Frederick County is Batty

Bats may seem a scary symbol of Halloween. They help a lot in controlling insect populations. A little brown bat (Myotis lucifugus) for example is estimated to eat up to 600 mosquitoes an hour and the big brown bat (Eptesicus fuscus) twice that volume of insects. Consider that our local mosquito problem has recently gotten worse with the influx of the Asian Tiger Mosquito, and bats can be viewed more positively.

Big brown bat

University of Maryland surveys at parks in Frederick County found several species of bats in our midst. In addition to the little brown bat and big brown bat, the eastern red bat (Lasiurus borealis), and eastern pipistrelle (Pipistrellus Subflavus) are also prevalent. Several other bat species may be seen in this area in lesser numbers, including the eastern small-footed bat (Myotis leibii), northern myotis (Myotis septentrionalis), the hoary bat (Lasiurus cinereus), and the endangered Indiana bat (Myotis sodalis). Little brown bats are about 3 to 4 ½ inches in length, with a wingspan of about 8 to 10 inches. Their flight is often low and changes direction frequently at speeds of about 20 mph. Little brown bats like to roost in hollow trees, caves and buildings. Big brown bats are about 4 to 5 inches in length, with a 12 to 13 inch wingspan. They fly generally straight at 20 to 30 feet above ground with speeds to about 40 mph. Both the little and big brown bats hibernate in the winter.

One of smallest bats in our area, Eastern pipistrelle, is about 3 to 3 ½ inches in length with awing span of about 8 to 10 inches. Also known as the tricolor bat, it roosts in rock crevices and sometimes buildings, overwintering in caves. The Eastern small-footed bat is slightly smallerthan the Eastern pipistrelle, and both species like to forage flying low and slow over streams or water at forest edge. These smaller bats have life spans averaging 6 to 12 year, shorter than the larger bats, which have approximately 20 year life spans.

Eastern red bats have a reddish coat, and are approximately 4 to 5 inches in length with a wing span of 11 to 13 inches. The Eastern red bat is one of the few bat species with differences in coloration between the sexes. Males are orange-red and females are a chestnut buff color. They roost mainly in trees about 8 ft off the ground, foraging for insects within about ½ mile of their roosts. Easter red bats migrate south over winter to warmer locations, remaining active. A single litter of up to 5 young is born in late spring.

The Northern myotis or Northern long-eared bat is approximately 3 to 4 inches long, with a wing span of 9 to 10 inches. Like the other bats in our area, it uses echolocation or sound waves to locate insects in flight, but with its large ears, this bat can also effectively find insects that are stationary. The sound waves bats use (in the 25 kilohertz to 115 kilohertz range) are higher than the approximately 20 kilohertz frequency that humans hear. The Northern myotis likes to roost in caves and does not migrate a great distance to overwinter. It typically hibernates in mines and caves during the colder months. Like other cave hibernating bat species, Northern myotis numbers have been greatly reduced by the white nose syndrome.

The hoary bat, the largest in our area is about 5 to 6 inches in length, with a wingspan of about 14 ½ to 16 ½ inches. It migrates further south to overwinter, returning in the spring and is known to fly long distances. The hoary bat has a swift, erratic flight pattern, cruising at about 20 mph, but due to its strength can approach 60 mph. The hoary bat gets its name from its white or silver-tipped back and chest fur. Its throat is yellowish with lighter colored fur under the wings and belly. The hoary bat liked densely wooded areas and roosts in trees. It is less susceptible to the white nose syndrome, as it typically is a more solitary bat that hibernates in hollow trees and outbuildings. It has similar size and coloration to the little brown bat, although the Indiana bat has pink lips whereas the little brown bat has dark lips. The Indiana bat prefers roosting in forested habitats during its active spring, summer and early fall months.

Unfortunately for bat species that hibernate in cave or mines and in large colonies, the White Nose Syndrome has become a deadly pathogen that has greatly reduced bat numbers in the last 7 to 10 years in the Eastern and Central US. The disease is named for the white fungus, Geomyces destructans, which infects the skin, especially the muzzle area, of hibernating bats. This irritation is believed to cause increased activity in the bats, which causes them to use up stored fat reserves, at a time when they should be dormant during hibernation. Western Maryland is in a central part of the Eastern US most infested with this fungus. Estimates by the US Geological Survey and US Fish and Wildlife service are that an 80% decline in hibernating bat populations has occurred. The hibernating species in general have smaller litters, often single births per year, which puts them at a disadvantage for recovery of the populations.

Recent emphasis on developing man-made bat habits for hibernation is to try to influence some of the at risk species to find alternative hibernation sites to the damp cave areas which provide a host for the white nose fungus. The impact on agriculture from increased insect damage is estimated in the billions, due to this decline in bats which consume large quantities of insects.

Article by Tom Anderson, FCFCDB member

Nature Notes for 1/27/2013