Mammals
Townsend's Big-Eared Bat
Corynorhinus townsendii · also called Townsends big-eared bat, lump-nosed bat
Hanging in a dense winter cluster with its enormous ears curled back like rams’ horns, a Townsend’s big-eared bat depends on one thing above all else for survival: being left completely undisturbed by visitors to the cave it calls home.
Overview
Townsend’s big-eared bat, Corynorhinus townsendii, is an insect-eating mammal native to mountain and forest habitat across a broad range spanning western North America. Its extraordinarily long, distinctively curled ears, extreme sensitivity to roost disturbance, and ability to evade the defensive hearing of certain moth species make it one of the more acoustically specialised and conservation-sensitive bats found anywhere in North America.
A bat that can’t tolerate visitors
Few bats respond as poorly to human disturbance as Townsend’s big-eared bat, which can abandon an entire roost site permanently after repeated visits, making the protection of undisturbed caves and mines essential to the species’ long-term survival.
Status
Least Concern overall, though several regional populations have declined due to roost disturbance, and some subspecies face more serious conservation concern than the species as a whole.
Townsend's Big-Eared Bat: common questions
How big are Townsend's big-eared bat's ears?
This species has extremely long ears, proportionally among the largest of any North American bat, nearly matching the length of its own body when fully extended, an adaptation believed to aid its highly sensitive echolocation and moth-hunting abilities.
What does Townsend's big-eared bat do with its ears at rest?
This species curls its long ears back like rams' horns while resting or hibernating, a distinctive posture that helps distinguish it from other big-eared bat species and reduces the ears' exposed surface area during inactivity.
Why is Townsend's big-eared bat vulnerable to human disturbance?
This species is unusually sensitive to disturbance at its roost sites, and repeated human visits to caves or mines, even without direct contact, can cause an entire colony to abandon the site permanently, making roost protection an important conservation priority.
How does Townsend's big-eared bat catch moths that can hear it coming?
This species produces echolocation calls at frequencies that can help it avoid detection by certain moth species capable of hearing incoming bat calls, giving it a meaningful edge in an ongoing evolutionary contest between predator and prey.