Upon leaving their roosts to feed, bats usually first fly to a pond or other water source to drink. A second feeding period may occur just before daylight. Most bats in the United States and Canada are insectivorous, catching small flying insects, many harmful, by sonar or echolocation. Some bats may consume up to one-half their weight of insects in a night. Many of the insects reported are harmful.
Many animals use sonar to navigate, locate, and avoid obstacles.
Bats use sonar for those purposes and to capture flying insects. High-frequency sounds, inaudible to humans, produce echos permitting bats to measure distance. Bats also make audible sounds. In the United States bats mate in the fall and winter but the female may retain sperm in the uterus until spring when ovulation and fertilization take place. Pregnant females congregate in nursery colonies in caves, mines, buildings, or other dark retreats.