Selection and use of Sleeping Sites by Coppery titi Monkeys, <i>Plecturocebus cupreus</i>

Sleeping site selection in primates has linked to predator avoidance, parasite avoidance, thermoregulation, foraging efficiency, home range defense, and risk avoidance. To test these hypotheses and to investigate the influence of other factors, such as group composition, we examined sleeping tree usage in nine wild groups of coppery titi monkeys, Plecturocebus cupreus, in Peruvian Amazonia. Titi monkeys used larger trees than the average trees in their habitat, preferred closed trees, slept in high concealed locations, retired before sunset, and generally avoided reusing trees on consecutive nights. These findings suggest that predator avoidance, parasite avoidance, and thermoregulation drive sleeping tree choice. Although groups never slept in feeding trees, they used multiple sleeping trees, and the distances between them and the first and last feeding trees of the day were short compared to daily travel distances, suggesting that foraging efficiency may play a limited role in sleeping tree selection. The home range defense hypothesis received no support, as sleeping trees were not concentrated near the range boundaries. Instead, groups preferred to sleep in the core areas, suggesting that they select sleeping trees to minimize the risk of intergroup encounters. Females typically entered the sleeping trees first, while males entered last when groups had offspring, probably reflecting the leading female role in pair-living species and the more active male role in anti-predator defense. This study suggests that predator and parasite avoidance, thermoregulation, and risk avoidance, along with group composition, influence sleeping site selection and patterns of use in P. cupreus.