Let's start by getting the obvious one out of the way first. Mosquitoes just suck (get it?). They're the deadliest creatures on the face of our planet, killing more people each year than all the sharks, hippos, and dolphins combined. As Joe Hanson explains in the video below, the few hundred mosquito species who feast on human blood – and it's only the females who do so – are directly responsible for the deaths of some 45 million people each year. That's because when the mosquito sucks up your blood, it leaves behind some Plasmodium parasites, which cause malaria. As Dickson D. Despommier, a professor of public health and microbiology at Columbia University told New York Times science writer Natalie Angier in 1990, ''about half of all people who have ever lived on earth have died from malaria or malaria-related problems... That's an astonishing notion."
Mosquitoes may be just the worst, but they've got their own blood sucking parasites to contend with. That's right; mosquitoes suffer from even tinier blood suckers. The little critters that suck the blood out of mosquitoes are tiny little midges called Culicoides anophelis. They were first discovered in 1922, but it was only recently that a group of researchers really paid them any real attention. As dangerous as mosquitoes are for us, imagine what it would be like to be a mosquito and to have to contend with a dinner-plate sized midge landing on you to suck out your blood. Kind of makes you feel bad for the mosquito, doesn't it?
Jennifer Frazer explains at Scientific American:
It has been found to parasitize at least 19 species of mosquito, but it has also been collected sucking blood directly from buffaloes and cattle.
Culicoides midges are known carriers of bluetongue virus, Oropouche virus and Schmallenburg virus while mosquitoes they parasitize carry Dengue, West Nile, and Japanese encephalitis viruses. If mosquitoes are flying dirty syringes that spread disease among humans, parasitic midges may further scramble the disease load, introduce new viruses to new vectors, and generally add another order of magnitude to disease transmission calculus. But no one really knows.
Catfish may look kind of freaky, what with those long barbels hanging down from their mouths, but what's even freakier is that there's a group of them in South America who drink blood. And not just any blood; they require it fresh from the source.
Researchers knew for some time that the small catfishes called pygidiids could be lured with raw meat and sometimes fed on dead mammals left in the water. In 1960, one researcher caught one of the blood-suckers and "permitted [it] to fasten onto his hand for a short while during which time it succeeded in drawing blood, apparently using its mouth as a sucking apparatus and rasping with the long teeth in the middle part of its upper jaw." It seemed, he added, "to be utterly avid for a meal of blood and had to be forcibly removed." Yum.
Given all that, it may seem like these crazy little catfish just go for anything bloody. But in 1959, the Cleveland Aquarium became home to 4 of the fish, called candirus. The keepers there tried to feed them frozen brine shrimp, living worms, chopped worms, raw smelt, minced raw smelt, freshly killed goldfish, or goldfish blood.
But the candirus weren't having any of it. For three days the candirus maintained their hunger strike. And then, on the third day, a half-pound goldfish was put into their aquarium. Almost immediately, according to the report, three of the four latched onto the goldfish under its gills and began sucking blood.
A candiru feasting on the blood of a goldfish at the Cleveland Aquarium, via Kelley & Atz (1964).
"Whenever a goldfish was introduced into the candirus' aquarium, [the candirus] swam rapidly around its head, touching, or nearly touching, it with their own," report the researchers. They didn't force their way inside; instead, they waited for the goldfish's gills to open naturally during respiration, and then they latched on. "Almost immediately after the anterior part of a candiru had disappeared under the gill cover, its belly would begin to swell with blood." Larger goldfish could sustain multiple feedings. Sadly, smaller goldfish usually died after just one attack.
Candirus aren't the only fish that feast on blood. Lampreys look more like aliens from another planet than regular old fish, but they're fish just the same. They live both in fresh and salt water all over the world, and while they're scary enough in their own ecosystems, they've even worse when they're invasive. When the Erie Canal first connected the Great Lakes with the Atlantic Ocean, the lampreys invaded. They completely decimated several native lake fish species, some of which are now extinct, and occasionally attacked humans as well…but only if they were poor hunters to begin with. The statistics reported by the USGS are striking: "Lake trout catch in Lake Huron fell from 3.4 million pounds in 1937 to virtual failure in 1947. In Lake Michigan, U.S. catch fell from 5.5 million pounds in 1946 to 402 pounds in 1953. In Lake Superior, catch dropped from an average of 4.5 million pounds to 368 thousand pounds in 1961."
What list of blood sucking critters would be complete without the aptly named vampire bat? All three vampire bat species are native to Central and South America, and all require blood to survive.
You can rest easy knowing that the hairy-legged vampire bat and white-winged vampire bat both prefer the blood coursing through the veins of birds. But the common vampire bat feeds mostly on mammals, including humans. The common vampire bat has a secret weapon for dealing with particularly furry mammals – it uses its razor-sharp incisors to shave away the hair, allowing it to pierce the skin with its remaining teeth and slurp up the oozing blood. And it's got another weapon. Inside vampire bat saliva are a set of compounds that prevent coagulation, keeping the blood bag bleeding for as long as possible.
It all sounds a bit macabre, but vampire bats have proven quite useful to researchers studying altruism in the animal kingdom. That's because bats that have eaten well on any given night will regurgitate blood into the mouths of hungry bats. And they don't just feed their own kin, making it truly altruistic. And that's good, because on another night, that well-fed bat might find itself in need of a square meal. At one time, researchers thought that hungry bats had to harass their friends in order to get some tasty blood vomit, but more recently they've seen bats approach their hungry colony-mates and offer up some blood vomit without being prompted. Now that is true friendship.
Photo via justinlindsay/Flickr.
There are blood sucking mammals, fish, and insects. But surely birds are more civilized? Wrong.
Meet the sharpbeaked ground finch, a bird that lives in the Galapagos that is also sometimes called the vampire finch. They don't rely solely on blood; like other finches, they peck at seeds. But every once in a while a vampire finch has a craving for the warm red stuff. So it seeks out one of the most iconic animals of the Galapagos, a seabird called a booby. It pecks at the bird's back until it draws blood, offering easy access for a nice warm meal. But they don't over-peck. They draw enough blood to eat, but limit their pecking. Otherwise, they'll cause too much pain and the boobies will chase them away or fight back. That means that there's a vampire dinosaur. Which would have made the Twilight movies far more interesting.
The vampire squid's Latin name, Vampyroteuthis infernalis, literally means "vampire squid from hell." It's a tiny deep-sea dwelling cephalopod, rarely growing over six inches in length, but it has giant eyes. It's actually got the largest eye-to-body ratio in the entire animal kingdom; a six-inch individual will have eyes around an inch in diameter, enabling it to better see in the dark ocean depths.
Sadly, the vampire squid doesn't actually drink blood; it lives by gobbling up marine snow. It gets its name instead because it appears to have a cape, made of webbing between its arms, reminiscent of the one often worn by Count Dracula.