Bats are mammals in the order Chiroptera. Their most distinguishing
feature is that their forelimbs are developed as wings, making them
the only mammal capable of flight. (Other mammals, such as flying
squirrels and gliding phalangers, can glide for limited distances
but are not capable of true flight). The word Chiroptera can be
translated from the Greek words for "hand wing," as the
structure of the open wing is very similar to an outspread human
hand, with a membrane (patagium) between the fingers that also stretches
between hand and body.
There are estimated to be about 1,100 species of bats worldwide:
about 20% of all mammal species.
About 70 percent of bats are insectivorous. Most of the remainder
feed on fruits and their juices; three bat species eat blood and
some prey on vertebrates. These bats include the leaf-nosed bats
(Phyllostomidae) of central America and South America, and the related
bulldog bats (Noctilionidae) that feed on fish. There are two known
species of bat that feed on other bats: the Spectral Bat or American
False Vampire bat and the Ghost Bat of Australia.
Most microbats are active at night or at twilight. But although
the eyes of most species of microbats are small and poorly developed,
the sense of vision is still functional, especially at long distances,
beyond the range of echolocation. Their senses of smell and hearing,
however, are excellent. By emitting high-pitched sounds and listening
to the echoes, the microbats locate prey and other nearby objects.
This is the process of echolocation, a skill they share with dolphins
The teeth of microbats resemble those of the insectivorans. They
are very sharp in order to bite through the chitin armour of insects
or the skin of fruits.
The finger bones of a bat are much more flexible than those of
other mammals. One reason is that the cartilage in their fingers
lacks calcium and other minerals nearer the tips, increasing their
ability to bend without splintering. The cross section of the finger
bone is also flattened instead of circular as is the bone in a human
finger, making it even more flexible. The skin on their wing membranes
is a lot more elastic and can stretch much more than what is usually
seen among mammals.
Because their wings are much thinner than those of birds, bats
can maneuver more quickly and more precisely than birds. The surface
of their wings are also equipped with touch-sensitive receptors
on small bumps called "Merkel cells", which is found in
most mammals, including humans. But these sensitive areas are different
in bats as there are a tiny hair in the center, making it even more
sensitive and detects and collects information about the air flowing
over the wings. Another kind of receptor cells are found in the
wing membrane in species who are using their wings to catch prey,
and is sensitive to the stretching of the membrane. These cells
are consentrated in the areas of the membrane where insects hits
the wings when the bats capture them.
Mother bats usually have only one offspring per year. A baby bat
is referred to as a pup. Pups are usually left in the roost when
they are not nursing. However, a newborn bat can cling to the fur
of the mother and be transported, although they soon grow too large
for this. It would be difficult for an adult bat to carry more than
one young, but normally only one young is born. Bats often form
nursery roosts, with many females giving birth in the same area,
be it a cave, a tree hole, or a cavity in a building. Mother bats
are able to find their young in huge colonies of millions of other
pups. Pups have even been seen to feed on other mothers' milk if
their mother is dry. Only the mother cares for the young, and there
is no continuous partnership with male bats.
The ability to fly is congenital, but after birth the wings are
too small to fly. Young microbats become independent at the age
of 6 to 8 weeks, megabats not until they are four months old. At
the age of two years bats are sexually mature.
Bats vary in social structure, with some bats leading a solitary
life and others living in caves colonized by more than a million
The fission-fusion social structure is seen among several species
of bats. The fusion part is all the individuals in a roosting area.
The fission part is the breaking apart and mixing of subgroups by
switching roosts with bats, ending up with bats in different trees
and often with different roostmates.
Studies also show that bats make all kinds of sounds to communicate
with each other. Scientists in the field have listened to bats and
have been able to identify some sounds with some behavior bats will
make right after the sounds are made.
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