Gathering Specimens For Island Fox Tooth Research

In 2019 Friends of the Island Fox supported a research project investigating whether cementum ring structures in teeth could be used to accurately determine island fox age at death. Research Project by Stacy Baker and Juliann Schamel.

Baker and Schamel updated us on their progress mid-March 2020.

"We went up to the Santa Barbara Museum of Natural History last week to collect teeth from the first seven skulls that they are processing for their collection," Schamel wrote in mid-March. An additional five skulls have since been processed.

The researchers explained that the island fox skulls came from Dr. Leslie Woods and the CA Animal Health and Food Safety Lab at UC Davis, which is responsible for conducting necropsies on island foxes when they die on the Channel Islands. These specimens are vital for biologists to understand cause of death, as well as underlying health problems. When an island fox dies, a necropsy (similar to an autopsy for a human) examines organs and tissues in detail to understand the cause of death. Necropsies are vital to identifying disease or any other threat, which might endanger other island foxes. The bodies of these individual animals are stored in special freezers at UC Davis to preserve tissue samples for future scientific investigations, like the tooth project.

During the final stages of the preservation process, cleaned skulls are soaked in cold water for several days. The researchers explain that "At that point in the process, the teeth are very loose and easy to pull out..." A single lower canine tooth was extracted from each skull. Once all of the skulls have been processed, Schamel added, "I think we will be ready to send all the teeth to Matson's Laboratory in Montana!"

See Mike Watling's story for more on how each tooth will be processed.

The plot below shows how fox age estimated by tooth wear does not always match-up with actual island fox age.

We know the actual age of island foxes that are micro-chipped as pups. Biologists performing health checks in the field, however, do not have access to this age information when they are examining individual foxes. They estimate the fox's age by the amount of wear on its teeth. This estimate puts the fox in one of five categories: 

• Age Class 0 - pup to 1 year
• Age Class 1 - young adult
• Age Class 2 - adult
• Age Class 3 - mature adult
• Age Class 4 - senior

The plot above shows data from 1300 exams of island foxes compared with their known ages. The larger the dot the more individuals fell into each category. The more you examine this plot the more you will see. For example: a 4-year-old island fox was almost as likely to be estimated as Age Class 3 as Age Class 2. A few 4-year-olds were estimated as Age Class 1 or Age Class 4. What do you see in the plot for island foxes that are 6 years old? Is tooth wear a reliable way to estimate island fox age? 

This data shows why the cementum research is so important. Island foxes live longer and eat a different diet from the southeastern gray foxes for which the tooth-wear age classes were originally designed.

This project also highlights the broad scientific community involved in researching island foxes. Biologists from Channel Islands National Park are working with the Santa Barbara Natural History Museum, UC Davis, and Matson's Laboratory in Montana, which specializes in cementum age analysis of mammal teeth. Science brings people together.

As this research project moves forward FIF will keep you updated on the findings. Scientific data is vital to making informed conservation decisions that maintain sustainable populations of island foxes.

Friends of the Island Fox invites biologists, ecologists, and other researchers to contribute to our understanding of island foxes. Applications for the FIF Research Grant 2020 are now available.

The island fox cementum analysis research project was made possible through a donation from Safari West.

Your Donations Help Make Research Possible 

On-Line Earth Day Event Sunday April 26th

2020 marks the 50th celebration of Earth Day. Connect and engage with the Channel Islands online. Join Friends of the Island Fox, Channel Islands Restoration and Channel Islands National Park on Sunday, April 26, 2020, from 3:00 - 5:00 pm PST for a special live event.

3-4 pm -- How we are working together to help the planet

Channel Islands National Park, Channel Islands Restoration, and Friends of the Island Fox will share their organizational mission, updates on their work, and home activities.

4-5 pm -- Virtual Earth Day presentations

CIR:  Why supporting our native ecosystem is important, using local examples and biofacts 

FIF:   Island fox recovery, status, and current threats … what you can do to help.

NPS: Biofact exploration, introduction to educational programs available online.

Please RSVP through EventBrite here: 

 CIR-FIF-NPS Earth Day Registration

Check this link for how to join an hour before the event: 

 EarthDay-CIR-FIF-NPS

Friends of the Island Fox Research Grant 2020

Friends of the Island Fox is currently accepting applications for the 2020 FIF Research Grant

The mission of Friends of the Island Fox (FIF) is to bring together conservation professionals and concerned private citizens to create public awareness about the island fox and to raise funds to support education, research, and conservation measures to ensure the island fox's survival and protect its island home.
 

In 2020, Friends of the Island Fox is making $5,000 available in grant funding to researchers working on projects that align with our mission.

2020 Grant Application pdf 

Applications will be accepted through August 31, 2020. Recipients will be notified September 28, 2020.

The more we know about island foxes, the safer their future will be.

Previous FIF Research Grant Recipients

2018: "The Channel Island Food Web–A Decade of Dietary Resource Use in Channel Island Fox: Implications for Reproduction, Recruitment, and Resilience in a Changing Climate." - Juliann Schamel, 2019 Update

2019:

1. "A Decade of Seasonal Dietary Resource Use in Channel Island Fox: Implications for Reproduction, Recruitment, and Resilience in a Changing Climate." - Juliann Schamel
2. "Assessing Cementum Annulation in teeth for determining age at death." - Stacy Baker and Juliann Schamel

Your donations to Friends of the Island Fox

help make this research grant possible

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:

Origins of the Island Fox

New Findings on Island Fox Diet

Epidemic Disease Threats to the Island Fox

More