|10/30/2019 3:20:00 PM|
Going To Bat
|The “hand” and the “wing” are both key to bats’ survival. The “wings” are not feathers but skin-like membranes stretched between the bones. |
A bat’s “hands” have a thumb that is not covered by the membrane which helps them grab their prey in mid-air.
“When the bats are feeding on insects,” said Larry Heaney, Negaunee Curator of Mammals at the Field Museum, “they use the ‘skin’ between the legs and the tail as a web to catch the bugs, and then they eat them.”
“Unlike insects and birds, which have relatively rigid wings that can move in only a few directions, a bat’s wing contains more than two dozen joints that are overlaid by a thin elastic membrane that can stretch to catch air and generate lift in many different ways,” wrote Ken Than in “Why Bats Are More Efficient Flyers Than Birds,” posted in LiveScience.com on Jan. 22, 2007.
“Their motions might seem erratic and graceless, but bats are more efficient flyers than birds. … [T]he secret to efficient bat flight lies in the furry creature’s flexible skin membrane and its many-jointed wings, which together create a shape-shifting structure that provides more lift, less drag and greater maneuvera-bility,” Mr. Than wrote.
He quoted Sharon Swartz, an associate professor in ecology and evolutionary biology at Brown University: “Every joint in the human hand is there in the bat’s wing and actually a couple more. … [B]ats are able … to make fine-scale adjustments during flight.”
By Mary Helt GavinAt dusk, the mammals classified as “hand-wings” fly from the darkness of their daytime roost – a cave, an abandoned building or perhaps a hole in a tree – using echolocation to navigate through the rich night air. They are bats, of the order chiroptera, from the Greek words for hand (chir) and wing (pteros).
Of the 1,200 species of bats worldwide and the 13 in Illinois, six are found in the Chicago area. Three of these, the little brown bat (Myotis lucifugus), the big brown bat (Eptesicus fuscus) and the red bat (Lasiurus borealis) are commonly found in Evanston, said Larry Heaney, Negaunee Curator of Mammals at the Field Museum of Natural History in Chicago. He has conducted extensive research in the Philippines, where there are about 900 species of bats.
Bats are not, well, “blind as a bat.” In fact, all bats have eyes and can see, and the large fruit bats in Africa, Asia and Australia have quite large eyes. But the bats in this country rely mostly on their keen sense of hearing, emitting sounds that reverberate from solid objects, allowing them to navigate among walls, tree trunks, people and animals to find dinner and return home. This echolocation is akin to sonar.
The little brown bat has about a 10-inch wingspan, and that of the big brown bat is two to three inches greater.
Both the big brown bat and the little brown bat have one baby, or pup, per year, and they often live 10-15 years. A wild bat can live more than 30 years. “They are really long-lived and very smart,” Dr. Heaney said.
Bats making a home in Evanston attics and garages are generally the little brown bat and the big brown bat. The red bats, with fur that looks like red or brown leaves, typically roost in trees.
“The red bats, with slightly larger wings, are really cute,” Dr. Heaney said. “The top surface of the skin around their tail is covered with long fur – they carry their sleeping bags with them.”
“You have to know when to look for bats in the trees,” Dr. Heaney said, “because, to the casual observer, they may look like birds.” They fly over Evanston gardens, parks and parkways, “chomping down on mosquitoes, moths and pests that damage plants. They are a benefit to everyone who lives in Evanston,” he said.
Probably there are no bats that overwinter in Evanston. The red bats fly down to the Ozarks or areas around the Gulf of Mexico, Dr. Heaney said, where they find cover in forests among fallen leaves. They wake up from time to time if there are bugs to eat.
Most of Evanston’s brown bats, big and little, head to Wisconsin, where they hunker down in caves and abandoned mines. In summer, when they are active, bats like to be hot. “When they’re hibernating, they want to be in a place a little above freezing,” Dr. Heaney said. During the winter months, they huddle in a tight space and remain entirely inactive until spring.
Winter is a dangerous time for bats, because of a fungus called “white-nose syndrome,” which apparently caught a ride to the United States from Europe and appeared in Illinois in 2013, Dr. Heaney said.
“Bats in caves are most vulnerable,” Dr. Heaney said. “This disease causes up to 90% mortality in hibernating species, and is now sweeping through the U.S. and Canada, killing millions of bats.” Colonies in the Midwest have not yet been hit as hard as those farther east, he said.
The fungus apparently annoys the bats enough to disturb their winter sleep, and when they wake up, they are unable to find food, so they essentially starve to death, Dr. Heaney said
Fear of Bats: Rabies and Vampires
People are afraid of bats because they are known to carry diseases. A bite or even a scratch from a bat can transmit the disease. “Rabies is a terrible way to die,”
Dr. Heaney said.
The Illinois Department of Public Health reports, “Since 1995 in the United States, more than 7,000 animals per year – most of them wild – have been diagnosed as having the disease. … In wild animal species, rabies is more common in bats, skunks, raccoons and foxes, but the disease also has been found in deer and in large rodents, such as woodchucks…. Most of the recent cases of human rabies that have occurred in the United States have been caused by rabies virus from bats. In Illinois, rabid bats can be found anywhere. Awareness that bats can be a source of the rabies virus can help people protect themselves.”
Nonetheless, IDPH says, “Although bats can carry the rabies virus, most bats are not infected with it. The only way rabies can be diagnosed in a bat, however, is by laboratory testing.”
