Host preference of the common vampire bat (Desmodus rotundus; Chiroptera) assessed by stable isotopes

We examined the host selection of common vampire bats (Desmodus rotundus) with stable carbon isotopes in all area that offered 2 isotopically contrasting food Sources, either introduced livestock living Oil C-4 plants or native rainforest mammals living Oil C-3 plants. We predicted that vampire bats Would have carbon isotope ratios (delta C-13) similar to those of livestock if they select exclusively cattle. The delta C-13 of vampire bats averaged - 10.3 +/- 2.6 parts per thousand (mean +/- SD) and was almost identical to that of livestock ((X) over bar = - 12.9 +/- 1.6 parts per thousand). Thus, both vampire bats and livestock are clearly members of the C4 food web. Typical rainforest mammals such as the fruit-eating bat Carollia perspicillata had a delta C-13 of -24.4 +/- 0.6 parts per thousand, which identified them as members of the C-3 food web. The stable carbon isotope si-nature of local vampire bats implies a high degree of preference for cattle. We suggest that the population expansion of D. rotundus is only indirectly linked to increasing host densities and is more directly related to the bats' preference for livestock over native mammals, probably because fenced-in cattle are a more predictable resource than free-ranging natural hosts.