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Tuesday, March 17, 2015

The Origins of the Island Fox by Courtney Hofman

(Thank you to our guest blogger, researcher Courtney Hofman) 

photo courtesy of Kevin Schafer
People have long wondered how the island fox first arrived on the Channel Islands. Did they swim? Were they swept out to sea on a piece of debris? Did Island Chumash and Gabrieliño people or their ancestors introduce them? Researchers have proposed a number of possible hypotheses of how the fox arrived but to test each hypotheses we must first examine the data on when foxes arrived on the islands.
For a long time scientists thought that island foxes had been on the islands for at least 16,000 years and some argued they had been there as early as 40,000 years ago (Aguilar et al. 2004). This is well before people arrived on the islands some 13,000 years ago. These early date estimates were based on island fox bones recovered from paleontological sites. However, direct radiocarbon dating of these same fox bones indicate that they are less than 7000 years old (Rick et al. 2009). Additional radiocarbon dates on island fox bones recovered from archaeological sites indicate that island foxes may have arrived on the islands approximately 7100 years ago, well after people.
When combined with radiocarbon dates, genetic data can also be used to test hypotheses about the origins of the island fox. Mitochondrial DNA is inherited from a fox’s mother and can tell us a lot about the history of the island fox. In my recent study, mitochondrial DNA was sequenced from 185 island and mainland gray foxes to explore how these different populations are related to each other (Hofman et al. 2015).

Median-Joining Network of Island and Mainland Mitochondrial DNA
By comparing these DNA sequences, we know that northern island (Santa Cruz, Santa Rosa, and San Miguel) foxes are closely related to each other while the southern island populations are more distinct (Santa Catalina, San Clemente and San Nicolas). Together with radiocarbon dates, mitochondrial DNA suggest that island foxes arrived on the northern islands between 9200 and 7100 years ago and were likely quickly moved by humans to the other islands. We cannot yet say how the foxes first arrived on the islands. More genomic and archaeological data are needed to distinguish between a human or natural introduction. 

  • Aguilar, A., Roemer, G., Debenham, S., Binns, M., Garcelon, D. and Wayne, R. K. (2004). High MHC diversity maintained by balancing selection in an otherwise genetically monomorphic mammal. Proc. Natl. Acad. Sci. U. S. A. 101: 3490–3494.
  • Hofman, C. A., Rick, T. C., Hawkins, M. T. R., Funk, W. C., Ralls, K., Boser, C. L., Collins, P. W., Coonan, T., King, J. L., Morrison, S. A., Newsome, S. D., Sillett, T. S., Fleischer, R. C. and Maldonado, J. E. (2015). Mitochondrial Genomes Suggest Rapid Evolution of Dwarf CaliforniaChannel Islands Foxes (Urocyon littoralis). PLoS ONE 10:e0118240.
  • Rick, T. C., Erlandson, J. M., Vellanoweth, R., Braje, T. J., Guthrie, D. A. and Stafford Jr., T. W. (2009). Origins and Antiquity of the Island Fox (Urocyon littoralis) on California’s Channel Islands. Quat. Res. 71: 93–98.

Tuesday, March 10, 2015

What Color Is An Island Fox?

photo courtesy of Kevin Schafer
What color is an island fox?

It might seem an easy question, but there is more to the color of a Channel Island fox than initially meets the eye.

At first glance an island fox (Urocyon littoralis) appears to be a mixture of white, reddish or rust, and gray markings, with a little black. The island fox's ancestor, the gray fox (Urocyon cinereoargenteus) has similar coloration, though typically less rust.

The primary color on an island fox is a grizzled gray along its back.

island fox back

This cryptic coloring provides very successful camouflage because it is not a solid color.

There is an underlying downy fur of a light tan, interspersed with long guard hairs. While some guard hairs are black, others along the back are variegated in color. A guard hair may be black, with a thin bit of brown, then white, and finally tipped in black. The combination of colors creates an overall appearance of gray.

island fox pup in the fog
However, the multiple layers of varying color create a break-up pattern; there is no solid color for the eye to discern. This allows the island fox to disappear into landscapes with low light levels–shade, twilight or fog.

island fox on mottled flooring at a medical facility

This characteristic also makes it challenging for auto-focus on a camera to successfully focus on island foxes. The fox in the photo to the left is actually standing, but it is hard to visually distinguish its back from the floor.

