Post-Release Survival and Behavior of Rehabilitated Vervet Monkeys (Chlorocebus pygerythrus rufoviridis) in Malawi

Published research on primate rehabilitation and release (R&R) is limited and studies suggest that released mortality is generally high. We investigated factors affecting survival and behavior of a rehabilitated troop of vervet monkeys (Chlorocebus pygerythrus rufoviridis) released into Kasungu National Park in Malawi in 2016 by the Lilongwe Wildlife Trust (LWT). Estimated troop survival 9 months after release was 45% when dispersing-age male disappearances were considered emigrations, which is comparable to other vervet monkey R&R. Using a combination of linear modeling, survival analysis, and social network analysis, we considered social rank, forest strata use, antipredator behavior, troop cohesion and social connectedness, and behavioral diversity across release phases as potential factors influencing survival. Our results suggest that socially connected individuals and juveniles were more likely to survive, with these factors more significant than sex, social rank, and antipredator behavior. Unexpectedly, antipredator behavior significantly decreased after release, which may be a factor linked to increased predation. Also unexpectedly, behavioral diversity decreased post-release, likely due to a significant increase in locomotion upon release and limitations with our ethogram. The observed mortality patterns suggest that R&R troops may benefit from pre-release training with platform feeders that encourage canopy use. When possible, individual life history data (e.g., captive-born, orphaned) should be collected at rescue and rehabilitation stages to help inform caretakers of unique needs. LWT's extensive pre- and post-release monitoring provides vital insights into the factors influencing this troop's survival. We urge other rehabilitation centers to follow this strategy to improve R&R programs.