Antrozous pallidus
(Pallid Bat)

Order: Chiroptera
Order Description: Bats
Family Description:

The dorsal fur is yellowish to pale-creamish brownish. The ears are large, up to five-eights of an inch (=15mm) across at the base and broadly rounded along the margin. The tragus Click word for definitionis less than one-half of the length of the ear.

Southern British Columbia south along the western and southern section of Idaho, most of Wyoming, and south west through Utah, Colorado, Kansas, western Oklahoma, Texas and Mexico, then west including Baja California and along the Pacific Coast through California, Oregon and the central portion of Washington. Specimens have been collected or identified at roosts in seven counties in Idaho.

Pallid bats frequent arid or semi-arid shrub steppe Click word for definition, grasslands and, to a lesser extent, higher elevation coniferous Click word for definitionforests. They roost Click word for definitionin rock crevices, mines, hollow cavities in trees, and occupied or vacant buildings. They may also roost in objects placed on the ground.

This species usually feeds on ground dwelling arthropods, gleaning scorpions, Jerusalem crickets, cicadas, beetles or smaller insects associated with flowers and cactaceous plants. Lesser amounts of flying insects appear to be consumed.

Pallid bats are gregarious Click word for definitionand may feed together at sites containing abundant prey. Because they have larger eyes than bats in the genus Myotis, feeding is likely aided by both sight and passive sound that indicates the location of moving prey. Maternity colonies may be large and move in relation to temperature conditions. Warmer temperatures are selected at maternity roosts. The winter ecology of this species is poorly documented. Individuals do not appear to migrate Click word for definitionor to hibernate Click word for definitionfor long periods and individuals have been observed flying during cold weather. Night roosting individuals emit audible calls that likely indicate the location of a group to other flying individuals but the exact function of these calls is poorly understood.

Species is gregarious Click word for definition. Usually forms clusters in diurnal Click word for definitionroosts Click word for definition(Yuma myotis may roost among pallid bats). May also gather in night roosts that are frequently near, but separate from, day roosts (40-75% of time away from diurnal roost may be spent at night roosts). Usually roosts in rock crevice or building, less often in cave, tree hollow, or mine (in Oklahoma, night roosts are typically in caves). Emerges from day roost relatively late; foraging peaks at beginning and end of nocturnal Click word for definitionactivity cycle. Captures prey on ground, after an aerial search; also takes prey in flight, within few meters of ground vegetation. Bimodal foraging Click word for definitionand audible communication is known. Species is largely inactive in winter, and is believed to hibernate Click word for definition(in Idaho, species is migratory).

Breeding occurs between October and February and sperm is stored until spring ovulation Click word for definition. Maternity colonies form in May or June. From one to three pups are born likely depending on the parity Click word for definitionof the female.

Copulation Click word for definitionusually occurs from October-December; fertilization Click word for definitiontakes place in spring. In U.S., usually 2, but sometimes 1, young are born from: late May-early June in California; mostly late June in Kansas; and probably early May to mid-June in Texas. Young fly at 6 wk, and are weaned in 6-8 wk. Maternity colonies are usually small, but may include up to 200+ adults, including some adult males.

Status: Unprotected nongame species
Global Rank: G5
State Rank: S1

Important State References:
Keller, B.L. 1987. Analysis of the bat species present in Idaho, with special attention to the spotted bat, Euderma maculatum. Dept. Biol. Sciences, Idaho St. Univ., Pocatello. 25pp.

Information written by Barry Keller,© 2000
Map image provided by
Stephen Burton,© 2000
Design by Ean Harker©1999, 2000.