Fox Foto Friday - Island Fox Status

photo courtesy of Megan Sarrail

Island foxes are a model of conservation success! 

In August of 2016, island foxes were removed from federal Endangered Species status on four islands. Over the past ten years, their survival has been monitored using radio tracking collars and annual health checks.

California's February-2026 issued "State and Federally Listed Endangered and Threatened Animals of California" lists island foxes as a California State "Threatened" species on all islands.

Update 3/31/26: Island fox friend and retired member of the Island Fox Conservation Working Group, Dale Steele, clarifies "All subspecies of the Island Fox have been listed as "Threatened" [by California] since 1971. The recently published list of state and federal listed species is the most recent update including other recent petition decisions but did not change or add the Island Fox. 

Why are island foxes still considered "Threatened" when their numbers have recovered across the islands?  

While conservation efforts have been very successful, each island fox population is unique, small and limited to a single island. Looking forward all island foxes will continue to face a range of threats–from introduced disease to climate change and human impacts.

Immediate threats to island fox survival will change, but keeping an eye on this tiny canine's challenges and successes will help to keep them thriving into the future. Conservation is a process, not a checkbox. 

2019 Island Fox Status Update

In 2018 most island fox populations were stable, but not without risk factors. 

As expected, high temperatures and below average rainfall in 2018 contributed to lower pup numbers and reduced adult survivorship across all islands. As first documented on Catalina Island, island fox reproduction is linked to annual rainfall. Fortunately, normal rainfall levels in 2019 should benefit all island fox populations.

In 2019 Channel Island foxes face four major threats:

• climate change: increasing regional temperatures and decreasing annual rainfall, which reduce food resources, increase wildfire threat, and promote parasite numbers
• biosecurity: the introduction of non-native plants, animals, and diseases
• parasites: rising tick numbers and tick-borne diseases; increased intestinal parasites on some islands
• reduction of management funding

The following update is drawn from FIF notes taken at the 2019 Island Fox Conservation Working Group meeting. Population numbers reported here are the official estimates from each island manager, as calculated from the fall 2018 count and reported May 21, 2019. Download the detailed 2019 Island Fox Status Update

Greatest Concern 
San Miguel Island foxes robustly recovered from 15 individuals in 2000 to over 500 by 2010 (lime-green line on graph below). As a smaller island, it will always have a smaller fox population. In 2015, however, following several years of drought, the population began declining. As of fall 2018, the population has dropped to an estimated 171 individuals (a decline of over 70%). This decline may involve several interconnected threats: climate change, biosecurity and parasites. Details regarding San Miguel will be posted in coming days.

Improved
San Nicolas Island foxes declined by 59% to 260 individuals during consecutive years of drought from 2012–2015 (pink line on graph above). The US Navy initiated native plant restoration projects in conjunction with Channel Islands Restoration. As these plants, like prickly pear cactus, mature they are providing food and habitat for island foxes and prey species. The fox population has increased to a more stable number–estimated 400 individuals. 

Stable
Santa Rosa Island foxes may have reached capacity for the island (pink line on "larger islands" graph above). Native vegetation is recovering and increasing resource options for foxes during periods of drought. No island foxes have been lost to golden eagles on this island or San Miguel since 2010. Parasites, including tick-borne disease, are a growing concern on Santa Rosa. FIF has refurbished 7 radio collars, and funded dietary research and health testing measures in 2019.

Santa Cruz Island foxes have reached capacity for their habitat. As a result the population decreased naturally during 2018 (green line on "larger islands" graph above). Parasites, especially tick-borne Lyme disease, are an increasing concern. Because the Cruz population has been stable since 2014, there is pressure to reduce funds for monitoring. This poses a potential threat because this population receives elevated contact from the outside world via island visitors. FIF has refurbished 20 radio collars for monitoring in 2019.

Santa Catalina Island foxes have also reached capacity for their habitat. In reaction to decreased rainfall, this population also declined naturally in 2018 (red line on "larger islands" graph above). Parasites, especially tick-borne Lyme disease, and biosecurity are an increasing concern for this population. Lyme disease and canine herpes virus were both introduced via human visitors and their pets. Monitoring of disease exposure is vital to this populations continued health. FIF has funded 5 new radio collars and health testing measures in 2019.

