Vampire Bat - Desmodus rotundus

“Hey guys, got some spare blood? Promise it wont hurt!”

Animals that consume blood for sustenance are sanguivorous. Sanguine means “consisting of, or related to, blood”.

Vampire bats are the only purely-sanguivorus mammals, and have razor-sharp teeth and numbing saliva to keep their food sources asleep. The blood thinners in their saliva keep the blood flowing for several minutes after the initial bite. 

Despite their blood-sucking nature, vampire bats are some of the few mammals that will adopt another bat’s young should the mother die of disease or from predators. The young cling to their mothers for over three months, and rely upon their mother’s milk to supplement their diet for between five to six months, until the young learn to hunt sufficiently well on their own.

The Animal Kingdom, Arranged After its Organization; Forming a Natural History of Animals, and an Introduction to Comparative Anatomy. A scientifically updated translation of the works of Baron Cuvier, 1854.

Of the 1100+ bat species, only three are sanguinovores. Their comparatively-huge neocortex (the part of the brain that controls “personality” and what we consider to be “interpersonal relationships” resides here) is thought to be a direct result of the difficult nature of blood-dependence.

Blood is a surprisingly poor food source. In terrestrial mammals (the vampire bat’s only food source), it’s completely water, sugars, and proteins, and the lack of fats in it means that if vampire bats don’t consume at least 50% of their body weight in blood every 48 hours, they will die.

Since vampire bats can’t take a sick day or a break because of a difficult birth, the other colony members will feed their ill or injured peers, a trait rarely seen below the level of primates. After all, when just two days out of the game means that you’re dead of exhaustion, it’s no longer “survival of the fittest” - it’s in the colony’s best interest to keep each other alive.