Big Brown Bat Eptesicus fuscus (Beauvois, 1796) - College of Forest ...

Diet.—Eptesicus fuscus is insectivorous
(Agosta 2002). Big brown bats are also
generalists and do not have a preference for
over-water versus over-land foraging sites.
They begin foraging within an hour after
sunset and spend an average of 100 min/night
foraging. Prey varies by geographic location
but generally consists of beetles, moths,
mosquitoes and dragonfl ies (Kurta and Baker
1990).
Diseases and parasites.—There are many
ectoparasites known to affect Eptesicus fuscus
including Cimex (bedbugs), Basilia (bat fl ies),
Ornithodoros (soft ticks), Leptotrombidium
(chigger mites), and Myodopsylla (bat fl eas)
(Kurta and Baker 1990). One species of
rosensteiniid mite,Nycteriglyphus fuscus, lives
in the guano of E. fuscus (Dood and Rockett
1985). To avoid ectoparasites, female big
brown bats may frequently change roost sites
(Agosta 2002).
Many endoparasites are also known to affect
E. fuscus, including nematodes from the
genera Allintoshius, Cyrnea, Physocephalus,
and Capillaria. Maseria vespertilionis is a
nematode that only infects the subcutaneous
tissue in the plantar surface of the bat’s feet.
Females that roost in colonies are frequently
infected whereas males are not. Big brown
bats are also infected with cestodes such
as Hymenolepis (tapeworms). Parasitic
trematodes include Dicrocoelium (liver fl ukes),
Limatulum, and Glyptoporus (Kurta and Baker
1990).
The big brown bat is a vector for St. Louis
encephalitis. A mosquito will bite an infected
bat and then bite a human, which is how the
virus is transmitted (Herbold et. al 1983).
Histoplasma capsulatum, a fungus, is found
in the big brown bat’s tissues and guano.
This fungus causes histoplasmosis (Darling’s
disease) in humans, cats, and dogs, which
affects the lungs (Bartlett et. al 1982).
Eptesicus fuscus is known to carry rabies
throughout the United States (Trimarchi and
Debbie 1977). However, local epizootics are
rare (Kurta 1979; Pybus 1986). In this species,
rabies infects the brain, brown fat, and salivary
glands (Kurta and Baker 1990) but is not
transmitted across the placenta (Constantine
1986). Incubation of the disease has been
observed to last up to 209 days (Moore and
Raymond 1970).
Interspecific interactions.—Common
predators include common grackles, longtailed
weasels, various owl species, house
cats, and bullfrogs. Interspecifi c competition
in foraging areas is known to occur between
Eptesicus fuscus and Lasionycteris noctivagans
(silver-haired bat), as well as Chordeiles minor
(common night hawk). However, the extent to
which these interactions occur in Mississippi
is not known (Reith 1980). Intraspecifi c
competition occurs at highly aggressive levels
but the signifi cance of these events is unknown
(Kurta and Baker 1990).
BEHAVIOR
Infant big brown bats will sound an “isolation
call” that can be heard from about 10 m away
when they are separated from their mothers
or fall from the nest. Females respond with
an ultrasonic chirping noise (Gould 1971).
Eptesicus fuscus has demonstrates a 24-hr
behavior rhythm that is persistent but inexact
(Twente and Twente 1987). Big brown bats
can use olfactory cues to distinguish among
individual colony members as well as between
young in a maternity colony, which may reduce
agonistic interactions (Boss et. al 2002).
Decreasing ambient temperature appears to
trigger hibernation in big brown bats. While
both the males and females will deposit fat in
anticipation of hibernation, females deposit fat
about one month earlier than males (Pistole
1988). Although females begin fat deposition
earlier, males enter hibernation fi rst (Phillips
1966). Big brown bats typically hibernate at
ambient temperatures below freezing (Barbour
and Davis 1969), using rock crevices, caves,
old buildings, and mines as hibernacula (Mills
et. al 1975). Most big brown bats do not
hibernate in colonies, but small groups are
common (Mumford 1958).