During a retirement project of former laboratory chimpanzees stress was analysed using non-invasive methods and personality traits and social behaviour was investigated. The chimpanzee population was divided into two groups, labelled as: Early Deprived (ED) and Late Deprived (LD) chimpanzees. ED chimpanzees were separated from their mothers with a younger age, were not peer reared and spent more years in deprivation than the LD chimpanzees. Personality was assessed in novelty test situations reflecting traits such as timidity and boldness. During the resocialisation process social interactions were recorded to assess dominance and social activity of individuals. Faecal cortisol metabolites (11-oxoetiocholanolone, 11beta-hydroxyetiocholanolone) and androgen metabolites (testosterone and epiandrosterone) were analysed through one and a half years of the rehabilitation project. ED chimpanzees responded with timidity to novelty tests and had significantly higher cortisol metabolite levels than LD chimpanzees. LD chimpanzees significantly initiated and received more social interactions and they reached a higher social rank than ED chimpanzees.
Both deprivation groups had a clear decline in their cortisol metabolites after onset of resocialisation, only the lowest ranking (= ED) had increased cortisol levels compared with their levels during laboratory. For testosterone a correlation could be found with the age but not with the social rank. In sum, this study showed that deprivation affects personality, social activity, dominance, and stress susceptibility.