A Tale of Two Foxes


Gray fox kits.  Photo credit:  Brian Murphy, Mt. Diablo Audubon Society

In February of 2018, a gray fox was brought to the Sonoma County Wildlife Rescue.  The fox appeared injured when it was found in a backyard in Glen Ellen. It was lying on its side, with back legs appearing immobile.  The rehab facility provided supportive care but the fox died during the night.  When the body was examined, no signs of trauma were found so the fox was sent to the Wildlife Investigations Lab to determine the cause of death.  During necropsy it was found that the fox was carrying two fetuses.  Tissues sent for analysis came back positive for bromethalin.  Bromethalin is a rodenticide sold under a variety of trade names over the counter to control rats and mice.  Labels specify that it must be placed in a bait station, but the wax blocks may be purchased separately.   Bromethalin is a neurotoxicant, which explains the lack of mobility found in the fox.

In April of 2018, another gray fox was found dead in Ben Lomand in Santa Cruz County.  When rescuers saw signs that she was lactating, they searched for her litter and were able to locate one of her kits.  This kit was brought to Wildlife Center of Silicon Valley and successfully reared with other kits.  The mother was sent to the Wildlife Investigations Lab to determine her cause of death.   This fox had died from anticoagulant rodenticide intoxication.  Four different anticoagulant rodenticides were found in her liver, three of which were second generation anticoagulants.  These materials were made restricted use in California in 2014, meaning that they can only be used by professionals for control of mice and rats in and around buildings.  They work by preventing the blood from clotting.  At necropsy, this fox had blood in her spinal cavity and chest cavity.  It is likely that she was exposed to the rodenticides when eating rodents.

Unfortunately, these cases are not rare.  They serve to remind us that we can unintentionally harm wildlife with our pest control practices.  For more information on rodent control that is safer for wildlife, please visit:

CDFW Rodenticide Page

Raptors are the Solution


Scientists Battle Mange Outbreak in Urban Kit Fox Population

For the past  5 years, the WIL and it’s partners the Endangered Species Recovery Program (ESRP), UC Davis, CDFW-Region 4, USFWS, and the California Living Museum (CALM), have been working together to help San Joaquin kit foxes living in Bakersfield gain the upper hand during a fatal epidemic of sarcoptic mange. 

Healthy male San Joaquin kit fox

Healthy male San Joaquin kit fox, #6833, in January 2017.

Kit Fox-6833_Male(3)_20170725_Mange-250px

The same male San Joaquin kit fox, #6833, months later in July 2017 – after becoming infested with mange.

Male San Joaquin kit fox after treatment for  sarcoptic mange.

Male San Joaquin kit fox, #6833, a month after receiving treatment for mange while at the California Living Museum, CALM. CALM is a permitted wildlife rehab facility in Kern County.

WIL environmental scientist and UC Davis graduate student, Jaime Rudd, was recently featured in a story about some of the ongoing work and it’s challenges. More about the research can be found on CDFWs Science Institute’s “Science Spotlight” website:

 Additional information about the outbreak, including a recent publication, can be found by following the link

New publication describes a mange outbreak in the endangered San Joaquin kit fox

The Wildlife Investigations Lab’s Deana Clifford and Jaime Rudd recently co-authored a publication with Brian Cypher from the Endangered Species Recovery Program (ESRP) describing a sarcoptic mange outbreak in endangered San Joaquin kit foxes inhabiting Bakersfield. These small foxes are only found in central California. Prior to the emergence of mange, foxes living in the city of Bakersfield were one of the most stable subpopulations of this endangered species.

A committed team of collaborators that includes ESRP, the California Living Museum (CALM Zoo), UC Davis, the California Animal Health and Food Safety Lab System (CAHFS, Davis), the California Department of Fish and Wildlife, and the U.S. Fish and Wildlife Service are continuing research and intervention efforts to minimize the conservation impact of mange on this endangered species.

To access the paper abstract, click here.

Full publication reference: Cypher, B.L., Rudd, J.L., Westall, T.L., Woods, L.W., Stephenson, N., Foley, J.E., Richardson, D. and Clifford, D.L. (2017). Sarcoptic Mange in Endangered Kit Foxes (Vulpes macrotis mutica): Case Histories, Diagnoses, and Implications for Conservation. Journal of Wildlife Diseases53(1); 46-53.

More information about our current research can be found following the link::


The signs of sarcoptic mange in wild kit foxes can be missed in the early stages. However, as the disease progresses and the mites proliferate, the devastating toll this disease has on an individual is easily apparent. Pictured is a mangy kit fox in the later stages infestation showing hair loss, thickened crusty skin, and emaciation (A). Kit foxes with severe mange cannot hunt and often succumb to starvation and hypothermia. The CALM zoo in Bakersfield is a licensed wildlife rehabilitator and has been providing the treatment and veterinary care needed to return affected foxes to good health (Photo B).

CDFW and NPS team up to get word out about poisoned fox near Point Reyes National Seashore

Last September, a gray fox was found dead at a residence in Inverness in Marin County with no signs of trauma.  Since the residence was adjacent to the Point Reyes National Seashore, the National Park Service investigated.  The gray fox was sent to their lab in Colorado and found to have unexplained hemorrhaging in the brain and lungs with no signs of trauma.  These are classic signs of anticoagulant rodenticide poisoning, so the liver was sent to be analyzed by the California Animal Health and Food Safety Laboratory in Davis. The liver contained a toxic combination of three different second generation anticoagulant rodenticides. These rodenticides – brodifacoum, bromadiolone, and difethialone – are only legally used by pest control professionals for rodent control in and around man-made structures. After eating these baits, rodents remain mobile for several days and can be eaten by wildlife or pets.


