Bats are the only true flying mammals, with about 925 different species identified. Of all these species, only the common
vampire bat is able to maneuver on the ground as well as in the air. According to Schutt (1998), vampire bats can move side to side and backward,
similar to a spider. Instead of taking off in flight from the ground, these bats actually launch themselves into the air with powerful pectoral
muscles. The force comes from the bat extending its hind knees, leaning forward and using its forelimbs. The bat also invokes its triceps
muscle and very long thumb. While the jump only takes about 30 milliseconds, the bat catapults itself about 4 feet into the air. Altenbach
(1979) comments, “although a few other species of bats move readily on the ground and some take off from the ground, no other species possess the
extreme terrestrial agility and jumping ability of Desmodus”. Once in the air, the transition into flight is basically one fluid motion.
Since the vampire bat feeds at ground level, their agility and fast take-off is an amazing advantage.
Feeding on the blood of animals like cows, pigs, and horses, the vampire bat requires about two tablespoons of blood each day.
Locating their prey is a combination of smell, sound, echolocation, and possibly heat (Altringham 1996). While they do not actually suck blood
from their host, they make a small incision and lap up the blood. Since they do not chew their food, they have fewer teeth of any other bat.
They generally approach their prey from the ground. “They have heat sensors on their noseleaf for locating capillary-rich areas of the skin;
modified canines for fur clipping; long, sharp incisors for painlessly opening a wound; anticoagulants to
prevent clotting; and a grooved tongue to help move blood rapidly to the mouth” (Altringham 1996). While the bat may consume up to 60% of its body
weight in blood and it only needs the red blood cells, it will begin excreting plasma before its meal is over. With a specialized stomach and
kidneys, the vampire rapidly removes the plasma as it may take up to twenty minutes to the bat to finish its meal (Altringham 1996). Due to length
of time and the invasive nature of its feeding, it is clear the vampire bat needs its deftness and agility to be successful. “Observations of
Desmodus scrambling over the backs and necks of animals prior to feeding (or to avoid movements of the host animal to brush them off), and running or
hopping about on the ground while feeding, illustrate the adaptive value of this effective terrestrial locomotion” (Altenbach 1996).
The unique social behavior of the vampire is most characteristic in their reciprocal altruism, in which animals return favors to
their mutual benefit. If vampire bats do not get their share of blood on a regular basis, they rapidly deteriorate. A bat may be close to
starvation within 2-3 days (Altringham 1996). Within social groups which largely refers to females as the males roost separately to defend
territories, bats that successfully feed will regurgitate back at the roosts to a hungry bat. Studies on the blood sharing behaviors indicate bats
will regurgitate to related and unrelated bats within the group. It is shown that they set up a buddy system, with pairs of bats forming tight
blood-sharing relationships (Altringham 1996). Refer to Figure 3 to see the weight-loss curve after feeding since donating more than 5% of its
body weight will push it too close to starvation (Altringham 1996).
Figure 3. Predictive curve of post feeding weightlosses in vampire bats (Desmondus rotundus). A donation of 5% of pre-feeding weight when at weight D
should cause a donor to lose C hours but provide the recipient at weight H with B hours. B >C for all E > F. See text for details. Redrawn from:
Wilkinson, G. S. 1984. Reciprocal food sharing in the vampire bat. Nature 308: 183.
Vampire bats are considered agricultural pests in many parts of Mexico and Latin America where rainforests have been cut down to make way for
grazing cattle. Here, control programs are initiated to cut down on health risks to the cows. According to Anastasia Toufexis (1995),” due
to the fear associated with the vampire bat, people routinely dynamite and burn caves or roosts. Unfortunately, people also destroy very helpful,
fruit eating bats that occupy the same areas. However, the vampire bat is not endangered at this point.
Currently, bats are in a single order, Chiroptera (hand-winged) and are thought to have appeared 65-100 myr, in the late Palaeocene
or early Cretaceous (Altringham 1996). They are divided into two subgroups, the megabats and the microbats. Megabats refer to the large,
fruit-eating bats confined to Africa, tropical Asia, and Indo-Australia (Altringham 1996). For our purposes, we will focus on the microbats that
are found on every continent and house our common vampire bat. The oldest fossil bat dates back 50 myr in the early Eocene period (Altringham
1996). There is poor representation of bats in the fossil record; however, some discoveries in Australia of extensive fossil bat fauna dates back
55 million years ago (Altringham 1996). Zimmer (1998) explains, “bats are not good candidates for paleontological study. When they die,
they usually disappear…often eaten by scavengers; if not, they decompose on the ground.”
Microbats show no close affinities to any other mammalian order, so this lack of a link suggests a very early origin. “There are a number of
cases where possibly closely related microbat species live on once adjacent, but now distant, fragments of Gondwanaland, the supercontinent which broke
up into fragments which now make up the land masses of the southern hemisphere” (Altringham 1996). When bats are thought to have been evolving,
the earth experienced dramatic diversification of flowering plants that became dominant over primitive plants of the Crenomanian period, 100-95 myr
(Altringham 1996). Insects were also supported by these flowering plants and insectivorous and frugivorous mammals must have had to
compete. The first bird dates back to the early Cretaceous, 135 myr, so they were quite abundant when bats appeared. Consequently, birds
were probably major competitors and/or predators for early bat species, which may have led to the nocturnal evolution of these small, nocturnal,
tree-dwelling mammals (Altringham 1996).
