Although they can reach speeds of 40 mph in flight, they usually remain within 1,000 yards or so of their roosts. Sometimes they hunt around street lamps near their roosts. Although usually solitary, these bats occasionally forage in family groups comprised of an adult female and her offspring. Red bats mate between August and October. As with most North American bats, the female stores sperm until spring, when fertilization occurs.
Females have two pairs of mammae.
Pups weigh a mere 0.02 ounce at birth and begin flying when 3 to 4 weeks old. In late fall, western red bats are thought to migrate to and hibernate in the southern part of their range. Dense body fur and various metabolic adaptations allow them to withstand subfreezing temperatures. Hibernating, or torpid, individuals respond very slowly to temperature changes. Laboratory tests indicate they will not arouse until ambient temperatures reach 66 degrees Fahrenheit.