Friday, April 03, 2020

Mites, Microbes, and Cancer in Santa Catalina Island Foxes by Alexandra DeCandia

(Thank you to our guest blogger Alexandra DeCandia a doctoral candidate at Princeton University)

Over the last few decades, we've realized that organisms are far more complicated than they initially appear. What may look like an individual fox is actually an ecosystem containing trillions of microorganisms on every square inch. [Figure 1]

Despite their tiny size, microbes influence important host functions, such as development, digestion, stress tolerance, behavior, and even immunity. Therefore learning more about these hidden actors can inform wildlife conservation of at-risk species in the modern molecular era.

Looking into the ear canal of an island fox.
Microbes may be particularly important to species that lack genetic diversity, such as Channel Island foxes, especially where disease threatens long-term persistence. On Santa Catalina Island, scientists discovered extremely high rates of ear canal tumors, where roughly half of adult foxes have growths in their ears. Although the exact cause is unknown, researchers linked ear mite infection to tumor growth and development. The most prominent hypothesis states that infection with ear mites leads to inflammation and rampant cell growth in the ear canal, which in turn leads to tumors. Thankfully, treating foxes with the acaricide Ivermectin has already decreased mite burdens and tumor rates in these foxes.

However, there's more to this story. We still don't fully understand how mite infection leads to tumor growth. In particular, my collaborators and I wondered whether microbes play a role in this system. For example, do mites disrupt healthy microbes and cause secondary bacterial infections? And do those infections then contribute to the chronic inflammation that precedes tumor growth?

Figure 2: Island fox is swabbed during health check
To address these questions, my collaborators at the Catalina Island Conservancy collected microbe samples by swabbing ear canals (and a few other body sites) of healthy and mite-infected foxes. [Figure 2] (This process is similar to cleaning your ears with a cotton swab, except you don't throw away the swab afterwards.) Once a bunch of foxes were swabbed, all samples were sent to New Jersey, where I extracted DNA, collected genetic sequences, and analyzed the data.

 The results came back loud and clear: microbes differed between mite-infected and uninfected ear canals. Rather than a rich community of diverse microbes (as seen in healthy ears), mite-infected ear canals had fewer microbial species present. We further found that the balance of microbes (know as "relative abundance") differed between infection groups.  [Figure 3]

Figure 3: Classes of bacteria found in swab samples
As it turned out, this pattern was almost entirely driven by an overabundance of one bacterial species: Staphylococcus pseudintermedius (Class: Bacilli, shown in brown in Figure 3).

Even though this microbe is commonly found on canid species (such as domestic dogs and foxes), it can become an opportunistic pathogen when healthy communities are disrupted. Once it proliferates, it can be incredibly difficult for the immune system or even antibiotics to eradicate, leading to chronic inflammation.

We now hypothesize that mite infection and secondary bacterial infection with Staphylococcus pseudintermedius contribute to chronic inflammation and tumor growth in Santa Catalina Island foxes. 

Photo courtesy of Glenn Jensen
Although further tests are needed to definitively establish causation, these insights into the microbial dynamics of mite infection can help us monitor the population for antibiotic resistant forms of Staphylococcus pseudintermedius that could cause a disease outbreak. They can further help us explore other open questions, such as why Santa Catalina Island foxes are the only subspecies with ear canal tumors, despite ear mites on other islands. As always in science, answers lead to more questions. But at least one thing is clear: there's more to this story (and indeed, to all organisms) than what initially meets the eye.  

Alexandra DeCandia, Department of Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey.

Read the full paper: Ear mite infection is associated with altered microbial communities in genetically depauperate Santa Catalina Island foxes (Urocyon littoralis catalinae)

More Research Regarding Island Foxes:

Friday, March 27, 2020

Fox Foto Friday - Meeting Up Island Fox Style

Island fox or human, it can be tricky to get to know someone new right now. A wildlife trap camera on Santa Rose Island captured these images of two island foxes meeting on a pathway.

