Terrestrial predator alarm vocalizations are a valid monitor of stress in captive brown capuchins (Cebus apella) (1999)

Boinski, S., Gross, T. S., Davis, J. K.

Abstract

We have most commonly, but certainly not always, documented TPAs being produced in association with the entrance into or presence of humans in colony rooms. Most predictably those humans are research technicians associated with manipulative research projects involving the capuchins. ... We found significant reductions in the mean TPA [terrestrial predator alarm] production rate by the group [8 individually caged adult males] in the enriched (toys, foraging box, and foraging box and toys) compared to the control condition. Mean TPA production was correlated to fecal cortisol and behavioral disorders. Our results are consistent with the interpretation that in conditions of low environmental enrichment the study subjects were more stressed, and therefore more reactive to the presence of a threatening terrestrial stimulus (human observer), than when in more enriched conditions.