Uncovering the Impacts of Population Decline on Disease Immunity in Channel Island Foxes by Nicole Adams

(Thank you to our guest blogger University of Southern California graduate student Nicole Adams)

Besides being adorable, why should we care about the island fox?

You probably know the story of the island foxes–that they suffered great population declines in the last two and a half decades. Over three years the northern islands’ fox populations declined 96-99% due to hyperpredation by goldeneagles. (In other words, unusually large numbers of island foxes were killed for food by golden eagles.) At the same time, on the eastern end of Santa Catalina Island there was a 90% population decrease in one year due to a canine distemper virus outbreak.

Fortunately, rigorous captive breeding programs were swiftly and effectively put in place to save the foxes from sure extinction on some of the islands. Island fox estimates as of 2014 show substantial population recovery. A conservation success story! This is great news for the stability of the Channel Island ecosystem, but should we declare victory and stop worrying about the foxes?

photo courtesy of Kevin Schaffer

I don’t think so. The number of foxes has increased, but such severe population declines can have lasting effects on the genetics of a population. Important questions remain. How much genetic diversity was lost due to these crashes? What type of genetic diversity was lost? Which genes were changed as a result? These questions are crucial to answer because genetic diversity allows the foxes to adapt to their ever-changing environment.

Foxes are continually facing health threats such as those caused by introduced species. Known health concerns in the island fox populations include a number of viruses, bacteria, and fungi that cause diseases. On Catalina, earmites in the foxes often lead to ear tumors. And a new pathogen, a spiny worm, is currently causing fox fatalities on San Miguel.

It is difficult to know when another outbreak like the one on Santa Catalina Island will occur, what the next pathogen will be, or how much genetic diversity will be lost. So it’s important that the fox populations are monitored for the presence of known pathogens and the emergence of new ones. Monitoring for pathogens can be easily done by non-invasive sampling, which allows useful animal material to be collected while causing the least amount of stress on the animal. Therefore, I am monitoring pathogens in fox populations by collecting scat samples, a smelly but non-invasive sampling technique.

Catalina Island fox sitting next to its deposited specimen at USC's Wrigley Institute of Environmental Studies; Photo courtesy of Nicole Adams

I received scat samples from all of the six inhabited islands as well as from captive foxes in zoos. I extracted all available DNA out of the scat samples including that from the fox, bacteria, fungi, and fox prey. Then I sequenced 16S rRNA, a common gene that can differentiate among species. I am currently processing the sequences from the scat samples and comparing them to known pathogen sequences in order to identify putative or possible pathogens.

USC undergraduate assistant, Lauren Stoneburner, weighing out island fox scat for DNA extraction. Photo courtesy of Nicole Adams

I will then compare the genetic diversity of a gene family associated with the immune system (major histocompatibility complex II) to the diversity of organisms found in the scat to better understand the current diversity of the immunity genes in the Channel Island fox and how this affects the health of individuals.

The complex population history, combined with ongoing health issues, contribute to the need for conservation of the island foxes. I look forward to sharing my results and conclusions and potentially informing the management practice of these curious critters.

Nicole Adams is a Graduate Student at the University of Southern California in Los Angeles, CA.

More Research Regarding Island Foxes:

Origins of the Island Fox

New Findings on Island Fox Diet

Epidemic Disease Threats to the Island Fox

More 

What Do Island-Fox Biologists Do?

Each autumn, field biologists work hard and long hours checking the status of Channel Island foxes. What do island-fox biologists do during the course of an autumn day?

Here are excerpts from some personal accounts from Santa Barbara Zoo Animal Care staff who elected to spend a week providing 64 volunteer hours assisting National Park Service biologists in Channel Islands National Park.

Scott Daugherty (on San Miguel Island):
Our job was to place radio tracking collars on some foxes and collect biological data, so the Park Service could get an accurate count of how many foxes were on the island, and could make observations about how well the whole population was surviving. This is all accomplished by dedicated individuals, trained to trap and handle the endangered foxes safely...

capture cage hidden under a shrub

One thing that I didn’t realize before actually getting out to the island was just how much work it is to participate in these kinds of studies. Just getting to the traps was almost half an hour of hard hiking, and the traps themselves were set 250 meters apart, making each day a minimum of 5 miles of tough terrain, nearly all of it off trail. Each morning, we would get up before sunrise, and hike out to our trapping grid by first light. Each of our 18 traps needed to be checked and reset, and most foxes that were caught needed to get a full work up...

The conditions on San Miguel can be harsh, with regular winds gusting at 30 mph, and the temperature fluctuating from a warm 75˚F during the day to close to freezing over night. Like the California condor, the Channel Island fox recovery is one of the great successes of conservation study and education, and I am extremely proud to be able to participate.

photo courtesy of NPS

Damian Lechner (on Santa Rosa Island):
In September, I went out to Santa Rosa Island to meet up with Angela from the National Park Service.  We set up 3 grids of traps, each consisting of 12 traps. ....  I was shown how to handle the Foxes and [spotted] Skunks that we trapped, check for parasites, record broken teeth, vaccinate the foxes, micro chip, collect blood and urine samples, collect weights, and take whisker samples. 

island fox having teeth checked; photo courtesy of CIC

(To minimize stress to these wild animals, the goal is to complete all data collection and health maintenance tasks in 12 minutes or less.)

After arriving back at the cabin around noon, we processed the blood and urine that we collected and restocked our kits for the following day.  We continued this for the rest of the week then we collected the traps and hiked out with them on our backpacks.  I learned a lot that week, helped to save Island Species and hiked countless miles.  I’m very appreciative for the opportunity given to me to contribute to this project and hope to go out to the Island again next year.

A huge Thank You to the island-fox Field Biologists for all they do on behalf of Channel Island foxes. Vaccinating island foxes against canine distemper and rabies is vital to their future survival. You can help this effort. FIF is trying to raise funds to protect 500 island foxes.

Our thanks also to the Santa Barbara Zoo and their Animal Care staff who care for Channel Island foxes on the mainland and put in countless volunteer hours to assist the National Park. Thank you also to the Santa Barbara Zoo for sharing the personal accounts of their staff.