VAMPIRE BATS!

Today is Halloween, so that means I get to write about some spooky, creepy subject such as vampire bats.  The main reason why vampire bats seem so creepy is because they only eat BLOOD.  They don't eat fruits or vegetables or muffins, which seems like a very unbalanced diet, but I guess it works for them.

There are actually three kinds of vampire bats, and they are called the common vampire bat, the hairy-legged vampire bat, and the white-winged vampire bat.  All of these bats live in tropical areas of the New World, including Mexico, Central America, and parts of South America.  The Common Vampire Bat is the most common of these three types, which is probably how it got its name, and it's the one I'm going to tell you about.

Photo by The Daily Texan

During the day, bats hang around upside-down in dark places like caves, wells, mine shafts, hollow trees, and buildings.  This is called "roosting."  Males and females roost together, with each male having a "harem" of about six females.  In one roosting spot, there might be only six bats, or there might be as many as two thousand.

As soon as it gets totally dark outside, the bats go out to start looking for food.  They have something called thermoreceptors which tell them where the warmest places are on their prey.  It's important for them to know this because the "hot spots" are where the blood is closest to the skin.  The only other animals that have thermoreceptors are boas, pythons, and pit vipers.

Common vampire bats like to feed on mammals such as horses, burros, cattle, goats, and pigs.  These animals are all much bigger than a bat, so the bats have to be very sneaky and careful.  They generally land on the ground and then walk around their victim.  Vampire bats are the only kind of bat that can walk, using their hind legs and modified thumbs.  The other types of bats have evolved to the point where they can only fly.

Anyway, the bat picks a spot where it hopes it can bite the victim without waking it up. The actual bite is made with just the front incisors, which are so very sharp that the bite is mostly painless.  A tiny little pool of blood forms where the animal was bitten.  This is where the bat feeds.  Meanwhile, some stuff in the bat's saliva keeps the blood from clotting.  Sometimes several bats all feed from the same bite wound.

Vampire bats have really good kidneys, and they start peeing out the blood plasma within a couple of minutes after they begin to feed.  They have to get rid of as much of the unneeded liquid from the blood as they can so that they can fly back to their roosting place with such a heavy load of blood inside them.  When the bats get back to their roost, the females feed their babies, and then everybody settles in for a long nap while they digest their food.

Picture taken at Sangayan Island,
Paracas National Reserve,
Departamento Ica, Peru, March 2005

One thing that's really nice about vampire bats is that they really help each other out.  If a baby bat loses its mother, other females will nurse it.  Also, if a bat didn't have any luck finding some nice blood to eat, that bat can ask another bat for food, and get a handout.  Except that bats don't have hands, so it's actually a regurgitation of food.

Mother bats take care of their young for a long time.  First of all, there is a gestation period of anywhere from 90 to 120 days, and after that, one baby bat is born.  Right after birth, the babies grow pretty fast, but then their growth slows down.  It takes a young bat about 300 days to get to its full adult weight.  The babies are usually not weaned until they are 9 months old.

One reason why people are so afraid of vampire bats is because bats carry rabies.  Well, bats do carry rabies sometimes, but the truth is that only 0.5% of bats have rabies.  If a bat gets rabies, it will probably die within a few days, so it doesn't have much of a chance to spread it.  There is more danger of bats giving rabies to cattle than to humans.

I'm not sure if I would like have a pet vampire bat living with us or not.  I think it would be tasty to eat one, but I also think it would be hard to get past all those sharp teeth.  Mom says she would not want something flying around in the house at night and biting us while we're sleeping.  I wouldn't really want that either, so I guess this is one time that Mom and I agree on something!