The remarkable recovery of the Anglo-Norman fox
Half-submerged sections of mighty Transverse Ranges, the Channel Islands stretch just off the coast of southern California. They are visible from almost anywhere along the central south-facing coast. In Isla Vista, if one peeks over an oceanfront balcony or stroll along the beach, the Santa Cruz and Santa Rosa Islands dominate the skyline.
The islands themselves are home to an incredible diversity of life. Beneath the waves lie vast forests of kelp, while on land, oak forests are interspersed with chaparral, meadows, and even two relict stands of elusive Torrey Pines. The most charismatic, perhaps, are the foxes.
“They’re certainly very smart and mischievous, but they also have a kind of fearless confidence that comes from being a top predator for so long. They will come to you, ”said Jessica Sanchez, wildlife biologist, veterinarian and epidemiologist at UC Davis.
Sanchez worked with the Channel Islands fox (Urocyon littoralis) since 2006, when it joined efforts to repopulate fox populations following a rapid decline that brought the species to the brink of extinction.
In the late 1990s, the foxes were on the precipice. On Santa Catalina Island, an outbreak of distemper virus – probably introduced from the mainland – killed 95% of all foxes on the island in 1999, while in the northern Santa Cruz Islands, Santa Rosa and San Miguel, the invading golden eagles began to feast. on foxes in large numbers.
“The eagles were [initially] attracted to the islands because there was an abundance of cattle like pigs and goats to feed on. There also remained open territories because native bald eagles had also declined at the same time due to DDT, ”Sanchez said. DDT, a chemical originally developed as an insecticide, is infamous for thinning the eggshells of many birds, especially birds of prey. It is now banned in the United States.
Unfortunately for foxes, their fearless nature and daytime lifestyle made them easy targets. Best of all, they were the perfect size to be picked up and brought to the nests as a nutritious meal for the chicks.
“They didn’t really have a lot of the escape behaviors that the mainland foxes did so they really suffered predation by these eagles and that just led to dramatic declines in the population,” Sanchez said.
Because of the different causes of decline, conservationists needed a multi-pronged approach to their recovery efforts. On the one hand, the golden eagles should be rooted out of the islands.
In order to hunt them, non-native ungulates, on which golden eagles preferentially fed, should be permanently eliminated. At the same time, work began to reintroduce the bald eagles to the islands to occupy their former territory and hunt any wayward golden eagles that were inclined to return.
Meanwhile, in order to revive their recovery, captive breeding and long-term fox monitoring programs have been put in place throughout the archipelago.
“When we brought animals into captivity to protect them from any outside threat, they actually bred very well in captivity… [while] with the threat of the golden eagle, we were able to physically remove them and change the landscape, ”Sanchez said.
The Santa Barbara Zoo, for example, has been very involved in the conservation of island foxes and has recently bring two orphaned foxes, Lewis and Clark, at the zoo.
In 2006, when Sanchez began working on the Channel Islands with the Institute for Wildlife Studies, a captive breeding program had already been successfully implemented; however, threats from golden eagles persisted.
In the following years that she worked there, Sanchez was able to observe firsthand the remarkable recovery of the foxes, with the release of the last animals from the captive breeding program on the northern islands and a transition to follow-up and management of only wild populations.
“The foxes were listed as critically endangered – on some islands there were only 15 foxes and all of them had been brought from the wild to captive breeding facilities,” Sanchez said.
“And we went from that to an all-wild and recovered population in 2016, when the three northern islands were taken off the list, which was reported as the fastest recovery of any mammal listed under the endangered species law. ”
Today, for many conservationists working with foxes, the focus has shifted to the next stage of recovery, with restoring native plants and removing invasive vegetation introduced during decades of animal husbandry. ranch. Perhaps eventually, the ecological balance that existed before human occupation will return.
Meanwhile, Sanchez herself is studying strategies for preventing and detecting epidemics if another disease recurs. In fact, the foxes of Santa Catalina are still considered near threatened due to the high tourist traffic the island receives, which increases the risk of another outbreak.
In his last research, Sanchez simulated the different strategies used to detect and prevent rabies and distemper virus with a spatial model. Working with data from foxes on San Clemente Island, Sanchez evaluated the effectiveness of preventive measures such as vaccine firewalls and randomly distributed vaccinations based on population density.
“Pathogen transmission appears to occur more quickly when there is a higher density of foxes, which has been shown with many other populations. So we are trying to determine, given a high or low density, where the pathogen is introduced, what type of vaccination distribution will be most effective? Sanchez said.
“I hope that our results will allow managers to identify guiding principles that they can then adopt and interpret based on the geography and fox population of their island. ”