chemicals in specific areas. Another balancing 

occurs when comparing early treatment of specific areas to later treatment of larger areas. 

The overall chemical use will be less with early treatment of specific areas.

Issue: One commenter was concerned that the perceived benefit of the proposed action does not 

take into consideration the negative impacts on the broader habitat. In addition, one commenter 

said that this proposed action provides benefit to only a few privileged people.

Response: The commenters should consider that wildlife on a refuge move in and out of 

the broader habitat, so any benefits to them positively impact adjoining ecosystems where 

they roam. This is the main benefit associated with treating animals for ticks on a refuge, 

which in turn benefits the general public. 

USDA-APHIS is responsible for (1) protecting and improving the health, quality, and 

marketability of U.S. animals by eliminating animal diseases, and (2) monitoring and 

promoting animal health and productivity. The Animal Health Protection Act of 2002, as 

amended, (7 U.S.C. §§ 8301-8317) provides broad authority for APHIS to prevent the 

introduction into or dissemination within the United States of any pest or disease of 

livestock (§§ 8303-8305). The Act authorizes prohibition and restriction of the 

importation, exportation, and interstate movement of animals moving in trade and strays, 

as well as exportation, inspection, disinfection, seizure, quarantine, destruction and 

disposal of animals and conveyances (§§ 8303-8308). This includes the ability to “carry 

out operations and measures to detect, control, or eradicate any pest or disease of 

livestock” and identifies specific cooperative programs as one way to achieve these 

actions (§ 8308). Subsequently, USDA-APHIS established the CFTEP, and FWS is 

supporting the CFTEP to minimize impacts caused by the invasive CFT on the broader 

landscape. 

While the livestock industry is a critical component of the South Texas economy, we also 

recognize the value of this unique ecosystem and the subsequent economic benefits 

ecotourism also provides to this region. 

Issue: Numerous commenters brought up nilgai as a point of discussion. Some asked for an 

explanation of the numbers or methods for reducing nilgai while others disagreed with the use of 
46

private contractors for removing nilgai. Many commenters wanted more nilgai public hunt 

opportunities. One commenter suggested offering an incentive for landowners to manage nilgai 

numbers on their property, which could result in an overall cost savings to the CFTEP.

Response: Nilgai removal is part of the baseline action (current management) and is 

considered under Alternative A, which is sometimes referred to as the “No Action 

Alternative”. It is not, however, part of the proposed action. Nilgai removal was 

considered extensively in the “Population Reduction of Nilgai in the Boca Chica Beach, 

Bahia Grande, and Brownsville Navigation District Areas, Cameron County, Texas”, 

September 2014 EA. Exotic nilgai are still an important host and reservoir for cattle fever 

ticks (CFT) on the refuge and USDA-APHIS and FWS will continue to work 

cooperatively to decrease nilgai and CFT numbers.

In addition, some landowners are voluntarily incorporating nilgai management. Although 

we do not have an official government incentive for nilgai reduction, CFTEP staff will 

continue to conduct outreach to landowners to explain how nilgai impact CFT 

populations.

Issue: Several commenters expressed concern about surrounding landowners remaining 

unwilling to minimize the population of nilgai on their land, especially since many landowners 

receive money for hunts. Subsequently, there is concern that even if all nilgai or hogs were 

removed from the refuge, they would come right back from the surrounding private properties 

potentially carrying CFTs.

Response: We acknowledge that the potential exists for nilgai or deer to carry CFTs from 

surrounding properties onto refuge property, which is why the proposed action involves a 

study. Both agencies will evaluate the information collected each year and will adjust the 

overarching CFTEP accordingly. We will continue to use a multi-faceted approach to 

deal with CFT infestations both on and off-refuge property in the environment, on cattle, 

and on wildlife. 

Issue: One commenter suggested that “nilgai reductions” was not an acceptable statement, and 

we should instead say “continue the hunting practices currently managed by the refuge” and 

“work with the refuge and surrounding landowners to implement treatment methods on nilgai to 

control and/or eliminate the CFT”. 

Response: At the moment, the only viable CFT control option for nilgai is removal. 

Refuge management will employ this method as needed. CFTEP and TAHC staff will 

continue to encourage surrounding landowners to assist with this endeavor on their own 

properties.

