General Overview
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Common vampire bats (Desmodus rotundus) are in the family Desmodontidae
(Alteringham 1998). The common vampire bat is seventy to ninety millimeters
long and weighs anywhere from fifteen to fifty grams (Nowak 1991). There
is sexual dimorphism in the common vampire bat’s size that favors the
female (Delpietro & Russo 2002). They are grayish-brown in color and
can be distinguished from other bats by its twenty teeth (Nowak 1991). They
have excellent sight, speed, and jumping ability (Turner 1975).
The common vampire bat is found from Northern Mexico south
through Brazil, Chile, and Argentina (Lord 1993; Nowak 1991). Common vampires
are the most
prevalent bats in Southeastern Brazil (Trajano 1996). It inhabits warm, humid
climates (Wilkinson 1985a; Lord 1993; Nowak 1991). Common vampires live in
trees, caves, abandoned buildings, old wells, and mines (Wohlgenant 1994;
Lord 1993). Within a roost- a bat’s nest- the humidity during the rainy
season is near one hundred percent constantly and very dark (Wilkinson 1985a;
Lord 1993). It feeds only on the blood of mammals (Delpietro & Russo
2002; Lord 1993). It acquires blood by biting its prey and licking the blood
from the wound (Lord 1993). Common vampire bats’ preferred prey are
cattle, horses, and livestock (Lord 1993). The predators of common vampires
are dogs, cats, owls, lizards, opossums, snakes, and humans (Wilkinson 1985a).
photo taken from www.batcrew.com
Common vampire bats are social animals (Park 1991). They live
in harems where there is a dominant male, multiple females (8-50), and offspring
from that year
(Lord 1993). In some cases there are multiple males that live in the harem,
called resident males (Delpietro & Russo 2002). Outside the harem there
are bachelor herds of males (Lord 1993). These males try to displace the
harem male in order
to gain reproductive access to females (Wilkinson 1985a).
The harem male mates with the females in his harem (Wilkinson 1990). When there
are resident males in the harem besides the harem male, the resident males also
mate but not as much as the harem male (Wilkinson 1985b). The males in the bachelor
herds do not mate, due to females refusing to copulate with them and males in
the harem defending the females (Lord 1993).
Common vampire bats participate in many social activities,
which are cooperative (Wilkinson 1986). Thermoregulation is a major factor
for vampire bats since they
do not hibernate like many small rodents (Delpietro & Russo 2002). Thus,
common vampire bats in the harem will invite bachelor males in to the harem so
that the bats can huddle together for warmth (Delpietro & Russo 2002). Female
common vampires also help each other raise their young, by feeding each other’s
pups (Wilkinson 1990). Also, vampire bats exhibit reciprocal altruistic behavior
(Wilkinson 1990). Common vampire bats share food with each other when a roost
mate is on the verge of starving (Lord 1993; Wilkinson 1990). The role of donor
and recipient bat changes from one sharing event to the next (Wilkinson 2001).
The stability of this behavior is maintained through finding cheaters in the
food sharing system (Wilkinson 1990). Social grooming is used to find cheaters
in the food sharing system, as well as clean parasites from roost mates (Wilkinson
1990; Wilkinson 1986).
Common Vampire Bat Homepage--General Overview--Mating System--
Feeding Behavior--Cooperative Behavior--References