Fox Foto Friday - How Old Is That Island Fox?

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.

Wildfire Can Threaten Island Foxes

Responding to wildfire on the Channel Islands raises a quandary, because there are positive and negative aspects to letting wildfire burn:

• Fire is a natural element on the Channel Islands. Many native plants depend on fire to open up areas for new growth, to renew the soil, or even jump-start seeds. As omnivores, island foxes depend on diverse and healthy native plants.
• Fire can provide unexpected abundance for predatory or scavenging animals, including island foxes. Smaller animals may get caught in the fire, while birds and larger animals might escape.
• Years of drought, however, have created areas with exceptionally dry vegetation and greater than usual build-up of wildfire fuel.
• Land animals, like the island fox, and some lesser-flying birds, like the island scrub-jay, can not escape a fire burning out of control that might consume an entire island.
• Santa Cruz Island is home to endemic plants and animals that only live on that one island and nowhere else in the world. If the entire island burned, some of these species might be driven to extinction.
• The National Park is tasked with protecting historic human cultural artifacts and structures that could be destroyed.
• People visiting the island can not easily evacuate on their own; they are dependent on sea or air transportation provided by others. The National Park must always consider visitor and staff safety.

Island scrub-jays only live on Santa Cruz Island

When lightning struck Santa Cruz Island during the night of Sept. 10th or early morning of Sept. 11th, all of these factors (and more) had to quickly be taken into account by officials at Channel Islands National Park.

2007 Catalina Island Fire

'Burnie Boots' - Catalina 2007

In 2007, fire raged up canyons and across hillsides on Santa Catalina Island. While only one female island fox was known to be injured in the fire, biologists later discovered that numerous island fox pups were lost to the flames because the fire occurred in spring and many pups were still too young to leave the dens where they were born. Catalina Island Conservancy biologists believe the injured female island fox risked her own life, walking across burning coals, to try and return to her pups in the den.

Wildfire is unpredictable, and in this incidence, the negative threats outweighed the potential positives. U.S. Forestry Service smoke jumpers were called in and they parachuted down to the island to put out the fire.

Fire on Santa Cruz Island 2017 - U.S. Forestry Dept. via Ventura Co. Star

The wildfire was first spotted by a concerned citizen on a boat. Threats to island foxes and the Channel Islands can come in many different forms. Some like disease from domestic dogs or introduced wildlife are similar to lightning, they may initially strike in one place, but the consequences can quickly spread across an entire island. Island foxes need all of us to be as vigilant as the boater who reported the wildfire - one person can make a difference.

Fox Foto Friday

Photo by Douglas E. Welch (http://Douglasewelch.com) June 1, 2013

An island fox (Urocyon littoralis) takes advantage of its natural camouflage to hide among the dry grasses of Prisoners Harbor on Santa Cruz Island.

Find out more about the properties of island fox fur that enhance camouflage and how identifying individual island foxes goes beyond color markings.

Tracking An Island Fox

Welcome guest writer Mike Watling. As a certified wildlife tracker and member of Ventura County Wildlife Trackers, Mike shares his expertise in identifying island fox tracks.

Visiting Santa Cruz Island this past winter, I was more excited than usual as it had rained a few days prior to the trip. The miracle of mud, following a rain, provides an excellent medium for studying the tracks left behind by animals. As a naturalist and wildlife tracker, I was looking forward to spending my day carefully observing the minute details of the delicate tracks of the Channel Island fox.

The island fox and its mainland cousin the gray fox are the only fox species capable of climbing trees. The island fox is the island's largest mammal and main predator; the top dog if you will.

Unlike the gray fox, which is primarily a nocturnal hunter, the island fox is active both day and night and can be readily observed foraging for lizards, insects, and fruit that comprise a large portion of its diet. To help conserve energy, foxes will often travel on the roads and trails found throughout the Channel Islands, leaving behind tiny tracks for the observant naturalist to find. 

Like all species in the Canidae family, the fox places its feet on the ground in a manner known as digitigrade. To put it simply, while they are moving, their body weight is being supported by the digits (toes) rather than the entire foot structure. In contrast, humans and bears are plantigrade, meaning the body weight while in moition is being supported by the entire sole of the foot. This characteristic is evident in the tracks left behind.

Consistent with all canids, the island fox has five toes on each forefoot. Toe one, the dew claw, is greatly reduced and located above the carpal pad on the inner leg. Only four toes typically appear in a track. The metacarpal pads, or palm,are fused together to form a larger rounded, yet triangular pad. The space between the toes and the pad, known as the negative space, forms an “H”.

The hind feet have four toes, and like the front, the pads are fused to form a narrow heel pad, which only partially registers in a track.  The negative space forms an “X”.
 
Island fox tracks are small, mostly symmetrical, approximately 1 to an 1 1/4 inches long by 13/16 of an inch wide, with the front track larger than the hind. The two inner toes tend to be close together and are often angled inward towards each other. Often the fur surrounding the foot will leave a visible impression in the track as well. The claws of the island fox are semi-retractable and slightly curved, and may not register. Even in mud, the claws appear very fine if at all. 

 
Island foxes generally move throughout their territory in a slight under-step trot. Having the shortest leg-to-body ratio of all the wild canines, the resulting track pattern is such that the front toes are visible ahead of a complete hind track.

While hiking the Channel Islands, take time to look closely on the side of the trail where you’ll likely encounter the tracks of the island fox, as well as other island inhabitants.  Quietly observe the entire area; look around for other pieces of evidence and you may be able to determine what the animal was doing.  Give pause, and for that moment, walk with the Island Fox. - Mike Watling