Vampires 101: An interview about vampire bats

I just spoke with a geologist who was fed on by a vampire bat while she slept outside just down the street from where I live. She found the small but bloody bite on her toe in the morning. In many years, vampire bats were almost never caught near Gamboa, Panama (where I live now) but since I’ve been here, people have caught 4 of them not too far away. Perhaps they are moving nearby because of some new large animals at the nearby zoo. (Or maybe they know I’m here!)

If you are bit by a bat, get a rabies post-exposure vaccination.

—-in other news—

I recently answered a bunch of questions from a journalist writing an article about blood-feeding. I thought my answers might also be of some interest to readers here, so I’m posting them below. I’m not posting his questions, because that might be some kind of copyright violation. (I did check to see if I own my own answers in an interview, and I think I’m in the clear). In the past, I’ve given interviews where journalists just use a tiny segment or quote (or misquote) which can completely distort what I was saying. So here’s the whole thing…(Sorry in advance for typos. It was an interview, not an article.)

On the public’s fear of vampire bats

Bats are perhaps the most misunderstood and maligned group of mammals. And of those more than 1300 species of bats, the three blood-feeding vampires are the most feared and hated, especially in Latin America where they live. Vampire bats are named after the mythical vampire legend, which actually pre-dates the discovery of the bat by European naturalists. As the name suggests, vampire bats drink nothing but blood, and throughout Central and South America, they most often feed on the blood of livestock. They only take about a tablespoon of blood, so they don’t kill the animal, but they can spread diseases like rabies. For this reason, they are considered a serious nuisance and a concern of animal and public health, and their populations are actively reduced in many areas by poisoning.

What most people don’t know about vampire bats is that they are actually incredibly intelligence and socially complex. Like primates, they form long-term social relationships and perform extensive social grooming. They possess a form of cooperative food sharing. If a bat comes back to a roost without getting a meal, other bats in her social network will regurgitate food for her, just like a mother bird does for her chicks. The difference is that the bats don’t just feed their offspring; they feed adults, both kin and non-kin that have helped them before. Bats that are more generous are fed more when they fail to feed. They rely on a social support network, and in that way, the bats have something analogous to human friendship. They also have very large brains and very large neocortex; they are outliers among bats in this regard.

I would say that the public’s relationship to vampire bats in Latin America is similar to North America’s relationship to the wolf in the last century. Both of these animals can be severe nuisance to farmers and ranchers. Teddy Roosevelt called wolves “the beast of waste and destruction” and the government policy was to kill them all until they were extirpated from an area. That’s essentially the policy towards vampire bats in Latin America. Now people in North America have a much more respectful and even reverential attitude towards wolves. We respect them for their intelligence, mystery, and their primal beauty. Maybe the same will happen with vampire bats.

On how vampires feed

Vampire bats have been observed feeding on many different kinds of wild and domestic animals, including horses, cows, goats, pigs, chickens, tapirs, peccaries, sea lions, even eagles and penguins. People can also be fed on by vampire bats, especially in the Amazon region of Peru and Brazil where humans might be even more accessible than livestock. The most common vampire bat (actually called “the common vampire bat”) prefers mammals. Another species prefers birds but will feed on mammals if available, and another rare vampire bat feeds exclusively on birds.

A vampire bat will usually feed on sleeping “host”. They walk or climb stealthily to an area where blood is close to the skin. They find this area using infrared heat receptors on their nose. They make a quick bite that removes a tiny divot of skin. Then they lick the blood that flows out. They have an anticoagulant in their saliva that prevents the wound from clotting too quickly. Often, the “host” does not even wake up.

These bats are quite stealthy and maneuverable on the ground. Unlike other bats, they can walk, jump, and even run on the ground. There is a slow-motion video online filmed by my friend Dan Riskin, check it out online. I think of them as “super bats” because they are super fast, super strong, super smart, etc.

