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

Results on the Coyote from Strawberry

We received lab results from the coyote that appeared to have died from anticoagulant rodenticide poisoning.  This coyote was found in weakened condition in Strawberry (El Dorado County) in early June and brought into Tahoe Wildlife Care.

It did not recover and was euthanized.

The lab findings were not surprising:  very high liver concentrations of the anticoagulant most commonly found in non-target wildlife: brodifacoum.  Another anticoagulant rodenticide was found in lower concentrations:  bromadiolone.

Anticoagulant exposure causes internal bleeding, including the subdermal bleeding seen here.

Rodent poisons containing brodifacoum can be purchased at grocery stores and hardware stores.  The U.S. Environmental Protection Agency has proposed limits on their availability but so far those limits are not in effect.

DFG urges residents to protect wildlife in their area by limiting use of products containing brodifacoum, bromadiolone, and difethialone.  These materials are the active ingredients in some rodent baits and have been found in a high percentage of our predatory and scavenging birds and mammals in California including hawks, owls, coyotes, foxes, mountain lions, and bobcats.

For more information on protecting wildlife from rodenticides, please read:


Be Careful with Our Feathered Friends

By Krysta Rogers and Stella McMillin

A few weeks ago, our avian disease specialist, Krysta Rogers, was notified of an ongoing incident in Kern County. A man reported finding two to five dead birds at a time near his bird feeder over a period of weeks.  This added up to 30 to 50 birds in total, most of which were mourning doves.

Often, mortality occurring near bird feeders is disease-related. Bird feeders can unnaturally congregate birds, increasing the chances of disease transmission. In particular, mourning doves are highly susceptible to a parasite that causes a disease called Trichomoniasis. This disease can lead to significant mortality of mourning doves; it tends to occur during the spring in doves that visit bird feeders.

However, in this incident a raptor and the neighbor’s dog also had died in the same location and a similar scenario had occurred the previous year. As such, this incident seemed to be more likely related to a toxin, rather than disease.

Our pesticide specialist Stella McMillin became involved to investigate the cause of death. Fortunately, Krysta and Stella were able to examine two doves that died during this incident.

Examining the doves, they found no evidence of disease. However, when they looked in the birds’ crops we found both of them full of the same milo seed-like material.  They showed a picture to the Kern County Agricultural Commissioner’s Office who suggested that it appeared to be strychnine bait.  So, they submitted the bait and livers from the birds to a diagnostic lab to test for strychnine and the results were positive.

Strychnine is used to control pocket gophers and is only legally applied underground to prevent exposure to non-target wildlife.  In this case, unless these doves had been using shovels, it appears that the application was not done properly.  Some formulations of strychnine are restricted only to those with applicator’s licenses but others are available to the general public.  Sometimes the general public is not aware that “the label is the law” – it is illegal to use a pesticide in a manner not specified by the label.  When a pesticide, particularly something toxic to vertebrates like strychnine, is not used properly, it poses a hazard to wildlife, pets and children, so investigation of these cases is important.

Now the difficult part begins – identifying the source of the strychnine and taking action to ensure that this situation does not occur again.

Although this incident was not related to disease, it is a reminder, that bird feeders, hummingbird feeders, and bird bathes, should be thoroughly cleaned at least once a week to reduce the chances of spreading disease.

For more information about how to keep birds healthy at bird feeders visit the National Wildlife Health Center (http://www.nwhc.usgs.gov/publications/fact_sheets/coping_with_diseases_at_birdfeeders.jsp) and Audubon (http://web4.audubon.org/bird/at_home/bird_feeding/feeder_maint.html).

A Sad End for a Coyote

By Stella McMillin

Lake Tahoe Wildlife Care called our lab over the weekend to report they had a coyote that had been found wandering in Strawberry, which is in El Dorado County. The veterinarian there examined the coyote and found unexplained bleeding around his mouth, which, when unaccompanied by signs of trauma, can indicate poisoning from a kind of rodenticide that thins the blood.

Anticoagulant rodenticides are a tough issue right now. They are legal, widely used, and few users know the impact they can have on wildlife. Predators and scavengers get exposed to rodenticides when they eat rodents that have been poisoned.

The veterinarian drew blood and confirmed that coyote’s blood clotting was impaired. The coyote did not recover and was subsequently euthanized.

From Strawberry, the coyote was brought to our lab by Tom, the rehabber. The necropsy went as expected – lots of blood, both under the skin and loose in the chest and abdominal cavities. There were no broken bones. It appears that the animal was bleeding to death internally.

We took liver tissue for our chemistry lab to examine. Monitoring studies reveal that the majority of predatory and scavenging wildlife in California are carrying residues of anticoagulant rodenticides in their livers.

DFG would like to see the more persistent and toxic of these rodenticides restricted so they could be used only by certified applicators. It is one measure we can take to reduce our impact on wildlife in California.

For more information on rodenticides, see http://www.dfg.ca.gov/education/rodenticide/.

As the person who monitors pesticide impacts to wildlife in California, I am often grateful to the wildlife rehab volunteers. They are often the ones who call our attention to poisoned wildlife and will sometimes go the extra mile, as Tom did, to drive the coyote over to our lab so we can work on it. This is particularly true in the case of the anticoagulant rodenticide issue, where many of the animals we have diagnosed have been brought to us through wildlife rehabilitation centers.

I’ll post chemical results when we get them back from the lab.