Since the 1990s, attacks by hematophagous bats on humans and domestic animals have been reported both on the continent and on the islands on the southern coast of Rio de Janeiro state. The density of vampire bats was investigated based on percentage of captures during control of Desmodus rotundus samplings and during bat diversity research. In the present work, 203 individuals of D. rotundus were captured from 1993 to 2009, which corresponds to 11.88% of all bat captures carried out for species control in local villages and 1.58% of all captures in faunistic inventories. The density of D. rotundus is high even on the recently occupied islands where domestic animals have been introduced. It is probable that this species dispersed from the continent to the islands due to the introduction of domestic animals.