As expected, high temperatures and below average rainfall in 2018 contributed to lower pup numbers and reduced adult survivorship across all islands. As first documented on Catalina Island, island fox reproduction is linked to annual rainfall. Fortunately, normal rainfall levels in 2019 should benefit all island fox populations.
In 2019 Channel Island foxes face four major threats:
- climate change: increasing regional temperatures and decreasing annual rainfall, which reduce food resources, increase wildfire threat, and promote parasite numbers
- biosecurity: the introduction of non-native plants, animals, and diseases
- parasites: rising tick numbers and tick-borne diseases; increased intestinal parasites on some islands
- reduction of management funding
San Miguel Island foxes robustly recovered from 15 individuals in 2000 to over 500 by 2010 (lime-green line on graph below). As a smaller island, it will always have a smaller fox population. In 2015, however, following several years of drought, the population began declining. As of fall 2018, the population has dropped to an estimated 171 individuals (a decline of over 70%). This decline may involve several interconnected threats: climate change, biosecurity and parasites. Details regarding San Miguel will be posted in coming days.
San Nicolas Island foxes declined by 59% to 260 individuals during consecutive years of drought from 2012–2015 (pink line on graph above). The US Navy initiated native plant restoration projects in conjunction with Channel Islands Restoration. As these plants, like prickly pear cactus, mature they are providing food and habitat for island foxes and prey species. The fox population has increased to a more stable number–estimated 400 individuals.
Santa Rosa Island foxes may have reached capacity for the island (pink line on "larger islands" graph above). Native vegetation is recovering and increasing resource options for foxes during periods of drought. No island foxes have been lost to golden eagles on this island or San Miguel since 2010. Parasites, including tick-borne disease, are a growing concern on Santa Rosa. FIF has refurbished 7 radio collars, and funded dietary research and health testing measures in 2019.
Santa Catalina Island foxes have also reached capacity for their habitat. In reaction to decreased rainfall, this population also declined naturally in 2018 (red line on "larger islands" graph above). Parasites, especially tick-borne Lyme disease, and biosecurity are an increasing concern for this population. Lyme disease and canine herpes virus were both introduced via human visitors and their pets. Monitoring of disease exposure is vital to this populations continued health. FIF has funded 5 new radio collars and health testing measures in 2019.
San Clemente Island foxes live on the most southern Channel Island (blue line on "smaller islands" graph above). In 2018, they were the first population to see deaths directly attributed to high temperatures. Reduced rainfall stressed the population and eight individual island foxes are known to have perished in the heatwave between June and July of 2018. Climate change is impacting this island fox most directly.
Download the detailed 2019 Island Fox Status Update