Rodenticide Exposure Among Endangered Kit Foxes Relative to Habitat Use in an Urban Landscape

Endangered San Joaquin kit foxes (Vulpes macrotis mutica) inhabiting Bakersfield, California exhibit a high incidence of exposure to anticoagulant rodenticides (ARs). We examined kit fox habitat use in an effort to determine potential sources of AR exposure. Kit fox capture, den, night, and mortality locations were assigned to one of 10 habitat categories. Using all available locations, foxes that tested positive for second generation anticoagulant rodenticides (SGARs) were located more frequently on golf courses while those testing negative were located more frequently in commercial areas. Foxes that tested positive for first generation anticoagulant rodenticides (FGARs) were located more frequently in industrial areas while those testing negative were located more frequently on golf courses. Based on night locations (when foxes are foraging), foxes that tested positive for SGARs were found more frequently in undeveloped and golf course habitats. Foxes that tested positive for FGARs were found more frequently in undeveloped, campus, and industrial habitats. Although available data were not sufficient to identify specific point-sources of AR exposure for foxes, golf courses appeared to be used more frequently by foxes exposed to SGARs. However, sources of exposure likely are abundant and widespread in the urban environment. Based on the results of this study, we recommend (1) investigating patterns of AR use in Bakersfield, (2) conducting an outreach program to emphasize the risk from ARs to kit foxes and other wildlife, and (3) continuing to monitor the incidence and patterns of AR exposure among kit foxes in Bakersfield

Protecting Nontarget Wildlife from Effects of Vertebrate Pesticides

The California Department of Fish and Game (DFG) recognizes the need for the availability of a variety of tools for vertebrate pest control and has a strong interest in ensuring that these tools are used in a way that minimizes impacts to nontarget wildlife. From 1992 to 2011, the DFG has investigated 44 cases of wildlife kills caused by vertebrate pesticides, resulting in the loss of 258 animals. While anticoagulant rodenticides were responsible for the loss of the highest number of incidents, incidents involving acute toxicants, such as strychnine and zinc phosphide, typically involved a greater number of animals per incident. Incidents of intentional poisoning of wildlife usually involved strychnine. There were no documented losses due to fumigants; however, such incidents are likely to go unnoticed because the carcasses remain underground

Protecting Nontarget Wildlife from Effects of Vertebrate Pesticides

The California Department of Fish and Game (DFG) recognizes the need for the availability of a variety of tools for vertebrate pest control and has a strong interest in ensuring that these tools are used in a way that minimizes impacts to nontarget wildlife. From 1992 to 2011, the DFG has investigated 44 cases of wildlife kills caused by vertebrate pesticides, resulting in the loss of 258 animals. While anticoagulant rodenticides were responsible for the loss of the highest number of incidents, incidents involving acute toxicants, such as strychnine and zinc phosphide, typically involved a greater number of animals per incident. Incidents of intentional poisoning of wildlife usually involved strychnine. There were no documented losses due to fumigants; however, such incidents are likely to go unnoticed because the carcasses remain underground

Investigation of Chlorophacinone-related Goose Deaths in Monterey County, California

In 2008, approximately 70 Canada geese were recovered dead in the Moro Cojo Slough area of Monterey County, California. Birds were necropsied and showed signs of abnormal internal bleeding. A total of 37 livers were analyzed for anticoagulants and 36 of these livers contained chlorophacinone. Death was attributable to chlorophacinone poisoning. Two turkey vultures and a barn owl also died, probably as a result of secondary chlorophacinone poisoning. The source of the chlorophacinone was not obvious, as chlorophacinone is used in several different forms on many different crops and also in commensal use. In addition, there often are several days between exposure and death, allowing the movement of the animal from the site of exposure. The ensuing investigations, which lasted several months, suggested that the exposure was due to expanded use of chlorophacinone pellets on artichokes used to control California voles. Subsequently, the label of the rodenticide product was modified to restrict its use when conditions favor goose presence in artichoke fields. No deaths have occurred since the label modification

Imidacloprid Poisoning of Songbirds Following a Drench Application of Trees in a Residential Neighborhood in California, USA

In March 2017, 26 American goldfinches (Spinus tristis) were found dead following a drench application of imidacloprid in California (USA). Identical seed fragments were present in the digestive tracts. Imidacloprid was detected in 4 separate pooled samples from 18 birds, in crop/gizzard contents (4.8 ± 1.3 ppm; range 2.2-8.5 ppm) and liver tissues (3.9 ± 0.6 ppm; range 2.1-4.8 ppm). We suspect that fallen elm (Ulmus sp.) seeds were contaminated with imidacloprid during the drench application and subsequently ingested, resulting in acute toxicity and death. Environ Toxicol Chem 2019;38:1724-1727. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC

Imidacloprid Poisoning of Songbirds Following a Drench Application of Trees in a Residential Neighborhood in California, USA.

