Sperm is stored in the uterus, and ovulation and fertilization are delayed until spring when the female emerges from hibernation. The young begin to fly at 18 days of age. After three weeks they have reached their adult size. Females reach sexual maturity by the end of their first year but males are not sexually active at all in their first year. Little Brown Bats eat a variety of small flying insects that include midges, mosquitoes and mayflies.
Bats are relatively quiet creatures.
The high-intensity FM echolocation used by the Little Brown Bat is difficult for the human ear to detect. Clicks can sometimes be heard as they are hunting and diving for food and especially when they are distressed. The accumulation of urine and feces, in an established colony inside a building, can be a cause for concern. A fungus that finds ideal growing conditions in this built up fecal matter can cause a lung disease called Histoplasmosis. Another concern is the incidence of rabies in bats, however, it is much lower than that in other native mammals.