Santa Barbara Island Closed Due to Storm Damage
Santa Barbara Island is currently closed to public access due to damage from the high surf associated with Hurricane Marie. More »
San Miguel Island Closure
In the interest of public safety, the U.S. Navy is closing San Miguel Island until further notice due to recent concerns of possible unexploded ordnance. More »
Townsend's Big-eared Bats
Quick and Cool Facts
On the Channel Islands, big-eared bats are found only on Santa Cruz Island. The species was first observed in 1939 on Santa Cruz Island in a historic 2-story ranch house at Prisoner's Harbor, which hosted a large maternity colony of over 300 individuals. Subsequent studies showed that the population resided in the same area until 1974, when the structure was removed. From 1974 to 1988, no other Townsend's Big-eared Bats were seen on Santa Cruz Island, before Dr. Pat Brown of UCLA, in 1991, was made aware of a colony of Townsend's roosting in the bakery room of the Scorpion adobe building. Presently, a large maternity colony continues to use the building and, occasionally, the rock caves in the Scorpion area. According to the 1994 Department of Fish and Game report, the Scorpion roost is one of only two or three coastal maternity colonies known to exist south of Pt. Conception.
In the summer, the females form a nesting roost. Males are solitary during the maternity periods. The maternity colonies consist of one or more small clusters, which rarely exceed 100 bats. Females are alert and active in the maternity roosts and prefer dark places for their roosts. These colonies form between March and June (depending on climate), with pups born between May and July. Maternity colonies choose sites that have warm, stable temperatures for pup rearing. Female bats usually only have one young a year. The newborns range in weight from 2.1-2.7 grams. There is a strong maternal bond and the young bats squawk when the mother is away. The young bats, however, grow quickly, being able to fly within three weeks. After two months, many of the young bats have left the nursery roosts, with male bats leaving before female. In their first year, male bats are almost certainly incapable of breeding while female bats are able to reproduce at the age of four months.
A study sponsored by the California Department of Fish and Game in the late 1980's documented a population decline of 40-60% in the past 30 years. Only about half of the maternity colonies known to exist in California prior to 1980 were active by 1991, resulting in an estimated 54% decline of adult females. Only three maternity colonies increased in size during the period, and all three are located in National Park areas (Point Reyes National Park, Lava Beds National Monument, and Pinnacles National Monument). Of the 23 roosts that are no longer available to bats, 9 (mostly buildings) have been demolished, 4 (all buildings) have burned, 4 (all buildings) have been renovated in such a way that bats were excluded, and 6 (including buildings, caves, mines, and a water diversion tunnel) have had the entrance closed.
Consequently, for this species to exist, minimization of human disturbance is essential. In additional, it is essential that habitat be preserved.
Human intervention may have helped conserved the population on the west coast of North America, because man-made structures provide a shelter for big-eared bats.1 Channel Islands National Park staff continues with a program of monitoring and surveying this species to ensure its well-being.
In 2008, the ICUN listed this species as Least Concern because of its wide distribution, presumed large population, the occurrence in a number of protected areas and because it wasis unlikely to be declining at nearly the rate required to qualify for listing in a threatened category. However, today the Townsend's Big-eared Bat, is state-listed as an Endangered species in Washington, a Sensitive species in Oregon, and as a Species of Special Concern in Texas, Montana and California, and they are on the Blue List in British Columbia.
Did You Know?
The Channel Islands are home to the most well-preserved archeological sites on the Pacific coast, with more than 10,000 years of continuous human occupation recorded.