In medieval paintings, both angels and demons have wings–but angels have birds’ wings, and demons have bats’ wings.
Bats have suffered a serious image problem throughout most of western history. (They fare better in the Orient, where they are often considered a symbol of good luck.) It’s probably got a lot to do with their nocturnal habits (evil shuns the light, after all), and their incredibly (to our eyes) grotesque facial features, but in reality, bats are nothing to be frightened of. Just the opposite!
Bats are the only mammals that have evolved true flight. They’re a very successful order of mammal, too, with more than 900 species world-wide, in two main branches: megachiroptera (flying foxes and Old World fruit bats) and mirochiroptera (everything else). The two branches are different enough that it’s possible they evolved separately, and don’t even share a common ancestor.
The megachiroptera are more primitive skeletally and rely mostly on vision in their search for food, while the mirochiroptera have almost all developed a sophisticated acoustic orientation system; they send out extremely high-pitched sounds whose echoes give them a clear sense of the space around them.
This “echolocation” is what makes bats so effective at night, and gives them an advantage over their prey–primarily insects, although bats have managed to colonize just about every niche of the food system. Various species eat small mammals, reptiles, birds, fish, other bats, fruit, flowers, nectar, pollen, leaves and, in the case of the infamous vampire bat, blood.
Bats range in size from the huge pteropus vampyrus, a flying fox with a wingspan of up to 1.5 metres, to the Philippine bamboo bat, whose wingspan never exceeds 15 millimetres.
Those wings are modified forelimbs in which the fingers are elongated and joined by membrane from the forearm or upper arm down the side of the body to the ankle or foot. The legs are usually joined by a two-layer membrane.
The facial features of bats are truly fantastic, like the gargoyles on ancient cathedrals. Many bats have large ears, convoluted noses and small eyes, which, along with the bat’s liking for the dark, probably gave rise to the saying, “blind as a bat,” even though many bats have excellent vision–especially, as you might expect, the Old World bats that don’t have the echolocation ability.
While it is possible to catch certain diseases from wild bats, just as it is possible to be infected by almost any wild (or domestic) mammal, the only bat that could truly be called harmful to man, and then only occasionally, is the vampire bat, not because of the small amount of blood it licks from the wound it inflicts but because it sometimes carries rabies.
In general, bats are beneficial, especially by controlling insects. (Particularly, in Saskatchewan, mosquitoes.) One study showed that some large colonies of Mexican free-tailed bats consume 6,000 tons of insects every summer. A study of the dung of 800 greater mouse-eared bats (and doesn’t that sound like a fun study?) indicated that they ate about 55,000 oak tortricid moths each night, close to 70 moths apiece. (Some insects have developed defenses against bats: zig-zagging flight patterns, special hearing organs so they know when bats are nearby, and even, in one species of moth, ultrasonic signals designed to confuse hunting bats.)
Bats eat so much because flying takes a lot of energy. It’s estimated a bat must eat 20 to 30 percent of its own body weight nightly, maybe as high as 50 percent in the case of pregnant females. (What sort of cravings does a pregnant bat get?)
Not only do insectivorous bats help protect humans and their crops from insects, the bats’ droppings, called guano, make excellent fertilizer.
In Saskatchewan there are eight common kinds of bats. The big brown bat, one of the most common, has a wingspan of about 30 centimetres and a body about 15 centimetres long.
The red bat, another common Saskatchewan variety, is the colour of red bricks and has a white spot on its shoulder. Most species of bats give birth to a single baby at a time, but the female red bat has two or three at a time and carries them in a pouch.
Like many other animals (and some people), northern bats either migrate for the winter or hibernate; the majority of bat species live in the tropics. The trouble is, fewer and fewer bats are living anywhere. While bats are sometimes killed by predators–owls, hawks, raccoons, skunks, snakes and even house cats–their biggest threat is humans. Because of the negative image bats have, they have often been eradicated indiscriminately, their roosting places blown up or poisoned or bulldozed. As well, like other animals near the top of the food chain, their tissues concentrate the poisons that may appear in only trace amounts in the animals or plants on which they feed.
The fossil record indicates bats have been around, essentially unchanged, for more than 50 million years, but in recent years their numbers have dropped dramatically. It would be a shame if these wonderful creatures disappeared because of human superstition.
The demons of bats’ nightmares must walk on two legs and have no wings at all.
