![](media/image1.wmf){width="1.3576388888888888in"
height="1.375in"}UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

November 15, 2006

Memorandum

+--------+-------------------------------------------------------------+
| Su     | Rodenticide Incidents Update                                |
| bject: |                                                             |
+--------+-------------------------------------------------------------+
| To:    | Susan Lewis, Chief                                          |
|        |                                                             |
|        | Kelly Sherman                                               |
|        |                                                             |
|        | SRRD                                                        |
+--------+-------------------------------------------------------------+
| From:  | Bill Erickson, Biologist                                    |
|        |                                                             |
|        | ERB 2/EFED                                                  |
+--------+-------------------------------------------------------------+
| Th     | Tom Bailey, Chief                                           |
| rough: |                                                             |
|        | ERB 2/EFED                                                  |
+--------+-------------------------------------------------------------+

OPP/EFED's ecological assessment of *Potential Risks of Nine
Rodenticides to Birds and Nontarget Mammals: a Comparative Approach*,
dated July 2004, presented the rodenticide incidents with birds and
nontarget mammals known at that time. The incidents are discussed in the
assessment, and individual incidents and residue levels are listed in an
attachment (Attachment D). Other incidents have occurred since then, and
additional reports prior to that time have become available. These
incidents are contained in OPP/EFED's Ecological Incidence Information
System (EIIS). The current report summarizes the available incident
information as of November 2006.

Most of the incident reports for the anticoagulant rodenticides were
submitted from the New York State Department of Environmental
Conservation (Wildlife Pathology Unit) or the California Department of
Fish and Game (Pesticides Investigation Unit). Anticoagulant incidents
are based on detection of residue or residues in liver tissue and
corroborating evidence from carcass necropsy. Such analyses are
expensive, and lack of sufficient funding limits the extent of analyses
and incident reporting. As discussed in the ecological risk assessment,
most incidents are not reported due to a variety of reasons. For
example, most animal carcasses are never found by humans, scavengers
quickly remove and consume carcasses, carcasses or ill animals
discovered by humans are not reported to proper authorities for a
variety of reasons, carcasses discovered and reported are not typically
analyzed for rodenticides, and various other reasons.

Incident reports are only one of several lines-of-evidence used to
evaluate risk. Other lines include acute toxicity, persistence of
compounds in body tissues of primary consumers (i.e., bait eaters),
information from laboratory and pen studies in which poisoned prey are
fed to predators or scavengers in various amounts for one or more days,
and data from field trials and operational control programs. In many
incident reports, the consequence of rodenticide exposure is not known,
although in many cases the examining toxicologist determined that a
rodenticide likely caused or contributed to the mortality.
Anticoagulants typically do not cause death until 4 to 10 days or more
after a lethal dose is ingested. However, exposed individuals become
progressively weaker and lethargic due to blood loss, and that added
stress may contribute to the proximate cause of death. Even if a
cause-effect relationship has not been determined for many incidents,
the findings of exposure of such a wide variety of nontarget wildlife,
both birds and mammals, is a concern. As discussed below, several
monitoring programs have found that a major portion of some animal
populations are being exposed to second-generation anticoagulant
rodenticides.

**Anticoagulant Rodenticides**

The second-generation anticoagulant rodenticides (SGARs) consist of
brodifacoum, bromadiolone, and difethialone. First-generation
anticoagulant rodenticides (FGARs) include diphacinone, chlorophacinone,
and warfarin. Both SGARs and FGARs are registered for use in and around
buildings, transport vehicles, and inside sewers; however, difethialone
and bromadiolone are labeled only for indoor use in "non-urban" areas.
Diphacinone and chlorophacinone also have field uses (e.g., orchards,
rangelands), including hand- or mechanical-broadcast applications for
pests such as voles and ground squirrels. These uses are described in
more detail in the ecological risk assessment.