IDPH notes warning signs of an infected bat: “Bats seen during the day, those found in a place where bats are usually not found (e.g., in a room in your home, on your lawn, etc.) or bats that are unable to fly are more likely to be infected than others. Bats, like all wild animals, should never be handled.”
People may not always know when they have been bitten by a bat, according to IDPH. “Bats have very small teeth, and marks made by these teeth may not be easy to see. If you find yourself in close proximity to a bat and cannot assure you were not exposed to it, you should call your doctor or your local health department; they can help to determine if you could have been exposed to rabies.
“For example, if you awaken and find a bat in your bedroom, if you see a bat in the room of an unattended young child, or if you see a bat near a mentally impaired or intoxicated person, a doctor or local health department should be consulted. Do not discard the bat and do not damage the bat’s head.”
The laboratory test will likely be for a rabies antibody, not for the disease itself, Dr. Heaney said. The antibody is a signal that the animal has been exposed to rabies at some point. It does not indicate the presence of an active disease.
As an example, he said, the City recently reported that a little brown bat found in an Evanston home was tested for antibodies for rabies. The test was the rabies virus Ag assay, not a test for live virus.
“This test means that the bat was exposed to the rabies virus at some point in its life, and it developed antibodies against the virus. This test does not tell us if the virus was live or if instead it was eliminated from the bat’s body by the immune system that produces the antibodies. These bats typically live for seven to eight years, but often for 20, and up to 34 years, so it might have been exposed to the virus long ago; we have no way to know for certain,” Dr. Heaney said.
The City’s notice about the dead bat added the caution that people should avoid any contact with a bat found on the ground and should have it tested.
Dr. Heaney strongly concurs with this advice. “If you find a bat on the ground, leave it alone. If a bat has a live virus, it is really loaded,” he said.
“Seeing a bat in the house or finding a dead or limp one on the ground “is very different from simply seeing healthy bats flying about in the evening, chasing after moths, beetles, and mosquitoes. In this case, they can simply be enjoyed for their remarkably agile flight,” Dr. Heaney said.
He added, “Given the rarity of rabies in bats in this part of the U.S., just using the obvious caution that we should use with any wildlife will avoid any problems. … People are far more likely to be killed by a dog, a cow, a horse or a lawn mower or to die from cat-scratch fever. … The bat that flies overhead when you are walking your dog poses no threat.”
The fear of bats that many people have come not from the threat of rabies but from the sensationalism of Hollywood, Dr. Heaney said.
Bram Stoker’s book “Dracula,” produced in this country as the film “Nosferatu,” tinge this nocturnal creature with horror.
Vampire bats do exist and are found principally in Mexico and Central and South America, according to National Geographic (kids.nationalgeographic.com). Their food is the blood of other mammals – cows, pigs, horses, birds and, very rarely, humans – which they lap as it oozes from the bite of their small, very sharp teeth.
“These bats are so light and agile that they are sometimes able to drink blood from an animal for more than 30 minutes without waking it up. The blood sucking does not hurt the animal,” National Geographic reports.
The American film industry capitalized on this combination or horror and fascination.
Dr. Heaney said, “Until Hollywood came along, people weren’t afraid, and these were America’s neighborhood bats.”
But there are still superstitions about this creature that dwells in caves within the earth and feeds at night.
Perhaps Sesame Street’s Count or Bruce Wayne, even at his darkest Batman, will be able to ease those fears about bats.
“They are cool critters,” Dr. Heaney says, “and deserve some good publicity.”
Flappers and Flitterers
The website etymonline.com traces the ancestry of bat “from the Old Norse leðrblaka, “leather flapper,” from Proto-Germanic *blaProto-Germanic *blak-, which goes back to the Proto-Indo-European root bhlag, meaning “strike.” If that is the case the original sense of the name for a bat “was likely ‘flapper.’”
In Old English, the word for bat was “hreremus,” from hreran “to shake” and rattle-mouse, an old dialectal word for “bat,” is attested from late 16th century, according to etymonline.
Other variants are “flitter-mouse,” reminiscent of “fledermaus,” the German word for bat, derived from the Old High German word fledaron “to flutter.”
Bats in the House
The Illinois Department of Public Health has the following advice about bats in the attic or the workspace or living area.
Flying In: Any bat that enters a home or work area must be captured – confined to a room, trapped in a box or captured in a blanket. IDPH advises wearing leather gloves to handle the bat, never using one’s bare hands. Anyone who does not feel comfortable capturing the bat or cannot do it safely should contact the City or county animal control to assist. Once the bat is captured, the local or county health department must be contacted so they can evaluate the exposure. Those who were in any way exposed to the bat must speak to the local health department before releasing the bat.
Living In: If a bat colony is present in a part of the house not actively lived in – the attic, for example – the home-owner should seal off any gaps to the space that are greater than ¼ inch and let the colony stay until the pups (young) are grown.
Getting Out: Exclusion remains the best way to prevent and control bats in a structure, but this can be done only between March 15 and May 15. Bats can be excluded by sealing exterior openings larger than ¼ inch by using caulk, expandable foam, plywood, mortar, metal flashing, steel wool or ¼ inch mesh screen or netting. Doors, windows and vents should have screens and be securely framed; chimneys should be capped and gaps around utility lines plugged.
More information about bats can be found on the IDPH website, dph.illinois.gov.
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