From: itannman@boris.ucdavis.edu (Ann Mansker)
Subject: Critter of the Week: Desmodus rotundus 
Date: 28 Oct 1998
Newsgroups: ucd.life 



Vampire bats ( http://bioinfo.kordic.re.kr/animal/animal3/VampireBat.jpg ) 
are probably the most maligned of a largely misunderstood order of
mammals.  Nearly a quarter of the known mammals are bats, comprising
nearly 1000 species; of those, only three live on blood.  All three
species are confined to Latin America.

The common vampire (Desmodus rotundus) is found in warm climates from
Mexico to northern Argentina. It lives in small colonies, usually
comprised of 20 - 100 bats.  The members of the colony know each other as
individuals through mutual grooming; recognition appears to be based on
scent and sound.  This sociality is vital to the survival of the
individuals; blood is nutritionally dilute, and a bat that is unable to
find food will starve to death in about three days.  Sick, injured or
simply unsuccessful bats will be fed by their close friends in the colony
via regurgitation. A bat that refuses to feed others will be shunned, and
other bats will not feed it when it has need.

Vampire bats do not sweep down out of the darkness to attack their prey.
Typically, the land some distance from a sleeping creature and creep up
quietly to make sure its intended victim is really asleep.  Desmodus is
the only bat that can walk, run and hop along the ground.  It tends to
feed on or near the ground, scraping a shallow wound on the ankle or foot
of its prey.  Powerful anticoagulants and an anesthetic in the bat's
saliva ensure that the creature has a plentiful and undisturbed meal.
They can consume more than their own body weight, which sounds more
fearsome than it really is -- Desmodus is a small bat, with an 8"
wingspan, and weighing in at only 1 oz.

Despite its diminutive presence, vampire bats can be an agricultural pest
in areas where they are especially abundant.  The other two vampire
species feed mostly on birds, while Desmodus attacks primarily domestic
mammalian livestock.  It will occasionally feed on people and wild
animals, but livestock present an especially easy target.