Weight:  8-14 grams

Wingspan:  30-32 centimeters

Distribution:  Western Canada, the western United States to southern Mexico and a few isolated populations in the eastern United States

Ecology and Behavior: These bats hibernate in caves or mines where the temperature is 12°C (54°F) or less, but usually above freezing.  Hibernation sites in caves often are near entrances in well-ventilated areas.  If temperatures near entrances become extreme, they move to more thermally stable parts of the cave.  They hibernate in clusters of a few to more than 100 individuals.  During hibernation, the long ears may be erect or coiled.  Solitary bats sometimes hang by only one foot. Maternity colonies usually are located in relatively warm parts of the caves.  During the maternity period, males apparently are solitary.  Where most males spend the summer is unknown.  No long-distance migrations are known.  Like many other bats, they return year after year to the same roost sites.

Food habits: It is believed to feed entirely on moths

Reproduction:  Mating begins in autumn and continues into winter.  Sperm are stored during winter and fertilization occurs shortly after arousal from hibernation.  One baby is born in June.  Babies are large at birth, weighing nearly 25% as much as their mother.  They can fly in 2.5-3 weeks and are weaned by 6 weeks.  Lifespan may be 16 or more years.

Status of Populations:  Locally common in the western United States, but eastern populations are endangered.




Thanks to T. L. Best, J. S. Altenbach, and M. J. Harvey for permission to reprint portions of Bats of the Western United States, 1998.