Continuous Provisioning Increases Breeding Success of Black-and-White Snub-Nosed Monkeys (Rhinopithecus bieti) in the Baima Snow Mountain Nature Reserve, Yunnan, China.

The high energy demands of primates during pregnancy and lactation often limit their breeding success due to the availability of food resources. Until now, few studies have focused on the effects of continuous provisioning on primate reproduction. To assess the impact of continuous provisioning on breeding success, we collected data on female reproductive status (primiparous or multiparous), maternal age of births, births, deaths, and sex of infants in a free-ranging semi-provisioned band (FSB) of Rhinopithecus bieti in China from 2010 to 2023. Our results indicate that provisioning significantly increases infant survival. After 8 years of provisioning, 11 females began a pattern of giving birth to infants in two continuous years, skipping reproduction in the third year, and resuming in the fourth year. Continuous provisioning led to a year-by-year reduction in the interbirth interval (IBI) and a gradual decrease in the primiparous age. The percentage of consecutively breeding females (CBFs) and their offspring increased annually and with the mother's ages. Conversely, the percentage of offspring from non-consecutively breeding females (NBFs) decreased over time and with maternal age. Each CBF annually produced 9.4% more infants compared to NBFs. Compared to NBFs, CBFs had a higher maternal age at births, a higher fertility rate, a higher infant survival rate, and a 11.7% shorter IBI. Furthermore, compared to the non-provisioned wild band (NPB), females in the FSB gave birth 128 days earlier, had an 18.9% annual increase in the number of offspring per female, and showed 1.2 times higher infant survival beyond 12 months. Our study demonstrates that provisioning significantly enhances reproductive success and population size. However, before promoting provisioning as a conservation tool to stabilize and recover endangered wildlife populations, it is essential to thoroughly evaluate its potential risks, such as nutritional imbalances, increased stress, and the transmission of diseases.