Why Bats Share Blood

  • Posted 11.17.16
  • NOVA

Vampire bats can only survive for a few days if they are unsuccessful in hunting for blood to eat. To prevent a fellow bat from starving, vampire bats will sometimes share their most recent blood meal. But, they have learned to only share with family and friends.

Running Time: 01:54


Why Bats Share Blood

Posted: December 2, 2016

Have you ever shared your dinner with a friend who was hungry?

Then you’re more like a vampire bat than you might’ve thought!

Vampire bats practice Hematophagy, which means they feed exclusively on blood.

But unlike their mythical counterparts, vampire bats don’t actually suck blood.

Instead, they use their razor sharp teeth to bite mammals—typically horses and cows—although sometimes humans!—and then lap up the blood  that escapes from the wound.

Fortunately for their victims, Vampire bats don’t take enough blood to kill.

But finding enough blood to eat isn’t always easy.

Vampire bats hunt on most nights, but if they are unsuccessful for more than 2 nights in a row, they will starve to death.

Fortunately, vampire bats, just like people, are often willing to help their friends.

In fact, to prevent a fellow bat from starving, female vampire bats will sometimes regurgitate a portion of their most recent blood meal into the mouths of nearby female vampire bats.

But proximity alone does not guarantee this behavior.

Vampire bats use a practice called reciprocal altruism: they learn to recognize bats who’ve shared with them in the past and they only share with them. This includes familial relatives, and current or former roost mates.

So far, in the wild, scientists haven’t found any evidence that male vampire bats participate in this food sharing process.

And while the reason for the divide between sexes isn’t completely understood, what is clear is that female vampire bats, like humans, get by with a little help from their friends.



Writing, Animation, & Editing
Brittany Flynn
Ari Daniel


Bat Footage
Gerald Carter
Vampire Bat Image
Uwe Schmidt
Cow Drawing: Jane Hawkey, Integration and Application Network, University of Maryland Center for Environmental Science

© WGBH Educational Foundation 2016

Related Links