BAT IN FLIGHTBrown Bat climbing a wall inside a house attic.BATS KEEPING WARM ON AN ATTIC CHIMNEY


---Bats, like humans, are mammals, having hair and giving birth to living young and feeding them on milk from mammary glands. More than 900 species of bats occur worldwide; they are most abundant in the tropics. Bats are second only to rodents in numbers among mammals and comprise about one-fifth of all mammal species.

Remember that Bats, like all wild animals and other mammals, may be a source of rabies.

 Exclusion or trapping of bats, by law, can not be done from 1 April through 1 September.

Worldwide, bats vary in size from only slightly over two grams (0.07 ounce - about the weight of a dime) to more than 1.5 kilograms (more than 3 pounds). The large "flying foxes" of Africa, Asia, Australia, and many Pacific islands may have a wingspan up to two meters (6 feet). United States bats vary in size from less than three grams (0.11 ounce) to 70 grams (2.5 ounces). The largest United States bat, the greater mastiff bat (Eumops perotis) occurring from central California south into Mexico, has a wingspan of approximately 55 centimeters (22 inches).

Bats are the only true flying mammals, and their maneuverability while capturing insects on the wing is astonishing. Bats belong to the mammalian order Chiroptera, which means "hand-wing." The bones present in a bat's wing are the same as those of the human arm and hand, but bat finger bones are greatly elongated and connected by a double membrane of skin to form the wing.

Bats primarily are nocturnal, although many fly early in the evening, sometime before sunset. Occasionally, especially on warm winter days, they are observed flying during daylight hours.

Reproduction and Longevity. Most female bats produce only one offspring per year, although some species give birth to three or four babies at a time. Most United States bats breed in autumn, and the females store sperm until the following spring when fertilization takes place. The gestation period (pregnancy) lasts only a few weeks, and baby bats are born in May or June. They develop rapidly, and most can learn to fly within two to five weeks after birth. Bats live relatively long lives for animals of their small size, some as long as 30 years.

Echolocation. Although bats have relatively good eyesight, most depend on their superbly developed echolocation (or sonar) system to navigate and capture insects in the dark. Bats emit pulses of very high-frequency sound (inaudible to human ears) at a rate of a few to 200 per second. By listening to the echoes reflected back to them, they can discern objects in their path. Their echolocation ability is so acute they can avoid obstacles no wider than a piece of thread and capture tiny flying insects, even in complete darkness.

Feeding. Insect-eating bats may either capture flying insects in their mouths or scoop them into their tail or wing membranes. They then reach down and take the insect into their mouth. This results in the erratic flight most people are familiar with when they observe bats flying around in the late evening or around lights at night. Bats drink by skimming close to the surface of a body of water and gulping an occasional mouthful.

Hibernation and Migration. Because insects are not available as food during winter, temperate-zone bats survive by either migrating to warmer regions where insects are available, or by hibernating. Hibernation is a state of torpor (inactivity) during which normal metabolic activities are greatly reduced. Body temperature is reduced and heart-rate is slowed. A hibernating bat can thus survive on only a few grams of stored fat during the approximately five-to-six month hibernation period. Bats usually lose from to their body weight during hibernation.

Several bat species hibernate in dense clusters on cave walls or ceilings. Clusters may consist of hundreds of bats per square foot. Summer "maternity" colonies of pregnant or nursing females of several species also congregate and cluster together.

Most United States cave bats spend winter hibernating in caves (or mines) and move to trees or building during summer. A few species reside in caves year-round, although they usually use different caves in summer than winter. Most cave bats are very loyal to certain caves and return year after year to the same caves, often to the exact location in the cave where they spent the previous winter.

Tree bats seldom enter caves. They roost in trees during summer days and spend winter primarily in hollow trees. Several species make relatively long migration flights between winter and summer habitats. The millions of Brazilian (or Mexican) free-tailed bats (Tadarida brasiliensis) that spend the summer in southwestern United States caves, such as Carlsbad Cavern in New Mexico, migrate up to 1,300 kilometers (800 miles) to and from their winter roosts in Mexico.