I am often
asked if all bats "suck" blood. In fact, there are no bats that
"suck" blood. Only 3 species out of the almost 1000 bat species,
are vampire bats. Vampires do not suck blood, they make a razor
sharp wound in their prey; then lap blood from the wound.
bats are the most feared and misunderstood of all bats. The very
mention of their name conjures up the vision of a large beast flying
through an open bedroom window, puncturing the neck of a sleeping
beauty, then sucking the life blood out of its unsuspecting victim.
In reality, there are no vampires (at least bats) anywhere in Europe
or the United States. The three species of true vampire bats all
reside in Mexico, Central America, and South America. They are tiny
creatures, no larger than a mouse, with an average weight of around
one-ounce (28.35 grams), and an average body length of 2.75" with
an 8" wingspan (19.44 centimeters). They have no interest in the
neck of a sleeping beauty, unless that sleeping beauty happens to
be a cow. Vampires feed on cattle, other livestock, and birds. Vampires
seldom bite dogs since dogs can hear sounds of higher frequency
than larger mammals and would likely waken.
vampires fed on the blood of wild animals and the population of
bats was held in check by the amount of food available. With the
influx of domestic cattle into Latin America, they found an inexhaustible
food supply and their numbers have increased dramatically.
The most studied
and familiar of species, the common vampire bat Desmodus rotundus
lives almost exclusively on mammal blood. The hairy-legged vampire
Diphylla ecaudata feeds almost exclusively on bird blood, and the
rare white-winged vampire Diaemus youngi prefers the blood of birds,
but also feeds on the blood of mammals. The licking of blood by
the Desmodus is the most thoroughly studied feeding behavior.
common vampire bat is a crevice dweller, sometimes roosting alone,
but most often in small colonies or in colonies of up to a thousand.
Members of these colonies will recognize each other individually.
Although there are some squabbles over territory, they do not use
their sharp teeth in a fight.
prefers a roost of almost total darkness; caves, old wells, abandoned
buildings, hollow trees, or mine shafts. They will sometimes move
from one daytime roost to another, which is closer to their prey.
This kind of activity indicates that they learn from experience
where their prey can be found. Vampires use rivers as navigational
tools as they move from one part of their range to another. The
rivers are easier to follow than wooded routes, and cattle often
graze in pastures near water.
their roost in after dark, often traveling in small groups of 2
- 6, flying just above the ground. They are most active around midnight.
Vampires locate and recognize their hosts by smell, appearance,
echolocation, radiated body heat, and breathing sounds. All bats
are great fliers, but the vampire is also a great walker. They literally
tiptoe up to their donor, jumping in all directions to avoid the
movements of their host. They can jump like a frog, leap straight
up into the air, or walk on two legs like a monkey!
waken the sleeping prey and their donor scarcely notices the painless
bite. They feed on only one donor per night, do not bite deeply,
nor do they struggle with their donor. It has been observed that
a vampire visited the same donor on several consecutive nights,
always opening the old wound. Often several animals can share a
bite, since it takes a while for the wound to close due to anticoagulants
that enter the wound from the bat's saliva. It has been observed
that a wound has bled for as long as 8 hours.
The same enzymes
in vampire bat saliva that keep a victim's blood flowing may soon
be used to fight heart disease in humans. Scientists believe those
anticoagulants will effectively dissolve human blood clots, the
major cause of heart attacks.
A blood meal
lasts about 25 minutes, although the entire process of locating
prey and making the incision can take up to 2 hours. The wound the
vampire makes is approximately 5 mm deep and 5 mm in diameter, and
does not cut arteries or veins. If you made a wound this size on
your body, it would produce about one drop of blood or less than
a gram. Different sources quote the amount of blood ingested by
a vampire to be between 5 and 8 teaspoons per night. This is a heavy
weight for a one-ounce creature to carry on the flight back to the
roost. Because warmer ambient air temperature demands less energy
expenditure, calculations have shown the net gain in energy through
the intake of blood is possible only in the Tropics.
of their highly specialized food intake, vampire bats have had to
adapt in many ways. Their mouth structure is different: they have
fewer teeth than most bat species, the incisors and canines are
shear-like, the cutting edge forming a "V" and all traces of crushing
surfaces are absent. Other indications of their liquid diet include
a tongue that is adapted to lapping, a short esophagus, and a slender
stomach adapted to stretch to hold and digest blood. Their wings
and body structure have adapted to taking off with a great load.
unlike some other bat species, vampires breed year round. After
a long gestation period of seven months, they generally give birth
to one youngster, on rare occasions, twins. The juvenile development
of vampires is very slow in comparison with other bat species. They
continue to be suckled up to nine months: the change from a milk
diet to a blood diet being difficult. This suckling time is three
months longer than the flying foxes, which are many times their
size and at least six months longer than most other bats. Relatively
early on the youngsters will lick small amounts of blood from the
mouths of returning adults. In their fourth to fifth month, he youngster
begins to accompany the mother while foraging. Again, unlike other
bat species, motherless youngsters are not doomed to starve. Other
females will adopt them.
do not accumulate large fat reserves, they cannot survive more than
two or three days without a meal. Vampires reduce the danger of
starvation through their impressive altruistic behavior. In response
to a specific pattern of begging behavior engaged in by animals
that have failed to obtain a meal, vampires will regurgitate part
of their meal to help another!
their complex anatomical and physiological specialization, and their
amazing social structure, vampires are surely among the most fascinating