General Tidbits:

Habitat and distribution: Desmodus rotundus range throughout South and Central America and Mexico, as far north as 175 miles from the US border (Dalquest 1955). Fossils have been found in the Mexican border states as well as Florida, all of which have suitable habitat and food sources, so it is postulated that they "have yet to reoccupy" their former range (Ray et al, 1988).

freeTailmap-www.thewildones.org (animals/mammals /vampire), edited according to (Koopman 1988). ------->

Vampires inhabit a wide variety of habitats, fitting with Trajano's description of bats as "ecologically flexible." Dalquest describes them as "the most adaptable of mammals", found in jungles, on arid coastal plains, in the mountains, in brush and mesquite plains, and deserts.

Vampires live mostly in trees and caves where temperatures are constant, it is dark throughout the day, and humidity is high. 60% is the minimum required in captivity (Schutt et al. 1999) though in the field during the wet and most of the dry season it stays at 100% due to proximity to water (Wilkinson 1985a).

Social Spacing
Social Organization
Mating System
Food
Reciprocal Altruism
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References

Physical characteristics: Vampires measure 2-3 inches from nose to "rump" as described by Dalquest and do not have external tails. Their forearm bone is 2 to 2.5 inches and their thumb is another 1.5" - longer than their hind feet! It is well developed and helpful in vampires' varied locomotion, which includes not only flying but crawling, climbing, walking, and running. Wingspan is 3.5 cm, and adult bats weigh on average 34.8 g (Bhatnagar 1988).

Enlarged ears aid in echolocation, though bats have very good eyesight as far as bats go, with a visual acuity angle of .7, meaning they should be able to detect a single cow at 130M (Turner 1975). The noseleaf typical of other bat species is much reduced (to the point that Dalquest states it as absent), though their excellent olfactory capabilities could explain their preference in breeds and estrous cattle. Echolocation pulses are orally emitted, so vampires fly with their mouths open for navigation, not in preparation to bite. Their capabilities are moderate compared to other bats, with a threshold of identity of .5 mm wires; they are "unspecialized." Prey is most likely detected by sound as vampires have an excellent auditory capacity and are quite sensitive to the slightest changes in sound, though eyesight is also used in detection. (Schmidt 1988)

As they need not chew blood, vampires have the fewest teeth of all bats, only 22. Only 10 of these, 6 incisors and 4 canines, are used in feeding (Houston Zoo 2002). They also differ from other bats in that they have no enamel (Greenhall 1988).

Locomotion: The common vampire (D. rotundus) and the white winged vampire (D. youngi) both have quadrupedal stances, though prey selection has optimized two different "locomotor morphologies." The common vampire has an elevated stance for agility, speed, and power (they are well-known for making flight-initiating vertical jumps). The white-wing has a crouched stance for stability and inconspicuousness, as they tend to climb around branches to get to their avian prey, attacking from below. (Schutt et al. 1999)

Altenbach describes 9 locomotor behaviors:
1: Hanging Postures: Vampires hang from horizontal or vertical surfaces by their hind limbs, preferentially with pectoral limbs in contact as well. This posture allows them to move their body parallel to the surface without having to reposition their limbs.
2: Climbing: Vampires usually climb a vertical surface backwards or head down with the body elevated off the surface.
3: Standing Postures: specialized to allow movement parallel to the surface without repositioning, like the hanging posture. The body is elevated, with weight resting on all four limbs.
4: Walking: the deliberate and "spider-like" gait is used when stalking prey from the ground. A faster gait involves alternating strokes, by side (imagine a bear's gait).
5: Hopping: faster than walking, now the alternation is front to back, with an "airborne" phase in the stride. (Imagine a cat's running gait).
6: Jumping: Vampire bats' most derived feature is their ability to jump, from either a horizontal or vertical surface. Jumps are variable and can be taken in any direction, including backwards (an avoidance jump), though most jumps leading to flight are within 90º of anterior.
7: Initial Wingbeats Following a Jump are usually of large amplitude. A steep initial climb is leveled off within a few wingbeats (If taking off from the ground).
8: Slow, Horizontal Flight: The average speed is 3m/sec, with an average wingbeat frequency of 12.2/sec.
9: Alighting on a Horizontal Surface: the motion typical of a jump is performed in reverse order; this is most likely conducive to vampire's almost silent landings.

