The Hoary Bat: One of North America's Largest and Most Widespread Bats

What it looks like

The hoary bat, Aeorestes cinereus, is one of North America's largest bats: it weighs 0.9–1.1 ounces, has a wingspan of 13–16 inches and a body 5–6 inches long. Its thick brownish-gray fur is frosted with white tips, its wing membranes are orange-brown, and its tail membrane is heavily furred.

Behavior

Hoary bats live alone, but mix with other bats while feeding and can be seen flying in large groups in spring and fall, during breeding and migration. They are most active about five hours after sunset, hunting above the treetops, along streams and lakeshores, and in tree-filled towns. By day they roost among tree foliage, and they may become torpid to save energy during the day and between feeding bouts. Like most bats, they echolocate — sending out rapid pulses of very high-pitched sound and listening for the echoes to find their way and their prey in the dark.

Diet

Mostly moths, but also flies, beetles, small wasps and their relatives, grasshoppers, termites and dragonflies. A hoary bat approaches its prey from behind, bites down on the abdomen and thorax, and drops the wings and head.

Habitat and range

They may prefer roosting in trees at the edges of clearings, but also live in dense forest, open woodland and wooded towns. Northern populations are believed to migrate to warmer places for winter, though no wintering sites have yet been found.

It is one of the most widespread bats in the Americas — from Argentina and Chile north through Uruguay, Paraguay, southern Brazil, Bolivia, Peru, Colombia and Venezuela, through parts of Central America, and across most of the United States and Canada, as well as the Galápagos Islands. In Hawaii, it is the only native land mammal.

Raising young

Hoary bats probably mate around the time of fall migration, with delayed fertilization: sperm is stored until eggs are released in spring. Females give birth hanging upside down in their leafy daytime roost, usually to two young in late spring or early summer. The young cling to their mother by day and are left hanging on a twig or leaf while she hunts at night; they can fly after about one month.

Conservation

Hoary bats are widespread and secure over much of their range, but they are among the bats most often killed by wind turbines, and may be vulnerable to deforestation and disturbance. The Hawaiian hoary bat, a subspecies, is listed as endangered by the U.S. Fish and Wildlife Service. White-nose syndrome has devastated some bat species in the eastern U.S., but so far no hoary bat deaths from it have been found.

In the Klamath Network parks

Hoary bats have been recorded in every Klamath Network park except Oregon Caves: uncommon in Lassen Volcanic and Whiskeytown, rare in Crater Lake and Lava Beds, and present in Redwood, where their numbers are unknown.

More: the Animal Diversity Web account, and M. J. Harvey, J. S. Altenbach and T. L. Best, Bats of the United States (1999).

Sources

Based on "Hoary Bats," Featured Creature, May 2015, prepared by Alice Chung-MacCoubrey, National Park Service, Klamath Inventory and Monitoring Network; a work of the United States government in the public domain. Its photographs, a copyrighted image and one by a non-federal photographer, are not reproduced.