On a recent three-day trip to Santa Cruz Island, I encountered at least a dozen island foxes across the southeast end of the island. Three at the beach at Scorpion Anchorage foraged in the cobblestones. Three more ran amok in the upper campground in Scorpion Canyon. Two were high on Montana Ridge frolicking through a stand of blue dicks. Several more scoured the dry creekbed at Smugglers Cove. This was more than I’d seen on one trip since the early 1990s.
Captive breeding of the endangered island fox helped stabilize their numbers across the rugged archipelago, with the last captive fox released on Santa Rosa Island. Since then their numbers have soared, more than doubling on Santa Cruz and San Miguel islands. In November, Channel Islands National Park and The Nature Conservancy felt confident enough to shut down captive breeding, but they didn’t envision this swift of a recovery.
“Their numbers are totally skyrocketing,” said Tim Coonan, a National Park Service terrestrial biologist. “Remove a primary mortality threat and you’ll have a fairly robust recovery.”
Coonan was referring to golden eagles that colonized the islands in the 1990s, decimating island fox populations across the chain. Initially lured to the national park by a healthy feral pig population on Santa Cruz, the non-native raptors soon realized the foxes were an easier kill on the three northern islands. The tiny house cat-sized predators have always been at the top of the food chain — until the golden eagles arrived. Around 45 of the predatory raptors were trapped, fitted with a GPS and relocated to northeastern California.
Coonan said island fox numbers on Santa Cruz Island are around 740, but that doesn’t include juveniles and pups, and he believes it’s more like 1,000 animals. That’s up from around 350 foxes from last year. Populations are also high on windswept San Miguel Island, with 280 island fox adults and pups combined.
“The island fox is approaching biological recovery pretty quickly,” Coonan continued. “We’re pretty much where we want to be at an 80 to 90 percent survival rate. A little eagle removal went a long way.”
Current numbers are based on grid trappings. Grids are 1,500 feet by 4,000 feet in size. About 18 traps are inside each grid, 250 meters apart.
Coonan said there are approximately 120 island foxes on Santa Rosa Island, but it was not an entirely accurate number because biologists used transect trappings. That involves trapping in a straight line on old cattle ranching roads and trails, which is sufficient for catching and radio collaring foxes. Reproduction on Santa Rosa has been slow in island fox populations, but their numbers are rising gradually.
“Santa Rosa is still slow,” he said. “We don’t have a good idea how many island foxes are on Santa Rosa, so we’ll be trapping in grids this summer.”
I asked Coonan if there will ever come a time when the unique ecosystem on the Channel Islands won’t be able to absorb the growing number of island foxes.
“Island foxes are able to self-regulate a carrying capacity,” Coonan explained. “They’ll stop having pups and slow down.”
— Local freelance writer Chuck Graham is editor of Deep magazine.