Behavioral and physiological stress responses to local spatial disturbance and human activities by howler monkeys at Los Tuxtlas, Mexico

Abstract

AbstractTo develop effective conservation and management actions, it is important to examine anthropogenic disturbance patterns and their impact on wildlife. We examined variation in the behavioral and physiological stress response of the Critically Endangered Mexican mantled howler monkeys Alouatta palliata mexicana in relation to two types of anthropogenic disturbance, habitat spatial patterns and presence of humans or their livestock (noise and presence nearby primates). We studied four groups (42 individuals) in two forest fragments at the Los Tuxtlas Biosphere Reserve for a total of 1100 observation hours, during which we recorded the howler monkeys’ vocalizations, locomotion and vigilance. We additionally collected fecal samples to determine the concentrations of glucocorticoid metabolites (fGCM). Howler monkeys vocalized less and moved more when in more spatially disturbed locations and when exposed more time to nearby noise but spent less time in locomotion when humans were present. fGCM were only related to human presence, suggesting that habitat spatial patterns are less of a challenge than human presence. This may be related to the generally unpredictable nature of the latter. Although our study does not allow determining whether the behavioral and physiological responses of howler monkeys to disturbance are costly, from a conservation standpoint it may be more prudent to assume that they are and design strategies to mitigate them. In this sense, actions aimed at reducing anthropogenic noise could benefit the conservation of Mexican mantled howler monkeys.