The variability in island fox fur also means that small hereditary changes in the fur can make large general changes in appearance. 

A little less black at the tip of the guard hairs and the overall appearance is much lighter. Such an island fox may appear more beige or brown and blend in better with the environment of the southern islands: San Nicolas or San Clemente. Lighter colored individuals may also be more successful hunting sand dune or beach habitats.

northern island foxes during captive breeding 2000-2006

A bit more black on the tip of the guard hairs and the overall coloring appears much darker and more gray. This coloring is more beneficial in habitats with denser vegetation, Santa Catalina, Santa Cruz and Santa Rosa Islands.

The plasticity of their camouflage coloring has helped island foxes remain successful hunters in varied Channel Island habitats.


Friday, February 06, 2015

Double Action to Save Catalina Island Foxes

Help Friends of the Island Fox reduce a major threat to the Santa Catalina Island fox (Urocyon littoralis catalinae): human trash

Yes, eating human food is bad for island foxes. Adults dependent on human food fail to teach hunting skills to their offspring. (Island fox diet) However, the greater threat is the attraction of trash and the behavior island foxes engage in to reach readily available human food waste.

The first problem is that standard trash and recycling containers pose a threat to these small foxes. This old trash can, next to a fence, allows an island fox to easily climb inside. The fox's diminutive size means it can easily fit through openings and fall into trash receptacles. 

Aging bins are an enticing hazard.

photo courtesy of Lesly Lieberman and CIC
Once inside, island foxes have a difficult time getting out of these containers. Trash can lids are designed to push open from the outside. Catalina Island biologists have documented numerous cases of island foxes dying inside trash cans.


photo courtesy of Julie King, CIC
The second issue is that accessible trash cans encourage island foxes to cross roads and enter dangerous areas. Notice the island fox under the left side of the trash can pictured here. It is pulling trash out of the rusted bottom of this can. 

Catalina Island Conservancy biologists Julie King and Calvin Duncan report: 

Between April and May 2014, four foxes were hit and killed by vehicles in close proximity to open trash cans near Bird Park in Avalon and two more were hit and killed there in November. It is unknown how many other foxes may have been hit by vehicles in the area but did not immediately succumb to their injuries, and were therefore not accounted for.

courtesy of Julie King, CIC
Car strike has become the greatest killer of island foxes on Catalina Island. The island fox pictured to the right was killed by a car, notice the trash can on the other side of the road (to the left). Clusters of unnecessary island fox deaths are occurring in areas adjacent to public spaces with numerous trash cans.
New "Fox Saver" trash bins

But there is a solution to the double threat: trash bins that island foxes can not access.

“Fox Saver” bins are the same sturdy containers used at Yellowstone and Yosemite National Parks to keep bears out of human trash. Opening the bin requires long human fingers. There is no opening for an island fox to easily enter.

Once the attraction of available human food waste is eliminated, we hope there will be less motivation for island foxes to cross roads, and maybe less attraction to venture into Avalon.

Purchasing these all-steel bins, shipping them to Santa Catalina Island, and installing them on a cement pad comes with a sizable price tag. Each bin costs $2,000. The Catalina Island Conservancy has a goal of replacing 150 trash bins across the island.

Friends of the Island Fox aims to raise $6,000 to fund three “Fox-Saver” bins to be placed in
Avalon's Bird Park area. This should actively reduce island fox deaths along one of Santa Catalina's busiest roads. Your donation will help meet this goal and save island fox lives.

The Catalina Island fox is making a strong recovery, but its current restored population combined with growing human activity  has increased direct human threats to island fox survival. 

Help us make a positive impact by funding 
"Fox Saver" bins!

Tuesday, January 27, 2015

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. 