**Avian incidents**

Residues of anticoagulants have been detected in 27 species of wild
birds (and 14 spp. of captive birds in zoo incidents), including owls,
diurnal raptors and vultures, corvids, and others (Table 1). Other dead
or ill birds were reported in some incidents, but the tabulated data
include only those birds analyzed for residues. Of the 290 individuals
in which anticoagulants were detected, SGARs were detected in 97% and
FGARs in 4% (3 birds contained both SGARs and FGARs). Brodifacoum was
detected in 87% of the 290 birds and bromadiolone in 13% (brodifacoum
and bromadiolone were both detected in several great horned owls).

**Table 1. Detection of Anticoagulant Rodenticides in Birds**

+-------------------------------------+----------+----------+----------+
| **Species**                         | **No.    | *        | *        |
|                                     | dete     | *SGARs** | *FGARs** |
|                                     | ctions** |          |          |
+=====================================+==========+==========+==========+
| **Owls**                            |          |          |          |
+-------------------------------------+----------+----------+----------+
| Great-horned owl (Number range      | 71       | 71       | 2        |
| CHAPTER*Bubo virginianus*)          |          |          |          |
+-------------------------------------+----------+----------+----------+
| Eastern screech-owl (Number range   | 18       | 18       |          |
| CHAPTER*Otus asio*)                 |          |          |          |
+-------------------------------------+----------+----------+----------+
| Barn owl (Number range CHAPTER*Tyto | 8        | 8        |          |
| alba*)                              |          |          |          |
+-------------------------------------+----------+----------+----------+
| \*Northern spotted owl (Number      | 2        | 2        |          |
| range CHAPTER*Strix occidentalis*)  |          |          |          |
+-------------------------------------+----------+----------+----------+
| Long-eared owl (Number range        | 2        | 2        |          |
| CHAPTER*Asio otus*)                 |          |          |          |
+-------------------------------------+----------+----------+----------+
| Barred owl (Number range            | 2        | 1        | 1        |
| CHAPTER*Strix varia*)               |          |          |          |
+-------------------------------------+----------+----------+----------+
| Snowy owl (Number range             | 1        |          | 1        |
| CHAPTER*Nyctea scandiaca*)          |          |          |          |
+-------------------------------------+----------+----------+----------+
| Northern saw-whet owl (Number range | 1        | 1        |          |
| CHAPTER*Aegolius acadicus*)         |          |          |          |
+-------------------------------------+----------+----------+----------+
| **Diurnal raptors**                 |          |          |          |
+-------------------------------------+----------+----------+----------+
| Red-tailed hawk (Number range       | 87       | 85       | 2        |
| CHAPTER*Buteo jamaicensis*)         |          |          |          |
+-------------------------------------+----------+----------+----------+
| Cooper's hawk (Number range         | 24       | 24       | 2        |
| CHAPTER*Accipiter cooperii*)        |          |          |          |
+-------------------------------------+----------+----------+----------+
| Golden eagle (Number range          | 13       | 13       |          |
| CHAPTER*Aquila chrysactos*)         |          |          |          |
+-------------------------------------+----------+----------+----------+
| \*Bald eagle (Number range          | 3        | 2        | 1        |
| CHAPTER*Haliaeetus leucocephalus*)  |          |          |          |
+-------------------------------------+----------+----------+----------+
| Red-shouldered hawk (Number range   | 3        | 3        |          |
| CHAPTER*Buteo lineatus*)            |          |          |          |
+-------------------------------------+----------+----------+----------+
| Sharp-shinned hawk (Number range    | 2        | 2        |          |
| CHAPTER*Accipiter striatus*)        |          |          |          |
+-------------------------------------+----------+----------+----------+
| Broad-winged hawk (*Buteo           | 1        | 1        |          |
| platypterus*)                       |          |          |          |
+-------------------------------------+----------+----------+----------+
| American kestrel (Number range      | 2        | 2        |          |
| CHAPTER*Falco sparverius*)          |          |          |          |
+-------------------------------------+----------+----------+----------+
| Peregrine falcon (Number range      | 1        |          | 1        |
| CHAPTER*Falco peregrinus*)          |          |          |          |
+-------------------------------------+----------+----------+----------+
| Unidentified hawk                   | 1        | 1        |          |
+-------------------------------------+----------+----------+----------+
| Turkey vulture (Number range        | 2        | 1        | 1        |
| CHAPTER*Cathartes aura*)            |          |          |          |
+-------------------------------------+----------+----------+----------+
| Black vulture (Number range         | 1        | 1        |          |
| CHAPTER*Coragyps atratus*)          |          |          |          |
+-------------------------------------+----------+----------+----------+
| **Others**                          |          |          |          |
+-------------------------------------+----------+----------+----------+
| Corvids (*Corvus* spp.Number range  | 20       | 20       |          |
| CHAPTERNumber range CHAPTER), 3     |          |          |          |
| spp.                                |          |          |          |
+-------------------------------------+----------+----------+----------+
| Turkey (Number range                | 5        |          | 5        |
| CHAPTER*Meleagris gallopavo*), wild |          |          |          |
| Number range CHAPTER                |          |          |          |
+-------------------------------------+----------+----------+----------+
| Captive birds (3 zoos), 14 spp.     | 15       | 15       |          |
+-------------------------------------+----------+----------+----------+
| Others, 4 spp.Number range CHAPTER  | 5        | 5        | 1        |
+-------------------------------------+----------+----------+----------+
| **Total birds:**                    | **290**  | **278**  | **17**   |
|                                     |          |          |          |
|                                     |          | *        | **(6%)** |
|                                     |          | *(97%)** |          |
+-------------------------------------+----------+----------+----------+