In March 2017, 26 American goldfinches (Spinus tristis) were found dead following a drench application of imidacloprid in California (USA). Identical seed fragments were present in the digestive tracts. Imidacloprid was detected in 4 separate pooled samples from 18 birds, in crop/gizzard contents (4.8 ± 1.3 ppm; range 2.2-8.5 ppm) and liver tissues (3.9 ± 0.6 ppm; range 2.1-4.8 ppm). We suspect that fallen elm (Ulmus sp.) seeds were contaminated with imidacloprid during the drench application and subsequently ingested, resulting in acute toxicity and death. Environ Toxicol Chem 2019;38:1724-1727. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC

Imidacloprid Poisoning of Songbirds Following a Drench Application of Trees in a Residential Neighborhood in California, USA.

In March 2017, 26 American goldfinches (Spinus tristis) were found dead following a drench application of imidacloprid in California (USA). Identical seed fragments were present in the digestive tracts. Imidacloprid was detected in 4 separate pooled samples from 18 birds, in crop/gizzard contents (4.8 ± 1.3 ppm; range 2.2-8.5 ppm) and liver tissues (3.9 ± 0.6 ppm; range 2.1-4.8 ppm). We suspect that fallen elm (Ulmus sp.) seeds were contaminated with imidacloprid during the drench application and subsequently ingested, resulting in acute toxicity and death. Environ Toxicol Chem 2019;38:1724-1727. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC

New Rodenticide on the Block: Diagnosing Bromethalin Intoxication in Wildlife

Bromethalin is being used more widely for commensal rodent control because of increased regulation on second-generation anticoagulant rodenticides. Wildlife losses in California are tracked by the California Department of Fish and Wildlife. Bromethalin is a neurotoxicant which is not thought to cause secondary poisoning. From August 2014 to January 2016, 24 cases of bromethalin intoxication were investigated in California. These include 11 raccoons, 11 striped skunks, one gray fox, and one fox squirrel. Most of these occurred in Marin County, where active surveillance of wildlife for rodenticide exposure is occurring. Bromethalin exposure should be evaluated when a wild animal that may have accessed bait is showing neurological signs. Trauma and distemper should be ruled out. Histological changes may be found in the central nervous system but are not always present. The tissue of choice for toxicological analysis is adipose. It is likely that bromethalin intoxication is under-reported in the rest of the state and may be mistaken for distemper infection or trauma. Primary exposure of wildlife to bromethalin could be prevented by placing baits in tamper-resistant bait stations

New Rodenticide on the Block: Diagnosing Bromethalin Intoxication in Wildlife

Bromethalin is being used more widely for commensal rodent control because of increased regulation on second-generation anticoagulant rodenticides. Wildlife losses in California are tracked by the California Department of Fish and Wildlife. Bromethalin is a neurotoxicant which is not thought to cause secondary poisoning. From August 2014 to January 2016, 24 cases of bromethalin intoxication were investigated in California. These include 11 raccoons, 11 striped skunks, one gray fox, and one fox squirrel. Most of these occurred in Marin County, where active surveillance of wildlife for rodenticide exposure is occurring. Bromethalin exposure should be evaluated when a wild animal that may have accessed bait is showing neurological signs. Trauma and distemper should be ruled out. Histological changes may be found in the central nervous system but are not always present. The tissue of choice for toxicological analysis is adipose. It is likely that bromethalin intoxication is under-reported in the rest of the state and may be mistaken for distemper infection or trauma. Primary exposure of wildlife to bromethalin could be prevented by placing baits in tamper-resistant bait stations

Anticoagulant Rodenticide Residues in Game Animals in California

Anticoagulant rodenticides (ARs) are used to control rodents around homes, buildings, and in agriculture. They have been found widely in predatory and scavenging wildlife as a result of secondary exposure and less commonly in herbivores and omnivores from primary exposure. While predators and scavengers have been monitored for AR exposure, very little information is available about AR residues in edible muscle tissue of game animals. Game animals may be exposed to ARs through direct consumption of bait, ingestion of contaminated food or vegetation, or consumption of contaminated prey items. Carcasses of three species of game animals (black bear, wild pigs, and mule deer) were collected opportunistically for this study from 2013 to 2015. Causes of death were mainly depredation, vehicular trauma, or hunter harvest. Sampling was performed in the field by California Department of Fish and Wildlife and US Department of Agriculture Wildlife Services staff. Tissues were analyzed for 37 deer in 11 counties, 120 wild pigs in 10 counties, and 12 bears in eight counties. The highest prevalence of AR exposure was found in bears, with 83% of tested livers containing ARs. Bear were most likely to be exposed to brodifacoum, a second generation AR used primarily in and around residences. Prevalence of exposure in wild pigs was 8.3%. Pigs were most likely to be exposed to chlorophacinone, used primarily in agriculture. More than half of pigs with AR residues in their liver also had AR residues in their muscle tissue. There were no AR detections in muscle samples tested for bears with AR residues in liver. None of the deer livers tested positive for ARs