The population has recovered to more than 1,500 after crashing to about 100 in the 1990s when the animals were ravaged by a distemper epidemic scientists believe was introduced by a pet dog or a raccoon from the mainland that hitched a ride on a boat or a barge.
The U.S. Fish and Wildlife Service listed the fox as endangered in 2004, prompting the Santa Catalina Island Conservancy and the Institute for Wildlife Studies to launch a $2 million recovery program that included vaccinations and a captive breeding facility.
"We're beyond proud," Ann Muscat, chief executive of the conservancy, told the Los Angeles Times. "It's a testament to what hard work, passion, money and the resiliency of nature can accomplish."
Despite their growing numbers, she said, "we can't relax. These furry treasures are still just one infected dog or raccoon away from extinction."
Catalina foxes are small -- weighing about 5 pounds -- and gray, with pointed noses, reddish ears and feet and black-tipped tails.
They live about 10 years and pair for life, conservationists said.