The Island Fox: The Little Mammal with the Big Job

Along the Path

By Susan Rothrock Deo

Something in our salty blood beckons us to the sea/ Something in our imaginations beckons us to islands

—Susan Lamb

Photo: Santa Cruz Island Foxes. Paul Blieden

Have you ever visited an island, perhaps one of our own California Channel Islands? They are indeed a
world apart. Biologists are intrigued by the adaptations plants and animals have made when isolated on
islands for thousands of years.

The island fox (Urocyon littoralis) is one of my favorites. It is found only on the six largest Channel
Islands. Its closest relative is the gray fox (Urocyon cineroargenteus). Scientists believe when sea levels
were lower during the last ice age, gray foxes swam or drifted on debris to the northern island(s). They
evolved special adaptations, including smaller size, to survive on the islands where resources were
limited. Island foxes are one of the smallest canids (group of mammals that includes wolves and dogs)
 in the world. Despite being the size of a housecat, they are the largest mammal on the Channel Islands. They have mottled gray fur on their heads and back; rufous or cinnamon on their belly, neck and legs; and white on their cheeks, throat and chest. Their tail has a black stripe along the top.

The Chumash, who lived on the northern Channel Islands and surrounding coast, considered the fox a sacred animal. They probably transported some to the southern Channel Islands when trading with the Gabrielinos, who lived on the southern islands and surrounding coast. Over the years, the foxes evolved that each island has a separate subspecies: Santa Catalina (Urocyon littoralis catalinae), the largest in size with the longest tail; San Miguel (Urocyon littoralis littoralis), the second largest with the shortesttail; Santa Rosa (Urocyon littoralis santarosae), average size with longest ears; San Nicolas (Urocyon littoralis dickey), lighter in color with longest legs and most bones in tail; Santa Cruz (Urocyon littoralis santacruzae), smallest in size with shortest legs; and San Clemente (Urocyon littoralis clemente).

Island foxes are omnivorous, eating insects, mice, reptiles, and native fruits. Some eat marine life also.
They can run very fast and because they are able to turn their front paws inward, they can climb trees searching for fruit or birds’ nests. They have no natural predators, so they are not afraid of people and are active both day and night, especially at dawn and dusk.

The island fox is a keystone species, crucial to the island’s natural web of life. Without the fox, too many
deer mice might overconsume plant materials or prey on eggs of low nesting birds, threatening these
populations. Many native plant species rely on the fox to eat their fruit and distribute the seeds through their scat. Insects and birds depend on this seed dispersal too. A few years ago, island foxes were endangered. Sheep, pigs and goats imported for ranching competed for the foxes’ food. Native bald eagles, who primarily ate fish, began to disappear from the islands. Excessive DDT (an insecticide)had accumulated in their food (fish) and then in the eagles. It caused their eggshells to be so thin that they broke and never hatched. Golden eagles moved in to fill the void, but they ate mammals, not fish. They found an abundant supply of sheep,
goats, pigs and, unfortunately, island foxes.

Thankfully, a “coordinated, organized and highly focused strategy was able to reverse the certain
extinction of an endangered population.” (National Park Service) The ecosystem balance and foxes’
success were ensured by: a captive breeding program of island foxes, removal of domestic sheep, pigs and goats, removal of golden eagles, and reintroduction of bald eagles.

Today the populations of foxes on all six islands have recovered. There are still threats, like
diseases such as canine distemper introduced from the mainland. However, conservationists continue to monitor the fox populations and vaccinate them against these diseases.

I’m looking forward to seeing an island fox in the wild one day. I hope you are too!

To learn more about the island fox:
National Park Service
Friends of the Island Fox
Catalina Island Conservancy Island Fox Recovery and Support
Search for YouTube videos about the Island Fox, such as this one.

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