Canine Length in Wild Male Baboons: Maturation, Aging and Social Dominance Rank

Abstract

Canines represent an essential component of the dentition for any heterodont mammal. In primates, like many other mammals, canines are frequently used as weapons. Hence, tooth size and wear may have significant implications for fighting ability, and consequently for social dominance rank, reproductive success, and fitness. We evaluated sources of variance in canine growth and length in a well-studied wild primate population because of the potential importance of canines for male reproductive success in many primates. Specifically, we measured maxillary canine length in 80 wild male baboons (aged 5.04–20.45 years) from the Amboseli ecosystem in southern Kenya, and examined its relationship with maturation, age, and social dominance rank. In our analysis of maturation, we compared food-enhanced baboons (those that fed part time at a refuse pit associated with a tourist lodge) with wild-feeding males, and found that food-enhanced males achieved long canines earlier than wild-feeding males. Among adult males, canine length decreased with age because of tooth wear. We found some evidence that, after controlling for age, longer canines were associated with higher adult dominance rank (accounting for 9% of the variance in rank), but only among relatively high-ranking males. This result supports the idea that social rank, and thus reproductive success and fitness, may depend in part on fighting ability mediated by canine size.

Explaining sex differences in lifespan in terms of optimal energy allocation in the baboon

“…Given that males hold their highest ranks during early adulthood (Galbany et al 2015), this is consistent with reports that those of highest rank achieve the greatest success in consortships (Packer 1979;Bulger 1993;Weingrill et al 2000). The expression in the second set of square brackets describes a sigmoidal decrease in fighting ability with condition, with ϑ denoting the steepness of this decrease and ν the condition at which the rate of decrease is greatest.…”

Canine and incisor microwear in pitheciids and Ateles reflects documented patterns of tooth use

“…However, this is an especially formidable challenge for canines where patterns are complicated because primates use these teeth in more than one biological role, from sexual display and fighting (e.g., McGraw et al, 2002;Leigh et al, 2008;Galbany et al, 2015) to ingestion and food fracture (e.g., Kinzey and Norconk, 1990;Rosenberger, 1992;Norconk et al, 1998;Barnett et al, 2005). However, this is an especially formidable challenge for canines where patterns are complicated because primates use these teeth in more than one biological role, from sexual display and fighting (e.g., McGraw et al, 2002;Leigh et al, 2008;Galbany et al, 2015) to ingestion and food fracture (e.g., Kinzey and Norconk, 1990;Rosenberger, 1992;Norconk et al, 1998;Barnett et al, 2005).…”

“…Interpretations of anterior dental microwear always require a baseline of observations derived from extant taxa with documented variation in tooth use in dietary and nondietary contexts. However, this is an especially formidable challenge for canines where patterns are complicated because primates use these teeth in more than one biological role, from sexual display and fighting (e.g., McGraw et al, 2002;Leigh et al, 2008;Galbany et al, 2015) to ingestion and food fracture (e.g., Kinzey and Norconk, 1990;Rosenberger, 1992;Norconk et al, 1998;Barnett et al, 2005).…”

Modularity of the anthropoid dentition: Implications for the evolution of the hominin canine honing complex

“…This threshold is arbitrary, but given the inconsistency of estimates of variance-covariance at small sample sizes (e.g., Ackermann, 2009), it was necessary to restrict analyses to those samples that are reasonably well represented. As canines (especially the C 1 ) wear (Walker, 1984;Leigh et al, 2008;Galbany et al, 2015) and often break at their apices, there were fewer adequately-sized samples available for their analysis within species; therefore, the sample size criterion was relaxed for C 1 height in a few cases. The smallest C 1 height sample size accepted was n ¼ 15.…”

“…In most nonhuman anthropoid primates, canines are used in visual threat displays and occasionally as weapons, especially during intraspecific conflicts (e.g., Walker, 1984;McGraw et al, 2002;Leigh et al, 2008;Galbany et al, 2015). Many anthropoid primates have tall, projecting canines; however, canine size varies between sexes and among species.…”