Tuesday, January 13, 2015

Island Fox at Santa Barbara Zoo

Join Friends of the Island Fox at the

 Santa Barbara Zoo
Fox Festival
Sunday, February 15th
11am - 3pm

The Santa Barbara Zoo provides a home to Channel Island foxes that are unable to survive in the wild. Throughout the recovery of endangered island foxes, the zoo's Veterinary staff and Animal Care staff have participated in conservation efforts across the islands and have helped write the book on how to care for this rare California species.

Currently there are only five island foxes in captivity and two of them live at the Santa Barbara Zoo. If you can't visit the Channel Islands, this is the closest location in southern California to see a live island fox.

On Sunday, February 15th, we will be helping the Santa Barbara Zoo celebrate all foxes. Included with zoo admission:
  • Fox related activities and crafts
  • Channel Island fox information booth with biofacts
  • Keeper talks and animal enrichment throughout the day

Come meet the Channel Island fox. Compare it to the African fennec fox. Decide for yourself with one is smaller. Which one has the largest ears? How is their coloring adapted for their habitat?

Purchase an island fox pin, T-shirt, guide, or stuffed animal from the FIF booth and help support island fox conservation!

Tuesday, December 16, 2014

Give the Gift of Saving Island Foxes

Since 2005, you have helped Friends of the Island Fox fund more than $60,000 in conservation efforts to save the endangered island fox.

In 2014 donors funded our  

In addition, in 2014 FIF:

In the year 2000, four subspecies of island fox were facing imminent extinction. San Miguel and Santa Rosa Islands each only had 15 surviving individual island foxes. On all six islands combined there was a total of approximately 1,400 island foxes. 

In just fourteen years, island fox populations have returned to historic levels. The official population numbers from 2013 estimate over 5,700 island foxes across all of the islands.

Maintaining this successful recovery of the island fox means continued monitoring. Disease and introduced threats can quickly impact these rare island populations.

This holiday season give the gift of directly saving an endangered species.
Donate through the "Island Fox Donation" box on the upper right hand side of the screen (the box with the smiling island fox).

Wednesday, December 10, 2014

Island Foxes Take a Holiday

It's that time of year when island foxes take a holiday, a holiday from family life.

courtesy of National Park Service
Channel Island foxes typically form monogamous pairs. A male and a female with adjoining or overlapping territories, mate for life. Their committed relationship helps them to successfully defend territory with important food resources and enables them to successfully raise offspring.

Pups are born helpless and require dutiful parental care to survive. While the female may not allow the male into the den to see the pups for a period of time, the male plays an important role in supplying the female and the pups with food.

After the pups have been raised to an age where they can fend for themselves, 6-8 months, they set out to find their own territories. Female pups tend to establish territories close to their parents, while male pups disperse to the opposite side of the island. Male dispersal may be a natural selection adaptation to avoid breeding with close relatives.

When the pups head out, the parents tend to take a holiday from each other as well. From November to early January, island foxes live a more solitary life. Perhaps this separation enables island foxes to find adequate food during the late fall and early winter. Perhaps it creates a greater opportunity for those who have lost a mate, to find a new one. Or perhaps, after a spring and summer filled with parenting, island foxes just need a break and a little solitude.

When the male and female reunite in late December - early January, they will be ready to start a new family in the spring.

As well as monitoring for unexpected fatalities, radio tracking collars help biologists to understand island fox movement and territory size.

Wednesday, November 12, 2014

New Findings on Island Fox Diet

Providing the best opportunity for island foxes to survive in the wild means understanding how they use resources and interact with other species.

Researchers, headed by Brian Cypher, examined the diet of island foxes across all six Channel Islands. Their findings have just been published in Global Ecology and Conservation, 2(2014) 255–66. Their article: “Multi-population comparison of resource exploitation by island foxes: Implications for conservation,” looks at the dietary differences between the six island subspecies, compares seasonal dietary shifts and dependence on introduced species, and recommends considerations for future conservation efforts. (Original paper)

The scientists gathered island fox scat across the six islands during four seasons in 2009. The scat samples were analyzed at California State University-Stanislaus’ Endangered Species Recovery Program office in Bakersfield, CA.

