Summit Outside: Bats: the flying mammals |

Summit Outside: Bats: the flying mammals

Dr. Joanne Stolen
Special to the Daily
Special to the Daily

Bats are associated with “things that go bump in the night”: scary things like like vampires, witches, evil spirits, and Halloween, and some people associate them the disease rabies.

In fact they are not a primary reservoirs of rabies, and they do not attack people. The true vampire bats which give the species a bad reputation are just three of some 900 species of bats and they rarely feed on human blood.

Bats are actually really fascinating, intelligent, animals; valuable to commerce, science, agriculture and natural ecosystems. They consume thousands of tons of flying insects in a year.

Scientists are fascinated by their many unique characteristics such as the ability to echolocate, and their ability to fly.

Bats are the only true flying mammals. Flying squirrels merely glide, but bats like birds are capable of powered flight and they are remarkably adept at it, surpassing in many aspects the considerable flying skills of birds. A bat flying at 40 miles per hour can make sudden right-angle turn in little more than the length of its body. Birds use only chest muscles to fly, but the wings of bats are powered by chest and back muscles. The down stroke is driven by the chest muscles keeping the bat airborne, and the power created by the back muscles produces forward momentum. Their flight is so efficient that a bat uses less than one-fourth the energy used by a terrestrial mammal to travel the same distance. Flight gives bats the mobility to travel far and wide for feeding and roosting.

Bats do see as all bats have image-forming eyes but they use complex sonar to navigate in their surroundings. A bat emits ultrasonic pulses that bounce off objects and return as echoes to the bat’s ears, where they are rapidly computed in their brain allowing them to maneuver appropriately. Most bats emit vocalizations through their mouths and that is why most bats have their mouths wide open while in flight. A little brown bat generates sound with the intensity of a smoke detector but fortunately these calls are above the range of human hearing. Can you imagine how much noise would fill the night air if we could hear the sounds of echo-locating bats? Bats can however make sounds low enough that humans can hear them and these are mostly social or communicative vocalizations. The squeaks and chattering of bats heard in a roost are of bats socializing.

Bats are considered mammals because they bear live young and nurture them with milk. Bats, like humans have two teats, a relatively long gestation period, and most bear a single young. They have hair, tightly regulated body temperature, and a well-developed nervous system. Their front limbs are modified into wings and the forearms and fingers are elongated, and connected by a delicate membrane of elastic skin that is leathery in texture.Bats have a metabolic system which is adjustable to the variable demands of activity. During rest (torpor) there is lowered metabolic activity and body temperature, which can last for a few hours, or even several months.

Eighteen species of bats are found in Colorado and sixteen of these are the so-called “common bats”. Nearly all members of this family are insect-eaters, and most are cave-dwellers. Bats come in a wide variety of sizes; Colorado’s western pipistrelle weighs less than a nickel. At the opposite extreme are the large, fruit-eating flying foxes of the Old World tropics, which may weigh over 2 pounds and have a wingspan of nearly 6 feet. All Colorado bats are insectivores. Little brown bats, which are common in Colorado, have been known to catch and eat more than 150 mosquitoes in less than 15 minutes, and they chew their food up to seven times per second.

Most of Colorado’s bats are found in caves, fissures, mines and old buildings but several species, however, use trees as roosts. Bats generally fly low over lakes or streams to drink, although some bats living in deserts do not drink at all, relying instead on insects to provide them with the water they need.

In Colorado, the long-legged myotis and the little brown bat feed by making continuous, repeated circuits. The long-eared myotis, and Townsend’s big-eared bat hover to take insects from leaves. The little brown bat captures single insects, first knocking them off balance with a wing-tip, and then pulls them into its’ mouths with a curl of the tail. Hoary bats take larger insects directly into their mouths.

Bat folklore and misconceptions goes back many centuries. The ancient Mayans considered bats gods of darkness and the underworld. In Medieval times, mere association with bats could result in dire consequences. The 16th century English poet John Heywood wrote that “these creatures that fly like birds, bite like beasts, hide by day and see in the dark can surely be neither flesh, nor fowl.”

Breckenridge resident Dr. Joanne Stolen is retired from teaching microbiology at Rutgers University.

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