Copyright © U.P. Bats 2022. All rights reserved.
U.P. Ba ts
Habitat and Roosting
The little brown bat lives in three different roosting
sites: day roosts, night roost and hibernation roosts.
Bats use day and night roosts during spring, summer
and fall while hibernacula are used in winter. Day
roost are usually found in buildings or trees, under
rocks or wood piles and sometimes in caves. Nursery
roosts are found in both natural hollows and in
buildings (or at least close to them). Nursery roosts
have also been found under sheet metal roofs of
trapper’s caches and attics of buildings. Night roosts
tend to be in the same buildings as day roosts,
however these roosts tend to be in different spots that
are more constrained and the bats pack together for
warmth. Bats rest in night roosts after feeding in the
evening which may serve to keep their feces away
from the day roosts and thus less noticeable to
predators. Brown bats typically hibernate in caves and
perhaps unused mines. Northern populations of bats
enter hibernation in early September and end in mid-
May while southern populations enter in November
and ends in mid-March.
Diet
Since many of their preferred meals are insects with
an aquatic life stage, such as mosquitoes, they prefer
to roost near water. Brown bats forage near bodies of
water and move in and out of adjacent vegetation.
Evening forages are done in groups and above the
water. They echo-locate to find their prey. They are
particularly good at hunting insects when they are at
close range and packed together. When hunting, little
brown bats capture prey both by gleaning and by
catching them in the air. When in flight, bats scoop up
the prey with their wings, while prey above water is
directly grabbed with the mouth.
Brown bats do not claim feeding areas like a
territory, however individuals frequently return to the
same feeding sites where they have previously made
successful catches. When hunting swarms, brown bats
usually select no more than two species. They feed on
more species when they are scattered. If they do not
catch any food, they will enter a torpor similar to
hibernation that day, awakening at night to hunt
again.
Mortality
Brown bats live approximately 6 to 7 years and often
live well beyond 10 years. Little brown bats are
preyed on by a variety of animals, including small
carnivores, birds, rats and snakes. Many predators
target bats when they are packed together in roosts.
Martens and fishers will snatch young or hibernating
individuals that have fallen to the ground. Brown bats
are also hosts for various parasites such as fleas, bed
bugs and lice. Bats are killed by accidents more often
than predators or parasites. They can get impaled on
barbed wire and burdocks or drown in floods during
hibernation. Pesticides can also kill them. However
DDT has little effect on the bats. They also seem to
have low levels of rabies. Little brown bats are now at
a higher threat due to white nose syndrome in eastern
North America. Many states have made special
considerations with respect to the disease, including
listing them as a sensitive or protected species.
Sleep
The average sleep time of a little brown bat in
captivity is said to be 19.9 hours per day. This long
period of sleep is thought to be a way of conserving
energy, by only hunting for a few hours each night
when their insect prey are available.
Echolocation and Communication
Little brown bats produce calls that are high intensity
frequency modulated (FM) and that last from less than
one millisecond (ms) to about 5 ms and have a sweep
rate of 80–40 kHz, with most of their energy at 45
kHz. Bats usually emit 20 calls per second when in
flight. When pursuing prey, a bat emits 200 calls per
second. It also emits a high-pulse repetitive call if it
wants to land. Bats that are in danger of colliding will
reduce the terminal portion of their sweep calls to 25
kHz, creating a "honking" sound. The bats also find
roosting sites by listening to the echolocation calls of
other individuals. Some complex vocalizations are
used by mothers and their pups.
About Bats
The Little Brown Bat is the most common species of bat in the Upper Peninsula and Northern Wisconsin area. As suggested by the bat’s
name, its fur is uniformly dark brown and glossy on the back and upper parts with slightly paler, grayish fur underneath. Wing
membranes are dark brown on a typical wingspan of 22–27 cm (8.7–11 in). Ears are small and black with a short, rounded tragus. Adult
bats are typically 6–10 cm (2.4–3.9 in) long and weigh 5–14 grams (0.2–0.5 oz). Females tend to be larger than males. Little brown bats
eat a variety of insects including moths, wasps, beetles, gnats, mosquitoes, midges and mayflies, among others.