Vampire Bat

A **Vampire bat** is any member of the subfamily **Desmodontinae**, a group of phyllostomid bats distributed throughout Mexico, as well as Central and South America.

### Evolution

Vampire bats are a diverse family of bats that consume many food sources, including nectar, pollen, insects, fruit and meat. The three species of vampire bats are the only mammals that have evolved to feed exclusively on blood (hematophagy) as micropredators, a strategy within parasitism. Hematophagy is uncommon due to the number of challenges to overcome for success: a large volume of liquid potentially overwhelming the kidneys and bladder, the risk of iron poisoning, and coping with excess protein. There are multiple hypotheses for how vampire bats evolved:

* They evolved from frugivorous bats with sharp teeth specialized for piercing fruit.
* They initially fed on the ectoparasites of large mammals, and then progressed to feeding on the mammals themselves (similar to the feeding behavior of the red-billed oxpecker).
* They initially fed on insects that were attracted to the wounds of animals, and then progressed to feeding on the wounds of the animals.
* They initially preyed on small arboreal vertebrates.
* They were arboreal omnivores themselves and began ingesting blood and flesh from wound sites of larger animals.
* They were specialized nectar-feeders that evolved to feed on another type of liquid.

The vampire bat lineage diverged from its family 26 million years ago. The hairy-legged vampire bat likely diverged from the other two species of vampire bats 21.7 million years ago. Because the hairy-legged vampire bat feeds on bird blood and it is the ancestral vampire bat, it is considered likely that the first vampire bats fed on bird blood as well. Recent analyses suggest that vampire bats arose from insectivores, which discount the frugivore, carnivore, and nectarivore hypotheses of origin. Within 4 million years of diverging from other Phyllostomidae, vampire bats had evolved all necessary adaptations for blood-feeding, making it one of the fastest examples of natural selection among mammals.

## Description

Vampire bats have short, conical muzzles, lacking a nose leaf and instead possessing naked pads with U-shaped grooves at the tip. The common vampire bat also possesses thermoreceptors on its nose. Vampire bats have front teeth adapted for cutting, and the back teeth are much smaller than in other bats. While other bats have almost lost the ability to maneuver on land, vampire bats can walk, jump, and even run by using a unique, bounding gait, in which the forelimbs instead of the hindlimbs are recruited for force production, as the wings are much more powerful than the legs. This ability to run seems to have evolved independently within the bat lineage. They are also capable of detecting infrared radiation; the only other known vertebrates capable of doing this are boas, pythons and pit vipers, all of which have pit organs.

## Behaviour and Ecology

### Roosting

Vampire bats tend to live in colonies in almost completely dark places, such as caves, old wells, hollow trees, and buildings. They range in Central to South America and live in arid to humid, tropical and subtropical areas. Vampire bat colony numbers can range from single digits to hundreds in roosting sites.

### Social Habits

The basic social structure of roosting bats is made of female groups and their offspring, a few adult males, known as "resident males", and a separate group of males, known as "nonresident males". In hairy-legged vampire bats, the hierarchical segregation of nonresident males appears less strict than in common vampire bats. Nonresident males are accepted into the harems when the ambient temperature lowers. This behavior suggests social thermoregulation. Resident males mate with the females in their harems, and it is less common for outside males to copulate with the females.Female offspring often remain in their natal groups. Several matrilines can be found in a group, as unrelated females regularly join groups. Male offspring tend to live in their natal groups until they are about two years old, sometimes being forcefully expelled by the resident adult males.

### Food-sharing

Vampire bats form strong bonds with other members of the colony. A related unique adaptation of vampire bats is the sharing of food. A vampire bat can only survive about two days without feeding, yet they cannot be guaranteed of finding food every night. This poses a problem, so when a bat fails to find food, it will often "beg" another bat for food. A "donor" bat may regurgitate a small amount of blood to sustain the other member of the colony. For equally familiar bats, the predictive capacity of reciprocity surpasses that of relatedness. This finding suggests that vampire bats are capable of preferentially aiding their relatives, but that they may benefit more from forming reciprocal, cooperative relationships with relatives and non-relatives alike.

### Diet

Vampire bats exhibit hematophagy, meaning that they feed solely on blood. They hunt only when it is fully dark. Like fruit-eating bats, and unlike insectivorous and fish-eating bats, they emit only low-frequency sound pulses. The common vampire bat feeds primarily on the blood of mammals (occasionally including humans), whereas both the hairy-legged vampire bat and white-winged vampire bat feed primarily on the blood of birds. Once the common vampire bat locates a host, such as a sleeping mammal, it lands and approaches it on the ground. It then likely uses thermoception to identify a warm spot on the skin to bite. They then create a small incision with their teeth and lap up blood from the wound.

The bat's saliva, left in the victim's resulting bite wound, has a key function in feeding from the wound. The saliva contains several compounds that prolong bleeding, such as anticoagulants that inhibit blood clotting, and compounds that prevent the constriction of blood vessels near the wound. In effect, vampire bats are among the few venomous mammals.

### Predation

There is apparently little data on what feeds on vampire bats, though it is known that *Desmodus rotundus* is hunted by owls and snakes.

## Genera

* *Desmodus*
* *Diphylla*
* *Diaemus*

## Citations

* https://animaldiversity.org/accounts/Desmodus\_rotundus/
* https://en.wikipedia.org/wiki/Vampire\_bat