San Clemente Island foxes live on the most southern Channel Island (blue line on "smaller islands" graph above). In 2018, they were the first population to see deaths directly attributed to high temperatures. Reduced rainfall stressed the population and eight individual island foxes are known to have perished in the heatwave between June and July of 2018. Climate change is impacting this island fox most directly. 

Download the detailed 2019 Island Fox Status Update

Friends of the Island Fox at Sierra Club Event

What is the current status of the endangered Channel Island fox? 

Come join us and find out.

Friends of the Island Fox will be joining the Ventura Sierra Club for an evening program hosted by Jim Hines. 

We'll be presenting a FREE family friendly program:

Island Foxes: In Their Island World

February 5th 2015

7-8:30 PM (Doors open at 6:15 PM)

at the Community Meeting Room

Ventura City Hall

501 Poli Street, Ventura, CA 93001

NOTE: Plenty of free parking behind city hall

We'll be talking about the vital role island foxes play in their island habitat, new information on island fox diet, the amazing recovery of all four endangered subspecies, and the future: concerns about impacts from changing climate, human trash, and biosecurity. 

As well as the presentation, there will be information on conservation efforts and educational displays. Compare your hand to a fox footprint. Compare an island fox to a gray fox or a red fox. How small is an island fox? How big is a golden eagle?

Bring your questions and then help us spread the word about protecting our rare Channel Island foxes. 

Channel Island Fox Status Update June 2014

photo courtesy of Dave Graber

photo courtesy of Kevin Schafer

The annual meeting of the Island Fox Conservation Working Group reported that the general status of the six subspecies of Channel Island foxes is GOOD.

All subspecies are maintaining stable populations of over 300 individuals. There are no known specific issues that put any of the Channel Island fox subspecies in eminent threat of extinction. Each island, however, faces its own concerns and challenges. 

  
Island Fox Update 2014 pdf, a specific island-by-island summary

• San Miguel Island - 577 (low of 15 in the year 2000). Population recovered with over 500 individuals since 2010. Concern: New threat from parasites.
• Santa Rosa Island - 894 (low of 15 in the year 2000). Population steadily increasing.
• Santa Cruz Island - 1,085 (low of 62 in the year 2002). Population recovered and stable with over 1,000 individuals since 2009.
• Santa Catalina Island - 1,852 (low of 103 in the year 2000). Population recovered and stable with over 1,000 individuals since 2010. Concern: Climate change impacts and high risk for introduced disease.
• San Clemente Island - 1,002 (not Endangered). Population stable. Concern: New disease threat connected to mineral particulates in the air.
• San Nicolas Island - 350 (not Endangered). Population high, but declining. Concern: Cause of decline currently unknown, see below.

Concerns:

As populations reach the carrying capacity on some islands, there are new challenges to island fox survival. Continued drought appears to be impacting prey and plant species on some islands, which in turn impacts the island fox. Not only are resources reduced, there may be new threats posed by parasites. (Spiny-headed worm on San Miguel Island).

raccoon stowaway on Catalina Express, Dec. 2013
photo courtesy of Ciara Virdan

Introduced disease remains a threat to all island foxes, especially on islands visited by people. Dogs, cats, and introduced species, like raccoons, are all avenues for disease to be transported to isolated and disease-naive island foxes.

 Canine distemper virus (CDV) caused the population collapse of island foxes on Santa Catalina in 1998-2000. Vaccination against CDV is part of protecting island foxes on all six islands. Island foxes, and many other wild species, are unable to withstand the standard CDV vaccine given to dogs and depend on a vaccine produced by Merial, the corporation that makes Frontline and other veterinary products. Unfortunately, there has been no production of the vaccine this year. If the vaccine is not available by fall counting and health checks, island foxes may go unprotected for the 2014-2015 year.

On San Nicholas Island where the fox population has been high and stable for years, annual monitoring has revealed a trend toward decline that is currently unexplained. A group of island foxes on San Nicolas Island will be radio collared in the fall during annual counting to help biologists determine the cause for the decline. (For more specifics see Island Fox Update 2014 pdf above)

Positive Notes:

While there are concerns regarding San Miguel and San Nicolas, island foxes are doing well. Working with U.C. Davis and veterinary pathologists, National Park biologists hope to determine the specific reasons behind the appearance of new parasites on San Miguel Island and the long-term threat they pose to the island fox population.

Monitoring with radio collars on San Nicolas Island will enable biologists to locate individual island foxes that die in a timely manner. Necropsies performed on these animals will help provide information regarding cause of death.

