General Description of Desmodus rotundus and its Social System
Vampire bats are small, only about the size of a thumb  weighing between  30 and40g (Turner 1975).  Interestingly, the females are usually slightly larger than the males (Mulheisen and Anderson 1994).  They are the most agile of bats on the ground, utilizing an elongated thumb to assist in walking, running, jumping, and scrambling (Wilson 1997).  The skeleton of vampire bats is also specialized for more support while moving about on the ground with heavier, stouter bones than most other bat species (Hill 1984).  This is impotant because vampires attack their prey from the ground.  They land near the animal and then approach on the ground before the attack.  Agility is also imortant in avoiding injury from the much larger prey during feeding.  Vampires eat only blood, and each night will eat about two tablespoons.  This is almost 60% of their body weight (Turner 1975).  After feeding, vampire bats are visibly distended and often are so full that they have difficulty in taking off on the return flight.  The teeth of vampire bats are specialized for their feeding methods.  Vampire bats have the lowest number of teeth of all bats at 20 (Hill 1984).  They have two very enlarged incisors that are razor sharp (Wilson 1997).  These are used to slice off about a 3mm patch of skin to create a shallow wound.  The blood flows freely from this wound with the assistance of anticoagulants in the vampire bat's saliva (Wilson 1997).  The vampire bat then uses its grooved tongue to lap up the blood from the wound.  The grooves on the tongue fallicitate this by helping draw up the blood to the mouth via capillary action (Hill 1984).   Vampire bats will feed for prolonged periods of times on the same wound, often as long as thirty minutes (Wilson 1997).  After feeding, the stomach of the vampire is severely distended.  Successful feedings are remembered, and the vampire will often return to the same animal when possible for subsequent feedings (Wilson 1997).  Vampire bats have a very good sense of smell, important in identifying members of their social groups as well as locating prey (Turner 1975).  The stomach of vampire bats is especially adapted to their diet of blood.  It is extremely elongated, resembling a tube, providing a large surface area for the absorption of the nutrients in the blood (Allen 1940).
    The social system of the bats is based on small groups of females, their offspring, and sometimes subadults, ranging on average from 8-12 individuals  (Kunz and Pierson 1994).  The members of these groups are not always related.  Genetic analysis of members of social groups confirm this, and show that blood sharing is not based on relatedness (Altringham 1996).  The males are usually relatively solitary and spend more time establishing and defending mating territories than engaging in social interactions.  In some cases, when there is an abundance of caves for roosting, the males and females tend to roost separately (Campanha and Fowler 1993).  The females roost with their young and therefore their roost is sometimes referred to as a nursery.  The caves house many small groups of bats and thus they are all in a large aggregate that can sometimes reach numbers as large  as 2000 (Dalquest 1955).  Females are polyestrous, with aseasonal birthings (Fleming 1972).  This is because the bats have a constant food supply and do not have to worry about waiting for optimal conditions for mating.  There is always food available  and so there is the ability to breed year round.
 
  • Habitat and habitat utilization
  • Social spacing
  • Social relationships
  • Social cooperation/altruism
  • Summary
  • Bibliography

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