But the foxes’ narrow genetic pool puts them in danger.
By Francie Diep
Two California Channel Islands foxes. (Photo: Pacific Southwest Region USFWS/Flickr)
Seeing a California Channel Islands fox feels a little like looking at a dollhouse replica of a famous building. The canines are about the size of house cats, but otherwise look just like the gray foxes that nose around the suburbs of Southern California. The Chumash people considered them sacred—a “pet of the sun, and possibly a dream helper.” In other words, they’re adorable. They’re also found nowhere else on Earth but the Channel Islands and, until recently, were in real danger of going extinct. They’re considered recovered now, but, according to a new DNA study, they may still be in peril.
It turns out that island foxes are 99.99 percent alike to one another, making them the most genetically similar wild animals known to science, according to the study, which is the first of its kind for the foxes. Their gene pool is 100 to 1,000 times smaller than any other animal scientists have DNA sequenced. “It’s a really dramatic absence of variation,” says Robert Wayne, a biologist at the University of California-Los Angeles and the senior scientist on a team that recently sequenced seven island foxes.
“It’s a really dramatic absence of variation.”
Yet the foxes may not be unique. On small islands, animals naturally tend to inbreed more than their mainland counterparts. Perhaps scientists simply haven’t yet fully grasped how genetically alike those other animals are. “It may be that many island species, particularly island vertebrates, have low genetic variability,” Wayne says.
Against all odds, island foxes seem to be doing fine, for now. That’s in large part due to an initiative, launched in 1999, that aimed to breed the foxes and to remove non-native animals from California’s Channel Islands. (For example, conservationists had to relocate nests of golden eagle, which would prey on the foxes.) With the Channel Islands fox population now appearing much healthier, the Fish and Wildlife Service has proposed a change to some populations’ official status, to remove them from the “endangered” list. But doing so would be a mistake, Wayne argues.
The foxes’ genetic similarity means their recovery might be more fragile than it seems. “I think they should reconsider,” Wayne says. “The foxes’ lack of genetic variation makes them more vulnerable to threats like disease and makes them less likely to adapt to change in their environment. I think we should be worried a disease might come in.”
With or without an “endangered” listing, Wayne thinks people can help cushion the foxes against the dangers of their own DNA. Conservationists will have to try to keep the foxes’ numbers as high as possible, to maintain a mixed gene pool. And they’ll have to be especially wary of accidentally importing diseases that might affect the foxes, such as canine distemper, which nearly wiped out Catalina Island’s fox population in 1999.
These are lessons that wildlife biologists should keep in mind for other endangered island species, Wayne says. Before his research, scientists had no idea animals could be so genetically homogenous and healthy. Now, folks interested in protecting other islands’ sacred foxes — or birds or lizards or sloths — may need to be extra careful with them too.