The most positive note of all is that the Island Fox Conservation Recovery Group continues to meet. Nothing is more important for the continued recovery of the island fox than bringing this group of people together who can share their expertise, their experience, and their creative solutions. Friends of the Island Fox thanks all of our donors who made this annual meeting possible!

Endangered Island Foxes Stabilizing But Need to Monitor Continues

courtesy of Kevin Schafer

The annual meeting of the Island Fox Conservation Working Group took place yesterday, hosted by Friends of the Island Fox. 

The good news is that the four endangered populations of island foxes on San Miguel, Santa Rosa, Santa Cruz, and Santa Catalina Islands continue to recover and stabilize. 

Island foxes on the two Navy islands, San Clemente and San Nicolas, are not considered endangered by the U.S. Fish & Wildlife Service (USFWS) and their populations remain stable and at high densities (number of individual animals per square kilometer).

The graph below shows population numbers for San Miguel Island through fall 2013. The population was initially estimated in 1994. Actual individuals were counted when island foxes were in captive breeding pens on the island. Through 2007, the island foxes on San Miguel were gradually returned to the wild. Wild population figures are estimated through an annual catching of individuals and computer extrapolation of that data. More on Counting Island Foxes.

The graph shows how San Miguel's population dropped dramatically due to golden eagle predation at the turn of the century. Fifteen surviving individuals became the founders of the current San Miguel Island fox subspecies; captive breeding by the National Park Service saved this subspecies from extinction.

The population has made an amazing and rapid recovery to a level greater than historically estimated before the crisis. Statistical analysis through fall 2013 calculated that for the fifth year in a row,  individual island foxes on San Miguel have a 90% chance of surviving through the next year and the potential for species extinction is very low.  

Currently the density of island foxes on San Miguel is very high, 10-20 individuals per kilometer in some habitat areas. National Park biologist Tim Coonan believes the data shows the San Miguel Island fox population has fully recovered and has reached the "carrying capacity" for this small island. This means the food and territory resources available on San Miguel can not support continued population increase. The minor population ups and downs since 2010 follow the pattern of a population responding to resource availability. 

Conservation efforts on behalf of the San Miguel Island fox have been very successful. Across Santa Rosa, Santa Cruz and Santa Catalina the stories of population recovery from the brink of extinction are all inspiring.

However, there is an additional cautionary chapter in the San Miguel story. As the island foxes in the National Park have recovered, funding has decreased for their management. The staff that works with the foxes on San Miguel and Santa Rosa has gone from six to three technicians. 

Since the end of 2013 thru May of 2014, seventeen radio-collared island foxes on San Miguel have died from peritonitis caused by a parasitic spiny-headed worm (the exact species is still being determined). This parasite has not been a problem on the Channel Islands before and typically does not cause mortality in canines. The spiny-headed worm is transmitted to the fox through another animal-species host that the fox has eaten.

Today as the biologists, veterinarians, land managers and government officials meet for a second day, they are sharing expertise and ideas about how to respond to this potential threat to the San Miguel Island fox. Over the next few months they will be looking for answers to new questions:

• What prey species is carrying the parasite?
• Have island foxes on San Miguel changed to a prey species that is a vector for this parasite?
• Across San Miguel Island a higher number of island foxes are appearing underweight. Are these foxes infected with the parasite as well?
• Is drought a factor in this problem?
• Is high population density a factor?  
• Why is the number of these parasites so high in individual foxes?
• During the fall count, there appeared to be a very low number of pups on San Miguel. Is this a natural response to high population density and reduced resources? Is the parasite impacting female health and therefore reproduction?
• Is the parasite a possible threat to other Channel Island fox subspecies?

Channel Island foxes are rare creatures. Prior to the near extinctions of 2000, little was known about this endemic California species. If there is one thing that has become obvious over the years, it is that change to the island habitat, either directly by people or indirectly through environmental toxins, climate change, or introduced invasive species, island fox survival requires vigilance. 

The continuity of public support and scientific experts engaged in island fox conservation is vital to maintaining this unique species into the future. Funding the Island Fox Conservation Working Group meeting is an important part of island fox conservation.

Stay tuned for more information from the Working Group meeting. 

The Science of Counting Island Foxes

courtesy of National Park Service

In 2000 when there were only 15 island foxes surviving in captive breeding pens on San Miguel, you could count them easily on your fingers.

