Townsend’s Big-eared Bat

Scientific name: Corynorhinus townsendii
Classification: Bat, mammal
Size: Wingspan is 12-13 inches (30-34 centimeters). 0.3-0.5 ounce (8-14 grams).


Medium-sized bat with extremely long ears and a small glandular outgrowth on each side of the snout. Dark-brown on back, lighter-brown on sides, underparts slightly paler. The membrane between hind legs full, wide and hairless. The combination of large flexible ears, nearly uniform color, and the lumps on the snout identify this bat.


Life Span:

Townsend’s big-eared bats may live 16 or more years.



Found throughout nevada, from low desert to high mountain habitats. Concentrated in areas offering caves or mines as roosting sites and preferring caves and mines where the temperature is 54 degrees f. (12 degree c.) Or less but usually above freezing.



Western canada, the western united states to southern mexico, and a few isolated populations in the eastern united states. No long-distance migrations are known.


Natural History:

Bats, like humans, are mammals. Every species has fur, a warm body temperature, gives birth to young that are not enclosed in an egg, and produce milk from mammary glands.

Bats have a superb echolocation system (sonar) that enables them to detect the precise whereabouts of any object, even tiny flying insects. Ultrasonic sounds made by bats as they fly through the air function to guide them through their habitat and to secure prey. The sound waves bounce off objects and return to the bat’s ears. Size, composition, and distance of each object can be assessed with incredible accuracy through the use of this echolocation technique.

Many bats, including townsend’s big-eared bat, are major predators of night-flying insects, including mosquitoes and numerous crop-eating insects. Unlike birds who capture insects with their mouths, bats use the membrane of their wings and tail to catch prey. Only after capture, and while still flying, do they reach back and bite, kill and swallow their prey.

Townsend’s big-eared bats hibernate up to seven months of the year in caves often near the entrance in well-ventilated areas. They move to more stable parts of the cave if temperatures near the entrance become extreme. Hibernation occurs in cluster of a few bats to more than 100.

Their long ears may be erect or coiled during hibernation. Solitary bats sometimes hang by only one foot.

Maternity colonies usually are located in the warmer parts of the cave. Males are apparently solitary during the maternity period. It is unknown where the males spend their summer.

No long-distance migrations are known, but they return year after year to the same roost sites.


Food Habits:

Townsend’s big-eared bats are believed to feed entirely on moths. Foraging occurs near vegetation and other surfaces and prey is probably gleaned from these surfaces.



Mating begins in autumn and continues into winter. Females store the sperm in their bodies during the winter, and fertilization occurs shortly after arousal from hibernation. One large baby, called a pup, weighs about 25% as much of its mother and is born may to july. It can fly in two and half to three weeks and is weaned by six weeks.



Unprotected. It is a former category 2 candidate for federal listing as threatened and endangered.


Reason for Status:

Serious population declines in the past forty years in parts of the western states have been noted. Roost size reductions have been documented in nevada. It has been proposed for state-protected status and is further classified a sensitive species in the “nevada bat plan”.


Management &Conservation:

Highly sensitive to disturbance at roost sites including: recreational caving; closure of mines for reclamation; renewed mining; survey methodology water impoundments; loss of building roosts; and bridge replacement. Management and conservation actions for this species have been incorporated into the “nevada bat plan” and other efforts.


Fun Facts:

Townsend’s big-eared bats can maneuver like helicopters to pluck insects from leaves or to drink from tiny pools. If you listen carefully on a warm summer night, you can hear individual bats emit calls which are audible to humans (sounds like clicks). These sounds are usually to communicate with other bats. Ultrasonic sounds are inaudible to humans and are used to locate prey. Contrary to popular beliefs, bats are not blind, do not become entangled in human hair, and seldom transmit disease to other animals or humans.
Some people think of bats as “flying rats,” but they are actually more closely related to primates, including humans, than mice.

Bats are the only mammals capable of true flight. Bats have lived in america since the age of dinosaurs.

Many garden pests can hear bats from over 100 feet away and will avoid areas where bats are present.

Bat droppings in caves support whole ecosystems of unique organisms, including bacteria useful in detoxifying wastes, improving detergents, and producing gasohol and antibiotics.