The island spotted skunk (Spilogale gracilis amphiala) is an insular endemic carnivore and a subspecies of the western spotted skunk (Spilogale gracilis). Little is known about their exact variations from the mainland spotted skunk and variations between locations, resolution of which awaits further genetic and morphologic evaluation. The skunk is only currently found on two islands off the southern coast of California (Santa Cruz Island, and Santa Rosa Island, where its occurrence is rare). Its presence has been recorded on San Miguel Island, but it has since been declared extinct in that area. The Channel Island skunk is one of two terrestrial carnivores on the islands, the other being the island fox. It is designated as a species of special concern by the state of California.
Distribution and habitat
Range
The island spotted skunk is endemic to the Channel Islands off the coast of Southern California. It currently is only found on Santa Rosa and Santa Cruz islands where it is widely distributed. There are previous reports of this taxon living on San Miguel island as well. Record of its inhabitance on San Miguel island ceased after the late nineteen hundreds and it is believed to be extirpated from this region. As of 2011, there were reportedly 3,000 Island Spotted Skunks on Santa Rosa island alone. However, after the recovery of the island fox in the mid-2000s, skunk sightings have become rare once again.
Habitat
The island spotted skunk exhibits habitat preferences similar to those of the mainland species. Its dens have been found in various types of locations including, but not limited to, beneath shrubs, open grasslands, rocky slopes, and beneath the roots of large trees. Difference in habitat preference varied slightly between the two islands. Skunks on Santa Rosa mainly being found in rocky canyon slopes, cactus patches, chaparral, coastal sage scrub, open woodland areas, and riparian habitats along streams. On Santa Cruz Island, skunks are found to prefer chaparral-grasslands, open grasslands, fennel-grasslands, and ravines. Skunks were also found to make dens beneath human dwellings and buildings.
Conservation efforts
Action has been taken to try and increase skunk populations on the islands. In the early 1980s 38,000 feral sheep were removed from Santa Cruz Island and cattle ranching operations terminated in 1988. Despite these efforts, feral pigs continue to pose a great threat to skunk populations as their rooting destroys skunk dens. Skunks are specialized in their resources and therefore sensitive to competition with feral pigs for invertebrate foods. The study found that genetic variation between the two island species was not consistent with the morphological variation and was much greater than that of the mainland species. This conclusion has led researchers to hypothesize that spotted skunks were brought to the islands either by rafting or intentionally by Native Americans. The genetic variation between mainland skunks and those on the islands is enough to cause researchers to propose that the taxonomic classification of the skunks as S. g. amphiala be reconsidered, and that each island population be considered a separate subspecies or even a new species separate from the mainland one.