Wednesday, July 29, 2015

Channel Island Fox Status Update 2015

photo courtesy of M. Solomon
The annual meeting of the Island Fox Conservation Working Group in 2015 reported that the general status of the six subspecies of California's Channel Island foxes is GOOD.

However, four of six islands saw dips or declines in population in 2014. The historic drought and its impacts on food resources is believed to be the cause. Biologists on Santa Catalina have documented a direct connection between rainfall levels and island fox reproduction. Years with drought-level precipitation result in reduced plant food and prey, thereby causing fewer island fox pups to be born or to survive. The extent of drought impact varies significantly by island.

Minimal drought impacts on Santa Cruz Island, 2015
 Despite the drought, recovery of the four endangered subspecies of island fox has been very successful and this spring (March 2015), the US Fish and Wildlife Service (USFWS) announced initiation of a status review of the four subspecies. 

Introduced disease continues to threaten all island foxes and a lack of canine distemper virus (CDV) vaccine safe for use in island foxes has been a major concern for two years. The Working Group took urgent steps, and Friends of the Island Fox participated, to determine the effectiveness of a newly available CDV vaccine.

courtesy of E. Gotthelf
All island fox subspecies are maintaining stable populations and there are no issues which put any Channel Island fox subspecies in eminent threat of extinction. The continuing drought, however, has more severely impacted island foxes on San Miguel and San Nicolas Islands. As seen in the past, each island faces its own concerns and challenges.

Island Fox Update 2015 pdf a specific island-by-island summary
  • San Miguel Island - 520 (low of 15 in the year 2000). Population recovered with over 500 individuals since 2010. Slight population dip. Concern: Threat from new parasites continues, as do drought impacts (see below)
  • Santa Rosa Island - 874 (low of 15 in the year 2000). Population recovery stalled by drought, but stable.
  • Santa Cruz Island - 1,750* (low of 62 in the year 2002). Population recovered and robust with over 1,000 individuals since 2009. No discernible drought impacts.
  • Santa Catalina Island - 1,717 (low of 103 in the year 2000). Population recovered and stable with over 1,000 individuals since 2010. Slight population dip. Concern: Drought impacts and human related impacts, including car strike, and high risk for introduced disease.
  • San Clemente Island - 1,230* (not Endangered). Population stable. Concern: Continued fatalities to automobile strike.
  • San Nicolas Island - 263* (not Endangered). Population has declined ~41% since 2012 because of drought impacts. Concern: Habitat destruction has left island foxes dependent on non-native plants and prey which have declined dramatically in the drought, see below.

The graph above shows population numbers on even years, therefore the dip from 2013 is not represented. For more detailed graphs see the Island Fox Update document. The numbers represented  are the official 2014 population figures reported at the Island Fox Conservation Working Group Meeting 6/16/15. *Population figures represent adults only.

Healthy plant and animal populations fluctuate normally with available resources. Recovered island fox populations naturally dip when there is not enough food, water, or territory. There is a natural limit to the number of island foxes an island can support, also known as carrying capacity.

Low rainfall has impacted food resources across the Channel Islands. However, islands have not been impacted equally. Some islands appear to have greater natural drought tolerance.

As recently discovered by analyzing island-fox diet, Santa Catalina and Santa Cruz Islands have greater native plant biodiversity than the other smaller islands. Native island vegetation evolved with periods of drought. Native plants are better able to survive and produce fruit vital for the survival of island animals. The greater the native plant biodiversity, the greater the survival options for island foxes.

island fox footprints among ice plant on San Nicolas
The island-fox-diet study pointed out that island foxes on San Miguel and San Nicolas Islands were dependent on plant and invertebrate species which had been introduced to their islands, replacing native plant habitat.  Unfortunately, these introduced plant species, especially, ice plant, and the non-native creatures that live in it–snails and earwigs, have declined dramatically during the last two years of extreme drought. The impact has been greatest on San Nicolas Island where average island-fox weight has declined and the population has dropped 41% since 2012.

Restoring native vegetation is the best long term solution for healthy island fox populations on these two islands. (for more on this topic, see the Island Fox Update 2015 pdf document above)

A secondary impact of the drought has been increased complications with parasites. Changes in diet and decreased general health leave island foxes more vulnerable to internal and external parasites. Here again, each island has its own specific parasite challenges. (See Island Fox Update 2015 pdf for details) (Spiny-headed worm on San Miguel Island first detected in 2013).

Introduced disease continues to pose 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. Efforts to verify the effectiveness of a new CDV vaccine for island foxes is currently underway.

Positive Notes:
courtesy of D. Mekonnen
There are early anecdotal signs that the small amount of rain this spring and summer may be improving resources on the islands. More island fox pups have been spotted this summer than during the last two summers. However, the official impact on the populations will not be known until counting begins in fall.
Monitoring with radio collars continues to provide important information to land managers. Radio collars have helped verify that no golden eagles have returned to eat island foxes on the northern islands. Radio collars were instrumental in determining the cause of island-fox decline on San Nicolas Island. And they continue to provide early warning of disease introduction. Radio monitoring collars will also enable land managers to ethically determine the effectiveness of the new CDV vaccine.

