Overview
Townsend’s Big-eared Bat (Corynorhinus townsendii) is a medium-sized vesper bat celebrated for its colossal ears, which reach up to nearly four centimeters in length—over one-third of its total body length. Distributed predominantly across the canyonlands and mountains of western North America with rare relict subspecies in the eastern United States, it is a quintessential cave dweller with an exquisite specialization for hunting moths.
Biology and Physical Characteristics
The most arresting physical feature of Townsend’s Big-eared Bat is its extraordinary pair of ears, which are connected across the forehead at their base. When the bat is at rest or in winter torpor, it curls its long ears backward in an intricate spiral resembling ram’s horns against its back. Its fur is soft and loose, ranging from pale cinnamon to slate grey, and its muzzle features two prominent glandular lumps on either side of the snout, which secrete musky pheromones during breeding season.
Behavior and Ecology
This bat is an agile, low-speed flier capable of hovering in mid-air to glean resting moths from foliage, rock faces, and tree trunks. Over 90 percent of its diet consists of lepidopterans (moths). To circumvent the sensitive ultrasonic ears of nocturnal moths, Townsend’s Big-eared Bat emits exceptionally quiet, whisper-soft echolocation pulses (whispering echolocation), stalking its prey undetected until it strikes with pinpoint accuracy.
Conservation and Human Impact
While classified globally as Least Concern by the IUCN, Townsend’s Big-eared Bat is exceptionally sensitive to human disturbance at roost sites. A single human intrusion into a winter hibernaculum can cause bats to awaken, depleting critical fat reserves and causing mortality. Two eastern relict subspecies (the Virginia and Ozark big-eared bats) are federally listed as Endangered in the United States, spurring cave gating and habitat protection initiatives.
Interesting Factoid
When hibernating, Townsend’s Big-eared Bat rolls its massive ears into tight spirals like miniature ram’s horns to protect the delicate skin from frostbite and prevent moisture loss.