Friday, January 24, 2020

Island Foxes and Island Spotted Skunks

On two of the Channel Islands, island foxes share their ecosystem with island spotted skunks.

The island spotted skunk is smaller than the island fox, and even more elusive. Because the skunk is primarily nocturnal, few people encounter them and, until recently, little was known about them.

When the island fox faced near-extinction on Santa Rosa and Santa Cruz Islands in 2000, people took note of the island spotted skunk for the first time. The first counting of island spotted skunks occurred when they were captured during island fox counting.

When the island fox population was low, the population of island spotted skunks soared. This gathering of spotted-skunk and island-fox cake pops, illustrates the overwhelming number of spotted skunks to island foxes. 

By 2014, however, the foxes were overtaking the skunks in reproduction and survival; island fox numbers almost equaled the estimated number of spotted skunks. As island foxes continued to increase across Santa Rosa and Santa Cruz Islands, the island spotted skunk population continued to decline dramatically. (Or at least, the number of island spotted skunks captured during island fox counting has declined.)

The gathering of cake pops–compiled by researchers Juliann Schamel and Angela Guglielmino–demonstrates how drastic the population shift has become.

What we don't know is: Why? Why have island spotted skunk numbers declined so much? What is the normal population relationship between these two species? Are island foxes out-competing island spotted skunks or is something else at play?

In the past few years, researchers have begun looking into the life and behavior of the island spotted skunk. FIF contributed support to researcher Ellie Boas to supply batteries for the first trap cameras that were put out to capture images of island spotted skunks. Researchers continue to try to capture images of island foxes and spotted skunks interacting, but it has been a challenge.

2020 opened with an important meeting of biologists, wildlife veterinarians, researchers, and invested organizations and institutions to pursue inquiry into the island spotted skunk. Following the example of the Island Fox Conservation Working Group and the successful conservation efforts for the island fox, the group will work to solve questions and develop action plans.

Friends of the Island Fox sends a resounding "Yip, Yip" to the newly formed Island Spotted Skunk Conservation Working Group. 

May we all work together to understand the important relationship between these two unique island species.

Thursday, January 09, 2020

How Structures in Teeth Could Provide Accurate Age Information for Island Foxes?

In October 2019, Friends of the Island Fox funded a research study, via a donation from Safari West, to investigate the use of cementum analysis as a method to determine island fox age at death. The current standard method for estimating age in island foxes is based on the wear of the upper first molar. This method is imprecise as tooth wear is heavily influenced by diet and varies significantly between islands and even among habitats on the same island.

Knowing the age at death is very valuable as it allows the National Park and other island managers to track the island fox lifespan. This is important as a fox who dies at age 9 or 10, after reproducing for many years, has contributed to the survival of the species. A fox that dies at 3 or 4 may not have had a chance to replace itself in the population or pass on its genes.

Image 1 - see sources below
Cementum is a thin mineralized tissue covering the root surface of teeth and functions as a tooth supporting device which anchors the tooth in the socket. Unlike bone, cementum is produced throughout one's life and forms annual layers (annuli)–a fact that makes it useful in aging techniques.

Cementum Analysis
To determine the age of an island fox after it has died, the lower canine tooth is removed and sent to the lab for aging.

Photo provided by S. Baker 2019
Once the tooth is received at the lab it is cleaned to remove any dirt and soft tissue, then undergoes processing to decalcify the tooth in preparation for analysis.

This makes the tooth very soft and pliable. The tooth is then preserved by fixing it in formaldehyde, also known as formalin, to preserve proteins and vital structures within the tooth. Next, it is embedded in a paraffin wax block which provides a support medium to make it easier to cut thin slices for examination.

The paraffin embedded tooth is cut into sections, approximately 15 microns thick (about the size of a droplet of mist or fog) on a device called a microtome, which is very similar to a deli slicer. The thin sections are mounted on glass microscope slides as the final step prior to analysis.

Paraffin embedded sample on a microtome being sectioned, courtesy M. Watling 2019
 The sections are stained with a special histological dye that is taken up by annuli at varying degrees (light blue or darker blue) depending on the amount of cementum laid down in a given year. This provides both a highlight and contrast for the purposes of counting the number of growth rings (aging) under a microscope.

