Behavioral Changes of Solitary Housed Female Pygmy Slow Lorises (Nycticebus pygmeaus) after Introduction into Group Enclosures

SIMPLE SUMMARY: Most pygmy slow lorises confiscated in the illegal pet trade cannot be released back into the wild and end up in captivity for the rest of their lives. In the wild, their home ranges are large relative to their body size and they maintain a fairly solitary lifestyle compared to other primates. With the aim of improving their captive wellbeing, we tested to see whether female–female group pairings were in the animals’ best interest by looking at their behaviors before and after being moved to social housing in a larger enriched enclosure. With one nesting site per animal and ample space to avoid each other, all females opted to nest in pairs, not alone, and spent their time socially engaged in affiliative behaviors. We found that female pygmy slow lorises are more social than often assumed and that housing them with conspecifics is probably beneficial to their well-being in captivity. ABSTRACT: Pygmy slow lorises (Nycticebus pygmaeus) are threatened with extinction in the wild. Their nocturnal lifestyle and small size make them difficult to study in their natural habitat, but increasing evidence suggests that they are more social than previously thought. Our study was designed to assess the sociability of pygmy slow lorises by transferring six adult females from solo cages into environmentally enriched group home cages at the Japan Monkey Centre’s Slow Loris Conservation Centre. Two females were paired to create one group, while the other four were placed together in a second group. We compared their social interactions, activity budgets, and postural behaviors before and after social housing was initiated. We found that all-female slow loris groups had a high degree of sociality, preferred to stay close to each other, nested together every night, and spent less time in locomotion and more time grooming than when living alone. These results suggest that female pygmy slow lorises actively seek companions when available. The captive housing of all-female groups of lorises could lead to better husbandry practices and improved animal welfare by allowing them to have conspecific companions. We conclude that isosexual groups of pygmy slow lorises should be preferred over single housing when possible.