Townsend’s Big-eared Bat

Identification

Townsend's big-eared bat is a medium-sized bat weighing 7–12 grams, with a total length around 10 centimeters and wingspan of approximately 28 centimeters. Its most distinctive feature is a pair of extremely long, flexible ears that dominate its appearance. The bat also displays small yet noticeable lumps on each side of its snout, another identifying characteristic that sets it apart from similar species.

Range & Habitat

This species is found throughout much of North America, ranging from southern British Columbia down the Pacific Coast and into the Great Plains, as well as Central Mexico. The species also maintains two isolated populations in central and eastern parts of the United States. A notable population inhabits Santa Cruz Island in the Channel Islands, California, where it was originally described and remains the only known colony in the Channel Islands; this colony currently resides in the Scorpion adobe building.

Townsend's big-eared bats require large cavities for roosting, including abandoned buildings and mines, caves, and basal cavities of trees. During summer, they inhabit rocky crevices, caves, and derelict structures. In winter, they hibernate in rocky crevices, caves, tunnels, mineshafts, spaces under loose tree bark, hollow trees, and buildings.

Behaviour & Diet

This species is a specialized moth hunter, feeding almost exclusively on Lepidoptera, though its diet may also include small flies, lacewings, dung beetles, sawflies, and other small insects. As a "whisper bat," it echolocates at much lower intensities than other bat species, making it difficult to detect with standard bat detectors. This quiet echolocation may be an adaptation to hunting moths, many of which can hear bat calls and employ defensive countermeasures. The bats exhibit 2–3 feeding periods between dark and dawn, interspersed with rest periods in locations separate from their daytime roosts.

Mating occurs in late fall, with females storing sperm through winter and fertilization happening in spring. A gestation period of 50–60 days produces a single pup per female. During summer, males and females roost separately; males typically remain solitary while females form maternity colonies ranging from 12 to 200 individuals (though colonies exceeding 1,000 have been recorded in the eastern United States). In winter, these bats hibernate singly or in small clusters, frequently waking to move within or between caves. One study recorded an average lifespan of 16 years.

Best Time & Places to See It

Summer is the best season to observe Townsend's big-eared bats, particularly in areas with suitable roosting habitats such as caves, abandoned mines, and old buildings. The species is most active during warm months when females gather in maternity colonies. The Santa Cruz Island population offers a notable opportunity for viewing, though access to the island may be restricted. Look for these bats emerging at dusk from their roosting sites near rocky terrain or abandoned structures.

Photography Tips

The bat's distinctive long ears and facial lumps make it visually striking when photographed, but capturing clear images requires patience and specialized equipment. Since these bats use quiet echolocation and are difficult to detect with standard bat detectors, locating them may require knowledge of local roosting sites. Photograph them during emergence times at dusk using high-speed flash or infrared equipment. Their slow, maneuverable flight—reaching speeds of only 2.9 to 5.5 meters per second—makes them easier to photograph in flight compared to faster-flying bat species, particularly when they hover near insects.