\* listed (endangered or threatened) species

**Mammalian incidents**

Anticoagulant residues have been detected in 218 mammals comprising 17
species, including the endangered San Joaquin kit fox (Table 2). SGARs
were detected in 92% of the individuals and FGARs in 18% (both SGARs and
FGARs were detected in some individuals). By rodenticide, brodifacoum
was detected in 83% of the 218 mammals, bromadiolone in 32%, diphacinone
in 13%, chlorophacinone in 6%, difethialone in 5%, and warfarin in 2%.
Brodifacoum and bromadiolone were detected together in some individuals,
especially bobcats and mountain lions but also several coyotes and kit
foxes.

**Table 2. Detection of Anticoagulant Rodenticides in Mammals**

+----------------------------------------+---------+--------+--------+
| **Species**                            | **No.   | **S    | **F    |
|                                        | detec   | GARs** | GARs** |
|                                        | tions** |        |        |
+========================================+=========+========+========+
| **Canids (wild)**                      |         |        |        |
+----------------------------------------+---------+--------+--------+
| \*San Joaquin kit fox (Number range    | 32      | 27     | 6      |
| CHAPTER*Vulpes macrotis mutica*)       |         |        |        |
+----------------------------------------+---------+--------+--------+
| Coyote (Number range CHAPTER*Canis     | 25      | 23     | 5      |
| latrans*)                              |         |        |        |
+----------------------------------------+---------+--------+--------+
| Red fox (Number range CHAPTER*Vulpes   | 5       | 5      |        |
| vulpes*)                               |         |        |        |
+----------------------------------------+---------+--------+--------+
| Gray fox (Number range CHAPTER*Urocyon | 3       | 3      |        |
| cinereoargenteus*)                     |         |        |        |
+----------------------------------------+---------+--------+--------+
| **Felids (wild)**                      |         |        |        |
+----------------------------------------+---------+--------+--------+
| Bobcat (Number range CHAPTER*Lynx      | 37      | 35     | 7      |
| rufus*)                                |         |        |        |
+----------------------------------------+---------+--------+--------+
| Mountain lion (Number range            | 30      | 28     | 5      |
| CHAPTER*Felis concolor*)               |         |        |        |
+----------------------------------------+---------+--------+--------+
| **Other carnivores**                   |         |        |        |
+----------------------------------------+---------+--------+--------+
| Raccoon (Number range CHAPTER*Procyon  | 10      | 9      | 2      |
| lotor*)                                |         |        |        |
+----------------------------------------+---------+--------+--------+
| Striped skunk (Number range            |         | 5      |        |
| CHAPTER*Mephitis mephitis*)            |         |        |        |
+----------------------------------------+---------+--------+--------+
| Badger (Number range CHAPTER*Meles     | 1       |        | 1      |
| meles*)                                |         |        |        |
+----------------------------------------+---------+--------+--------+
| Long-tailed weasel (Number range       | 1       | 1      |        |
| CHAPTER*Mustela frenata*)              |         |        |        |
+----------------------------------------+---------+--------+--------+
| **Others**                             |         |        |        |
+----------------------------------------+---------+--------+--------+
| Opossum (Number range                  | 5       | 5      |        |
| CHAPTER*Didelphis virginiana*)         |         |        |        |
+----------------------------------------+---------+--------+--------+
| White-tailed deer (Number range        | 7       | 5      | 2      |
| CHAPTER*Odocoileus virginianus*)       |         |        |        |
+----------------------------------------+---------+--------+--------+
| Gray squirrel (Number range            | 57      | 51     | 9      |
| CHAPTER*Sciurus carolinensis*)         |         |        |        |
+----------------------------------------+---------+--------+--------+
| Others, 4 spp.                         | 5       | 4      | 1      |
+----------------------------------------+---------+--------+--------+
| **Total mammals:**                     | **218** | *      | **39** |
