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