On Sunday morning on the last weekend in February, a caller to San Francisco’s Animal Care and Control reported a gray fox acting lethargic in the Presidio. The caller sent some photos of the fox and said people were approaching and petting it.
Alarmed at what sounded like humans interacting with a sick animal, Animal Care and Control officers went looking but couldn’t find the fox. Presidio Trust ecologist Jonathan Young searched the next day, and also couldn’t find the fox. It’s rare for foxes to appear in the Presidio in the daytime, Young says, and between that and the reported behavior, he too suspected it was sick.
“In those photos, it doesn’t look normal,” he said. “I think something’s going on, primarily in the raccoon populations, but it’s spilling over potentially into this fox if not other foxes.”
San Francisco Animal Care and Control spokesperson Deb Campbell said the city’s shelter has received noticeably more calls about sick raccoons and skunks so far this year than last year. She said callers have reported skunks or raccoons “walking in circles, crusty eyes, curled up in a ball on their front porch. In odd areas. Just acting abnormally during the daytime, stumbling,” she said. “It makes them sound disoriented. A sure sign something’s not that right.”
Animal Care and Control hasn’t examined the raccoons it has captured, so Campbell said she wasn’t sure what had affected them. It’s not rabies, she said, which tends to be the public’s first concern. Though a rabid bat might fly through from time to time, Campbell said San Francisco hasn’t seen a land mammal with rabies in decades.
WildCare Assistant Director of Animal Care Brittany Morse said the San Rafael-based rescue group’s doctors have seen an outbreak over the last two years of a virus called canine distemper, which would account for the fox’s symptoms. Distemper is an upper respiratory disease that spreads by close contact. Though dogs can be vaccinated against it, the virus can cause a wide range of problems in wild animals, starting with classic cold symptoms and proceeding to loss of appetite, lethargy, gastrointestinal distress, muscle twitches, paralysis, and death. (Canine distemper virus, as perhaps the name implies, is not a risk to humans.)
After seeing an unusual number of hospital admissions in 2020, WildCare started testing all wild mammals that came through its doors, symptomatic or not. Since then, Morse said, 30 animals including skunks, raccoons, foxes, coyotes, and even a river otter have tested positive for distemper, about half the total number of animals tested.
“We do know from the other centers, they’re also seeing distemper,” Morse said.
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Still, canine distemper is one of a number of cyclical serious illnesses that periodically affect local mammals. Young said the fox might also have been suffering from rodenticide poisoning. He hoped lab tests of sick raccoons would help establish whether it’s a continuation of the distemper outbreak or something else.
The California Department of Fish and Wildlife leads investigations into animal disease outbreaks, but has not yet had a chance to recover or examine any animals from San Francisco, wrote Jaime Rudd, the non-game health specialist for the agency’s Wildlife Health Lab, in an email Tuesday. “Distemper is the most common disease we observe in our wild carnivores – notably in gray foxes, raccoons, and striped skunks with occasional spillover in coyotes and other fox species,” Rudd wrote.
Rudd said the Wildlife Health Lab has received animal remains from neighboring counties near San Francisco, and results from those tests are pending. A dispatcher at the city of San José’s Animal Care and Services said they haven’t seen anything unusual so far this year.
A number of viruses and pathogens persist in the environment and move between species. A 2018 study of ten live Presidio coyotes showed that two had antibodies indicating a recent distemper exposure, and another had antibodies indicating a previous parvovirus infection. Eight had suffered from toxoplasmosis, an infection caused by a parasite that spreads in cat feces.
Distemper can flare up for several years, then recede. Morse said that when the current North Bay outbreak started in 2020, it had been seven or eight years since the last one. A Fish and Wildlife press release from February 2020 notes that CDFW also saw an uptick in cases statewide in 2020, and that outbreaks can “temporarily reduce some local carnivore populations.” An outbreak in the Palo Alto Baylands in 2016, for example, wiped out two dozen foxes that independent wildlife researcher Bill Leikam had been watching for years. While it’s not clear what causes the virus to cycle, the disease spreads more rapidly when animals are in closer proximity.
Morse, Campbell, Young and Rudd all said a potential disease outbreak is a reminder to keep pet vaccinations up to date and keep dogs away from wild animals. “Those [diseases] are in the environment and can spill back and forth between wild and domestic animals, and between species,” Young said. “Don’t pet the sick gray fox please.”
Gray foxes are common in the Bay Area but less so in San Francisco. In the Presidio they are generally driven away by coyotes or killed by cars, Young said. Camera traps capture their photos from time to time, especially at night on the east side of the park, and most recently in October 2021. Young said neighbors have told him the foxes live in backyards around Cow Hollow, and perhaps forage in the Presidio under cover of darkness. The last time he saw a gray fox in person was in 2018, when Presidio Trust biologists found three dead foxes in the span of five days. Two had been killed by cars, their skulls crushed, and then thrown up off the road onto the hillside. One was found on the golf course, torn apart and surrounded by coyotes – though Young said he doesn’t know whether the coyotes killed it or just scavenged it after it too had been roadkilled.
“If there are foxes living in the Cow Hollow neighborhood,” Young said, “you wonder if there’s one or two individuals who have been around long enough to know, ‘Don’t live in the Presidio. Forage at night one or two times, but live in the neighborhood where you’re safe.’”