Today all Channel Island foxes across the six islands where they live are back in the wild. (A few rescued individuals from San Clemente Island can be seen in mainland zoos.) The recovery of the endangered island fox on San Miguel, Santa Rosa, Santa Cruz and Santa Catalina Islands has been record-breaking and the days of counting all of the physical island foxes are long gone.
 

courtesy of National Park Service

The process of counting foxes on each island begins in the fall with special capture cages.

These cages are set up either at the cross sections of grids or along a string depending on the island and its topography (More on strings and grids)

Cages in an area are set out over the course of a specific number of nights and checked each morning. On Catalina, each string is run for four consecutive nights; after that, typically the majority of individuals would be foxes that had already been captured on previous nights. Each island fox is identifiable because it has a Passive Identification Transponder (PIT) microchip. An island fox caught for the first time receives a PIT tag. From that point on the PIT tag allows it to be recognized as a specific individual. It can take weeks for biologists to evaluate each island.

Over the course of all the capture nights, the number of individual island foxes, their gender, ages and location caught are documented. Island foxes are quite territorial, therefore it is unlikely that a fox caught in one area of the island would be found on a different area of the island during the month of counting. (If it is, that is important too.)

The data is input into a modeling program for analysis. Different programs may be used on different islands and over the years land managers may change which program they use. The modeling program calculates the density of island foxes in specific habitats across the island and estimates a total island population.

Sometimes, however, it takes a human brain to see complexity in the numbers. On two islands where recovery has been robust over the past few years, San Miguel and Santa Catalina, the estimated population numbers appear to be higher in 2013 than they were in 2012.

But observations on both islands conclude that drought may have reduced births and did cause starvation in a number of pups last summer, prior to counting. How could the population number increase while the number of surviving pups decreased significantly?

Biologists Calvin Duncan and Julie King from the Catalina Island Conservancy explain that on Catalina they caught a greater number of adult island foxes that had not been counted for a number of years. Young animals are more likely to be curious and challenged with finding food; they venture into capture cages more readily. Once an animal is in the cage, no other can be caught that night. This year, on the fourth night of capturing, they were still finding a high percentage of animals that had not been caught on previous nights.

courtesy of Kevin Schafer

The increase in the population number for Catalina is warranted because of the number of unique individual animals that were counted. But rather than an increase in the population, the number represents a refinement of the estimate toward greater accuracy.

On both San Miguel and Santa Catalina Islands, island fox numbers have surpassed historic population figures. Both islands may have reached carrying capacity, or the number of individual animals that can find the territory and food resources necessary for a healthy life. As the drought continues this summer, there may be further impacts not only on pups, but also on older individuals.

Counting island foxes provides an important picture of island fox recovery, but observations throughout the year, health checks, blood tests, data collected from radio-collared island foxes and necropsies is vitally important to understanding the whole recovery picture.

Which Island Foxes Wear Radio Collars?

island fox with radio tracking collar; courtesy CIC

Island fox populations are returning to normal levels across the six California Channel Islands where this rare species lives. With hundreds of island foxes on each island, the number of radio-collared animals is limited to a representative group. Typically 40-60 individual animals wear radio-tracking collars on each island.

 Which island foxes receive radio tracking collars?

Island foxes that wear radio-tracking collars are typically younger–ages 1-4 years old. Island foxes can live 8-10 years in the wild, with rare individuals living to age 12 years. Younger animals are more likely to move across the islands as they try to find a mate and establish their territory. (Female that traveled across Catalina's isthmus) 

While some radio-collared island foxes are individuals with specific survival challenges (Burnie Boots and three-legged island fox), most collared island foxes act as disease and predator sentinels. If something happens to these foxes their demise is quickly brought to the biologists' attention because of the radio collar. When an island fox stops moving, even breathing, for over six-eight hours the collar signals a specific mortality signal. Using the signal, biologists can locate the island fox's body, discover the cause of death and take action. (Listen to radio signals on our Audio/Video page)

“Being able to identify the threats greatly improves our ability to understand and protect this unique species,” says Julie King, director of conservation and wildlife management for the Catalina Island Conservancy. Once the carcass is collected it is sent to the California Animal Health and Food Safety Laboratory to ascertain the exact cause of death.

