Saved from Extinction, Southern California’s Channel Island Foxes Now Face New Threat to Survival

Once threatened by disease and predators, foxes inhabiting six of Southern California’s Channel Islands were saved from extinction by the Endangered Species Act. Now, a new study shows they face a different threat: their own lack of genetic diversity.

Tiny foxes — each no bigger than a five-pound housecat — inhabiting the Channel Islands off the coast of Southern California were saved from extinction in 2016. However, new research reveals that the foxes now face a different threat to their survival.

Suzanne Edmands, professor of biological sciences at USC Dornsife College of Letters, Arts and Sciences, and Nicole Adams, who earned her PhD from USC Dornsife in 2019, found that the foxes’ genetic diversity has decreased over time, possibly jeopardizing their survival and the biodiversity of the islands.

“The findings of this study highlight the alarming fact that the foxes currently inhabiting six of the Channel Islands possess extremely low genetic diversity, rendering them potentially more susceptible to dangers such as disease outbreaks and climate-induced environmental shifts,” Edmands said.

As the largest native land animals on the islands located 22 miles off the coast of Southern California, these bushy-tailed, big-eared creatures play a vital role in regulating plant and animal communities by consuming various food sources, including fruit, insects, snails, lizards, birds, and rodents. In fact, many plant species rely on them to distribute seeds through their scat.

“The importance of these animals to the overall biodiversity of the island can’t be over-emphasized. Without them, we could lose other species as well,” Edmands said.

A previous study done in 2018 lacked sufficient sampling to detect changes in genetic variation. This new study used a broader sampling method, comparing historic museum specimens and modern blood samples.

Interestingly, the results indicated extremely low genetic variation even before the population declines. It also revealed that the genetic variation had dropped even further since population numbers fell. The islands that experienced the most severe losses, San Miguel and Santa Rosa, also showed the greatest reduction in genetic diversity. Santa Cruz and Santa Catalina, two islands where populations fell moderately, displayed mixed changes in genetic diversity metrics.

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