Echolocation--Contrary to popular opinion, bats are not blind. Although they can see quite well, many bats have a sonar system called echolocation for locating prey. Echolocation works by bats’ emitting a series of high-pitched squeals through their mouth or nose (these pulses usually are inaudible to humans). These sounds bounce back to the bats, thus enabling these remarkable animals to navigate in total darkness. The echolocation is so sensitive that bats can detect objects as thin as momofilament fishing line. The echolocation calls, or pulses, are produced in the larynx, or voice box, by forcing air past thin vocal membranes that only bats have. Most bats give signals through their mouth, but some emit pulses through a complex nose structure. Some bats use tongue clicks instead of vocal cords. Usually, the echoes are received by large funnel-shaped ears. Many bats have a vertical flap, called a tragus, inside each ear. The tragus may help direct the incoming echoes. Bats’ ears are specialized for frequencies in the ultrasonic range. Nerve impulses generated by these sounds are transported to the brain for processing. Bats also use echolocation to help them identify their young in crowded
When insect-eating bats search for food, they often emit sounds at 10 pulses per second. Once they locate a meal, bats may emit pulses as high as 200 pulses per second as they chase and capture prey.
Bats are therefore natural “bug” consumers. Large colonies of bats can eat tons of insects each night.
Bat Biology and Lifestyles
Depending on species, bats have many different lifestyles. Some bats are solitary and hang in tree foliage, attics, barns, and other protected places during the day. Other bats are colonial and cluster in caves and
mine tunnels. When they are at rest, bats hang with their heads down.
Male and female bats tend to remain separate in summer. Mating occurs in early fall. However, in a process known as delayed fertilization, sperm is stored in the females’ reproductive system until the following spring when ovulation occurs and embryonic development begins. The young bats, known as pups, are born in spring. The newborn bats are blind and furless and are nursed by their mother until they are 6 weeks old. Young bats begin to fly by the time they are a month old.
Bats have one of the slowest reproductive rates for animals their size. Most bats in northeastern North America have only one or two pups a year, and many females do not breed until their second year. This low reproductive rate is somewhat offset by a long life-span, often over 20 years. The little brown bat, common in North America and in West Virginia, is the world’s longest- lived mammal for its size, with a life-span over 32 years, although it is rare for a bat to live this long.
During the winter, some bats migrate south in search of food, while others hibernate through the cold weather when insects are scarce. Bats that do migrate usually travel less than 200 miles, often following the same routes as migratory birds.
Bats prepare for hibernation by putting on fat to last through the cold weather. Bats may also move from nursery caves suited for rapid growth of their young to cooler caves with stable winter temperatures. When a bat hibernates, its body temperature drops almost to air temperature, and respiration and heartbeat become very slow. Throughout the winter, bats eat nothing, surviving by slowly burning fat accumulated during the summer. Bats can be roused from hibernation fairly easily and may fly around for 15 minutes after being disturbed, thereby