The recovery of the Catalina Island fox (Urocyon littoralis) across six Channel Islands was recently recognized by island wildlife managers. At the gathering, Catalina Island Conservancy Wildlife Conservation Manager Katie Elder shared findings related to the 2024 trapping efforts, highlighted research partners and the new fox hotline.  

Status of Catalina Island Fox 

Catalina’s fox population overall is healthy at 10.17 foxes per square kilometer (.38 miles) – or an estimated 1,974 foxes across the entire island. Of the six Channel Islands where island foxes are found, San Clemente has the lowest population density with only 3.5 foxes per square kilometer. Catalina Island foxes are the only one of the six subspecies of island foxes that is still federally listed as a threatened species. Catalina’s island foxes almost went extinct when in 1999 a raccoon infected with distemper arrived on the Island after stowing away on a boat. The foxes had no natural defense against distemper, and the population was nearly wiped out. The Conservancy now vaccinates foxes against canine distemper virus and rabies. These vaccines are donated by the Friends of the Island Fox, which just celebrated 20 years of operation. 

Each fall, foxes are lured by bait into a trap, and once captured, they are examined and vaccinated. A smaller number are fitted with radio collars and remain unvaccinated. These collars produce radio signals which allow biologists to find the fox and check for survival. This process provides a necessary indicator of any sudden population decline from disease or other threats. 

Conservancy staff reported 394 physical fox examinations and vaccinated 341 of them. Staff also treated 371 foxes with topical ivermectin to combat ear mites. According to Senior Director of Conservation Lauren Dennhardt, Catalina completes a high level of fox exams because the Island is at great risk for biosecurity issues due to the large number of tourists and accompanying pets, invasive species and a population of people who permanently live on the Island.  

Mysterious Ear Tumors  

By physically assessing so many island foxes, Conservancy staff are able to assist independent researchers. This year, the Conservancy supported research into fox microbiomes, the complex environment of microorganisms that live in and on an organism. They also researched COVID levels in the fox population and gene expression in foxes that have ear tumors. The Catalina Island fox is the only Channel Island fox that experiences ear tumors, which are present in roughly half the foxes on Catalina. Research revealed that mites that infest the ears of the fox change the animal’s microbiome, leading to a staph infection. As Staphylococcus pseudintermedius flares, “the antibiotic-resistant infection leads to chronic inflammation of the foxes’ ears,” which produces inflamed tissue that promotes tumors.  

The author of the Princeton University report, Dr. Alexandra DeCandia, concluded that mite infection is linked to a proliferation of bacteria. This is tied to the chronic inflammation associated with tumors. Though researchers are still trying to solidify the cause-and-effect relationship, they say the correlation between mites and ear tumors is obvious and illustrates how important an animal’s microbiome is to overall health. The fact that the Catalina Island fox has such little genetic diversity may be a reason that roughly half of the population has ear mites, researchers said. With less genetic variation, the island foxes may be more vulnerable to parasites and less able to fight off infection. 

Working Together 

The treatment of foxes with ivermectin has successfully led to decreased instances of cancerous tumors, Elder said. Now the techniques for managing ear mites that have been developed on Catalina Island are being used on other islands to manage ear mite issues with their foxes.  

Findings such as the cause of the ear tumors are critically important to the well-being of the island fox. 

“This working group is so special because it is a conglomeration of passionate land managers, researchers from a range of disciplines, veterinarians, conservationists and fundraisers that all leave their egos at the door and work collaboratively toward understanding and protecting these charismatic endemic canids,” said Elder.  “It is rare in conservation to have so much expertise present in the room in order to tackle and share information about conservation efforts.” 

Everyday people can also contribute to the health of the species by using the fox hotline to report fox injuries and deaths. Island staff can assess a dead fox to better understand the cause of death. An injured fox may be taken to a veterinarian for assessment. The idea for the fox hotline was brought to Catalina by the working group after it was first established on San Clemente Island.  

Protecting the environment for native species, such as the Island fox, is a top priority for the Conservancy. Efforts over the years have allowed the threatened fox to recover, but continued protection measures are necessary to ensure the species thrives on the Island. 

 

To report an injured or deceased fox on Catalina Island, immediately call or text the Catalina Island Conservancy at 310-606-9424. Please provide the following details: 

• Your name and contact information 

• The fox’s location 

• Any details about the situation, including photos if possible