Sexual dimorphism occurs in many mammals and has been shown to occur in common Vespertilionid bats, with females larger in size than males. Female mammals are sometimes larger than males in order to be able to carry their offspring while pregnant. Males exhibit larger size in order to compete for a mate or territory, as seen in lions. Measuring sexual dimorphism can help explain mating and roosting behavior of species that are not well known, and to see if patterns of dimorphism are constrained from a phylogenetic context. Vampire bats’ teeth are highly specialized to extract blood from their prey, meaning that they would not be expected to be dimorphic between males and females. Any dimorphisms found in this study will be useful to better understand the extent of competition and self-protection present in vampire bats. This study investigated patterns of sexual dimorphisms in three different vampire bat species: Desmodus rotundus, Diphylla eucaudata, and Diaemus youngi. Skull size and canine size of males and females of each species were measured from skulls of museum collections and digital photographs. In all three species, male canines were found to be significantly larger than female canines. Diphylla eucaudata, Diaemus youngi, and Desmodus rotundus male canines were an average of .19, .27, and .23 mm longer than females, respectively. In Desmodus rotundus, the male skulls were found to be 3% smaller than the females. These results show that males use their canines for more than just feeding, which motivates further research on this subject.
