RELEVANT NATURAL HISTORY
Bats first appeared on Earth more than 55 million years ago, long before the advent of humankind. Over time, bats diversified and eventually comprised ¼ of all mammal species. Wherever they lived, bats played a vital role in the ecology of that region. Today, there would not be diverse ecosystems, from rain forests to dry cactus forests, if not for bats.
Bats can be found almost everywhere on earth, where they play vital roles as pollinators, seed dispersers, and as a natural insect control. More than 500 species of crop plants and 530 flowers rely on bats for pollination and/or insect control. Currently, there are 1400 known kinds of bats, ranging in size from bumblebee (Kitty’s hog-nosed bat – Thailand) to eagle size (Golden-crowned flying fox, Philippines). Forty-four kinds inhabit North America, and nine kinds call Connecticut home.
All of Connecticut’s bats are insectivores. They range in size from an 8” wingspan (Tri-color and Eastern small-footed bats) to a 16” wingspan (Hoary bat). All nine kinds consume countless numbers of insects annually, including those that harbor pathogens and those that destroy crops.
Connecticut’s bats: Big brown bat (Eptesicus fuscus), Little brown bat (Myotis lucifugus), Northern long-eared bat (Myotis septentrionalis), Eastern small-footed bat (Myotis leibii) Tri-color bat (Perimyotis subflavus), Indiana bat ( Myotis sodalis), Eastern red bat (Lasiurus borealis), Hoary bat (Lasiurus cinereus), and Silver-haired bat (Lasionycteris noctivagans). The first six are classified as crevice bats, the remaining three are migratory foliage-roosting bats.
Bats are not flying mice. The order is Chiroptera (hand-wing), which includes two extant groups, Megachiroptera (Old World Fruit Bats) and Microchiroptera (echolocating bats). All of New England’s bats are Microchiroptera.
Hand-wing: Bats are the only mammals capable of true powered flight, an adaptation that evolved early in bat ancestry. Bats have five fingers. The thumb protrudes from the top (leading edge) of the wing and is used for climbing and grooming. A bat’s fingers are elongated and connected by the wing membrane, a double layer of tough, elastic-like skin. A bat’s wings are very flexible and the bat makes necessary adjustments to the wing shape during flight.
Bats have remarkably long lifespans not found in other small mammals. For example: big brown and little brown bats have a natural life expectancy of 30 plus years.
Hibernation and migration: As winter approaches, some species of bats migrate to warmer states (foliage bats), while others hibernate (crevice bats). Hibernation is a state of deep sleep; bats enter into this state in autumn, and awaken to emerge in early spring. Bats seek sites that maintain a steady cool/cold temperature and adequate humidity. During hibernation, bats rely on stored fat reserves.
Bats are not blind; they have very good eyesight. However, for hunting and navigating at night, microchiroptera rely on echolocation, an innate, highly sophisticated sonar system that enables bats to “see with their ears.” A hunting bat emits sound waves from its mouth that pinpoint exactly where objects are. The echoes bounce off the object and back to the bat’s highly specialized ears. The bat receives the information loud and clear, but the sonar signals are above the range of human hearing.
Bats communicate with each other through “social calls,” which are within the range of human hearing. Bats also use vocalization as warnings when they feel threatened, and a youngster will vocalize if separated from their mother.
Bats use various natural and man-made structures for shelter, including caves, mines, ledges, tree cavities, buildings, and tunnels. Some bats prefer living alone (foliage bats), while other species reside in colonies (crevice bats). Where bats choose to roost is often determined by the season. In the winter some may hibernate in caves or abandoned mines, and in the summer they’ll choose an attic, barn, or bat house.
Most bats roost in an upside-down orientation. Specialized tendons in their feet lock into place, enabling them to do so without falling. Bats don’t weigh enough for gravity to affect their blood flow so they don’t get lightheaded, but bats do use gravity to fall into flight. Hanging upside down is the most energy-efficient way to take off because a bat cannot run along the ground with enough speed to easily attain flight. There are some exceptions: the pallid bat of the southwest, some free-tail bats, and the vampire bat of Central and South America can take off from the ground without effort.
Mating ensues just prior to hibernation and/or winter migration. The female stores the sperm overwinter, and gestation takes place the following spring (delayed implantation). Depending on the species, the pups are born in late May, in June or July, and are weaned from 32 to 40+ days after birth. Like all mammals, bat pups nurse from the mother’s mammary glands. Most females of breeding age give birth to a single pup once a year, but Big brown bats often have twins, Hoary bats usually have twins, and Eastern red bats may produce two-to-four pups each year. Crevice bats form maternity colonies where females roost together and give birth to their pups. Eastern red bats and Hoary bats roost alone with their pups, and Silver-hair bats sometimes form small maternity colonies. Nursery colonies contain only females and their young; adult males and non-breeding females roost elsewhere. The mother nurses her pup until it’s ready to fly when it is about four weeks old. She then teaches the juvenile the necessary skills for survival.
PROVIDING TEMPORARY CARE
DO NOT handle a bat with bare hands, and do not attempt to rehabilitate the bat on your own. To do so could jeopardize your safety as well as the life of the bat. Provide minimal temporary care for the bat until help is obtained:
- Line a box with an old t-shirt so the bat has a surface to hang upside-down.
- Create some pleats in the shirt so the bat can hide if it wants to. (Make sure any tape that is used is secured well so the bat won’t get stuck.)
- Put a small amount of water in a small, shallow container like a vitamin or baby food jar lid.
DO NOT provide any type of food whatsoever – to do so can cause organ failure to critically dehydrated bats. Make sure a top is secured to the box as some bats can squeeze through a crack as thin as 1/2. If you must handle the bat please remember to wear thick gloves (even though rabies is rare in bats, if the bat bites you it will need to be euthanized and tested). Until a rehabilitator is located, keep the box in a secure, quiet room and keep children and pets away.