San Miguel Island deer mouse, courtesy of C. Schwemm
The researchers discovered that sixteen species were most frequently found in island fox scat or droppings:
  • Animal Prey - island deer mice, birds, lizards, beetles and beetle larvae, Jerusalem crickets, silk-spinning sand crickets, and grasshoppers
  • Plant Fruits - from toyon, manzanita, prickly pear cactus, and summer holly
  • Introduced Species - earwigs, European snails, fruits of ice plant and Australian saltbush

toyon fruit, courtesy of K. Dearborn
Like many members of the canine family, island foxes are generalists when it comes to searching for food. They hunt small prey, search out seasonal fruit, but will also eat carrion. To survive on the Channel Islands, island foxes have evolved to exploit all available food resources. The graph below is a simplified comparison of the frequency with which different items appeared in the diet of the six island fox subspecies over a year. (for complete tables and percentages see the original paper, below)

Arthropods in the Diet
An interesting finding is the importance of numerous insect species. Insect parts constituted a “significant proportion of each scat.” The dark purple band in the graphic above depicts the frequency of insects found in scat on each island. On all six islands, beetles were a primary food item year-round (most identifiable were darkling beetles and ten-lined June beetles). Insect prey offers calorie-rich food for little energy expenditure, making them an efficient food source. In addition there was evidence island foxes occasionally ate cockroaches, dragonflies, butterfly caterpillars, and wasps.

European earwigs are now found across North America, including the Channel Islands. This introduced species has become an important food resource for island foxes. Earwigs were a primary food source on San Nicolas, San Miguel, Santa Rosa, and Santa Cruz, and were an important food source on San Clemente in the spring and on Santa Catalina during the fall and winter.

Crustaceans–beach hoppers and various crabs–were occasionally found in scat, demonstrating that some island foxes search for food along shorelines. Introduced European garden snails are now found on several of the Channel Islands and island foxes have included them in their foraging. On the two islands, San Clemente and San Nicolas, garden snails (red band on graphic) have become a primary food resource for island foxes.

Vertebrate Prey 

island fox with 3 deer mice in jaws, courtesy NPS
Many people think of foxes as primarily mammal and bird predators. While the island fox does hunt, these larger prey items appeared less frequently in the diet than you might think. The blue band represents the frequency of deer mouse remains and the green band represents the frequency of lizards (on San Clemente and San Miguel) or birds (on Santa Rosa). At a glance you can see that lizards and birds are not primary food sources on three islands and, on all islands, deer mice are less frequently found in the diet than insects.

Some additional prey animals were found occasionally in fox scat: Catalina California ground squirrels (only found on Catalina), scavenged seal or sea lion, spotted skunk (competitors on Santa Rosa and Santa Cruz), a few black rats, a house mouse, and a bat. While island foxes have been seen catching snakes, no evidence of snake remains was found in 2009.

Native Fruiting Plants

Santa Cruz Island fox in tree searching for fruit
The larger the Channel Island, the greater its plant diversity. The two largest islands, Santa Cruz and Santa Catalina, offer island foxes abundant plant resources. On these two islands, native fruit is a major part of the diet. The orange band on the graphic above shows that, on Santa Cruz, the primary island-fox diet consists of insects and fruit. 

On Santa Rosa, where large introduced browsing animals (deer and elk) continued to degrade native plants until 2011, deer mice were more frequently found in the diet than fruit. As the plant resources on Santa Rosa Island recover, researchers will be watching to see if fruit becomes a greater part of the island fox diet.

While fruit is an important part of the diet for most island foxes, there can be a great deal of difference in the species consumed between islands. The chart below shows the plant species found in the scat with a more than 10% frequency. 

On Santa Catalina and Santa Cruz the number of native plant species is high and no introduced non-native plant species are used frequently by island foxes. The islands that have suffered the greatest alteration of their native plants, San Clemente, San Nicolas, and San Miguel, are currently sustaining island foxes with introduced plant species. Notice on San Miguel, no native plant fruit was found to be consumed by island foxes.

Conservation Implications 

Removing introduced animal species from the islands has eliminated some carrion opportunities for island foxes. However, carrion of large introduced animals is not believed to have ever been a primary food source for these omnivorous canines.

