The classic image of a vampire is a tall and pale human aristocrat - but did you know that a considerable number of real-world animals exhibit vampiric behaviour?
Vampire bats are probably the best known hematophagic (blood drinking) animal (with three species known to exist in South America. They feed solely on blood, which presents its own set of challenges - the large volumes of liquid, protein and iron can be quite harmful. The bats possess specialised kidneys and gut bacteria to help them filter out the excess and survive.
The bats use thermal receptors located in their nose to help them detect blood-flow near the skin of prey, allowing them to find a good "donor" site to bite. Thanks to their hearing, they can even detect the regular breathing pattern of a sleeping (and thus defenceless) animal.
In contrast to regular bats, vampire bats can move on the ground using their wings and legs, and are even capable of "running" and jumping - all the better to stealthily sidle up to a prospective meal. Finally, the bite of a vampire bat carries specialised saliva into the wound - this acts as an anticoagulant and encourages blood flow.
Despite their image, vampire bats are rather social animals, huddling in colonies to retain heat in cold temperatures. They also can "share" meals, sometimes regurgitating blood for a fellow bat that didn't have a successful hunt.
Bats are not the only flying bloodsuckers out there. The Oxpeckers (birds of the Buphagidae family) also have a taste for hematophagy. They perch on the backs of grazing animals, feeding on the various ticks, flies, and grubs that parasitize them. Unfortunately they also help themselves to the flesh and blood of any wound on the animal's back, even picking them open with their sharp beaks.
There's also the vampire ground finch (Geospiza septentrionalis) that hails from the Galapagos Islands. This strange bird has an even stranger diet, supplementing nectar and carrion with eggs and blood pecked from blue-footed boobies and other birds. Even weirder, the birds of the island don't attempt to resist - it seems that the pecking is close enough to "grooming" behaviour (where the finch removes parasites from another bird) that the boobies are fooled.
If bats have a contender for "most recognised bloodsucker" it would be the mosquito. This is slightly misleading as it's only some female mosquitos that seek out blood. Normally they feed on plants, but use a meal of blood to produce a clutch of eggs. They hunt by scent, injecting the victim with anticoagulant saliva and sucking up a bellyful of blood.
In contrast, moths from the genus Calyptra use a hollow proboscis to extract blood from mammals. Oddly, it's only the male moths that do this - scientists theorise that salt taken from the blood is passed from the male to female during courtship, then passed on to any eggs. Outside of mating, the moths use their sharp proboscis to puncture fruit and flowers for juice and nectar.
Amblyoponinae ants are another interesting example, as they drink the hemolymph (blood) of their own grubs, earning them the moniker of Dracula ants. They do this because adult Dracula ants are incapable of consuming solid food, so they bring captured prey back to their grubs, who can. As a side note, Amblyoponinae hold the record for fastest moving animal alive thanks to their jaws, which they can "spring load" before hurling captured prey into a solid object to incapacitate it. The jaws go from 0 to 200 miles per hour in speed, and they do it in 0.000015 seconds. How's that for supernatural speed?
Leeches are another classic, attaching themselves to prey that wades nearby and drawing out their blood from a small incision. While not all leeches are parasitic, the majority will inject Hirudin (an anticoagulant) into any wound they cause, then hang on to the prey until full. Humans used leeches for bloodletting in primitive medical practices, and they still find use in reconstructive surgery. Coagulated blood can be removed from the site of an operation if a leech is allowed to attach itself nearby. This allows normal circulation to occur, bringing fresh blood and nourishing regrowing flesh.
Though the vampires of legend are often harmed by water, there are real hematophages dwelling in the deep. The lamprey is one such fish. It lacks a jaw and resembles an eel with a toothed disk instead of a mouth. Around half of the known species of lamprey are parasitic, attaching themselves to large fish using their "teeth" to anchor themselves. Once attached, the lamprey will scrape the surface tissue of the prey until reaching blood, and then produces anticoagulants to keep the buffet open. Interestingly, lampreys are able to withstand higher quantities of urea (a big part of urine) than most animals, since fish blood contains a considerable amount.
So why did these creatures become hemophages? Well, blood is a rich source of proteins and lipids (fats) and thus a great source of food... if it can be safely obtained. As such, it's no surprise that some animals would specialise in hematophagy, especially if they already had suitable feeding equipment like the sharp proboscis of a mosquito or moth. After all, it's a short jump from biting fruit to biting flesh.
Not all hematophagic animals require blood to survive. Some only use it as a dietary supplement when available, to give them a boost while reproducing. Furthermore, most hematophages leave their victims alive and functional - and thus available for later feedings!
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.