Novel Scent Enrichment Enhances Socio-Sexual and Olfactory Behaviors in Zoo-Housed Gentle Lemurs

The Alaotran gentle lemur (Hapalemur Alaotrensis) is one of the most endangered primates in the world and shows a low success rate in captive breeding programmes. We tested a novel scent enrichment, made up of a synthesized mixture likely conveying information about female fertility, on four unsuccessful breeding pairs (n = 8 subjects) living at the Jersey, Birmingham, London (United Kingdom) and Mulhouse (France) zoos. We evaluated the effects of the scent enrichment on behavior (515 h of observation) and fecal endocrinology (cortisol and testosterone measurements) (n = 180 samples) comparing pre- enrichment, enrichment and post- enrichment phases. We found a small effect by sex on olfactory behaviors related to the enrichment. We also found that both male and female sexual behaviors significantly increased during the enrichment. Conversely, we did not find any significant change related to enrichment in cortisol and testosterone levels, whilst some effect by the zoo environment. Our results show little effectiveness by the scent enrichment as the lemur hormone levels did not change significantly and the lemurs continued to fail to reproduce following the enrichment. Nevertheless, our findings highlight that biologically relevant scent may trigger natural species-specific behaviors, with potential implications for enhancing behavioral health and management of zoo-based endangered lemur species.