Wildlife Database Detail

U.S. DEPARTMENT OF THE INTERIORBUREAU OF LAND MANAGEMENT
California

	Western Pipistrelle Parastrellus hesperus 1-National Park Service; 2-USGS, Western Ecological Research Center
Type of Animal:	Mammals
Class:	Mammalia
Order:	Chiroptera
Family:	Vespertilionidae
Federal Status:
State Status:
Occurrence:
Habitat:	Desert,Scrubland,Caves,Mines
Description:	Western pipistrelles are the smallest bats in the United States at less than four inches long! They are also one of the smallest mammals in the world, falling second only to shrews. They are abundant in their range and are relatively easy to identify. Pipistrelles have yellow-brown body hair with dark black faces that look like masks. In flight, this species is both slow and erratic, unlike most other bats. Western pipistrelles are typically the first bats to appear each night within their range. They may emerge from their roosts as early as one hour before sunset. Most individuals have retreated back to their roosts by two hours after sunset. They are also occasionally seen flying during the day. During this period of activity they feed on a variety of insects and drink water by dipping their lower jaws into a pond or stream while in flight. This species roosts in rock crevices near permanent water sources. In cold areas, they may hibernate in caves and abandoned mines. In spring and summer females may be found in maternity colonies. Most bat species form large maternity colonies with over 100 individuals, but western pipistrelles are unique in that they form small colonies with up to only 12 individuals. Females produce one litter of two young each year. The young are born in June and are completely independent by July. This bat was classified as Pipistrellus hesperus until 2006. Bats are the only true flying mammals, and they occur in almost all areas around the world. There are 1000 species of bats, 46 of which occur in the United States. Bats make up 25% of all mammals. Unfortunately there are many myths about bats. They are not blind and do not become entangled in human hair. Some bats may carry rabies, but not all. In fact, less than 1% of the population carries rabies. The best way to avoid contracting rabies from them is to not handle them. Bats typically only bite in self-defense and will leave humans alone unless provoked. Like all bats, western pipistrelles are a very important component of our ecosystem. Bats are nocturnal and begin flying soon after sunset. During this time they forage for flying insects such as moths, beetles, flying ants, and mosquitoes. They depend on echolocation to locate their prey. The bats emit short, high-pitched sounds that echo. By listening to the echo they are able to figure out where obstacles are located, even obstacles as thin as a piece of thread! Bats are natural predators of the insects that are considered to be agricultural pests. Without bats, farmers would be forced to increase their use of chemical pesticides, which could increase the price of our produce and cause negative effects on other wildlife that live in and around agricultural areas. In desert habitats, bats are the primary pollinators of giant cacti. The bat population is in steady decline due to numerous factors. The main reason for the decline is human interference, such as habitat destruction and alteration. Bats live in natural structures like caves, but they also live in manmade structures such as bridges and abandoned mines. Vandalism in these areas drives the bats away and kills many of them. Activities such as building bonfires under bridges can also cause them to die from smoke inhalation. Many bridges and mines also contain maternity dens, so these detrimental activities not only kill the adults but the new generations as well. You can help protect bat populations by avoiding areas that may contain bats. If you must enter a bat roost area, be careful to leave the area as you found it.
Effort:
References:	Jameson et al. 1988. California Mammals. Wilson et al. (editors). 1999. The Smithsonian Book of North American Mammals. Whitaker (editor). 1998. National Audubon Society Field Guide to North American Mammals, Revised Edition. Zeiner et al. (editors). 1990. California’s Wildlife, Volume III, Mammals. Hoofer, Van Den Bussche,Horáček, Journal of Mammology 2006, "Generic status of the American pipistrelles (Vespertilionidae) with description of a new genus"
Other Sites:	Life history account, California Dept. of Fish and Game (PDF file)
Field Office(s):	Bakersfield; Barstow; Eagle Lake; Mother Lode; Palm Springs; Redding; Ridgecrest; Ukiah