How can you tell the age of an island fox?
Biologists used to determine general age by looking at an island fox's teeth. Individuals with worn teeth were thought to be older animals. Island foxes living in dune areas, however, may consume sand while eating insects and crustaceans. Sand wears away the teeth and can make an island fox appear older than it really is.
Most island foxes are in their prime from 2-6 years old. The island fox pictured above no longer has the pricked-up pointy ears of a youngster. His battered right ear has been bitten a few times by other island foxes, a sign that he is an adult with a little mileage. Compare older foxes vs. younger foxes
Some island foxes can have ears torn off in territorial deputes with other island foxes. Island fox missing an ear.
Initially it was believed that island foxes lived 8-10 years in the wild. But ID microchips have provided specific information on individual island foxes. On Santa Cruz Island the oldest documented island fox was a female born in the captive breeding program that lived to be 12 years old. On Catalina Island, numerous island foxes have lived to be 12, while several individuals have neared 13 or 14 years old.
The individual island fox above is probably between 4 and 10. It's hard to guess by appearance alone. His microchip and annually collected health-check data can tell us specific information about his life. Collecting scientific data on island foxes is helping us to understand their lives in greater detail.