The picture of cementum annuli in the photo below indicates the growth rings with the black arrows.
Image 4 - see sources below
If it is possible to accurately determine a fox's age at time of death, it can be used to monitor average longevity and to investigate many questions across all six of the Channel Island. Questions such as:
  • What age group of foxes are most likely to be hit by cars?
  • How old were foxes collected during annual mortality monitoring?
  • Do males or females have a greater lifespan?
Friends of the Island Fox is committed to research that will expand understanding of island fox biology and behavior. The more we know about island foxes, the more we can protect their future.
- Mike Watling, FIF Advisory Committee 

Image sources
  • Image 1 - The chemical and microbial degradation of bones and teeth. Advance in human palaeopathology. John Wiley & Sons - Scientific Figure on ResearchGate. Available from (accessed 17 Dec., 2019)
  • Image 4 - Tochigi, Kahoko & Aoki, Yukino & Maruyama, Tetsuya & Yamazaki, Koji & Kozakai, Chinatsu & Naganuma, Tomoko & Inagaki, Akino & Masaki, Takashi & Koike, Sinsuke. (2019). Does hard mast production affect patterns of cementum annuli formation in premolar teeth of Asian black bears (Ursus thebetanus)? PLOS ONE. 14.e0211561. 101371/journal.pone.0211561 

Tuesday, December 10, 2019

The Legacy of Island Fox M152

Island fox M152 became known to all of us in 2018.

We watched this male fox on Santa Rosa Island get a radio collar. His health check was profiled and compared to his health history. Over the summer he avoided capture for 2019 health checks, but through September his radio collar tracked his normal activity.

Recently we received notification from the National Park biologists: "We are sad to report that M152's mortality was confirmed...on October 12."

M152 appeared to have died right after the biologists left Santa Rosa to do health checks on San Miguel in late September/early October. Though he appeared to have died from natural causes, his body had gone undetected too long in the warm weather for a necropsy to determine exact cause of death.

But because M152's radio collar signaled his death, and biologists were able to find his body. That means his story continues:

M152 was found quite a way from the location where he had been captured in 2014 and 2018. It may be that the reason he was not consistently captured was because his territory only tickled the area where foxes are counted.

Despite his death, a whisker sample was taken from M152. This will add to the cumulative story of his diet through the stable isotope study (supported by FIF). Researchers will be able to chronicle his diet through the drought and back into a rainy 2019. His whisker will also provide information on what he was eating or how his diet changed as he neared the end of his life.

Biologist Juliann Schamel says, "M152 was one of the few collared foxes on Rosa whose exact age-in-years we don't know..." When he was first captured in 2014, it was estimated that he was 1–2 years old, by looking at the wear on his teeth. 

His canine teeth have been preserved. A FIF funded research project in progress is evaluating if structures in the canine tooth can be used to verify island fox age at death. If this research is fruitful, we may be able to determine M152's age when he died. Was he the 6–7 years old that was estimated or was he older?

M152's radio collar still had two years of battery life, so it was cleaned up, disinfected and deployed on a male fox born in 2019. Male pup M164 was collared in November in the Cherry Canyon area. Cherry Canyon is frequently visited by day hikers on Santa Rosa. Because young males under a year old tend to disperse to find their own territory, M164 may take this story into a completely different part of the island.

M152 was the fox face that encouraged donations in 2019 and helped fund a record 40 radio collars for island foxes across the Channel Islands. We are sad to say "farewell" to him, but his legacy lives on.

Friday, November 29, 2019

Fox Foto Friday - Happy Foxgiving

Across the Channel Islands, island foxes thank you.

These rare creatures live only on six islands and no where else in the world. (About Island Foxes) Your concern and donations have helped bring them back from the edge of extinction and are vital to protecting their future.

Friday, November 15, 2019

What Can We Learn From An Island Fox Tooth?