About VampCam

Vamp cam was set up by Organization for Bat Conservation in Bloomfield Hills, Michigan. They have a great educational facility where the public can visit and see many species of bats from all over the world and learn about their ecological importance. The director Rob Mies had the great idea to put up a web cam last year so anyone in the world can watch the vampire bats. I piggybacked off this by creating a website where people could volunteer to score social behaviors for me (like grooming). It was a kind of social experiment to see if people would actually do it. It also allowed me to go back and watch video footage of anything especially interesting. So far, people from as far away as Australia have recorded about 70 observations. And a few people have emailed me about something they see. I have also heard that people have used it in the classroom. I still enjoy checking in on the bats now and then. Over the next 2 years, if I get this NSF funding, I’m hoping to develop it more into a citizen science project in collaboration with Organization for Bat Conservation.

About vampire bat infrared perception

The bats can detect subtle heat with their nose at a distance of about 16 cm or 6 inches. The only other animals that can do this are some snakes, like pit vipers. Vampire bats have evolved their own way of doing it, which is different than the snakes. There’s a protein that all vertebrates appear to have for detecting heat. The protein is called TRPV1; it is “tuned” to temperatures above 43 deg C. In vampire bat noses, the bats have a special version of the same protein that can detect temperatures as low as 30 deg C. In the rest of their body, they created the normal version. This is the typical way that new abilities evolve. You take an old adaptation and you tweak it to serve a new function.

No, the heat sensing has nothing to do with echolocation or biosonar, which is another special sensing ability used by vampires and most other bats to navigate in darkness. In addition to biosonar, and the “normal” senses, sight, smell, touch, hearing– vampire bats also have specialized low frequency hearing. One idea is that they use this ability to learn the breathing sounds of their prey, but this has yet to be confirmed.

On how bats use their wings

Bat biologists have identified more than 60 ways bats use their wings (besides flying). These including fanning themselves, defending themselves, hiding, courtship displays, holding objects, grooming, crawling, swimming, and capturing prey. For instance, most people don’t realize that bats that catch insects in the air use their wings as nets.

On bat parasites and parasitism

Vampire bats have more parasites than the average bat. In the neotropics, many of the bats have small bat flies called “streblids”. And there are mites and other things too, but I don’t know much about it. Bruce Patterson, an expert on bat flies, led a study where they counted bat flies on 53 bats in Venezuela and the vampire bats were ranked 5th and 6th in terms of how many bat flies they had.

These streblid flies can get around. I was in Belize with a colleague who was marking both bats and flies. She put a tiny drop of paint on each fly. She released one bat with a marked fly, and soon thereafter caught a different bat with the same fly! Apparently, the released bat went back to the roost and the fly switched hosts.

But yes, vampire bats are parasites, and they have parasites. And I would not be surprised if someone has studied the parasites on the bat flies. There are many microscopic protozoa like Trypansoma that are parasites on blood-feeding insects.

It also seems to me that being a parasite is the easiest way to make a living as a non-plant. You exploit a host, but without killing it. Parasitism is actually not too far from symbiosis, and it’s easy to make an evolutionary transition between the two relationships. If you extract resources from another organism (a parasite), it would benefit you even more to keep that organism alive and even help it reproduce (no longer a parasite), as long as you can still benefit yourself. That way, there’s less evolutionary pressure for your partner to evolve defenses. That’s essentially what humans do with domestic plants and animals when we take their fruits, seeds, and milk; we also help them reproduce more than non-domestic lineages.

I would argue that parasites (if you include pathogens) are the most important force in evolution. For example, it seems that parasites are the reason that sex exists, but that’s another story…”the red queen hypothesis”

But I wouldn’t call the bats bloodsuckers, since they don’t suck blood. When they feed, I think they look rather more like a cute cat lapping up milk (maybe that’s a stretch).

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About Gerry Carter

I study the behavioral, sensory, and social ecology of vampire bats. http://socialbat.org.
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