Issue: One commenter suggested that the agencies should allow landowners to provide 

assistance with the distribution and maintenance of the ivermectin-treated corn feeders due to 

the lack of CFTEP staff and funding. He also noted the EA references working with landowners, 

but there is nothing in the Alternatives section referencing this idea.

Response: Budget constraints and lack of personnel will continue to be a logistical issue 

in filling and maintaining feeders. However, the proposed action outlined in this EA is for 
47

placement of feeders on refuge land. Any approved Special Use Permits will include 

limits to feeder access and require protocols to negate the harm of non-target species.

In addition, federal rules require this use of ivermectin to be conducted by TAHC and 

CFTEP personnel only. FDA rules for extra-label use require a valid veterinary-clientpatient relationship. As the state agency responsible for stewardship of white-tailed deer, 

Texas Parks and Wildlife Department (TPWD) is the client. We have a signed 

Memorandum of Understanding with the TPWD to this end. 

Likewise, the FDA requires the authorized agencies to comply with strict recordkeeping 

requirements regarding the location of each feed site and the amount of product used in 

each of the feeders. The FDA also requires authorized agencies to ensure compliance 

with withdrawal of the product prior to commencement of the deer hunting season. These 

requirements can only be met when USDA-APHIS and TAHC personnel administer the 

product.

USDA-APHIS and FWS appreciate bringing the oversight regarding landowner 

communication in the Alternatives section to our attention. We updated the alternatives to 

reflect our continued desire to communicate frequently with landowners surrounding the 

refuges.

Issue: A few commenters expressed an interest in having the CFTEP embrace the methods being 

developed by Dr. Goolsby (nematodes and wasp). One commenter said the state and federal 

governments should help fund his research.

Response: While biocontrol methods are of interest to USDA-APHIS, biocontrol 

methods are not part of the proposed action described in this EA. Dr. John Goolsby is 

employed by USDA-Agricultural Research Service, so USDA-APHIS is indeed aware of, 

and has funded, Dr. Goolsby’s efforts. Currently, he is still conducting field research 

regarding biocontrol methods that could assist the CFTEP. Should this biocontrol method 

ever become a viable option, USDA-APHIS will prepare environmental documentation 

(NEPA, Endangered Species Act compliance, etc.) assessing its potential use in South 

Texas.

Issue: One commenter expressed his displeasure with having CFTEP personnel on his private 

property. 

Response: The CFTEP and TAHC are disappointed to hear about this dissatisfaction with 

its staff. If there is ever a problem, please contact the area supervisor so we can 

understand how to better serve you.

Issue: One commenter suggested that the proposed study take place on private ranches that 

might benefit from the study instead of on the refuge.

Response: Ivermectin-treated corn is currently being used to control ticks on ranches 

outside of the refuge (see “Cattle Fever Tick Eradication Program Use of Ivermectin 

Corn Final Environmental Assessment”). The proposed study introduces another 

potential tool that could be used to eradicate ticks in South Texas. Cattle under systematic 

treatment, in addition to white-tailed deer fed ivermectin-treated corn, in areas where 
48

there is no other year-round method to eliminate ticks, could help to eradicate CFTs from 

the landscape, which is a benefit to everyone in South Texas. It is important to note that 

grazing cattle that are on a systematic treatment is a proven method of eradicating CFTs.

Issue: One commenter asked what would happen if a tick was missed on cattle at the refuge, and 

this cattle was shipped north.

Response: As with cattle in any part of the permanent or temporary quarantine zones, 

USDA-APHIS and TAHC follow protocol to minimize the risk of this scenario 

occurring. In addition to routine treatments of cattle grazing on the refuge, there are 

additional inspections and treatments required for movement of these animals off of the 

refuge to livestock markets. Any cattle removed from the study area will be scratch 

inspected and treated with an acaricide at least twice, even if no ticks are found. These 

inspections and treatments are administered by TAHC and USDA-APHIS personnel. 

Because of this process, it is highly unlikely that any viable ticks will be moved on 

livestock from this property.

