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Scientist Simon Ripperger spends his days strapping tiny computers to the furry backs of vampire bats in Panama. These tracking sensors document social interactions in a process called biologging.
"We found that bats that developed friendships in captivity kept hanging out when released back into the wild," he says. "As well, the successful hunters shared blood with hungry members of their colony."
Contrary to their name, vampire bats don't suck blood from unsuspecting humans. They typically target cattle, using their teeth to make a tiny puncture wound, then lapping a teaspoon or two of blood with their tongue. They live mainly in Mexico, and Central and South America. But the U.S. Department of Agriculture (USDA) reported last year that vampire bats could arrive in the Southern United States in the next two decades.
Toni Piaggio, a USDA scientist, reported development in the vampire bats' native habitats and warming temperatures have inspired the winged mammals to move north to Mexico.
"It's getting warmer, farther north and south," Ripperger explains. "So bat species that occur in the tropics can move further away from the equator."
There are three species of vampire bat: common, white-winged and hairy-legged. All depend on blood to survive. A bat that goes without a meal for two or three days can starve to death. Fortunately, they have a social network made up of several partners who feed one another.
"One bat licks the mouth of another bat, and that one starts (spitting up swallowed) blood," Ripperger explains. "As well, bats that are fatter will notice that someone is starving, and then approach them and feed them."
Vampire bats look out for their colony members in other ways, as well. Ripperger describes how a doctoral student from his lab at Ohio State University observed two female bats who groomed each other and shared food.
"They had a strong social bond," he said. "And then one of the females who had a very young pup got sick and died. The mother's friend took over and adopted the offspring. It was amazing."
Other species of bats have obvious roles in nature. Some pollinate flowers. Some scatter seeds, and others eat mosquitoes. This type of role is less obvious for vampire bats, but that doesn't cause Ripperger to admire them less.
"Not every species needs to serve a purpose in the eye of a human to find a place in the world," he says. "They've conquered a certain niche — drinking blood — which is quite amazing for a mammal. It's really rare, and I think it's reason enough to exist."
One of the things he appreciates most about vampire bats is how smart they are. He describes catching them in a mist net — mesh fabric suspended between two poles — and holding them in his glove.
"They will turn around and look you in the eye, and you sense that this animal is intelligent," he says. "When you hear about vampire bats, you think of blood, and it's scary. But if you work with them, you figure out that they are super-social and super-interesting creatures."
Fun facts about Vampire bats
- Scientists are studying a protein called draculin in bat saliva, which may help people who've suffered a stroke by breaking down blood clots.
- Bats locate blood vessels in the prey's skin by using a heat-seeking sensor in their nose.
- Vampire bats approach their prey on the ground. They can run more than three feet per second.
- Vampire bats roost in dark places such as caves and tree hollows, sometimes with several other bat species. Colonies typically have 20 to 100 bats, though people have discovered roosts with more than 5,000.