Maximum Gape in Developing Macaca mulatta
Stephanie L. Canington, Cassandra M. Turcotte, Eva M. Hernandez‐Janer, Michala K. Stock, Catalina I. Villamil, , Michael J. Montague, Melween I. Martinez, Scott A. Williams, Susan C. Antón, James P. Higham, Myra F. LairdABSTRACT
Objectives
Maximum gape and bite force are two key metrics of primate craniodental performance, but without mitigating adaptations, large gapes are associated with reduced bite force. Primate craniodental morphology undergoes functional transitions across development, but how these performance variables vary with life‐history transitions is unknown.
Material and Methods
Maximum gapes of 211 rhesus macaques (
Results
In vivo gape did not differ from isometry relative to body mass and jaw length across developmental stages by sex, but jaw leverage was significantly lower in larger compared to smaller macaques. The largest developmental differences occurred between pre‐prime and prime individuals. Canine length scaled with positive allometry against body mass and jaw length in males but not females, while maximum gape scaled with negative allometry relative to canine length in both sexes.
Discussion
These results indicate that macaques undergo a functional tradeoff between jaw leverage and gape around the onset of sexual dimorphism. Pre‐prime macaques exhibit relatively greater jaw leverage, whereas adults maintain proportionate gape relative to body and jaw size at reduced mechanical advantage. The eruption of large canines in males does not influence linear gape outside of size differences captured by body mass and jaw length.