The blood sometimes flows from the wound for as long as eight hours, as the saliva of the bat may delay coagulation of the blood on the wound. Desmodus sometimes consumes so much blood at a meal that it is barely able to fly. The feeding period may not be more than 30 minutes in length. Practically any warm-blooded animal that is quiet may be attacked by a vampire bat. Domestic animals often are victims because of their accessibility, but vampires seldom bite dogs, since dogs can hear sounds of higher frequency than some of the larger mammals are able to hear and so may detect the bat's approach.
Stock raising in some tropical areas is uneconomical because of attacks by vampires.
These bats bite sleeping humans, but not often. The quantity of blood lost is usually not great, though it may be smeared extensively and present a startling appearance. The danger of infection is probably greatest when the flow of blood from the wound is not particularly rapid and the vampire, as a result, actually licks the wound. The bats may die of the diseases they transmit. There is one, rarely two, young per birth.