Annual island fox health checks, serology testing, and counting identify threats to island fox survival early, so that actions can be taken to protect island populations.

‘Fox-Saver’ bins on Santa Catalina and the Navy's education outreach on San Clemente are all helping to reduce the number of island foxes hit and killed by cars.

Thank you to the Island Fox Conservation Working Group and all of the important work that has helped island foxes recover from the brink of extinction. Thank you also to the many participants on our June Santa Cruz Island Trip that have allowed us to show you their photographs.

Tuesday, July 14, 2015

FIF Helps Meet Urgent Need For Channel Island Foxes

At the Island Fox Conservation Working Group meeting on June 16th, we learned of a serious threat looming over Channel Island foxes. The Canine Distemper virus (CDV) is highly contagious and deadly to these small canines. It nearly caused the Catalina Island fox's extinction in 1999.

Since that emergency, Channel Island foxes have been vaccinated for CDV with a specific vaccine designed for ferrets. Unfortunately, the vaccine has not been produced for two years. Island land managers have only been able to use vaccine they had on hand, leaving the majority of island foxes unprotected for the last two years.

A new CDV vaccine has recently become available, however it is unclear whether it will be effective for island foxes. There is great urgency to test the new vaccine before fall counting and health check season. This is the only time when a large number of island foxes are handled by biologists on all islands.

Safe capture cages allow island foxes to be captured for health checks
island fox radio-tracking collars
As part of an emergency effort to verify the effectiveness of the new CDV vaccination, five island foxes will be tested on each island. Each of these individuals, which have never been vaccinated for distemper before, will be caught, blood tested, vaccinated with the new vaccine, radio-collared, and released. 

These radio-collared individuals will be caught again a month later and their blood will be tested to verify that they have built-up antibodies against the disease. ID microchips and records on each animal enable biologists to know which island foxes can participate in this test.

This is an extra unexpected cost for each island. Friends of the Island Fox committed to quickly fund:

FIVE radio-tracking collars for Santa Rosa Island ($1,500) 

FIF Santa Cruz Island Trip 2015
Thanks to the participants on our Santa Cruz Island Trip and generous private donors, we have provided these important funds. 
The vaccine is currently being tested across the islands. If the new CDV vaccine provides protection to Channel Island foxes, we may be raising money for vaccinations to protect as many individuals as possible this fall.

Your support helped us to pledge this important financial commitment. Thank You to all of our conservation supporters.

Tuesday, July 07, 2015

Observing Channel Island Fox Behavior on Santa Cruz Island

Santa Cruz Island, Channel Islands National Park
Participants in the Friends of the Island Fox trip to Santa Cruz Island on June 20th had a beautiful day and an opportunity to observe behavior between individual wild Channel Island foxes. Fifteen years ago, when this subspecies of Channel Island fox was facing extinction, such an opportunity was unthinkable.

The island foxes on Santa Cruz Island have made a strong recovery. A baby boom of foxes occurred on Santa Cruz between the fall count in 2007 and 2009. The population jumped from 350 to 1,200. Adult survivorship has been very high, which means we are seeing an increasing number of island foxes between the ages of 5 and 8 years old. These are mature individuals. Island foxes are believed to be in their prime between 2-5 years of age and are estimated to live 8-10 years in the wild.

This trip two elderly animals were noticeable by their broken-down ears and minor injuries to legs and tails. These injuries were most likely inflicted by younger adult island foxes protecting territory. The campground offers an area where infirm animals can potentially find resources, while having some protection from other foxes. 

We observed this older island fox lying down on the ground between campsites where people were active at tables. His coloring camouflaged him well in the dappled shade.

When some campers left their site, a healthy adult island fox checked out their table area. We watched as the slightly larger, but older animal, approached. We didn’t know what to expect.

Submissive behavior of elderly island fox toward another adult.
However, when the older fox got within five feet of the table area, it lowered its head submissively to the younger animal. The younger fox did not chase the older animal or show aggression, yet it physically communicated to the older fox not to approach any closer. Without any direct contact, the older fox was sent off into the bushes.

photo courtesy of Daniel Mekonnen, 2015
We saw 8 - 10 adult island foxes (none were radio-collared individuals). 

We watched island foxes searching for food, retrieving figs, and eating them (Check out the video by Douglas Welch). (The fox jumps up into a shrub at ~2:48) A large percentage of the Santa Cruz Island fox’s diet is fruit.

We’ll have more on the status of the Santa Cruz Island fox in an upcoming Island-by-Island Update. At the Island Fox Conservation Working Group meeting, biologists from The Nature Conservancy reported that a female island fox, born during captive breeding on Santa Cruz, recently passed away at age 12. She is the oldest wild island fox scientifically documented on Santa Cruz Island. Biologists were able to accurately date her age and follow her life because of her ID microchip.

We also had a fantastic encounter with common dolphins on our boat ride home. Hundreds of these colorful dolphins were feeding and swimming right next to us. Look closely and you will see a youngster swimming beside its mother. We saw numerous young dolphins.  (Video of the common dolphins by Douglas Welch).

More photos of the Friends of the Island Fox Trip to Santa Cruz Island:
A special thank you to trip participants Eric Gotthelf, Douglas Welch, Michael Solomon and Daniel Mekonnen for their photos.