FIF Supports Research into the Impact of a Genetic Bottleneck on Island Foxes

When a population declines to a small number of survivors and then increases dramatically over the next few generations, there are always questions about genetic issues.

Meet Elisabeth Leung a student at the University of California at Riverside. Working with her advisor Professor Ellie Armstrong, Leung is “Exploring founder contributions from the captive island fox breeding programs for Santa Rosa and San Miguel Island using genomic sequencing.”

FIF is supporting Leung’s research because she is delving into an important question with long-lasting consequences for island foxes.

 

Around 26 years ago, the island fox populations on Santa Rosa and San Miguel Islands dropped to a critically low number: 15 surviving individuals on each island. When we look at Santa Rosa’s estimated population of 2,536 island foxes in 2023, all of them have descend from just 12 individuals in captive breeding: 4 males and 8 females.

Elisabeth Leung’s investigation will look directly at the genetics of the original founding individuals on Santa Rosa Island and San Miguel Island and compare their DNA to their descendants on the islands today.

 

Why is this important? Typically a population has some members with genetic-related health issues, maybe a tendency toward heart problems, a physical deformity, or an increased occurrence of specific cancers. Usually, these individuals are a small minority in the population because they are less successful passing on their genes before they die. When survivors are randomly chosen, rather than because they have traits that drive their success, traits that are not necessarily beneficial can increase across a population; this is called “genetic drift.”

With just 4 males contributing to the first generation of captive-born island foxes on Santa Rosa Island, if just one of those males carried a gene that increased health risks, a greater percentage of the population could be impacted. The recovered population might then have higher numbers of individuals with non-beneficial genetic traits. Overtime this would be expected to cause “inbreeding depression”–a magnification of negative traits and reduction in species vigor.

The Florida panther (Puma councilor coryi) is a well-known example of “inbreeding depression.” Genetic problems arose as the population became very small, leading to reduced male fertility and noticeably kinked tails. The inflammation response of Santa Catalina Island foxes to ear mite infestation may be linked to genetics or epigenetics and is currently being investigated by Alexandria DeCandia at the Smithsonian.

biologist examines island fox ear during health check

Though geneticists have raised concerns about island foxes, there is no evidence of current genetic problems.

Today genetic research can delve deeper into DNA and health-related issues than it could 26 years ago. See FIF Grant for Transcriptomic Research

Leung’s research will help us understand the evolutionary impact of recovering from a small founding population. Has there been genetic drift in the fox populations on these two islands? What has changed or not changed in island fox genes?

To examine these changes, the lab at UC Riverside is also creating the first island fox reference genome. The island fox pictured here is fox “25205” on Santa Rosa Island. Blood samples from this island fox will be used to assemble the first complete island fox genome.

Genetic research has entered a golden age and donors like you are helping uncover important genetic information to help island foxes survive into the future.

Conservation Working Dogs and Zoos Helping Wildlife

photo courtesy of TNC and WD4C

 

Meet “Moose” a hard-working canine with the nonprofit organization Working Dogs for Conservation (WD4C).

Moose recently completed a tour of duty on Santa Cruz Island as part of a multi-organizational effort to find a better way to gather information on island spotted skunks.

Island spotted skunks only live on Santa Rosa and Santa Cruz Islands. As island foxes recovered on these islands, island spotted skunks seemed to have declined. There is concern for these rare little skunks and a lack of understanding about their relationship with island foxes. Do island foxes directly impact island spotted skunks? Do they compete for similar resources?

Friends of the Island Fox has supported several research investigations into this relationship:

• C. Gagorik and V Zhang: "Examining habitat use and movement patterns of island foxes and island spotted skunks on Santa Cruz Island”
• J. Schammel: Dietary overlap and change between island foxes and island spotted skunks on Santa Rosa Island
• J. Owen: Genetic relationships of spotted skunk subspecies
• D. Thomaier: Occupancy modeling of island spotted skunks on Santa Rosa and Santa Cruz Islands using field cameras 

In 2024, the question arose about western spotted skunks in captivity that might participate in research studies as a control for island spotted skunks. FIF’s Education Director, Keri Dearborn, did an internet search and found “Boo” a female western spotted skunk at the Sequoia Park Zoo. Boo and her two brothers had been orphaned when they were very young. Though they were rescued, they became imprinted on humans and couldn’t be returned to the wild. Boo was living at the Sequoia Park Zoo in Eureka and her two brothers were at the Turtle Bay Exploration Park near Redding.

 

While Thomaier’s field cameras have documented island spotted skunks, to-date identifying individual skunks in images has been very difficult. Island spotted skunks push off radio collars and typically avoid capture.

Lara Brenner, Island Scientist with The Nature Conservancy, had been working with a conservation dog to sniff out invasive Argentine ant colonies on Santa Cruz Island. Could a conservation working dog locate island spotted skunk dens? Finding scat and dens would be less invasive than capturing skunks and might open up a whole new way to determine their numbers.

Moose gets suited up for work

 

Moose had experience tracking grizzly bears and locating their dens. Could he do the same job for tiny island spotted skunks? Protocol for a test was put in place. Because island foxes are susceptible to canine diseases and because island foxes can be a source of disease for dogs, Moose was up-to-date on all of his vaccinations.

The two zoos collected soiled bedding and feces from the three western spotted skunks. The fragrant material was sent to a WD4C training location in Montana, where Moose learned to identify spotted skunk scent. Would the western spotted skunk scent be close enough to the island spotted skunk scent for Moose to be successful?

 

Toward the end of 2024, Moose and his handler traveled to Santa Cruz Island. Moose “hit the ground running,” Brenner says. As a conservation working dog, he wears a special harness with bells and a GPS locator. Brenner explains that the GPS locator “is so that we can record his tracks and understand [his] search effort… i.e. how far does Moose have to go and how long does he have to sniff before he finds a skunk?”

On the first day, Moose signaled his handler that he’d found an island spotted skunk den. 

Working the hillsides with a canine nose, detection dogs are more efficient than people and have a higher success rate locating a target species. Over three weeks, Moose found several den sites, including this one with an island spotted skunk at home, and 12 scats.

Island spotted skunk in den (courtesy of TNC)

Can DNA from the scats identify individual island spotted skunks? Can genetic meta-barcoding of scat samples identify specific dietary items for island spotted skunks and island foxes? We’re just at the tip of learning how working dogs like Moose can contribute to island conservation?

courtesy of TNC and WD4C

 

This project is a multi-institutional collaboration between Sequoia Park Zoo, Turtle Bay Exploration Park, The Nature Conservancy, Working Dogs for Conservation, and Friends of the Island Fox. The biggest credit goes to the four-footed collaborators: the three western spotted skunks who are helping their wild counterparts and a very talented working dog named Moose.