Plants as Enrichment? The Effect of Live Plants on the Behavior and Welfare of Indoor-Housed Titi Monkeys (Plecturocebus cupreus).

The biophilia hypothesis states that humans have an innate tendency to enjoy the presence of greenery due to vegetative-rich areas serving as adaptive environments during our evolutionary history. It is possible that other extant primate species may show a similar response to the presence of plants, but direct experimental interventions on indoor-housed primates, with plants isolated as a variable, represent a gap in the literature. In this study, 20 coppery titi monkeys (Plecturocebus cupreus) housed indoors were exposed to foliage outside of their home cages. Behavior following introduction to plants was recorded and compared to behavior following baseline and control object conditions. The addition of both the plant and control object was associated with a decrease in stereotypic behaviors and an increase in affiliative behavior between bonded mates compared to baseline. The addition of the live plant was associated with increased grooming, and monkeys spent significantly more time looking at the live plant compared to the control object. The reduction in stereotypic behaviors and increase in affiliative behaviors provide support for plants as a potential enrichment strategy. The increase in grooming, combined with greater visual attention to plants, suggests that titi monkeys may have an evolutionary affinity towards plants.