The Success of Post-Release Vervet Monkeys (Chlorocebus pygerythrus hilgerti) in Kenya: An Analysis of Pre-Release Threat-Awareness Tests, Training, and Post-Release Success

Abstract

We are in the midst of a primate conservation crisis as 75% of the world’s primates are in
population decline. However, translocation attempts are a promising option to reinforce and
reestablish struggling primate populations. While factors that often result in translocation failures
have been identified in previous research, there is still a poor understanding of what aspects of
rehabilitation creates or predicts repeatable success post-release. This thesis is an analysis of
Andrea Donaldson’s original case study on the rehabilitation release of vervet monkeys,
Chlorocebus pygerythrus hilgerti, in Diani, Kenya. I aimed to evaluate the efficacy of pre-release
threat-awareness tests and electrical wire training by investigating the behavioural responses of
the vervet monkeys, how their individual traits may influence their response, the influence of
social learning, and the predictive nature of their response to these tests and training on their
post-release survival and success. Before release, the vervets underwent awareness tests for the
predicted threats found in their anticipated habitat, which included baboons, dogs, humans, and
snakes, and they were trained to avoid electrical wires. The responses of each vervet were
recorded and statistically analysed. Results indicated that vervets showed inconsistent threat
response improvement during rehabilitation; however, electrical wire training was effective.
While no statistical correlation was found between a vervet's background and their response
score, their survival rates upon release into the wild were comparable to those of a wild control
group. Additionally, observing another individual receiving a shock during pre-release training
had no subsequent effect on the number of shocks administered to the observer during electrical
exposures. These findings affirmed the efficacy of these methods of rehabilitation pre-release
and indicated that future research can further perfect the process of threat training and testing to
promote post-release success.