Creatures of the Amazon
Vampire Bats

By Mike Collis

A Common Vampire Bat

There are 3 species of vampire bat, all of which live in Central and South America and the Carribean island of Trinidad and Tobago. The Common Vampire Bat (Desmodus rotundus) or the Leaf-Nosed Vampire Bat and the other 2 being the Hairy-Legged Vampire Bat (Diphylla ecaudata), and the White-Winged Vampire Bat (Diaemus youngi).

They prefer warm and humid climate. Tropical and subtropical woodlands and open grasslands are where they look for their prey. Vampire Bats roost in trees, caves, abandoned buildings, old wells, and mines. Vampire Bats will roost with other bat species but they are the most dominant.

Vampire Bats are the world's only parasitic mammals. They feed mainly on the blood of cattle and other livestock but do feed on other rainforest mammals like the tapir. In fact they will seek to satisfy its hunger on any type of mammal's blood including humans. These bats prefer the blood of females, perhaps because of the higher hormone content.

The Vampire Bat has short hair, with silver-grey fur underneath and darker fur on its back. They have small rounded ears, the lower lip is grooved, and a flat nose. A very strong clawed thumb on each wing helps it climb onto its prey. The bats are about 3.5 in long with a wingspan of 7 in. They normally weigh about 2 oz, but this can double after feeding. It has less teeth than most bats and the upper incisors lack enamel which keeps them razor-sharp. Vampire Bat males are smaller than females.

Skeleton of the vampire bat showing it's cannine incisors

Vampire Bats hunt at night, using echolocation to locate their prey. They feed in an area of 3 to 5 miles radius from their home roost. When a bat selects a target they very slowly approach their prey on the ground while they are sleeping. Vampire bats are the only bats able to move on the ground. Then it jumps onto its prey targeting the rump, flank, or neck using heat sensors in its nose to locate blood vessels close the surface of the skin. It cuts open the animal's skin with its razor-sharp teeth, peels away a small sliver of skin, and laps up the blood with its long tongue. Lateral grooves in the tongue are used to channel the blood into its mouth. The blood does not clot because the bat excretes an anticoagulant from its saliva. While feeding, the blood is kept in a cardiac notch. Bats feed for 30 minutes after which time they are so swollen with blood, they can hardly fly. They hide on the ground and wait for the blood to digest and urinate to reduce their weight to enable them to fly. Vampire Bats often return to the same animal to feed night after night. They protect their host and will fight off intruding bats while feeding. Usually no more than 2 bats feed on the same animal at the same time, although young are allowed to feed with their mothers.

Male Vampire Bats are polygynous, and have many mates. Dominant adult males form harems of females which they defend rigorously. A male and his females compose a "harem". Harems often include other subordinate males. The dominant male has preferential rights with the females and sires about half of the young in the group. The second dominant male fathers the second-most offspring, and so on. Harem males are the only ones that mate with the females in the harem. Bachelor males try to mate with harem females when they can, but the females usually deny them. Sometimes dominant males are rejected by females, possibly to avoid inbreeding.

When Vampire Bats mate it usually takes three to four minutes. During mating the male bat mounts the female from behind, grips her back with his teeth and inseminates her. Although there is no mating season as such, and they mate throughout the year although actual pregnancies rise during the rainy season. After a gestation period of about 7 months one baby is born. Females look after the young and mothers often leave the baby with another female when they go to hunt. On their return the mother calls its baby to feed on its milk. Baby Vampire Bats feed only on their mothers milk for the first 3 months of their lives. After this time they are fed on a mixture of their mother's milk and regurgitated blood. After 6 months the young join their mothers to hunt but still feed on their mothers milk untill they are 9 months old.

Because Vampire Bats carry rabies and because it feeds on livestock they are considered a pest. The International Union for the Conservation of Nature (IUCN) have declared Vampire Bats to be creatures of "least concern".

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