These animals are "vampire bats". A very good example is found in these bats.
Vampire bats live in packs, hiding in trees and other places during the day, while coming out at night to feed on the blood of animals, usually cattle, these tiny bats approach their prey. and silently sinks its tiny needle-like teeth into the animal's skin and continues to drink blood for about 20 minutes.
But these bloodsucking animals also have a sense of community. It happens that if a bat does not get blood for 4-5 days, it dies. But his companions satisfy his hunger and save him from dying.
 A bat that gets a stomach full of blood, shares a portion of that blood with its hungry partner and spits out a portion of its drunken blood. Bats that give and take blood may be related to each other, or they may not be related at all.
But what is even more surprising is that the bat that is given blood remembers its helper, and when the helper is in need, he gives blood to satisfy his hunger and repays the favor. Is.
This animal behavior is called "Reciprocal Altruism", and it is rarely seen in animals.