Natural History: There are three species of bats labeled as vampires living today: the hairy-legged vampire (Diphylla ecuadata), white-winged vampire (Diaemus youngi), and the common vampire (Desmodus rotundus), on which this website focuses. When a reference is made to simply "bat" it is referring to D. rotundus, unless otherwise specified. Vampires were rare in eastern Mexico in prehistoric times (Pleistocene era), but the conquest by Europe brought large numbers of domesticated animals, easy bait (Dalquest 1955). Since then vampires have increased in numbers and are limited in population not by food, which is abundant and in large herds, but by suitable roost sites. They are the most common bat species in the karstic (limestone) caves of Brazil (Trajano 1996) but in the absence of caves will roost in any dark crevice, such as buildings and hollow trees.

Lifespan: Through Rexford D. Lord's study on annual growth rings in vampire bat teeth, a maximum lifespan of 18 years in the wild has been determined, with the longest in captivity being 19.5 years (Wilkinson 1988).

Predators: opossum, coyote, raccoon, skunk, red-shouldered hawk (Greenhall 1988). Wilkinson includes owls, snakes, and lizards as potential predators. The most notable predator, however, is man. Vampires have been known to spread rabies, equine and bovine trypanosomiasis, and Venezuelan equino encephalomyelitis (Turner 1975), among other nasty surprises. Their wounds also provide entry points for parasites and bacterial infections. Rabies is not very deadly to vampire bats and they thus make excellent vectors. They are considered a pest; millions of livestock are lost per year due to disease, and Dalquest goes to great lengths to discuss extermination possibilities. It is estimated that in 1984 a combined 14 Latin American countries lost about $42.3 billion in US dollars. Previously poison gas, burning, dynamiting, blocking off caves and trees, and shooting had been attempted (Dalquest 1955, Lord 1988), but in 1972 the anticoagulant method was devised. An anticoagulant mixed in Vaseline was applied to vampires fur, where it was then licked off by the bat and other members of its colony, causing mass fatal internal hemorrhaging. Anticoagulants can also be injected into the rumen of bovines, where it spreads to the blood in small enough amounts to be harmless to the herd but still fatal to vampires (Lord 1988).

Predator defense: Vampires' main defense is hiding. They remain in the deepest, darkest roosts they can find during the day and only come out at night. They vary their foraging time based on lunar cycle (Wilkinson 90); they are extremely lunarphobic and will delay foraging until the moon has set. By hiding and only emerging in darkness vampires remain almost invisible to potential predators. (Wimsatt 1969)

Temperament: Vampires are feisty critters, Dalquest warning that they must be handled "with extreme care, for they move swiftly and bite viciously." Due to the anticoagulant in their saliva, wounds are slow to heal. Dalquest also describes the vampire's tenacity of life, describing many methods of killing that fail (such as asphyxiation). Even when shot and injured, vampires manage to "hop, scurry, or fly" out of reach. (Dalquest 1955)

In many South American regions locals insist vampire bites on humans are bites de las brujas (witches) and refuse to accept their actual source. Though attacks on humans do occur (and when they do, it is usually multiple attacks on one person and none on another. People's "susceptibility" varies, much like bug bites), we are last on their priority list. (Dalquest 1955)

Vampires are also intelligent, learning quickly in captivity and in the wild. Trajano noted that over the course of her 2-year study bats caught at recapture sights decreased, while observations of bats avoiding the mist nets and using alternate entrances increased. (Trajano 1996)

It is disputed whether D. rotundus tames easily in captivity. Schutt et al. found that they did not, though Altenbach and Wimsatt have said they do, as is also the implication in DeNault et al's study on male reciprocity.

Please note this is an undergraduate website created for Animal Behavior 323 at Davidson, College, NC, by Julie Perry. Questions, comments, suggestions, corrections: please email Juperry@davidson.edu

© Copyright 2002 Department of Biology, Davidson College, Davidson, NC 28035 - - - - - - - - - - - - - - - - - - - - Last updated: 19 April 2002