Should an outbreak occur in a new area, USDA-APHIS and TAHC will follow their 

response plans and apply resources to eradicate these new outbreaks. An outbreak of 

CFTs in Jim Wells County, which is north of the permanent tick quarantine line, included 

infested cattle and deer. It was recently cleared up after following agency response plans. 

An outbreak in Kleberg County that involved infested nilgai and cattle was also recently 

cleared up following a reduction in nilgai numbers and systematically treated cattle.

Issue: One commenter asked if any plans had been made to continue to attract white-tailed deer 

to the corn feeder sites from August to January when ivermectin-treated corn cannot be used due 

to required withdrawal periods. This would establish a continuous pattern of use for the deer.

Response: When deemed strategic and as resources permit, the CFTEP does attempt to 

employ the use of untreated corn as part of the management of potential CFT hosts offrefuge property. As part of the Special Use Permit on the refuge, however, feeders will 

not be filled during non-treatment periods.

Issue: One commenter asked how many sites on refuge property are anticipated to be designated 

for each treatment combination. The commenter also asked if there was an estimated length of 

the grazing season.

Response: Specific treatment combinations and sites are still being determined. 

Deliberations with external consultants, CFTEP and TAHC managers, and refuge 

management are ongoing. Grazing season lengths will depend upon presence/absence of 

CFTs and other factors, including forage conditions.

Issue: One commenter asked for clarification about the stocking rate. They noted that the 

recommended stocking rate is 50 animal units among the three units of Laguna Atascosa 

National Wildlife Refuge (LANWR) and wanted to know if these animal units were intended to be 

on an annual or monthly timeframe. Additionally, the commenter wanted to know if there are 

recommended stocking rates for grazing the tracts of land on the Lower Rio Grande Valley 

National Wildlife Refuge (LRGVNWR).
49

Response: The USDA-NRCS recommendations refer to annual stocking rate; these 

recommendations are intentionally on the conservative site. The USDA-NRCS also 

recommends routine monitoring on a monthly basis to evaluate the areas to determine if 

adjustments may be needed to prevent overgrazing. Recommended stocking rates are not 

currently determined for the LRGVNWR or additional areas on LANWR.

Issue: One commenter asked that if the results of the experimental cattle grazing program show 

a reduction in CFTs, that such methods be applied to other areas of the South Texas Refuge 

Complex (STRC). They also asked that implementation of such measures be fully described in 

future documents on CFT eradication. The commenter also believes that subsequent CFT

eradication plan documents should include methods to keep feeders attractive to white-tailed 

deer during the months where ivermectin-treated corn is not being supplied.

Response: The scope of this EA includes all FWS lands that fall within an established 

quarantine area (permanent, temporary, or control purpose/buffer) on LANWR and 

LRGVNWR. If needed, USDA-APHIS and FWS will consider other areas of these 

refuges for experimental cattle grazing. Likewise, if we would like to implement these 

proposed actions in areas not covered by this EA as part of our adaptive management 

program, we will prepare additional environmental documentation outlining the proposal. 

As part of the Special Use Permit, feeders on refuge lands will not be filled during nontreatment periods. 

Issue: One commenter noted that cows are difficult to round up.

Response: We understand the challenges with grazing, gathering, inspecting, and treating 

cattle. In that regard, for this effort, instead of using bulls, cows, and calves, we will use 

gentle steers and/or heifers, and also may provide range cubes as a tool to gather cattle.

Issue: Several commenters suggested that no environmental impact study has been conducted to 

determine how many head of cattle per given acre, if any, these refuges specifically could 

tolerate and how much time would be required to re-establish the ecological balance after cattle 

have been allowed on the land.

Response: We will minimize adverse impacts by not exceeding stocking rates prescribed 

by USDA-NRCS. The USDA-NRCS already completed a grazing management study for 

several units of the LANWR and will do so for additional units where grazing may be 

beneficial for CFT eradication. To minimize the impact to the ecological balance of the 

refuge, the recommendations are intentionally on the conservative side. However, 

USDA-NRCS recommends routine monitoring on a monthly basis to evaluate areas to 

determine if adjustments are needed to prevent overgrazing. The assessment will be made 

by either USDA-NRCS or another qualified grazing management specialist. We cannot 

provide a time frame for how long it will take to re-establish the ecological balance 

because it would be speculative, but we have identified buffer zones and avoidance 

measures to protect thornscrub habitat, wetlands, threatened and endangered species, 

cooperative farm fields, thornscrub restoration sites, core ocelot monitoring sites, high 

public use areas, and administrative areas. These mitigation measures will reduce the 
50

time needed to restore the ecological balance of the refuge areas after the study is 

complete.

