Evaluating the impact of synthesised scent enrichment on behavioural and endocrine responses in captive alaotran gentle lemurs (Hapalemur alaotrensis)

Abstract

The Alaotran gentle lemur (Hapalemur alaotrensis) is one of the world’s most endangered primates and shows low success rates in captive breeding programmes. This study tested biologically relevant scent enrichment using two synthesised mixtures likely to convey information about female fertility on the behaviour of three unsuccessful breeding pairs in captivity. Specifically, we compared the baseline and enrichment periods by combining behavioural observations (n = 240 h) with faecal endocrinology (n = 80 samples), focussing on cortisol and testosterone measurements via enzyme immunoassay techniques. Then, we tested two different mixtures to assess potential behavioural differences and evaluate the effectiveness of olfactory enrichment using scented and unscented cotton strips. Olfactory behaviours differed by sex and enrichment conditions, with both sexes exhibiting increased behaviours during enrichment compared to the baseline. Sexual behaviours increased during the enrichment period, with variations in frequency between males and females depending on the condition. No significant changes were observed in faecal cortisol levels. However, one male showed a significant increase in testosterone during the second enrichment mixture. Nevertheless, overall differences between baseline and enrichment were not significant. Our findings suggest that while the scent enrichment showed limited effectiveness, biologically meaningful scents may trigger species-specific behaviours.