How do we estimate the age of island foxes? In the past, age has been estimated by visible wear on the first upper molars. This method is imprecise because island foxes have varying diets and sand may be consumed while island foxes are foraging. Sand can add excessive wear to teeth. A two-year old fox living along a shoreline or in a dune area, may have more wear to its teeth than a five-year old fox living in an island's interior.

male canine tooth from Santa Rosa Island
Friends of the Island Fox is excited to fund research into a scientific technique, which may determine the age of a fox after it has died. A donation from Safari West has enabled FIF to fund a second research project this year with investigators: Stacy Baker and Juliann Schamel.

What Is the Research?

Most wild mammal teeth annually add a layer of a hardened substance called cementum along a tooth's root. When the tooth is divided horizontally, rings of the layers become visible. Counting these rings can provide the animal's age at the time of death. Baker and Schamel will work with the Santa Barbara Museum of Natural History and the University of CA, Davis, to analyze canine teeth from deceased island foxes. Analyzing tooth samples from island foxes with known ages at the time of death will help verify the methodology.

Why Is It Important?

An island fox that dies when it is 9 or 10 years old is a mature adult. It probably has had an opportunity to reproduce and pass on its genetic diversity. An island fox that dies when it is 2 or 3 years old is still a young adult. It may not have had the opportunity to successfully reproduce. To make the best long-term conservation decisions, it is important to understand the age of island foxes at their death. 

If this technique works for island foxes, it will provide valuable data to inform a variety of questions:
  • How does tooth wear vary from island to island?
  • Which age group of island foxes are most likely to be hit by cars on populated islands?
  • Is there a difference in lifespan between males and females?
  • Is lifespan different from island to island?
  • Can this method identify when the lifespan of a specific island fox population is changing?
This last question is very important. If young foxes become the largest group suffering moralities or if the lifespan on a specific island begins declining, investigation and conservation efforts are needed immediately.

Friends of the Island Fox is committed to research that will expand understanding of island fox biology and behavior. The more we know about island foxes, the more we can protect their future.

This research is entirely funded by donations. 
Your donations make a difference.

More Island Fox Research:
FIF Research Grant - Whisker Isotopes 2019
FIF Research Grant - Whisker Isotopes 2018

Other Island Fox Research Papers

Friday, October 11, 2019

Health Checks for Catalina Island Foxes

biologist checks island fox's teeth
Across Catalina Island biologists are counting island foxes and giving them health checks. Foxes are caught in safe capture cages.

Catalina's population has recovered from the 1998 crisis caused by the introduction of the disease canine distemper. It is natural for populations of wild animals to adjust from year to year. We now know there is a direct connection between rainfall levels and successful island fox reproduction.

The return of drought conditions in 2018 caused an estimated 20% decline in island fox numbers on both Catalina Island and Santa Cruz Island. The Good News is everyone expects 2019's return of normal rainfall levels and a cool spring will bolster plant and animal resources and restrengthen island fox numbers.

We'll be waiting to hear what the biologists find in the field.

island fox receives a distemper vaccination
Lara Brenner, Wildlife Biologist for the Catalina Island Conservancy (CIC), reminds everyone that "Disease is the number one threat to Catalina Island Fox populations." During health checks, biologists monitor fox weight, body condition, and look for "new and emerging health issues."

Catalina is the most visited Channel Island. "Visitors can help protect the Catalina Island fox from disease," Brenner says, "by keeping their pets on a leash when not indoors and by staying up-to-date on your pet's vaccinations." No one wants their pet to pass-on or receive an illness while on vacation.

Wild raccoons are still a possible way for disease to be introduced to any of the islands. Brenner reiterates "Boaters should check their craft for stowaway, non-native animals (like raccoons) that could transmit a fatal disease." 

These simple actions are big steps toward protecting island foxes.


Friday, September 27, 2019

Fox Foto Friday - Where's M152?

Remember this face from last year? M152 is a male fox on the eastern side of Santa Rosa Island. 

This year he was not counted during the annual count and health checks in his area. But don't fear... M152 is doing well. We know he is still in his territory and going about his daily life because he is wearing a radio-tracking collar.

