Ecological stress and linear enamel hypoplasia in Cebus

Although it is assumed that monkeys in some environments experience more nutritional or physiological stress than others, little research has been conducted on this topic. This study examines the relationship between linear enamel hypoplasia (LEH) frequency, a physiological indicator of stress, and environmental stressors. To test this relationship, LEH frequencies were calculated for 144 Cebus from 54 locations in Brazil. Habitat, temperature range, and annual rainfall were compared between individuals with and without LEH. The LEH frequency for Cebus from semideciduous forests was significantly higher than that for monkeys from coastal areas, the rainforest, and the savanna (chi(2) = 9.97, df = 1; P = 0.0016). A significantly higher LEH frequency was also found for monkeys living in environments with the mean annual temperature between 15 and 18 degrees C than for those in environments greater than 18 degrees C (chi(2) = 7.74, df = 1, P = 0.0054). However, no significant difference was found between LEH frequency and annual rainfall (t = 1.22, P = 0.23) or the average difference in rainfall between the driest and wettest months (t = 0.77, P = 0.44). These results indicate that levels of physiological stress can differ among environments and that habitat and temperature, but not precipitation, may be driving the difference in stress levels among environments.