A quick sniff can tell an island fox a lot about another fox. The female on the left is figuring out if she knows this male. Has she detected his scent before or is he a newcomer to her area? She can evaluate his health and what he's been eating in a sniff.

The two island foxes also communicate to each other through their physical stance. Tail and ears up - she is being friendly. Head down and tail at a medium height, he is letting her take the lead.

Both of these island foxes look healthy and well fed. Notice the female is also wearing a radio-tracking collar. Biological technicians on the islands are monitoring this female island fox. During summer counting, we may learn whether or not this meeting led to pups. 

Island foxes know all about epidemic disease. COVID-19 does not impact dogs or island foxes, but other viruses are a serious threat to them. Find out more about the current threat from canine distemper.

Island foxes on Catalina Island survived a catastrophic epidemic from 1998–2000.   

Monday, February 17, 2020

Distemper Virus on the Rise in California Winter 2020

Wildlife veterinarian Dr. Deana Clifford, a longtime island fox advocate and member of the Island Fox Conservation Working Group, was on the radio for the US Fish & Wildlife (USFWS) warning about the rise of canine distemper virus in California this winter.

2019 was a good year for wildlife, including island foxes. On the mainland, raccoon, striped skunk, and gray fox populations have all increased. (The gray fox is the ancestor of the island fox.) State wildlife agencies are also seeing an increase of canine distemper virus (CDV) among these species. Distemper is the dog equivalent of measles–it impacts the neurological and respiratory system, is highly contagious, and can be deadly to pet dogs and wild animals.

The collapse of the Santa Catalina Island fox population in 1998 was caused by a wild raccoon carrying CDV that was transported to the island. The introduction of distemper from this one raccoon nearly wiped out the Catalina Island fox.

island fox being vaccinated
Ideally, between 100 and 300 island foxes are vaccinated against CDV and rabies on each island. This ensures that if an introduction of distemper occurs at least a minimal number of island foxes might survive. Distemper is highly fatal among island foxes. On Santa Cruz Island, it means 100 would survive, but approximately 2,000 island foxes would perish. 

island fox with a radio-tracking collar
Introduced disease is the primary threat to island fox survival. This is why monitoring is so important and why FIF helps fund radio collars and health checks.

The USFWS and Friends of the Island Fox urge you to 
protect your pets, wildlife, and the island fox

Vaccinate your pets against the canine distemper virus (CDV).

Wednesday, February 05, 2020

Won't You Be F257's Valentine?

It's February – time to help the unique island foxes that live on California's Channel Islands!

Why does Friends of the Island Fox ask for your donations? 

Funding is essential for island fox conservation.

You can help this pup.
Won't you be her Valentine?

Island fox F257 is a female 10-month-old island fox. Last summer she was captured on Santa Rosa Island during annual health checks. A sample of her blood was taken, she was micro-chipped, and a whisker was collected for diet analysis.

In December of 2019, she was fitted with a radio-tracking collar funded by FIF and had another whisker removed for analysis.  
All of this work–the examination and work by the technician; blood sample testing, the microchip, radio-tracking collar, and diagnostic research on the whiskers–requires funding.

That is where you can make a difference. We ask you to donate, so FIF can help fund important island fox conservation work across the Channel Islands in conjunction with the various island land managers.

Pup F257 has so much to tell us.

Throughout her life, when captured, her microchip reveals her identity. Her data, gathered during annual check-ups, will form her profile history. Data collected on individual foxes is valuable for researchers and understanding how to keep island fox populations healthy and stable. Her radio collar will monitor her movements and safety.

The analysis of her two whiskers will tell us how her diet has changed from a very young pup to her life at 10 months old. If the winter rains don't return and F257 faces her first year in drought conditions, will she change her diet? FIF's Research Grant recipients are investigating important science on island fox health. Are foxes finding adequate nutritional food in their island ecosystem? Can we expect F257 to live a lifespan of 8–12 years?

This young pup is starting her life on Santa Rosa Island. You can be part of her success. Your donation will help make sure she is watched over and healthy.

Please be a Valentine for F257 and all the other island foxes
Donate today – Thank You!

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.