Issue: Several commenters wanted to know what the effects on the CFT from the last two 

freezing conditions are in the last 40 days in the Rio Grande Valley.

Response: We know from past research that it takes several hard freezes to impact CFT 

populations, and usually the impact does not reach eradication. Furthermore, inspections 

of wildlife and cattle conducted following the most recent freezing events have confirmed 

continued presence of the CFT.

Issue: One commenter wanted to know if the proposed grazing and corn feeder sites will be near 

the AC Tidal Zone or Laguna Madre, or near enough to question effects of contaminated feces 

from surface runoff.

Response: Feeders will not be placed within 50 meters (approximately 164 feet) of 

wetlands. Maintaining a buffer zone between ivermectin-treated corn feeders and 

wetlands will mitigate for potential impacts to wetlands or waterways.

Issue: One commenter asked about the chance of spreading Chronic Wasting Disease as a result 

of using ivermectin-treated corn.

Response: USDA-APHIS, TAHC, and FWS recognize Chronic Wasting Disease as a 

serious concern for both captive and free-ranging cervid populations. While this disease 

has been identified in a few areas of Texas, the disease is not currently present in South 

Texas where the proposed action would take place. The TAHC has regulatory authority 

for reporting and tracking this disease in alternative livestock. Both TAHC and TPWD 

work together to address risks, develop management strategies, and protect game from 

Chronic Wasting Disease. Subsequently, should this disease become established in South 

Texas, the CFTEP would reevaluate the use of feeders to minimize the spread of Chronic 

Wasting Disease.

Issue: One commenter suggested the CFTEP consider implementing the proposed action in 

North Texas instead of South Texas. They also asked why the USDA does not promote plantbased diets instead of meat.

Response: The Permanent Tick Quarantine Zone is located in South Texas, and the 

current outbreaks exist in this region. While there are numerous cattle operations in North 

Texas, without CFTs, this land would not be ideal for determining if various management 

strategies are effective in eliminating this tick.

In the USDA’s 2015-2020 dietary guidelines, the USDA includes a healthy vegetarian 

eating pattern. In addition, it states that a diet higher in plant-based foods and lower in 

calories and animal-based foods is healthier (USHHS and USDA 2015). While this is an 

overarching conclusion, it does not negate USDA-APHIS’ mission of protecting both 

animal and plant resources from agricultural pests and diseases. The CFT is one such 

pest.
51

Issue: Several commenters suggested the agencies give increased hunts, bag limits, and nilgai 

culls more time to work. 

Response: The CFTEP and FWS have been removing nilgai from refuge property since 

2014. After more than 3 years of nilgai removal as an additional management method, 

and increased CFT outbreaks in recent years, the CFTEP identified a need to explore 

additional management methods as part of its adaptive management program. 

Issue: Several commenters suggested that the USDA and FWS provide more hunting 

opportunities. 

Response: While we are not opposed to additional hunting opportunities, we do not have 

the authority to change these regulations. Hunting regulations are promulgated by the 

TPWD for white-tailed deer, which are considered native wildlife. There is no season for 

nilgai, which are considered exotic wildlife. Nilgai can be hunted off-refuge property any 

time of the year with a valid hunting license.

The LANWR offers public hunting opportunities for white-tailed deer, nilgai antelope, 

and feral hogs. In 2017, the LANWR provided three archery hunts and 250 permits were 

made available for each hunt. There were seven firearm hunts and 35 permits were 

available for each hunt. The FWS has increased the bag limit for white-tailed deer from 

two deer to five to expand efforts to control CFTs. The FWS will continue to explore 

opportunities to expand public hunting on the refuge.

Issue: Several commenters suggested there was a need for an extended public comment period, 

as well as a public hearing.

