Interview with a vampire...bat expert.
As part of our podcast episode ‘Blood-Sucking Science’ we interviewed Dr Daniel Streicker, from the University of Glasgow, about vampire bats, how they hunt in the dark and feed on their prey.
How do vampire bats hunt in the dark?
They have a variety of different sensors that they use to find prey, and these sensors work at different scales. For figuring out where they are, where they fly out in the beginning of the night, to where they find their
prey, I think they must rely on memory, maybe a little bit of smell, just to know where to start looking.
Once they get into the vicinity of the animals that they want to feed on, they can use some pretty amazing senses. One of those is the ability to recognise breathing sounds. They can tell if an animal is in a deep sleep by the way that it is breathing. So obviously if you are going to try to feed on an animal, that is drink its blood, it is much easier if that animal is really knocked out in sleep. There are even some reports that they can use those breathing sounds to help recognise individual animals, so they can go back to the same animal night after night. This makes a lot of sense if you are a vampire bat, because then you just have to lift off the scab from the night before and continue drinking.
But when it comes to making a new wound, one of the key challenges is probably figuring out where on the animal to bite. These bats have some pretty amazing heat sensing organs that allow them to figure out what's the warmest place on the animal's body, because that's where the blood is flowing closest to the skin.
Where on a body would a vampire bat normally feed?
It depends on the animal that they are feeding on. When it comes to things like cattle, we often see bites on the neck or ears or around the hooves. In humans, because humans are also bitten by these bats occasionally, you'll see bites on the fingers or toes or the head.
When mosquitoes bite an organism, they will release an anticoagulant. Do vampire bats work in the same way?
Yes, in exactly the same way. They have a different kind of anticoagulant in this case, that is called Draculin. But they do not inject it into their victim, but rather the way that these bats bite is they have these tiny triangular teeth, which are razor sharp. And so, they use those teeth to dig out a tiny hole about five millimetres in diameter. When the blood starts flowing, they don’t use any sort of suction the way mosquito might, but rather they are lapping up the blood. As they lick that wound, they're constantly coating it with more saliva, and that
saliva contains the anticoagulant which keeps the blood flowing.
Do you think there are any other potential parallels between vampire bats and the Dracula myths?
The obvious one that comes to my mind is rabies, because rabies is a disease which could potentially cause people to become aggressive and attack other people. That is one of the ways that rabies transmits, by changing the behaviour, I suppose to make it more progressive. However, I do not think that rabies is the origin of Dracula myths. The Dracula myth is more of the Eastern European thing and there have never been vampire bats in Eastern Europe.
There has been quite a bit of research looking at the blood inside the stomach of bats and identifying the species on which the bat has actually fed. Can you tell us a little bit about that?
Yeah. So, we can put a flexible plastic needle down the vampire bats throat and suction out just a tiny bit of its blood meal. From there, we use a complicated genetic technique called metabarcoding, which basically allows us to amplify the DNA sequence of part of the DNA that's present in that blood meal. That can be compared to databases, which tell us what animals the bats are feeding on.
Typically, the bats will feed on cattle or other domestic livestock when they're around. Cattle seemed to be preferred, but you can see them feeding also on horses, donkeys, pigs, they are quite adaptable. In areas where there is not so much livestock things get a bit more interesting. You can find populations of vampire bats that specialise on sea lions along the Pacific coast of South America for example. But it's difficult to catch bats and actually get those samples in those contexts to be able to know the whole diversity of animals that they might be feeding on.