The Carlisle Mosquito Online

Friday, September 15, 2006


Eastern Red Bat (Lasiurus borealis)

Red Bat in COLOR (Photo by Joe Warfel)
On August 16, I was walking on the East Farm Trail of Great Brook Farm State Park, and had crossed the gas pipeline into Chelmsford where Great Brook leaves Carlisle. There is a large wetland there, where I like to check for birds. At 1:30 p.m. I saw a reddish-brown "bird" flying over the wetlands, which at first I thought was a Wood Thrush, but certainly not where I would expect to see one. The flight pattern was in broad circles, and erratic, with sudden reversals of direction, unlike the flight of most birds. When I finally got it in my binoculars, I saw that it was a bat. I watched it for about five minutes, until it finally flew to the north. I have seen a Red Bat only one other time, about ten years ago in fall, at Odiorne Point State Park along the New Hampshire seacoast. Our birding group saw a Red Bat flying around in mid-afternoon, an unusual time for a bat to be foraging.

Most bats roost during the daytime and feed around dawn and dusk, but the Red Bat is known to feed during the day. If there had not been good light when I saw this bat, I would not have known it was a Red Bat and not some other species. Red Bats roost alone during the day hanging upside-down from a leaf or branch of a deciduous tree, usually four to ten feet above ground. The area under the bat must be open, because it starts flight by dropping off the branch. When roosting, the bat resembles a dead leaf. Red Bats hunt in forest clearings, over water and around streetlights in suburbs.

Capturing flying insects

Bats, being the only flying mammals, are in their own order, Chiroptera, a Latin word meaning "hand-wing." The four "fingers" of the bat's "hand" are elongated, and a tough membrane between the fingers forms the wing. Bats use echolocation to capture flying insects. The bat produces a high-pitched cry, which reflects off nearby objects and potential prey. The bat can determine the location of the object from the time delay between the cry and its echo. A membrane in its ear closes while it emits the cry, so that it hears only the reflected sound. According to Godin, a flying bat can detect a mosquito only six inches away in 1/1000 second (one millisecond)! Red Bats eat flying moths, flies, bugs, beetles, crickets, cicadas and other insects.

Red bats can have up to five pups, although most bats have only a single pup. The breeding period is August to October and the young are born the following spring. Red Bats spend the winter at the latitude of Washington, D.C. southward to the Gulf States, and will return to the same breeding area the following spring. Red Bats can live 12 years.

Joe Warfel took the photo of the bat shown here, and wrote: "I photographed the bat in May of 2002 alongside the trail to Weeks Pond one afternoon at the Habitat Audubon sanctuary in Belmont, Mass. It was hanging (asleep, I presume) in a small bush at shoulder height only a couple of feet off the trail. I took a few images of it, some with ambient light only and then a few with flash as here. It did rouse a little but seemed not too disturbed. I quickly finished so as not to disturb it too much, though it seemed more interested in going back to sleep than fleeing." Joe thought it was a female because of the "frosted" appearance of the fur; males are usually redder than females.

References: 1. A. J. Godin, Wild Mammals of New England, DeLorme Publishing Co., Yarmouth, ME, 1977. 2. K. Williams and R. Mies, Stokes Beginner's Guide to Bats, Little, Brown, and Co., Boston, 2002.

The writer thanks Joe Warfel of Eighth-Eye Photography for permission to use his photograph.

2006 The Carlisle Mosquito