Response: USDA-APHIS and FWS appreciate the public’s concern regarding the 

proposed action. The public comment period was open for 32 days, and we received 180 

comments via regulations.gov, as well as several comments we received directly from the 

public. We read through all of the comments carefully. Aside from suggestions to make 

the proposed study more robust, these comments did not introduce topics we had not 

already considered. In addition, the draft EA received significant attention in the press 

and was subsequently distributed widely. 

The CFTEP has identified the benefits of a public hearing and intends to reach out to the 

public regarding various aspects of the Program.

Issue: One commenter suggests that the tick population is not as serious a threat as perceived.

Response: The CFTEP has historical data suggesting that the CFT, once found across 14 

southern states, is indeed a serious threat to the livestock industry (Texas A&M AgriLife 

Research no date). CFTs were introduced to the New World through livestock brought 

from other countries by colonists and explorers in the early 1500s (Anderson et al. 2010). 

The ticks and their associated diseases, especially bovine babesiosis (cattle fever), pose 

serious problems to warm-blooded animals. Babesiosis generally is characterized by 

extensive loss of red blood cells due to breakdown of the cellular membrane; this leads to 

anemia, jaundice, and death (CFSPH 2008). Some estimates of mortality are as high as 

90 percent (as cited in Giles et al. 2014). Infected cattle may exhibit neurological 
52

disturbances characterized by incoordination, seizures, muscle tremors, hyperexcitability, 

aggressiveness, blindness, head pressing, and coma. In addition, CFTs are capable of 

causing blood loss, significant damage to hides, and an overall decrease in the health 

condition of livestock. Less severe cases may be characterized by weight loss and 

secondary bacterial infections. Due to these wide-ranging symptoms, babesiosis can 

cause devastating economic losses to owners of affected herds (CFSPH 2008). By 1961,

when the last U.S. pocket of the southern cattle tick was eliminated from Florida, direct 

and indirect economic losses caused by CFTs were high—estimated to be $130.5 million, 

which would be approximately $3 billion today (USDA 2010). If the ticks had not been 

eradicated from the United States, today’s cattle industry losses from disease and CFTs 

could amount to approximately $1 billion annually (USDA 2010).

Issue: One commenter suggests that it is impossible to eradicate CFTs.

Response: Eradication of CFTs is not impossible, but the challenges are greater adjacent 

to the border with Mexico (due to stray domestic animals and wildlife movement), which 

is the basis for the permanent tick quarantine zone. Away from the border, successful 

eradication has already been demonstrated. Efforts to keep CFTs within the permanent 

quarantine zone are critical because recent modeling suggests environmental suitability 

will shift by midcentury, creating suitable tick habitat across the southeastern United 

States and southern California (Giles et al. 2016).

Issue: Multiple commenters expressed concerns about the increase in activity and potential 

threats to all wildlife in the Refuge, including endangered species such as the ocelot, in which 

the most common fatality is due to vehicles. 

Response: The FWS is committed to the recovery of the endangered ocelot and will work 

with USDA-APHIS and TAHC to minimize impacts. As outlined in Section 4.6 of the 

EA, vehicles will be required to travel at reduced speeds (not to exceed 25 mph). 

Additionally, the FWS will be providing awareness and education training to all USDAAPHIS and TAHC staff operating this program to help reduce potential vehicle 

collisions.

Under the proposed action, necessary buffer zones will be identified prior to 

implementing experimental grazing on any refuge units to protect sensitive areas to 

include thornscrub habitat, wetlands, and other threatened and endangered species 

considerations. Refuge staff will survey any proposed fence lines to ensure there are not 

any denning ocelots. Additionally, thornscrub habitat will not be cleared for placement of 

feeders, and feeders will be placed in open areas away from brush habitat.

Issue: Multiple commenters expressed concerns about how putting cattle on the refuge will 

diminish the quality of the refuge, lessen visitation, and reduce ecotourism in the area. In 

addition, commenters expressed concerns because the refuge is used heavily by the public for 

various uses such as tram tours, biking, hiking, and hunting.

Response: The proposed action has the potential to impact other public uses at the refuge. 

Grazing is being proposed as an experimental use and will be continuously monitored. 

