I've written about the Channel Islands off the coast of California several times. I had the good fortune of recently spending a weekend camping on Santa Rosa Island, the second largest of the Channel Islands by area. Like many islands, California's Channel Islands are home to many unique species of plants and animals. In spite of the fact that five of the eight islands are usually visible from the mainland coast, the natural evolutionary laboratory that islands tend to foster is in full operation on these islands.
Of all of the unique species found on the Channel Islands, among the most endearing is the island fox (Urocyon littoralis). Descended from the gray fox ((Urocyon cinereoargenteus) found on the mainland, the most obvious difference between the two species is the decidedly diminutive size of the island fox. Indeed, the island fox is among the smallest members of the canine family of species. Typically the head-and-body length is 18–20 in. (48–50 cm), shoulder height 4–6 in. (12–15 cm), and the tail is 4–11 in. (11–29 cm) long, which is notably shorter than the 10–17 in. (27–44 cm) tail of the gray fox.
Of the eight islands in the Channel Islands archipelago, six host island fox populations. The two islands that don't are simply too small to support even such a small carnivore permanently. The fox populations on each island are officially recognized as separate subspecies. And while they can still interbreed, each subspecies exhibits differences in genes and external appearances. For example, the number of tail vertebrae is different in foxes on each island.
Unfortunately, like so many unique species found on the Channel Islands, the story of the island fox is tinged with tragedy. While arriving on the northern islands sometime between 10,400 and 16,000 years ago, when sea levels were lower and the islands more accessible, and likely being brought to the various southern islands by native Americans sometime between 4,300 and 800 years ago, populations of island fox began to decline precipitously on Santa Catalina, Santa Cruz, Santa Rosa, and San Miguel Islands in the 1990s.
The decline on Santa Catalina, one of the southern islands, was the result of the introduction of canine distemper from some mainland source. The outbreak of this disease resulted in the death of 90% of the island foxes starting in 1998.
The decline of the populations on the three northern islands was the result of the appearance of golden eagles on the islands. While the islands had been the natural home of bald eagles, the arrival of golden eagles tipped the balance against the island fox, which became easy prey for the more predatory golden eagle. Losses on the northern islands ranged from 93% on Santa Cruz, to 96% on San Miguel, to a staggering 99% on Santa Rosa.
The good news is that steps were taken in time to reverse these losses, and these unique little predators that hold the title of largest native terrestrial mammal on the islands and of being the only carnivore unique to California have made remarkable comebacks.
Today's photo was taken on Water Canyon Beach on Santa Rosa Island and shows the tracks of one or more foxes that had been searching the beach for food.
This photo was taken with a Canon EF 17-40 mm f/4L USM lens zoomed to 40 mm on a Canon EOS 5D Mk III. The exposure was set to 1/350 sec at f/16 and ISO 800.
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