Cure Discovered for Cancer Affecting Endangered Foxes

For years, the endangered Santa Catalina fox on California’s Catalina Island has had the highest prevalence of tumors ever documented for wildlife. Half of all the adult foxes had ear tumors, the majority of which were malignant. (The foxes most likely to die from the tumors were older and had other health issues.)

Along with the tumors, nearly all of the Santa Catalina foxes examined between 2001 and 2008 were infected with ear mites.

But now those numbers are dropping, thanks to the findings of two new studies by UC Davis in conjunction with researchers from the Institute for Wildlife Studies (IWS) and Catalina Island Conservancy.

One study looked into the prevalence of the tumors, while another examined the effectiveness of treatments with small amounts of acaracide, a chemical used to kill ear mites in dogs and cats.

“We established a high prevalence of both tumors and ear mites, and hypothesized that there was something we could potentially do about it, which now appears to be significantly helping this population,” said Winston Vickers, the study’s lead author and an associate veterinarian with the UC Davis Wildlife Health Center at the UC Davis School of Veterinary Medicine.

During a six-month pilot program in which Santa Catalina foxes were treated with acaracide, the number of ear mite infections was greatly reduced. Prior to the program, more than 98 percent of the fox population was infected. That number is now just 10 percent.

“It’s rare to have a success story,” said the ear mite study’s lead author, Megan Moriarty, a staff research associate at the UC Davis Wildlife Health Center. “It was interesting to see such striking results over a relatively short time period.”

The ear mite treatment is having a positive impact on pups as well as adults. Prior to 2009, about 90 percent of all pups had ear mites, which they got from their parents. By 2015, only 15 percent of pups had ear mites.

santa catalina fox

Winston Vickers, a UC Davis wildlife veterinarian, swabs the ear of a Santa Catalina Island fox.
Photo credit: Megan Moriarty/UC Davis

The Catalina Island Conservancy has been trapping and treating foxes for many years. While the idea of trapping foxes might stir up some really unpleasant images, the process is actually gentle and humane. Foxes are lured into grass-lined cages containing cat food mixed with loganberry jam, which they apparently find delicious.

The foxes are physically examined, given distemper vaccinations, treated for ear mites and other parasites, and given a microchip.

“They are the best-cared-for wild animal on the planet,” John Mack, conservation and education chief for the Catalina Island Conservancy, told the Daily Breeze in 2013. “There are animals we’ve known their whole lives. In my business, it’s uncommon to have a personal relationship like this with animals.”

The Santa Catalina fox is one of six subspecies of the island gray fox that is native to California’s Channel Islands. (They were originally brought to the islands by Native Americans thousands of years ago.) By 1999, only about 100 of the foxes survived on Catalina Island. It wasn’t tumors that were killing them off, but canine distemper.

To restore the population, the IWS and Catalina Island Conservancy launched a Catalina Island fox recovery program. Using captive breeding, distemper vaccinations and close observation, the number of foxes rebounded. As of 2010, there were around 900 foxes on the island; by 2014, the population had increased to more than 1,700.

As a downside of this growth, the U.S. Fish and Wildlife Service is considering whether to remove the Santa Catalina fox from the endangered species list. If this happens, conservation groups will continue to monitor the foxes.

“Even if the status changes, there are impacts or threats that occur on the island that conservation action would need to be done in perpetuity for the continued survival of this species,” Calvin Duncan, wildlife biologist for the Catalina Island Conservancy, told the Daily Breeze last month.

Photo credit: Julie Lynn King/Catalina Island

210 comments

Jeanne R
Jeanne Rabout a month ago

Thank you for sharing.

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Jeanne R
Jeanne Rabout a month ago

Thank you for sharing.

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Jeanne R
Jeanne Rabout a month ago

Thank you for sharing.

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Jeanne R
Jeanne Rabout a month ago

Thank you for sharing.

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Jeanne R
Jeanne Rabout a month ago

Thank you for sharing.

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Siyus Copetallus
Siyus Copetallusabout a year ago

Thank you for sharing.

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Georgina Elizab McAlliste
.about a year ago

very interesting thank you

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Monica R.
Monica Rabout a year ago

Good work. Now keep them save!

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Colleen Prinssen
Colleen Prinssenabout a year ago

not Rick Simpson phoenix tears?

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Sara G.
Sara Gabout a year ago

Good news. I hope next we find a way to protect them from humans.

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