|                                        |         | *201** |        |
|                                        |         |        | **(    |
|                                        |         | **(    | 18%)** |
|                                        |         | 92%)** |        |
+----------------------------------------+---------+--------+--------+

\* listed (endangered or threatened) species

**Extent of SGAR Exposure in Wildlife Populations**

The extent of exposure to SGARS has been reported for several species in
the U.S., Canada, and the UK (Table 3). The data from New York also
include detections of FGARs, but they comprised only 5% of all
detections. In both New York and Ontario, SGARs were detected in more
than 80% of all great horned owls analyzed and in more than 50% of the
red-tailed hawks. Other owls and raptors in which SGARs are frequently
detected include Eastern screech-owls, Cooper's hawks, kestrels, and
kites. SGARs also have been detected in 71 to 84% of the kit foxes,
bobcats, and mountain lions analyzed in California. Clearly, more
information is urgently needed on the potential impacts such exposure
may be having on populations of wild canids, wild felids, and raptors.

**Table 3. Widespread Detection of SGARs in Nontarget Birds and Mammals
in the U. S. and Elsewhere**

+---------------------------------+--------------------+---------------+
| **Location/**                   | **no. analyzed**   | **%**         |
|                                 |                    |               |
| **Species**                     | **for liver        | **positive**  |
|                                 | residue**          |               |
+=================================+====================+===============+
| ***New York:***^a^              |                    |               |
+---------------------------------+--------------------+---------------+
| All (15 species)                | 265                | 48\*          |
+---------------------------------+--------------------+---------------+
| Great horned owl                | 53                 | 81            |
+---------------------------------+--------------------+---------------+
| Red-tailed hawk                 | 78                 | 58            |
+---------------------------------+--------------------+---------------+
| Eastern screech-owl             | 22                 | 45            |
+---------------------------------+--------------------+---------------+
| Cooper's hawk                   | 50                 | 36            |
+---------------------------------+--------------------+---------------+
| ***California:***^b^            |                    |               |
+---------------------------------+--------------------+---------------+
| San Joaquin kit fox             | 32                 | 84            |
+---------------------------------+--------------------+---------------+
| Bobcat                          | 39                 | 79            |
+---------------------------------+--------------------+---------------+
| Mountain lion                   | 35                 | 71            |
+---------------------------------+--------------------+---------------+
| ***Ontario:***^c^               |                    |               |
+---------------------------------+--------------------+---------------+
| Great horned owl                | 24                 | 87            |
+---------------------------------+--------------------+---------------+
| Red-tailed hawk                 | 30                 | 57            |
+---------------------------------+--------------------+---------------+
| ***United Kingdom:***^d^        |                    |               |
+---------------------------------+--------------------+---------------+
| Red kite (*Milvus milvus*)      | 20                 | 70            |
+---------------------------------+--------------------+---------------+
| Kestrel (*Falco tinnunculus*)   | 36                 | 67            |
+---------------------------------+--------------------+---------------+
| Polecat (*Mustela putorius*)    | 100                | 31            |
+---------------------------------+--------------------+---------------+
| Least weasel (*Mustela          | 10                 | 30            |
| nivalis*)                       |                    |               |
+---------------------------------+--------------------+---------------+
| Stoat (*Mustela erminea*)       | 40                 | 23            |
+---------------------------------+--------------------+---------------+

