Group Prerelease Training Yields Positive Rehabilitation Outcomes Among Juvenile Mantled Howlers (Alouatta palliata)

Wildlife rehabilitation presents many challenges, especially when anthropogenic threats yield large numbers of naive juvenile animals. In particular, many primates obtain survival skills such as the identification of palatable foods, avoidance of unsafe substrates, and antipredatory behaviors from conspecifics, and require prerelease training by humans in the absence of opportunities for social learning. Nonetheless, few primate rehabilitation programs quantitatively evaluate the success of prerelease training programs, making the establishment of best practices for many species difficult. Here, we quantitatively assess whether three juvenile mantled howlers (Alouatta palliata) gained independence from humans and increased their frequencies of naturalistic behaviors while participating in a rehabilitation program in Panama that consisted of daily "bush outings" with an operant conditioning component. We evaluated the role of rehabilitating animals in groups in particular, by determining whether the three rehabilitants were more likely to exhibit naturalistic behaviors when in closer proximity to conspecifics. Across the 54-day study period, all three rehabilitants improved significantly in at least two out of the three tested metrics (approaching humans less frequently, traveling higher into the canopy, and spending more time foraging for forest foods). Individuals were more likely to venture into trees and less likely to approach humans when in close proximity to conspecifics, suggesting that group rehabilitation positively impacts the acquisition of naturalistic behaviors by this species. Our results support previous notions of prerelease training as a crucial rehabilitation tool, and highlight the importance of group rehabilitation in programs targeting social animals, even when naturalistic group compositions cannot be approximated.