Both male and female island foxes can be sentinels. These individuals are not vaccinated against the two most threatening diseases to island foxes–rabies and canine distemper. (FIF vaccination funding) 

courtesy of Jason Bean

Reading information from the radio-collars varies across the islands. On flat-terrain islands radio receiver towers pick up the signals of island foxes in their area and relay the information to a computer terminal. Mountainous terrain is more challenging; on some islands radio-collar signals are picked up from the air by small aircraft, weekly or biweekly. On other islands, biologists with hand-held antennae and a receiver locate island foxes from vehicles or on foot.

In 2014 FIF has the goal to fund our 100th radio collar. With your help we will reach that goal. 

Good News on Channel Island Fox Recovery

Have you heard the good news? 

All four of the subspecies of endangered Channel Island foxes are doing well. In fact, three of the subspecies are considered to be close to recovered. What constitutes recovery?

1. Population numbers that have returned to healthy levels
2. Reduction of threats (those that caused the original near extinction and/or new challenges to survival)
3. Stability of the first two for at least five years

A graph of the population figures from Santa Cruz and Santa Catalina Islands shows the rapid declines toward extinction in the late 1990s. (Caused by unnatural golden eagle predation on Santa Cruz and introduced distemper virus on Santa Catalina.) 

From 2000 to 2007 island foxes increased in captive breeding facilities on each of the islands and were gradually released into the wild. Once the threats to their survival were reduced, populations of island foxes increased rapidly in the wild. Golden eagles were relocated and bald eagles were reestablished on the northern islands, while vaccinations for distemper and rabies were instituted across the islands.

On both Santa Cruz and Santa Catalina the island fox populations now fluctuate around a number that represents the carrying capacity or maximum population that can survive on each island's resources. The population of any living species alters naturally in response to available food, water and habitat.

The population numbers for island foxes are compiled annually by biologists in the field each autumn. These hard-working people  from across the six islands come together each year in June with veterinarians, scientists and government officials to discuss the status and threats to each of the six subspecies of island fox. We will have more from the annual meeting of the Integrated Island Fox Recovery Team as we compile our notes. It's been a happy busy week.

Pat Meyer Talks About the Island Fox

Friends of the Island Fox founder Pat Meyer recently was interviewed on a television program in Ventura County, California. 


Hear her talk about how the island fox became endangered, how she was motivated to start a public outreach and education non-profit organization, and how conservation efforts have helped take the island fox from critically endangered toward recovery. 

 

Friends of the Island Fox joined with the Channel Islands Park Foundation in January 2011.

Island Fox Populations Recovering

photo courtesy of Kim Michaels, KimMichaels.com

What is the current status of the endangered Channel Island fox? In 2012 the Channel Island fox is robustly heading toward population recovery! Across all islands 90% of the population is surviving on an annual basis.

Every June biologists working with the endangered Channel Island fox come together to share information and update each other on the island foxes populating their island. June Meeting

The general consensus is that endangered populations on San Miguel, Santa Cruz and Santa Catalina Islands are all headed toward or reaching levels of recovery. (Habitat) The Santa Rosa Island fox is now increasing in number, but still is at a much lower population number than before the predation crisis caused by golden eagles and habitat destruction.

Island foxes are counted annually across the California Channel Islands in the late summer and early fall.  Animals are captured in safe traps so they can be given health checks, fitted with radio collars and given vaccinations. Friends of the Island Fox financially supports these conservation efforts.

In 2012 FIF financially supported 14 radio monitoring collars and provided funding for vaccinations against the distemper virus for 450 island foxes.

The official population estimates from 2011 are:

• San Miguel Island - 581 (up from 15 individuals in 2000)
• Santa Rosa Island - 449 (up from 15 individuals in 2000)
• Santa Cruz Island - 1302 (up from ~80 in 2000)
• Santa Catalina Island - 1542 (up from ~103 in 2000)
• San Nicolas Island - ~500
• San Clemente Island - 795

numbers represent the Santa Rosa Island population (pink line)

The recovery of the endangered Channel Island fox is one of the fasted recoveries of an endangered species in North American history. The populations on San Miguel and Santa Catalina Islands have surpassed historically recorded numbers and this year the slight drop in population on Santa Cruz Island was seen as a stabilization of a population that has reached the island’s carrying capacity.

This year the Island Fox Working Group discussed the process for delisting the island fox from the Endangered Species List. Continued monitoring to assure the populations are stable is vital to this process. You can play an important role by helping support island fox monitoring.