This demonstrates the importance of having two ways to monitor island foxes. 

Annual counts and health checks allow biologists to check the health and well-being of individual animals while they have them in-hand. This provides a snapshot of the population's health as a group at a specific time.

Radio-tracking collars enable the monitoring of individual foxes throughout the year. Their movements in an area can be tracked and if something happens to them, their radio collar reports to  biologists.

M152 did not come into a capture cage this year. Perhaps he was finding plenty of food because of the normal rainfall this spring and saw no reason to enter a capture cage. Perhaps when he came across a capture cage, another fox was already in it.

M152 is a pretty wily fox. We think he is approximately 5–6 years old. In that time he's only been captured twice: in 2014 and last year in 2018. ID micro-chips make is possible for each island fox to be tracked as an individual.

We're sorry that the biologists didn't have a chance to weigh him, check his health, and take a whisker sample this summer. It would have been great to compare to his last health check.

But other foxes did get examined and their stories are important too.

Friday, September 20, 2019

Fox Foto Friday - Time for Health Checks!

Across the Channel Islands, island foxes are being counted and given health checks. This island fox on Santa Cruz Island also received a refurbished radio-tracking collar funded by Friends of the Island Fox. See her as she is released.

For the next three years this radio collar will tell biologists that this island fox is up and moving around in its environment. It will also give off a mortality signal to alert biologists if something should happen to this individual island fox. Rapid response to mortalities enables a quick response to disease or threats to other island foxes. 

What are the current threats to island foxes in 2019?

Monday, September 09, 2019

FIF Research Grant to Investigate Further Into Island Fox Diet

Friends of the Island Fox is happy to announce that Juliann Schamel's research investigating island fox diet through stable isotopes in whisker samples has been chosen to receive the FIF Research Grant for 2019. 

an island fox stash of deer mice
This second year of support will enable analysis of additional data sets to identify seasonal dietary items during drought and important to successful reproduction. It has long been believed that deer mice are a vital food item during breeding and pupping season. Is it true? Does availability to a specific food source influence successful reproduction? If island foxes do not have accesses to abundant deer mice are they less successful as parents?

The grant will also expand the study to look at island fox use of marine resources. Do island foxes use marine foods during drought? If so, which island foxes are able to make use of marine resources?

Island fox whiskers provide an amazing record of what an individual island fox has been eating over 5–6 months. All food items are made up of carbon and nitrogen, but each kind of food has a different balance of elements and therefore a different signature. These individual isotope signatures are recorded in the fox's whisker. More on Schamel's initial research.

Schamel's initial whisker data set went to the lab this spring. At the Center for Stable Isotopes at the University of New Mexico, each individual whisker is divided into tiny sections and processed in a mass spectrometer.

An island fox that eats the same kind of food (all deer mice or all plant fruit) for a period of time will show an isotope graph that is fairly flat. The mixture of carbon to nitrogen will remain the same. But if an island fox changes up its diet dramatically, a spike will appear in the graph showing a change in the isotopes laid down in the whisker.

Comparing these results for known individual island foxes, living in known habitats, will provide valuable data on how sustained drought impacts island fox diet and how diet impacts their ability to survive and thrive.

The FIF Research Grant is completely funded by YOU. Without your donations to FIF this research would still be a dream. 

Donate today to support island fox conservation research.

Thank you to all of the 2019 grant applicants for sharing your research goals with FIF. There is so much more to learn about island fox health, behavior, and interactions with other species.

Applications for the 2020 Research Grant
will be available April 15, 2020

Friday, August 23, 2019

Fox Foto Friday - The Endangered Species Act Saved This Fox

 Just over two years ago, the Channel Island fox was removed from the Endangered Species List.

The Endangered Species Act saved this fox!

 Survival shouldn't be political.

Saving a species is a very complicated task, and it requires a coalition of people all working together to make it happen. 
We shouldn't abandon the Endangered Species Act.
We should embolden it, embrace it, and help the world become a better place. 

The Endangered Species Act (ESA) has provided the necessary protection and attention to help save four subspecies of Channel Island foxes from extinction.