They specialize in eating moths and can travel up to 10 miles during a single evening of hunting. They occur throughout the West and use a variety of habitats, almost always near caves or cave-like roosting areas. They prefer open roosting areas in large rooms and do not tuck themselves into cracks and crevices like many bat species do. Their preference for open spaces in caves makes them easy to detect and vulnerable to vandalism. Summer maternity colonies range in size from a few dozen to hundreds of individuals.
Maternity colonies choose caves that have warm, stable temperatures to rear their pups.
Males remain solitary during the maternity season. Winter hibernating colonies are comprised of males and females and range in size from individuals to several hundred, sometimes thousands of bats. Hibernation sites are chosen based on a narrow range of cold, stable temperatures. Townsend's big-eared bats are very sensitive to human disturbance. Researchers have documented that a single human entry into some colonies has caused the bats to abandon the roost, although not all colonies are that sensitive.