Removing introduced non-native plant species is a major goal across the Channel Islands, but this study reveals an important caution. Island foxes are consuming introduced ice plant and the garden snails it harbors. Before invasive ice plant and Australian saltbush can be removed, native fruiting plants will need to be reestablished so that island foxes have enough resources to survive.

Future Study
This study provides the first comprehensive look at island fox diet across the Channel Islands and through the seasons. However, it represents one year: 2009. Native plant resources fluctuate with annual weather. Climate change and drought are impacting native plants and fruit production. Have impacts to plant resources in 2013 and 2014 challenged survival for island foxes and their smaller prey, which are also dependent on plant foods? Have island foxes altered their diet in the face of drought? (Parasite threat from food source on San Miguel) Can conservation measures to restore the natural ecosystem be managed so that resources are not compromised for island foxes? And will island foxes expand their diet as their ecosystem is restored? Continued study of island fox diet is vital to informed conservation decision making.

Download the original Research Paper “Multi-population comparison of resource exploitation by island foxes: Implications for conservation”

Friday, October 10, 2014

How Small Is An Island Fox?

Santa Cruz Island fox, courtesy of Anita Machlis
Frequently the size of an island fox is compared to a house cat. However, that can be a bit misleading. 

While house cats average from 8-10 pounds in weight, some breeds can easily weigh up to 18 pounds. Cats typically stand 8-10 inches at the shoulder.

Island foxes on the other hand are considerably smaller. While size varies between the islands and the subspecies, adults range from a weight of 2.35 to 6 pounds. Their fur may give the appearance of bulk, but most island foxes are quite slight in their physic. Finding enough food is always a challenge for these island dwellers. 

The length of the legs varies between islands, but the tallest of the island foxes only stand 8 inches at the shoulder. The Santa Cruz Island fox, the smallest, typically stands 6.5 - 7 inches at the shoulder. 

In actuality, island foxes actually weigh 40% less and are 22% shorter than the average house cat.

While felines are designed for leaping and vertical climbing, island foxes have somewhat weak legs. They can run and climb horizontally, but they are not leapers.

Can you guess what this is?

This is the view from inside a recycling trash can. Island foxes have narrow bodies. The largest males have heads that are only 2.5 inches wide. If an island fox can get its head into an opening, it can usually get the rest of its body through as well. Most island foxes can easily fit through the opening for a can or bottle. 

Human trash can be attractive to an animal that has a hard time finding enough food. Once an island fox gets into a recycle bin or a slightly open trash can, it has a very hard time getting out. 

 How do island foxes measure up to other small fox species?
  • kit fox (Vulpes macrotis), North America: 4 - 4.85 pounds; stand 12 inches to the shoulder
  • fennec fox (Vulpes zerda), Africa: 3 -3.5 pounds; stand 8 inches to the shoulder
fennec fox (Vulpes zerda), courtesy of Pat Meyer
The kit fox and the fennec fox are more closely related to each other than either is to the island fox. Because of the range in size among island fox subspecies, some island foxes are smaller than fennec foxes. Some weigh more than kit foxes, but all are shorter than kit foxes. 

Monday, September 22, 2014

Island Fox Presentations for Audubon Chapters

How can you learn more about the current status of the Channel Island fox?

Friends of the Island Fox educators will be giving presentations at three different Audubon chapter meetings in Southern California over the next few months.

We'll be talking about the how the island fox became endangered, the efforts to save them, as well as the different island fox populations and their current status–successes and challenges.  

Come out and join us at one of the following locations:

Thursday, Sept. 25, 2014 - 7:00 PM

The San Fernando Valley Audubon
Encino Community Center 
4935 Balboa Blvd., Encino, CA

island scrub-jay

Tuesday, Nov. 18, 2014 - 7:00 PM

Palos Verde / South Bay Audubon
Madrona Nature Center 
3201 Plaza del Amo, Torrance, CA

bald eagle

Thursday, March 19, 2015 - 7:30 PM

El Dorado Audubon
El Dorado Nature Center in Long Beach
7550 E Spring St, Long Beach, CA

Island foxes have a very interconnected relationship with the birds in their ecosystem.

Or for information about Island Fox Programs for your organization or club contact