Impacts of illegal trade on socio-emotional and behavioural skills in macaques

Abstract

Decades of research have illuminated the consequences of early adverse rearing experiences in laboratory macaque populations. However, knowledge of the impact of traumatic episodes in non-laboratory settings remains limited. This study investigates the socio-emotional and behavioural impacts of illegal trade on five macaque species, all victims of poaching. We studied 53 focal subjects residing at the Lao Conservation Trust for Wildlife (LCTW), a former zoo converted into a rescue and rehabilitation centre. We categorised their past experiences into seven aspects, encompassing maternal care and interactions with conspecifics. We assessed social engagement and cooperation by analysing social behaviours and employing the Social Responsiveness Scale. Emotional resilience was evaluated by measuring anxiety levels and the occurrence of abnormal behaviours, supported by a welfare questionnaire. Additionally, the introduction of Cattell’s 16PF questionnaire in macaques for the first time aimed to reveal the influence of traumatic experiences on their personality traits. Our findings underscore the significance of early social exposure to conspecifics. Macaques deprived of juvenile social contact show reduced social behaviours and a tendency towards social avoidance in adulthood. Human-reared macaques display increased abnormal behaviours in social contexts, which compromises welfare. Social deprivation with conspecifics during infancy negatively affects psychological stimulation and overall welfare, with prolonged time in illegal trade correlating with increased anxiety levels. Personality traits, such as ‘Calmness’ and ‘Unfriendliness’, are shaped by rearing conditions, with macaques deprived of social interaction showing higher levels of introversion. In summary, the more time macaques spend in human care with minimal exposure to conspecifics, the more pronounced the impacts on anxiety, abnormal social behaviours, and personality traits, highlighting the significant long-term effects of early rearing conditions on their socio-emotional development.