Tuesday, October 19, 2021

Estimating Island Fox Age Using Cementum Rings In Teeth

Slides of tooth specimens - S. Baker

In October 2019, Friends of the Island Fox funded a research study by Stacy Baker and Juliann Schamel, via a donation from Safari West, to investigate the use of cementum analysis as a method to determine island fox age at death. The results are in and the answer is, well mostly yes, but...

To conduct the analysis 31 teeth from island foxes, whose age was known when they died, were sent off for testing. Of the 31 samples, 28 were aged accurately to within 1 year of their known age, two teeth were underestimated by 3 years and one was underestimated by 4 years. This underestimation primarily occurred with older foxes.

plot of accuracy in aging island foxes using tooth cementum, S. Baker 2021

The data suggests that for younger and middle age foxes–up to approximately age 7–cementum analysis can provide an accurate assessment of age at the time of death. (A more accurate assessment than estimating age by tooth wear.) For more senior island foxes, however, the accuracy of the method drops significantly. 

What are the factors that led to a misread of the older fox teeth? 

According to Baker, the study's principal scientist: "Tooth condition may perhaps play a role, as two of those teeth out of four were determined to be of lower quality for aging according to the Matson's Lab. This also may be unavoidable, since broken and decayed teeth become more prevalent as individuals age." (Matson's Laboratory in Manhattan, Montana, specializes in aging mammals using teeth.) With the limited sample size from the older fox population, more analysis is warranted to tease out the factors that may play a role in the reading error. In the wild, foxes are known to live 10–12 years on some islands. (K Dearborn personal communication)

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. It's Science for Fox Sake! - Mike Watling, FIF President

Full Report: Using Cementum Annuli to Estimate Age in Island Foxes by S. Baker, 2021 

This research project was made possible through Friends of the Island Fox, a donation from Safari West, and in partnership with the National Park Service, Santa Barbara Museum of Natural History, and UC Davis.

Friday, October 08, 2021

Can I Feed An Island Fox?


Please don't feed island foxes.

If there is one thing to remember when you visit the Channel Islands, this may be the most important. Wild animals who receive food from people frequently pay the consequences.

Emily Hamblin, Senior Wildlife Biologist on Catalina Island conveyed the news about a female fox. "We were very saddened this month to receive a call about a roadkill fox [hit by a car] on Stage Road. As soon as we heard the location, we knew which fox we were going to see."

The female Catalina Island fox was first caught as a pup in 2012. Most years she was captured and given a health check. There were physical signs that she had mothered pups. This year she received her health check and, despite being an older fox at nine years old, she was in good health.

"She was always gentle, didn't bite," Hamblin wrote, "and was easier to work with than the average fox. After we released her, she stayed nearby in the road instead of running off. From these actions, it was clear she was being fed by humans."


It was just two days after her health check that Hamblin was retrieving the female fox's body from the road. Part of the biologist's job is to investigate fox deaths. 

"It is hard for me not to feel a bit of hopelessness as I respond to these calls over and over again...When people feed foxes on the road, they are essentially conditioned to think that dinner is in the middle of the highway. Far too often, this behavior results in foxes being unintentionally lured to their death."


This island fox's death was preventable. 

We can warn drivers about foxes near roads. We can provide Fox-Safe bins to keep island foxes out of trash and lockers for campers, but only people can make the choice to protect island foxes. 

When you feed an island fox, you threaten its life. Island foxes that seek food from people end up entrapped, entangled, and in danger.

Save an Island Fox - Don't Feed It.

Read Emily Hamblin's full story in the Catalina Islander