The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Relative canine size as a fitness signal: a test for positive allometric scaling in intraspecific samples of adult male baboons


Department of Cell and Molecular Biology, Northwestern University

Thursday All day, Clinch Concourse Add to calendar

Exaggerated canine teeth in male baboons are often attributed to sexual selection in social groups where male competition for females is frequent and extreme. Scholars posit that the canine functions within a display context to facilitate male-male assessment of fighting ability but tests of the hypothesis are lacking in baboons. Positive allometric scaling of secondary sexual characteristics within adult males of a species is documented in the mammalian literature concerning fitness display and sexual selection. Theoretically, larger males increase reproductive success by investing in relatively larger display features that advertise overall body size and fitness to male competitors or choosey females as long as feature overbuilding is not associated with viability costs. A test of this scaling pattern in the primate canine utilizes large intraspecific samples of adult male Papio anubis, Papio cynocephalus, Papio ursinus, Papio hamadryas, and Theropithecus gelada. Canine height and canine longitudinal areas are regressed against known body weight in Papio anubis and Papio cynocephalus, and a size surrogate for the remaining species, using reduced major axis regression. Positive allometry is demonstrated in Papio anubis and Papio cynocephalus supporting the hypothesis that larger males with relatively larger canines are able to signal overall body size to conspecifics, but support is not found for Papio ursinus, Papio hamadryas, or Theropithecus gelada. The results suggest that selection regimes influencing relative canine size across males within a species are variable between baboons emphasizing the need for an intraspecific and intrasexual approach to canine selection in sexually dimorphic primates.

Funding provided by the Wenner Grenn Foundation

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