Each Halloween, you’ll see them come out in plastic and rubber varieties, genuinely creeping people out for their cultural connotations. Vampire bats have become icons of fear, mostly for their nocturnal behavior, and are associated with terror, mostly for their diet. But blood is actually the perfect food for these South American creatures: It’s inside the body of every vertebrate animal, and it contains red and white blood cells, so it’s rich in proteins. And yet, despite blood’s status as an excellent food source, feeding on it is rare in the animal kingdom.
Of course, there are drawbacks to an all-blood diet: While the dry-matter phase of blood is about 93 percent proteins, only 1 percent is carbohydrates. Plus, blood is relatively low in vitamins, and it can potentially contain pathogens.
This Halloween week, we’re at the bleeding heart of vampire season. While the below four animals below might not be Dracula, it doesn’t mean you’d like to encounter them at night, lest you become a blood feast yourself.
1. Bed Bugs
The common bed bug, or Cimex lectularius, is a parasitic arthropod the size of an apple seed. But don’t be fooled by its stature: This creature’s very existence is in opposition to human happiness. That’s because bed bugs only survive on blood — and what they really want is human blood. They’re built for it.
Bed bugs are specially equipped to find and bite humans: Studies show that they can smell more than 100 compounds in human skin. They use this skill to sniff us out, feed on our blood, and leave us covered in itchy bites. In a 2017 paper published in Scientific Reports, scientists point out that bed bugs are especially attracted to the odor of sleeping humans and are drawn to stinky laundry. The bed bug has also gone through a global resurgence — not great news for us, its favorite food.
Lampreys are extremely metal. There are nearly 50 species of these jawless, eel-like fishes, some that live in freshwater and others salt. They’ve essentially remained unchanged as an animal for the past 340 million years and have survived through at least four major extinction events. They’ve done this by doing what they do best: Biting and sucking.
The mouth of a lamprey would embarrass the Sarlacc. It’s a large, oval suction cup filled with razor-sharp horn-shaped teeth. Its tongue is also a razor — there are just razors everywhere. When a lamprey attaches itself to a victim, it scrapes against the animal with its scary tongue and sucks out the host’s blood and bodily fluids. While a lamprey isn’t a large creature — different species range in size from five to 40 inches in length — it doesn’t give a heck. Lampreys have been known to leap on and attach themselves to basking sharks and minke whales. They don’t care — they can heal themselves even after sustaining severe nerve damage.
Beyond just being creepy, they are also devastating populations of fish in the Great Lakes of the United States. According to the Great Lakes Fishery Commission, lampreys — which are considered invasive in the US — prey on most species of Great Lakes fish and make life extremely difficult for fisheries. The fish that manage to make it out alive don’t fare too well afterward: During months when sea lamprey populations are at their highest, up to 85 percent of fish not killed by the suckers are still scarred by lamprey attack wounds.
3. Vampire Finches
If you are a seabird and you live on Wolf Island, life is pretty darn good. As the most remote part of the Galapagos archipelago, it’s the perfect place to dive into the surrounding ocean for food. But the Sharp-beaked Ground Finch (Geospiza difficilis) is not a seabird. So instead of eating fish, it drinks blood.
Commonly known as the vampire finch, this bird pecks the skin of the neighboring seabirds — larger avians like Red-footed Boobies — with its sharp beak until it draws blood. Sometimes it will even feast on the blood of another bird after it dies. This extreme behavior, most common in periods when there are no seeds to eat, is theorized to have evolved from a time when the finches were pecking at other birds to eat their parasites. Now, they peck away knowing nutrient-rich blood will be the prize — a process that seemingly doesn’t seem to bother the birds they attack all too much.
4. Vampire Moths
Vampire moths, much like vampire bats and vampire finches, also drink blood. These moths, however, don’t need to consume blood to survive. Scientists think the practice isn’t obligatory but facultative; vampire moths don’t need to suck blood to survive, they just do it to supplement their diet. And the exact reason why they drink blood isn’t known (though it’s hypothesized to be a salt acquisition strategy). What they do know is that it’s seemingly only the males that decide to feast.
These creepy moths are able to drink blood because of their modified probosces: The moth’s tubular mouthpart is equipped with barbed hooks. It typically uses this wicked anatomy to pierce thick- and hard-skinned fruits like peaches, plums, and oranges. However, eight of the described species within the moth genus Calyptra, have also been observed using their proboscis to suck the blood from mammals. Five of these eight are known to pierce human skin.
Vampire moths are native to Asia and Europe, and they appear to bite humans more often at higher elevations and prefer other mammals at lower elevations. However, they are beginning to appear more often in Finland — a phenomenon that appears to be driven by the moth’s need to adapt to climate change, which, at the end of the day, is spookier than any blood-sucking beast.