Salt Creek Greenway Association
The Salt Creek Greenway
Purpose and Partners
Places to Visit
Special Greenway Projects
EXPLORING THE WORLD OF BATS
by Jeff Rapp, Crab Tree Nature Center, Forest Preserve District of Cook County
July 27, 2014
Fossil records date the presence of bats on Earth going back 40 to 50 million years. Their body makeup has changed very little throughout time.
Bats are the only mammal which can fly. Bats play a vital role in a variety of ecological niches and economies around the world. More than two-thirds of bat species are insectivorous, eating a wide variety of insects.
Bats can be found nearly everywhere on Earth except for Antarctica and the northern Arctic. There are over l,200 species of bats worldwide. Bats comprise the second largest order of mammals on the planet after rodents. Bats belong to the Chiroptera order (or hand wing). There are 47 species of bats in North America of five families.
The bat's head and body is covered with fur. The wings are hairless membranes like skin extending over four fingers. The wings are folded up against the body when the bat is resting and open to a full extension during flight.
Some species are as small as the bumblebee bat which weighs only 0.06 ounces. The flying fox bat has a six-inch wingspan and can weigh about three and a third pounds.
The most famous bats are the vampire bats of Central and South America. They are adapted to feeding on the blood of livestock. This bat is often misunderstood and dramatized, prompting myths and mysteries in fiction and theatre. But bats do not feed on human blood, and contrary to the Dracula fantasies, they do not attack humans. However, an enzyme in bat saliva has a medicinal use as a clot thinner and is used to treat stroke victims.
Other fascinating bats include the tube-lipped nectar bat which has a tongue longer than its body and the fish swimming bat which can scoop up fish beneath the water with its long toes.
A little brown bat can eat almost its own body weight in insects every night - the rate equivalent to about 3,000 mosquitoes or other similar small insects during the foraging hours from dusk to dawn.
About one-third of bat species specialize in feeding on fruit and nectar. They pollinate agave, bananas, avocados, dates, figs, peaches, mangos, cloves and other fruits. Fruit eating bats also disperse seeds which germinate into a wide variety of tropical fruit plants. They also play a role in regenerating rainforests.
Twelve species of bats are known in Illinois. They are protected under the Wildlife Code.
Some of these bats include species known to so stay In Illinois year around and hibernate in caves or mines during the cold season. Some migrate to warmer climates.
Little Brown Bat
Northern Long-Eared Myotis
Big Brown Bat
Gray Bat (Federally endangered)
Eastern Red Bat
Big-eared Bat (State endangered)
Big Brown Bats (Greg Schechter, photographer)
When bats hibernate, known as torpor, they conserve energy by reducing body function, temperature and heart rate to a minimum. Bats can survive on fat reserves for six months when in torpor.
The cave regions of southern Illinois and the valleys of the Mississippi and Illinois Rivers are excellent habitat for colonies of hibernating bats. Bats also hibernate in old mines and abandoned buildings. Bats huddle together to keep warm and hang upside down by their feet when they are at rest.
Bats become active and emerge from torpor when the weather turns warm and spring insects become abundant.
But if bats are disturbed during hibernation and their metabolism is activated at a time when it is too early in the spring and there are no food sources available, their fat reserves can be depleted. This causes their immune systems to suffer and weakens their ability to recover and survive until insects arrive.
Pregnant females leave their winter caves and mines to return to their summer homes where they give birth and raise their pups. Female bats produce one pup or two at the most once year. The pups are ready to fly at three weeks of age. Pups nurse for up to six weeks. A bat colony is known as a crèche. Bats do not build nests. Some female species live in maternity colonies while they are raising their pups.
In addition to living in caves and mines, bats also find shelter beneath loose tree bark, in hollow trees, or other convenient places like abandoned buildings or attics for protection from the weather and predators. If bat habitat has been destroyed and bats are displaced, bat houses can be put up to provide shelter for them. Attracting bats benefits farmers and subdivisions bothered by insects as a natural method to control pests.
Without bats to help control insects and agricultural pests, crop yields would be lower, produce costs could be more expensive and more pesticides would need to be used, introducing toxins into the environment.
Bat predators include owls, hawks, raccoons, minks, cats and snakes. Humans are also a serious threat to bat populations as we destroy their natural habitat and open space with developments and logging and close caverns and other places of shelter.
Bats have very poor eyesight. They use echolocation when flying to help them maneuver and track prey. The ultrasonic sound pulses bats emit helps them determine the size and identity of prey, where it is and how to avoid obstacles. Wind turbines are very dangerous for migrating bats and birds. Turning blades lower air pressure to 150 mph and cause oxygen to form bubbles. This damages bat lungs and interferes with their ability to breathe. 600,000 bat deaths are recorded each year caused by wind turbines.
Sounds emitted by bats are at a very high frequency and cannot be heard by humans.
The guano produced by bats in caves has been mined as fertilizer.
Bats can live up to 30 years in the wild. Bats prefer to avoid contact with humans. Some bats can carry rabies but being bitten or infected by a bat is rare. However, if a bat is encountered in your home, garage or barn, try to give it time to escape. Open the windows and doors. If a bat is found on the ground and appears sick or injured, call the local Department of Animal Control. Do not attempt to pick up a grounded or trapped bat. Keep children and pets away from the injured or trapped bat.
Bat colonies are declining everywhere at alarming rates. The consequences are devastating for natural ecosystems, agriculture and international economies.
Biologist inspecting a Northern Long-Eared Bat with White Nose Syndrome (USFWS)
One of the most serious threats facing bats is a disease called white-nose syndrome (geomyces destructans). This disease was introduced from Europe in 2006. European bats are immune to this disease. But the bats of North America are defenseless against this fungus and have died at a rate of 80% to 90% of the population since the disease was first discovered on the East Coast of North America. The disease has now killed more than 5.7 million cave-dwelling bats in the eastern third of North America.
White-Nose Syndrome has just been confirmed in LaSalle, Monroe, Hardin and Pope counties in Illinois. The Illinois Department of Natural Resources has closed all caves to prevent bats from entering and being exposed to the fungus.
The fungus depends on the cold and humid conditions of caves for its survival. The fungus can linger on the walls in these environments for years. When bats arrive at caves for winter hibernation, they are exposed to the fungus. As their body temperatures drop into torpor, there skin is vulnerable to the infection. There is no known treatment or cure.
It is believed that the fungus damages blood vessels in the wings which leads to dehydration and emaciation. By spring, the bats have become too weak to fly, migrate and forage for food, resulting in death. Some bats are strong enough to survive for a while, but their reproductive rates may be reduced and they are unable to give birth and raise pups, resulting in a plunge in bat population numbers.
It is thought that the little brown bat, one of the most common North American species, might be extinct by 2026.
White Nose Syndrome and Bat Hibernation Areas - July 28, 2014 Click for Map
But there is hope. Conservationists are working on a solution to save bats. It has been discovered that applying bleach to the walls of caves destroys the fungus. Since disinfecting walls in natural caves or mines is impossible, man-made hibernating caves are being built as alternative bat habitats. After the bats leave in spring, the structures can be disinfected, making them safe for next year's hibernating bats.
Only time and trial will determine whether man-made caves are an answer to save our nation's bat populations.
For more information about bats, go to:
University of Illinois Extension, Living with Wildlife in Illinois
Bat Conservation International
Jeffery.Rapp: www.fpdcc.com - 847-381-6592
Photo by Valerie Spale
|Return to Main Menu|