Western Pipistrelle

Pipistrellus hesperus

Western pipistrelles begin their foraging flights very early in the evening hours, making them one of the most diurnal of North American bats. The Western pipistrelle (Pipistrellus hesperus) is the smallest bat in the United States.

Family:

Vespertilionidae (evening bats and vesper bats)

Description:

Western pipistrelles are small brown-gray bats with distinct black, leathery facial mask, ears, and patagium. Beneath, they are pale brown-gray. This tiny bat can weigh only up to 6 g or .21 ounces. Total length less than 3 inches.

Habitat:

Western pipistrelles inhabit a variety of habitats, ranging from rocky canyons, cliffs, and outcroppings to creosote bush flats. They are the most abundant of North American bats that are found in deserts, but are found at higher elevations in arid brush lands, grasslands, and even some forests. Water is a very important resource determining the distribution of this bat. Because of the high proportion of protein in their diet, the arid environment that they inhabit, and the subsequent high levels of evaporative water loss, western pipistrelles generally roost close to a water source.

Range:

Western pipistrelles occur from southern Washington to the southern portion of Mexico including the Baja peninsula. Stretching from the west coast of California, its range includes Arizona and New Mexico, spreading into western Texas and extreme western Oklahoma.

Diet:

Western pipistrelles are insectivorous bats that feed on a variety of insects depending on the time of year. Prey items are located using echolocation. They can consume about 20% of their weight in insects per night.

Breeding:

Copulation and insemination first occur in the fall. Sperm may be retained within the female through the winter. Young are born in June and July, after a 40 day gestation period. There are usually two offspring.

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