Is There a Link Between Matriline Dominance Rank and Linear Enamel Hypoplasia? An Assessment of Defect Prevalence and Count in Cayo Santiago Rhesus Macaques (Macaca mulatta)

Abstract

Linear enamel hypoplasias are developmental defects ranging in appearance from microscopic to macroscopic furrows in enamel that encircle the tooth crown. Environmental stressors, including lack of food and infectious diseases during early periods of development, are known to induce hypoplasias in human and nonhuman primates. Social correlates of hypoplasias have not been extensively studied, however. Here, we examined the relationship between matriline dominance rank and linear enamel hypoplasia prevalence (i.e., absence or presence) and count (the total number of hypoplasias observed) in free-ranging rhesus monkeys (Macacca mulatta) in Cayo Santiago, Puerto Rico. We sampled 86 female offspring from low-, mid-, and high-ranking matrilines. Our results show that although hypoplasia prevalence and count were numerically higher in the combined group of low-and mid-ranking matrilines than in high-ranking matrilines, this effect was not statistically significant. There was, however, a significant negative relationship between age and hypoplasia prevalence, as well as between age and mean number of enamel defects, likely due to the attrition and abrasion of enamel that wear away shallow defects as individuals age. Future studies would benefit from using large sample sizes and collecting detailed behavioral data to determine if and when social status mediates enamel defect formation.