Summer 1998

[TEXT ARCHIVE WEB-PUBLISHED MARCH 2002.
ORIGINAL PRINT PUBLICATION DATE: SUMMER 1998.]

Red bat: Camouflaged bug buster

By Sheryl De Vore

Walk through a grove of trees in a forest preserve this summer and the region's most colorful bat may be clinging upside down to a branch though you may never see it. The eastern red bat (Lasiurus borealis) wears a conspicuous russet fur that Henry David Thoreau likened to the hue of a ripe cattail head, but it can camouflage itself remarkably well.

The red bat lives alone — not in colonies — hanging by day among leaves, against tree trunks, or under loose bark flakes, where it might be mistaken for a dead leaf. Here, in summer, the female red bat remains suspended from a branch all day long as her two-to-five young cling to her, feasting on her milk. This species actually migrates south like birds, instead of overwintering in Midwestern caverns as do other of the region's bats.

Red bats mate while flying, in late summer or early fall. The female stores the sperm until she ovulates in spring. By the time she migrates back north in spring, she is ready to give birth. At night, she leaves her nursing young to feed on moths and other insects. A single red bat may consume 3,000 insects in one night.

Seeing a red bat, or any of the eight bats that migrate through or bear young in the region, is difficult. Hearing their high-pitched sounds is impossible. But scientists now have a new device enabling them to "hear" bats in the field. A bat detector, which can discern different bat species' calls, is helping the region's researchers gain valuable information on how urbanization affects bats and which habitats attract them.

Stan Gehrt, a wildlife research biologist for the Max McGraw Wildlife Foundation in East Dundee, has worked for three years with the Cook County Forest Preserve District and The Nature Conservancy to determine the presence of bat species at 15 forest preserves including Black Partridge Woods, Sand Ridge Nature Center, and Poplar Creek. Researchers also began working at five McHenry County sites this summer.

Visiting the preserves at dusk from early June through early fall, they use the bat detector to collect and amplify sounds that are then recorded and brought back to the lab. A computer digitizes the sound patterns, which identify the bat species.

The red bat and the big brown bat were the two most common bats detected at the study sites. "We detected red bat activity at 90 percent of the preserves, and most all summer long," says Gehrt. "These preserves may be very important habitats for the red bat, which is probably using the trees and foliage for roosting."