They primarily feed on moths, although they are known to also glean insects from the ground and off vegetation. The Townsend's big-eared bat is listed as a US Fish and Wildlife and a California species of concern and a Forest Service sensitive species. Once considered the rarest mammal in North America, a living spotted bat was not observed until the mid 1950's. However, we now know they are more widespread, although they remain uncommon and patchy in occurrence, preferring wild, undisturbed areas. Spotted bats are moth specialists.
Many moths have a simple hearing system to avoid bats by detecting their echolocation calls.
Spotted bats stealthily avoid such detection by emitting their primary echolocation call at lower, humanly audible, frequencies, and at lower amplitude. The lower amplitude calls require larger ears to detect the returning echoes of their calls. The spotted bat is listed as a US Fish and Wildlife and a California species of concern.