Flight in bats is one of the most fascinating evolutionary elements and currently has two theories on the table, the arboreal and the cursorial
(Altringham 1996). The arboreal suggests that tree or cliff dwelling ancestors evolved flight through a series of gliding stages. The
cursorial theory, which is more recent, requires the animal take a running leap with wings outstretched sending it into the air from a glide to flight
(Altringham 1996). With a basically absent fossil record in regard to flight, there is room for theory but little evidence.
To be successful night fliers, bats needed a more sophisticated system. Echolocation is orientation by analysis of echoes from
sound pulses. Due to the level of sophistication, it is presumed echolocation evolved alongside flight (Altringham 1996). Ancestors of
microbats probably emitted ultrasonic sounds in a simple form of echolocation, which became more sophisticated as bats became more adept fliers
There are some recent discoveries in bat evolution that contradict common bat ancestry. The most widely accepted theory linked megabats and
microbats in the same evolutionary line. Now, there is a body of evidence suggesting convergent evolution, where evolutionary change causes
unrelated species with different histories to acquire striking similarities. The controversy has megabats, primates and dermopterans closely
related while microbats are independent (Altringham 1996). Some compelling evidence is the absence of echolocation in megabats and their limited
distribution to the Old World tropics. Altringham (1996) expands, “this evidence is very diverse, from factors as simple as a consideration of
body size ranges, to the analysis of the amino-acid sequence of hemoglobin, obtained using modern molecular biology techniques.”
Desmondus Rotundus evolved as singivores, a strange niche that is unique to bats in the New World. Indeed, all three members
of the Desmodontinae family feed on blood exclusively. Vampires may have evolved from feeding on the insects and larvae on the wounds of large
mammals (Altringham 1996).
The common vampire, Desmodus rotundus, is widespread in the tropical and sub-tropical areas of the Americas. It occupies
rainforests as well as deserts, making its home in hollows, caves, trees, and even buildings. Usually, they live in colonies of about
one-hundred bats but can reach up to two-thousand. Preferring the blood of large mammals, the introduction of domesticated horses, cattle, and
pigs has meant an increase in its numbers over the last three-hundred years (Altringham 1996). Vampire bats move into subtropical Chile and
Argentina, but they are not excluded from temperate climates. Indeed, where there is prey, there could be a population of vampires. It is
suggested, then, that the limits to its distribution is due to the inability to transport quantities of food sufficient to maintain a high body
temperature in cool to cold places (Kunz 1982). Please refer to Figure 2 for Desmondus Rotundus distribution.
Map of Distribution:
Other interesting issues
Central and South America are alive with folklore about the vampire bat. Legend has it that bats are filthy, feeding on human
blood or that they have supernatural powers allowing them to change shapes from man to bat. While these legends may sound strange, there is
recorded evidence of human hosts. Glover Allen (1939) talks about bats feeding on humans, “while travelling down the Amazon valley, he (Dr.
William Farabee) awoke one morning to find that a vampire during the night had gouged a small piece of skin from the tip of his nose and had evidently
feasted while he slept, for the wound was still bleeding slightly” (98). Not all tales are negative; bloodletting has traditionally held healing
qualities. For example, the Mexican monk who came down with a violent fever and was given a death sentence by morning. But, the next day,
the monk was on his way to recovery. “It seems that his feet had been left uncovered and that during the night, a vampire bat had entered the
room, which, having bitten his toe and lapped his blood, had so reduced the fever that the sick man recovered” (Allen 1939).
While Western literature has embraced the vampire bat making it almost cliché, they did not appear in early vampire myth. The European folklore
of vampires did not incorporate the bat probably because they did not occur in that region (McKaig 1999). Some Gypsy folklore involved the
vampire bat but in a rather benign role; sometimes the bat’s bones would be carried in a small bag for luck (McKaig 1999). Regardless of the
history, vampire bats appear in our modern context as creepy blood-sucking creatures. They are represented in Halloween festivities often with
blood dripping from their fangs. The most recent representation of our flying mammal was the motion picture, Bats, where a colony of bats wreaks
havoc on a small Texan town. The trailers showed a swarm of screaming bats busting through car windows attacking the unassuming kids seated
Adams, Rick A. and Scott C. Pederson. Jan 1994. “Wings on Their Fingers” Natural
History vol. 103, p 48-55.
Allen, Glover Morrill. 1939. Bats Dover Publications; Harvard University, New York.
Altenbach, J. Scott. 1979. Locomotor Morphology of the Vampire Bat, Desmondus
Rotundus American Society of Mammalogists; University of New Mexico, New Mexico.
Altringham, John D. 1996. Bats, Biology and Behavior Oxford University Press;
University of Leeds, New York.
Kunz, Thomas H. 1982. Ecology of Bats Plenum Press; Boston University, New York.
McKaig, Angie. 1999. “Vampire Bats”
Scutt, William. “Vaulting Vampires” March 1998. Discover v. 19, no. 3. P 14.
Toufexis, Anastasia. Aug 1995. “Bat’s New Image” Time vol. 146, p 58-59.
Zimmer, C. Nov 1998. “Into the Night [Bat Evolution]” Discover v. 19; no. 11, p 110-
* Photograph URL for Figure 1 and 4,
** Map URL for Figure 2,