Hoary Bats

Hoary bat face, male

Copyright J.N. Stuart, Stuart Wildlife (https://www.flickr.com/photos/stuartwildlife/6223243823/in/photolist-atYrjs-atVKzi)

General Description

The hoary bat, Aeorestes cinereus, is one of North America’s largest bats, weighing from 0.9-1.1 ounces, and having a wingspan of 13-16 inches and a body length of 5-6 inches. They have a luxurious coat of brownish-gray fur with frosted white tips, orange-brown wing membranes, and a heavily furred tail membrane.

Behavior

Hoary bats are solitary, but associate with other bats while feeding and can be seen flying in large groups in spring and fall during the time of breeding and migration. Hoary bats typically reach their peak activity at five hours after sunset. They forage above the tree tops, along streams and lake shores, and in urban areas with abundant trees. They spend summer days roosting amongst the tree foliage. To conserve energy, they may become torpid (sluggish) during daytime hours and between feeding bouts at night. Like most bat species, hoary bats use echolocation to navigate and capture insects in the dark. They emit rapid pulses of very high-frequency sound and listen for the echoes to detect objects in their path.

Feeding

Hoary bats predominantly eat moths, but may also feed on flies, beetles, small wasps and their relatives, grasshoppers, termites, and dragonflies. To catch its prey, the hoary bat approaches from behind, takes the insect’s abdomen and thorax in its mouth, and bites down, dropping the wings and head.

Habitat

Hoary bats may prefer roosting in trees at the edge of clearings, but are also found in heavy forests, open woodlands, and treed urban areas. Northern populations are believed to make seasonal migrations to warmer winter habitats, but overwintering sites have yet to be documented.

Reproduction

Hoary bats are thought to mate about the time of fall migration. Mating is likely followed by delayed fertilization, a process in which the sperm is stored and later used to fertilize eggs ovulated in the spring.

Hoary bats give birth to their young while hanging upside down in their daytime leafy shelter. They typically have two young in late spring to early summer. The young cling to the mother during the day, but are left hanging onto a twig or leaf while she forages at night. They can fly on their own after about one month.

Conservation Status

Hoary bats are widespread and secure over much of their range. However, this is one of the most common bat species to be killed by wind turbines, and it may be susceptible to deforestation and human disturbance. One subspecies, the Hawaiian hoary bat, is listed as endangered by the U.S. Fish & Wildlife Service. The fungus that causes white-nose syndrome has devastated some bat species populations in the eastern U.S. but so far, no such mortalities of hoary bats have been found.

Distribution

The hoary bat is one of the most wide-ranging bat species in the Americas. It is found in South America, from Argentina and Chile, north through Uruguay, Paraguay, southern Brazil, Bolivia, Peru, Colombia and Venezuela, through parts of Central America, and into most of the United States and Canada. It also occurs in the Galapagos Islands. In Hawaii, the hoary bat is the only native terrestrial (non-marine) mammal.

Where to See Locally

Hoary bats have been documented at all Klamath Network parks except Oregon Caves. They are uncommon in Lassen Volcanic and Whiskeytown and rare in Crater Lake and Lava Beds. They are present in Redwood, but their abundance is unknown.

More Information

http://animaldiversity.org/accounts/Lasiurus_cinereus/
Harvey, M. J., J. S. Altenbach, and T. L. Best. 1999. Bats of the United States. Arkansas Fish & Game Commission.

Prepared by Alice Chung-MacCoubrey
NPS Klamath Inventory & Monitoring Network
Southern Oregon University
1250 Siskiyou Blvd
Ashland, OR 97520

Featured Creature Edition: May 2015

Thumbnail image by Dr. J. Scott Altenbach