Little Brown Bat (Myotis lucifigus)
The Great Lakes region is home to many species of bats. Among the most common
is the little brown bat (Myotis lucifigus), with a range covering most of
the continent and extending as far north as any bat in North America.
The little brown bat is a small mammal, measuring 80-95mm (3.1-3.7 inches)
from head to tail and weighing 6-12 grams (0.2-0.4 ounces). Its coat is an
olive-brown to dark-yellowish brown on the back and paler underneath. The
generic name Myotis, which means “mouse ear” in Latin, presumably comes
from its mouse-like ears which measure 13-16mm (0.5-0.6 inches).
brown bats use echolocation to find and capture prey. They emit pulses of high
frequency sound (20-130 kHz) that bounce off nearby objects. The bats then use
the echoes to determine the object's distance, size, and shape. They feed
primarily on aquatic insects, including mayflies, caddis flies, and stoneflies.
They will also feed on other flies, wasps, moths, and beetles to supplement
their diet. Typical summer foraging areas include forest edges, along streams
and lakes, and sometimes in small cultivated fields. Young little brown bats can
eat up to 1.8 grams of insects/night; lactating females can eat up to 3.7 grams
of insects/hour due to increased energy demands.
Little brown bat habitat and behavior vary seasonally. Males and females
typically spend the summers apart from one another. They come together again in
early fall when courtship and mating are initiated. After mating, they’ll
over-winter in moderately sheltered hibernacula, including caves, mine tunnels,
and occasionally in hollow trees. Upon leaving their hibernacula in spring,
females will form small groups and move to summer roosts where they bear and
nurse their young. These nursing sites are typically used year after year. Young
are typically born from early June through early July, and are usually capable
of flight within 21 days. Little is known about the summer whereabouts of males,
though they appear in common places such as caves, forests, and occasionally
considered a warm-blooded mammal, the little brown bat has the ability to
withstand drastic changes in body temperature. This probably explains why summer
nursery colonies can survive in areas where night temperatures reach near
freezing and day temperatures are very hot. During times of rest, little brown
bats enter a physiological state called torpor. As with hibernation, torpid bats
experience reduced heartbeat, respiration, and body heat. Torpid bats can
“awaken” within a relatively short time to feed, drink, or even switch positions
on the roost.
While predation is not a problem for little brown bats, hundreds are killed
each year by exterminators for taking roost in homes or other human dwellings.
This is unnecessary, as sealing the point of entry after bats have left for the
night is much cheaper, safe, and effective. The next time you look towards the
sky at dusk, keep your eyes open – you may just catch a glimpse of a little