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Smithsonian National Museum of Natural History, North American Mammals

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  Chiroptera · Vespertilionidae · Pipistrellus hesperus

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Pipistrellus hesperus

Western Pipistrelle

Order: Chiroptera
Family: Vespertilionidae

  Click to play (0:04, 415 kb)
Credit: New Mexico Bat Call Library, W. L. Gannon
Image of Pipistrellus hesperus
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Conservation Status: Least Concern.

Western pipistrelles sometimes leave their roosts before sundown, and can be mistaken for late-flying butterflies, because they are so tiny and fly slowly and erratically, with much fluttering of their wings. Most common at low elevations in desert scrub and arid grassland habitats, they are also found in adjacent woodlands. Although they range over the arid West, western pipistrelles require a ready source of water—a lake, stream, or even a swimming pool. They—and some shrews—are the smallest mammals in North America, with weights ranging from 2—6 g. In spite of their tiny size, western pipistrelles usually give birth to twins, which are born and raised in small maternity colonies. The largest colony yet found comprised just four female bats and their eight young.

Also known as:
Canyon Bat

Sexual Dimorphism:
Females are larger than males.

Range: 60-86 mm

Range: 2-6 g


Allen, H., 1864.  Smithsonian Miscellaneous Collection, 7:43.


Mammal Species of the World (opens in a new window).

Distribution of Pipistrellus hesperus

Image of Pipistrellus hesperus
Click to enlarge. (150kb)