\* 6 (5%) positives were first-generation anticoagulants: 3 diphacinone,
2 warfarin,

> 1 chlorophacinone; 122 (95%) positives were second-generation
> anticoagulants: 108 (84%) brodifacoum and 28 (22%) bromadiolone (note:
> brodifacoum and bromadiolone were both detected in 15 birds)

^a^ Stone et al. (2003). Bull. Environ. Contam. Toxicol. 70:34-40

^b^ California Department of Fish and Game, Pesticides Investigation
Unit;

U. S. National Park Service

^c^ National Wildlife Research Centre, Canadian Wildlife Service

^d^ Shore et al. (2003). Environ. Poll. 122:183-193

Burn et al. (2002). Aspects Appl. Biol. 67:203-212

McDonald et al. (1998). Environ. Pollution 103:17-23

**Non-anticoagulant Rodenticides**

Considerably less incident information is available on the
non-anticoagulant rodenticides. Some incident information is available
for zinc phosphide (ZP; Table 4) but none for bromethalin or
cholecalciferol. Most ZP incidents are for waterfowl and wild turkeys.
Based on the species and numbers impacted, most ZP incidents likely were
due to field applications rather than homeowner use.

**Table 4. Zinc Phosphide Incidents**

+------------------------------------+---------------+-----------------+
| **Species**                        | **No.         | **No.           |
|                                    | incidents**   | individuals**   |
+------------------------------------+---------------+-----------------+
| **Birds**                          |               |                 |
+------------------------------------+---------------+-----------------+
| Turkey (Number range               | 17            | 71              |
| CHAPTER*Meleagris gallopavo*),     |               |                 |
| wild                               |               |                 |
+------------------------------------+---------------+-----------------+
| Canada goose (*Branta canadensis*) | 8             | 157             |
+------------------------------------+---------------+-----------------+
| Snow goose (*Chen caerulescens*)   | 2             | \~390           |
| and/or                             |               |                 |
|                                    |               |                 |
| White-fronted goose (*Anser        |               |                 |
| albifrons*)                        |               |                 |
+------------------------------------+---------------+-----------------+
| Mallard (*Anas platyrhynchos*)     | 1             | 29              |
+------------------------------------+---------------+-----------------+
| **Mammals**                        |               |                 |
+------------------------------------+---------------+-----------------+
| Red fox (Number range              | 1             | 2               |
| CHAPTER*Vulpes vulpes*)            |               |                 |
+------------------------------------+---------------+-----------------+
| Gray squirrel (Number range        | 2             | 20              |
| CHAPTER*Sciurus carolinensis*)     |               |                 |
+------------------------------------+---------------+-----------------+
| Eastern cottontail (*Sylvilagus*   | 1             | 1               |
| *floridanus*)                      |               |                 |
+------------------------------------+---------------+-----------------+
| **Total:**                         | 32            | 670             |
+------------------------------------+---------------+-----------------+