Gray fox at the Point Reyes National Seashore.  Photo: NPS/Bernot

Members of the public cannot obtain these materials over the counter. Due to their harmful impacts to wildlife second generation anticoagulant rodenticides became restricted use materials in California in July 2014.

To protect local wildlife, the National Park Service and the California Department of Fish and Wildlife urge safer rodent control such as exclusion and trapping.  It is also recommended that residents ask any pest control company that they employ not to use these materials on their property.  The two agencies are teaming up to get the word out locally to prevent another incident near Point Reyes National Seashore.  However, this is not a unique situation.  Monitoring in California has found that the majority of predators and scavengers, such as foxes, bobcats, mountain lions, coyotes, and raptors,  are still being exposed to these materials.

Be a good neighbor to your local wildlife and help spread the word!

To learn more, please visit the CDFW webpage:


Another Turkey Vulture Poisoned by Euthanasia Drugs

CDFW Wildlife Investigations Laboratory has confirmed that another turkey vulture has been poisoned by the veterinary euthanasia drug pentobarbital near Inverness, in Marin County (see map below). The massive bird with its six-foot wingspan has recovered and will be released near Inverness (Marin County) on Tuesday, August 11 at 2 p.m. Reporters who would like to see this vulture return to the wild should call 415-806-8637 Tuesday for the exact location.


CDFW confirmed pentobarbital exposure in six turkey vultures in San Rafael in 2014, but the source of the exposure remains unknown. Those birds were taken to the wildlife hospital operated by the nonprofit WildCare in San Rafael. WildCare is a CDFW-approved wildlife rehabilitator.

Wildlife officials are concerned that the July 2015 admission of an additional pentobarbital-poisoned vulture to WildCare indicates that more wildlife are at risk.

Pentobarbital is a drug used by veterinarians to euthanize companion animals, livestock and horses. If the remains of animals euthanized with pentobarbital are not properly disposed of after death, scavenging wildlife – such as turkey vultures and eagles – can be poisoned. Veterinarians and animal owners are responsible for disposing of animal remains properly by legal methods such as cremation or deep burial.


Turkey vultures are protected by the federal Migratory Bird Treaty Act and California Fish and Game Code. Euthanized remains that are not disposed-of properly are a danger to all scavenging wildlife.

CDFW asks members of the veterinary and livestock communities to share this information with colleagues, to prevent additional poisoning. WildCare also asks the public to pay attention to grounded turkey vultures and other raptors and scavengers.

Pentobarbital-poisoned birds appear to be dead. They have no reflex response and breathing can barely be detected. The birds appear intact, without wounds or obvious trauma. Anyone finding a comatose vulture should call WildCare’s 24-hour Hotline at (415) 456-SAVE (7283) immediately.  Anyone with information about possible sources of pentobarbital-contaminated animals should contact the California Department of Fish and Wildlife at (916) 358-2954.

Toxicological analysis was performed by the California Animal Health and Food Safety Laboratory in Davis.

Anticoagulant Rodenticide Update

Anticoagulant rodenticide exposure in wildlife has been an issue of concern both in California and nationwide. Currently, the USEPA, is continuing to move towards removing the most harmful of products from consumer venues.


Here in California, the Department of Fish and Wildlife is working with the Department of Pesticide Regulation with the aim of restricting access of these materials to only certified applicators.

The process is not a fast one but rest assured that we are committed to protecting wildlife from these materials. You can do your part by avoiding rodent control products with the active ingredients brodifacoum, bromadiolone, difethialone, and difenacoum.

To get the message out, Raptors are the Solution produced this video with young (and very talented) filmmaker Ian Timothy. Enjoy!!!

Some Perspective on Rodenticides

By Stella McMillin

Barn owls are common victims of secondary exposure of anticoagulant rodenticides. Photo Credit: Cornell Lab of Ornithology.

Most of the pesticide-related wildlife problems I deal with currently involve rodenticides.  It is not hard to see why – a material that is toxic to rodents is generally toxic to other vertebrates.  Yet, rodents cause a great deal of damage to agriculture and they are household pests, and so the need for rodent control is real.  While we can recommend non-chemical measures be used whenever possible, we also need to be realistic about the continued use of rodenticides so we can continue to play a part in the regulation of these products.

Anticoagulant rodenticides have been the focus of attention lately for good reason.  Several recent studies have shown widespread exposure among predators and scavengers to anticoagulant rodenticides.  Here at the Wildlife Investigations Laboratory, we have received a few hundred carcasses of wildlife that have been killed as a result of these materials, including San Joaquin kit foxes, mountain lions, bobcats, coyotes, red foxes, gray foxes, black bears, kangaroo rats, golden eagles, great horned owls, barn owls, turkey vultures, Cooper’s hawks, red-shouldered hawks, red-tailed hawks, American kestrels, wild turkeys and Canada geese.

The U.S. Environmental Protection Agency and the California Department of Pesticide Regulation are working on regulatory solutions to decrease unintended impacts associated with anticoagulant rodenticide issue.  Regulation is certainly a step in the right direction. However, regulation of one pesticide often increases the use of another pesticide with a similar function.  And so, as rodenticide use evolves, we must remain vigilant in our protection of wildlife.

One rodenticide I’m keeping my eye on is strychnine. In California, we went nearly a decade without any reported cases of wildlife poisoned by strychnine.  Now, in the last couple of years, we’ve had several.  So, what’s going on?  Is it just coincidence or is it due to the increased regulation of anticoagulant rodenticides?

This is a good example of why education about proper use practices is so important.  Certainly some pesticides are more likely than others to cause problems, including those that are extremely toxic, not selective or persistent.  But even the more environmental friendly pesticides can cause problems if they aren’t used properly.  So we keep our eyes open and keep working together to protect wildlife.

Photo credit: Alison Kent, Wildlife Health Center, UC Davis