There’s no time like October to talk about vampire bats!
Content Warning!!! - the following article includes picture of blood, blood sucking animals, and open wounds. Proceed with caution.
Vampire Bat Species
There are three species of vampire bats: the Common vampire bat, the Hairy-legged vampire bat, and the White-winged vampire bat.
Common vampire bats are found in Central and South America. They feed mostly on livestock, preferring horses over cows and females over males. They are highly social animals. They have a high number of cooperative behaviors, including regurgitating food and mutual grooming. They are capable of maneuvering on land, including running and leaping. They have the least number of teeth of all bats, and have good eyesight along with their use of echolocation.
Hairy-legged vampire bats are found in Central and South America, including Belize, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Peru, and Venezuela. They feed on both birds and mammals. They are generally solitary, but may roost in small groups and may roost with the common vampire bat.
White-winged vampire bats are found in Central and South America, including Argentina, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, and Venezuela. Their preferred food source is birds, however they will occasionally prey on mammals, like cattle and goats. They are social animals and roost with many other species of bats, including the common vampire bat.
Hematophagy
All vampire bats drink blood. A diet of blood is known as hematophagy. It is incredibly uncommon in the animal kingdom. Besides vampire bats, some notable hematophagous animals include worms, arthropods like mosquitoes and ticks, leeches, fish like lampreys and vampire fish, and birds like vampire finches, hood mockingbirds, oxpeckers, and the Tristan thrush.
Hematophagy is classified as either obligatory or facultative. Obligatory hematophagous animals cannot survive on any other food, like human bed bugs. Facultative hematophagous animals can get nutrition from sources outside of blood in sexually mature forms. For example, certain species of mosquito will feed on pollen and fruit juice to survive, but require blood to produce their eggs.
Hematophagy can cause many problems. A blood diet can result in excess protein, risk of iron poisoning, and can overwhelm the kidneys and the bladder. However, vampire bats have evolved beyond these issues and their bodies are built for their blood based diet.
Science isn’t quite sure of the origin of hematophagy in bats, but a couple of hypotheses stem from these bats initially eating something else, before moving to blood. These alternate types of feeding include feeding on parasites before moving to feed on the host and feeding on insects attracted to wounds before moving to feed on the wounds. Other hypotheses propose that vampire bats evolved from frugivores, nectivores, carnivores, or arboreal omnivores. However, a study in 2012 proposes that bat ancestors most likely ate insects, with a bit of fruit, and all other feeding methods were derived from that. Since the earliest living vampire bat is the hairy-legged bat and they have a diet of mainly bird blood, it is thought that vampire bats first evolved to predate on birds.
Feeding
Vampire bats hunt only in complete darkness. They find their target by emitting low-energy sound pulses and using infrared radiation and thermoreceptors to find a good spot to feed where the blood is close to the skin. They land on the ground to approach their target, using their legs to run, jump and walk. If they’re faced with fur or hair, they use their teeth to shave a spot to get to the skin. Vampire bat incisors lack enamel which makes them permanently sharp. They produce an anticoagulant in their saliva to prevent blood from clotting while they feed.
Vampire bats will eat 30-40% of their body weight in one feeding, hindering their ability to fly. They process water out of the blood quickly and excrete it to be able to fly again, and can launch themselves off the ground.
Vampire Bats and Humans
Vampire bat saliva has been helpful in medical circumstances. Their saliva contains a protein called Draculin, after the infamous vampire Dracula. Since they produce an anticoagulant, vampire bat saliva can be used to increase blood flow, specifically in stroke patients. A 2003 study tested a drug to help stroke patients, but the drug was abandoned in 2014 after disappointing results.
Vampire bats can choose to feed on humans and can carry rabies. However, only 0.05% of vampire bats carry rabies, and the risk of human infection is much lower than that of livestock infection. Bats infected with rabies are often clumsy, disorientated, and unable to fly, and die 2-10 days after showing symptoms. Around the world, 99% of cases of rabies in humans come from domestic dogs.
We hope you learned something about vampire bats with us today, especially as we head into the most batty holiday of the year. Happy Halloween!
To all our batty friends out there, stay spooky!
