The following is an excerpt from Wildlife of Nebraska: A Natural History by Paul A. Johnsgard (Bison Books, 2020).
From Chapter 2: Mammals
Family Vespertilionidae (Vesper Bats)
Bat. Corynorhinus townsendii .
HL (NW), Ra
Identification: This easily identified pale-brown bat has huge ears (up to 1.5 in. long) and unique fleshy glandular growths on each side of its snout. (It was once called the lump-nosed bat, and its
Latin name translates as Townsend’s club-shaped nose.) Total length 90–112 mm (3.5–4.4 in.); wingspan 30–34 cm (11.8–13.3 in.); weight 9–13 gm (0.3–0.4 oz.).
Voice: This species is a “whisper bat,” echolocating at much lower sound amplitudes than other bats, and thus it is difficult to obtain sound recordings. For humans to hear the sounds these bats produce while echolocating, it is necessary to reduce the playback speed to one-tenth the recording speed. Their sound pulses range in duration from several to a few hundred per second. Ultrasonic frequencies above 20 kHz (20,000 cps) are used for prey detection and identification, since only extremely high frequency sounds will be reflected back from tiny objects such as moths as small as 3–10 mm (0.1–0.4 in.) in length. Lower-frequency sounds serve for general in-flight
orientation, such as avoiding large objects. Vocalizations below 20 kHz are used for social interactions, such as adjusting spacing behavior in colonies, mother-offspring interactions, aggression, and warning calls.
Status: This remarkable-appearing species is rare, occurring only in northwestern Nebraska, and so far is reported only from Sheridan County. These bats might become active as early as late afternoon but usually begin feeding after dark, with most foraging occurring four or five hours after sundown. Big-eared bats are a hibernating species and often choose old mines or caves as hibernacula. A hibernaculum in Jewel Cave, Black Hills, is one of the largest known in the United States (Higgins et al. 2002). They are also fairly sedentary, not moving far from their summer home ranges to their winter quarters. Home ranges have been estimated at 200–5,900 acres (0.8–24 sq. km) (Armstrong, Fitzpatrick, and Meaney 2011).
Habitats and Ecology: This bat’s huge ears not only are used to transmit sound into the bat’s ear canal but also might even help to impart lift during flight. When the bat is sleeping the ears are
rolled back over the head, resembling a ram’s horns. Rather than specializing entirely on eating moths (about 80 percent of their diet), these bats also eat caddisflies, flies, and other insects.
Breeding Biology: The “lumps” on the side of the nose of this bat are glandular, and males scent-mark their courted females prior to copulation. Mating occurs during fall and winter while the bats are in their hibernacula, and sperm is stored until spring. Gestation lasts 56–100 days, with the single offspring being born in May or June. Initial flight occurs about three to four weeks of age, and weaning is completed by six weeks.