The Influence of Behavioral Selection on Dental Variation in Domesticated Silver Foxes

Abstract

The relationship between canine tooth size and social signaling has long been observed in wild carnivore and primate populations. In several of these species, it has been well‐established that larger canine size is directly correlated to social structures where agonistic interactions are commonplace. However, canine teeth are difficult to study in the wild because they serve multiple roles in addition to social signaling, such as food acquisition and guiding functional occlusion of the jaws. The Russian silver fox experiment represents a long‐term, controlled study where foxes have been selected for a behavioral phenotype toward either non‐aggression or hyper‐aggression. Results from the experiment have demonstrated that an increase in the range of variation of several soft tissue features accompanies selection for non‐aggression. In the absence of food‐related selective pressures, the influence of behavioral selection on dentition can be observed. The objective of this study is to compare the variation present in the gross dental sizes of canine teeth, which serve both social and food‐related roles, and carnassial teeth (maxillary P4 and mandibular M1), which play critical roles in mastication, as a result of selection solely on behavioral phenotype. We employed univariate and multivariate comparisons of maxillary canine, maxillary fourth premolar, mandibular first molar mesiodistal length and buccolingual breadth, as well as maximum height and crown height of the canine. These data were collected in sex‐balanced samples of unselected (n=51), tame (n=48), and hyper‐aggressive (n=50) experimental strains. Results indicate that the canine tooth is the most variable tooth across all three strains. This is in line with observations recorded in wild fox populations. However, foxes in the aggressive‐selected strain exhibit significantly reduced variation in canine crown height compared to the tame and control groups, further supporting hypotheses that the canine is strongly influenced by behavioral selective pressures favoring aggression. The patterns of variability in the tame‐selected strain tend to mirror those in the unselected strain, albeit with greater degrees of sexual dimorphism present in the variation. This provides further evidence that canine teeth are under strong selection relative to behavioral pressures and supports hypotheses that selection on behavior can affect the rate of variability of structures.Support or Funding InformationUniversity of Iowa College of Dentistry; University of Missouri; University of North Texas Health Science Center