Relationships between food provisioning patterns, stress and reproductive parameters of Sichuan snub-nosed monkeys (Rhinopithecus roxellana)

Inadequate body condition in wild animals (especially lactating and gestating females) may be caused by intense physiological stress, which compromises reproductive success, thereby reducing population growth rates. Our study troop of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) at the Shennongjia Nature Reserve were subjected to two different food provisioning patterns: (i) an interactive pattern (all family units fed together; 2006–2008) and (ii) an individualistic pattern (family units fed separately; 2009-2012). We postulated that fecal glucocorticoid metabolites (FGM) and birth rates would differ significantly between monkeys subjected to these two feeding patterns. Behavioral ranks were assigned by Dominance Index (DI) values. A Machine Learning (ML) approach was used to assess correlations between behavioral ranks and infant mortality. We collected 841 fecal samples from 12 adults (7♂, 5♀) and monitored survival of infants borne by 16 females in the period 2006–2012. Infant survival rates were 78.26% % and 93.10 % when the troop was fed interactively and individualistically, respectively. FGM values obtained when provisioning was interactive were significantly higher than when provisioning was individualistic. In cold seasons, FGM values obtained when provisioning was individualistic were much reduced in comparison with interactive provisioning. Low rank among females greatly increased the risk of infant death. Thus, nutritional stress caused by provisioning pattern is a major contributory factor to overall physiological stress in Rhinopithecus roxellana females in the Shennongjia Nature Reserve.