The Island Fox is restricted to six of the California Channel Islands off the coast of southern California, USA. The population has suffered declines of more than 80% in recent years, primarily caused by Golden Eagle predation and possible introduction of canine disease (e.g., canine distemper virus (CDV)). Population decline is expected to continue.
Population trend: Decreasing
Habitat and Ecology: Island Foxes occur in all habitats on the
islands including native perennial and exotic European grassland, coastal sage
scrub, maritime desert scrub, Coreopsis scrub, Isocoma scrub, chaparral, oak
woodland, pine woodland, riparian and inland and coastal dune.
Although fox density varies by habitat, there is no clear habitat-specific pattern. When fox populations were dense, foxes could be trapped or observed in almost any of the island habitats, except for those that were highly degraded owing to human disturbance or overgrazing by introduced herbivores. More recently, foxes have become scarce owing to precipitous population declines. On the northern Channel Islands where the declines are principally a consequence of hyperpredation by Golden Eagles (Aquila chrysaetos) (Roemer et al. 2001a, 2002), foxes are more numerous in habitats with dense cover, including chaparral and introduced stands of fennel (Foeniculum vulgare) (G. Roemer, pers. obs.).
Major Threats: The current primary threats to the species include Golden Eagle predation on the northern Channel Islands (Roemer 1999; Roemer et al. 2001a, 2002) and the possible introduction of canine diseases, especially CDV, to all populations (Garcelon et al. 1992; Roemer 1999; Timm et al. 2000). All populations are small, several critically so, and are threatened by demographic stochasticity and environmental variability. The small populations are especially vulnerable to any catastrophic mortality source, be it predation, canine disease, or environmental extremes (Roemer et al. 2000).
Recently, there has also been a management conflict between island foxes and the San Clemente Island loggerhead shrike (Roemer and Wayne 2003). Island Foxes were euthanized on San Clemente Island in 1998 as part of a programme to protect nesting shrikes (Elliot and Popper 1999; Cooper et al. 2001). Although euthanasia of foxes has stopped, a number of foxes are now retained in captivity each year, during the nesting and fledging stage of the shrike, and subsequently released back into the environment. The impact to fox reproduction and the potential disruption of the social system are unknown, but may be significant. These actions may have contributed to a 60% decline in the fox population on San Clemente Island (Cooper et al. 2001; Schmidt et al. 2002; Roemer and Wayne 2003). Considering the precipitous declines in foxes on four of six islands and the continued decline in the San Clemente population, this current management practice needs further scrutiny.
A more detailed summary of the biology and conservation status of this species from the CSG's Canids: Foxes, Wolves, Jackals and Dogs - 2004 Status Survey and Conservation Action Plan) is available on-line here.
Island Fox © Coonan
For more photos and videos of this and other wild canid species, see:
English: California Channel Island Fox, Island Gray Fox;