Bats

Myotis lucifugus, little brown bat, Myotis septentrionalis, the Northern long-eared bat, Lasionycteris noctivagans, the silver-haired bat and Myotis sodalis, the Indiana bat are among some of the thirteen bat species native to Illinois.  All bats are in the order Chiroptera, and they are the only mammal that truly flies.  The order name means “hand wing” which aptly describes the wing which is composed of a thin membrane stretched over the four fingers of a bat’s hands.  The fingers can be spread when in flight or folded tightly together against their body when at rest.  The thumb protrudes from the end of the forearm as a small claw providing assistance when walking or climbing.  When flying, bats do not flap their wings as birds do, but move their wings in a circular “swimming” motion that provides not only lift, but great agility in the air.

Bats have small eyes and are thought to be able to see fairly well, but they use echo-location as a means of identifying insects or objects while in flight.  This process involves the bat emitting a series of supersonic squeaks through its mouth, 30-60 per second, and hearing the returning echo when the sound bounces off an object.  The complex ear can identify the direction, size, density and movement of the object.  While in flight, a bat can catch a flying insect with its open mouth.  Another method to eat-on-the-wing, especially when flying through clouds of insects, is to trap them in the folds of its wings.  Bats have the ability to scoop these insects out of each wing while still in flight, sometimes somersaulting in mid-air while eating.  A single bat consumes about 1000 insects an hour and will eat 6,000 – 8,000 mosquito-sized insects every night.

Bats spend most of their time “roosting”: resting or sleeping in a particular spot.  Males and females tend to roost separately except during breeding season in late fall.  Generally, they have two roost sites, one for daytime and another at night.  Since most species tend to feed during late evening or nighttime hours, the night roost is near the feeding areas.  This roost may be changed throughout the seasons as insect food groups tend to become more abundant at different sites. 

Life spans vary by species, but generally bats in our area live about 30 years.  Due to loss of habitat, widespread use of pesticides and herbicides, and direct persecution, bat species in Illinois have been declining for the past several years.  However, on warm summer evenings, especially over quiet ponds or streams, pay close attention to the air above you and enjoy the small acrobatic flyers taking advantage of the abundance of available insects.

Author: Don

Hi, I'm Don, a woodland steward, certified burn boss, University of Illinois Extension Master Naturalist, and Certified Interpretive Guide. I enjoy hiking, nature photography, wildlife observation, and model railroading View all posts by Don