The FWS will use an adaptive management approach for the experimental cattle grazing 
53

program and retains the right to remove or adjust stocking rates of cattle if there is 

resource damage or serious conflicts with other programs on the refuge. To ensure 

transparency about the proposed action, we added additional information about the 

potential impacts to visitors of the refuges to Section 4.6.

Issue: A few commenters would like the proposed action delayed until adequate baseline data 

can be collected regarding the current conditions of plant communities in impacted areas of 

LANWR. 

Response: The FWS will work with USDA-NRCS in the development of the production 

report to incorporate monitoring procedures/protocols to collect baseline data of 

vegetative communities when evaluating a unit to determine grazing feasibility. The same 

procedure/protocol will be used annually to evaluate vegetation changes. 

Issue: One commenter asked that we provide any updates via numerous media formats. 

Response: Any decisions or changes to the proposed action that we make following the 

public comment period will be made available to the general public. Periodic updates 

regarding the progress of the study may be provided as well.

Issue: Numerous commenters expressed concerns about environmental impacts from other 

proposed projects in the area including proposed Border Wall expansion, LNG export facilities, 

natural gas pipelines, and SpaceX. 

Response: Additional information has been added to the EA under Cumulative Impacts 

Section 4.7. Though many of these projects have yet to be implemented, the FWS will 

continue to coordinate on projects impacting national wildlife refuges and through the 

Endangered Species Act Section 7 process to minimize impacts to trust resources, to the 

extent possible. 

Issue: One comment letter stated that this action requires an Environmental Impact Statement 

(EIS) instead of an EA because the proposed actions will take place on two national wildlife 

refuges that contain 26 federally listed and proposed endangered species. An EIS should be 

required to further analyze these impacts, as well as evaluate additional reasonable alternatives 

to avoid them. 

Response: There is the potential to have adverse impacts on four of the 17 listed species 

in the project area; however, the fact that threatened or endangered species or their 

critical habitat may be affected by the proposed action does not automatically require 

FWS to prepare an EIS. In an EA, the USDA and FWS are required to address the 

potential adverse effects on endangered and threatened species and their habitat within 

the action area. The USDA and FWS have met this requirement in Section 

4.5. Applicable regulations require FWS to address these potential adverse effects when 

measuring the intensity of the impact of the proposed action. In deciding whether to 

prepare an EIS, the USDA and FWS will write a determination explaining whether the 

intensity of effects, caused by the proposed action, on threatened and endangered species 

and their habitat rise to the level of being significant, thus requiring preparation of an 

EIS. 
54

Issue: One comment letter stated that the proposed USDA/FWS actions, specifically feeding 

ivermectin-treated corn to white-tailed deer, and placing cattle on both refuges to “soak up” 

ticks, are not appropriate or compatible uses of these national wildlife refuges as defined under 

the National Wildlife Refuge System Administration Act of 1966, as amended by the National 

Wildlife Refuge System Improvement Act of 1997.

Response: The CFTEP actions under the proposed action are considered refuge 

management activities. As outlined in 603 FW 2, refuge management activities that do 

not require a compatibility determination include: prescribed fire; water level 

management; invasive species control; routine scientific monitoring, studies, surveys, and 

censuses; historic preservation activities; law enforcement activities; and maintenance of 

existing refuge facilities, structures, and improvements. Under the proposed action, the 

management activities conducted by USDA-APHIS/TAHC is for invasive species 

control. Recurrent CFT outbreaks are increasing in locations within the Permanent Tick 

Quarantine Zone and outside of the zone in the CFT free area of South Texas (USDA 

2013). Despite a permanent quarantine zone on the border, CFTs have occasionally 

expanded and include the current project area. The proposed action is to implement 

CFTEP management to control or eradicate the invasive tick. Section 1.4 of the EA has 

been updated to include information about invasive species control. 

Issue: One comment letter stated that “The No Action” alternative is in fact nothing of the sort

as there are many extensive cattle tick eradication efforts that the FWS has done and continues 

to do.

Response: “No Action Alternative” is a NEPA term that is used to describe an action that 

has not yet taken place, such as building a cell tower, or to describe a situation where 

there will be no change from current management direction or level of intensity. 

However, the USDA and FWS recognize your concern and have clarified what we mean 

by “No Action Alternative” in the Final EA.