The differential expression of dental sexual dimorphism in subspecies ofColobus guereza

Data on dental sex differences in seven of the eight currently recognized subspecies of Colobus guerezareveals a range of expression of sexual dimorphism. Males of most subspecies are larger than females throughout the dentition and this is especially pronounced for the canines and P ₃ For C. g. guerezaand C. g. gallarum,however, sex differences in the canines and P ₃ are less pronounced and females are often slightly larger than males in noncanine dental measurements. C. guerezasspp. occupying comparable habitats express similarities in the degree of maxillary canine dimorphism. In addition, for those subspecies distributed above the equator, there is also a cline of decreasing maxillary canine dimorphism from west to east in a progressively more northern direction. This cline corresponds to the occupation of increasingly more arid habitats, and reduced dimorphism is the result of larger maxillary canine size in females. We propose that this pattern of sexual dimorphism is related to differences in the relative intensity of predation pressure, guereza social organization, and energetic considerations. That the mandibular canine does not exhibit a similar trend of sexual dimorphism suggests that larger maxillary canines in females may function as weapons.