Post-release survival rates and welfare of rehabilitated vervet monkeys in Malawi

Abstract

Research on primate rehabilitation-release (R&R) is limited, and released troop mortality is generally high. We investigated factors affecting survival and welfare of a rehabilitant troop of vervet monkeys (Chlorocebus pygerythrus rufoviridis) released in Malawi in 2016. Using 9 months of pre- and post-release data from the Lilongwe Wildlife Trust (LWT) and linear modeling, survival analysis, and social network analysis, we considered several potential factors influencing survival. The LWT troop survival rate was 36% and results suggest high ranking individuals, juveniles, and highly socially connected individuals were more likely to survive. Mortality patterns suggest released troops may benefit from platform feeders that encourage greater canopy use, more time at the release site before the rainy season when predation is more common, and predator-awareness training. Future studies using behavioral diversity to assess welfare should use detailed ethograms to capture unique behaviors. LWT’s extensive pre- and post-release monitoring provides vital insight into the troop’s survival. Other rehabilitation centers should follow this strategy to help improve primate R&R programs.