Balancing Reproduction and Survival: Seasonal Body Mass Dynamics in a High-Altitude Primate (Rhinopithecus bieti)

Area of Science:

• Primate ecology
• Mammalian physiology
• High-altitude adaptation

Background:

• Seasonal body mass fluctuations in mammals are linked to ecological constraints and reproduction.
• Understanding these dynamics in high-altitude primates facing extreme temperatures is crucial.
• Few studies link body mass changes with activity budgets in these environments.

Purpose of the Study:

• To investigate the effects of environmental stress and mating on body mass dynamics in black-and-white snub-nosed monkeys (Rhinopithecus bieti).
• To correlate seasonal body mass changes with activity budgets in this high-altitude primate species.
• To understand energy allocation strategies balancing survival and reproduction.

Main Methods:

• Conducted monthly non-invasive monitoring over a full annual cycle.
• Collected 464 body mass records from free-ranging adult monkeys (127 male, 337 female).
• Analyzed seasonal variations in body mass and correlated mass loss with mating activity and activity budgets.

Main Results:

• Both sexes showed peak body mass in spring and autumn, with declines in winter and sharper drops during the mating season.
• Male mass loss positively correlated with the number of mates.
• Activity budgets shifted seasonally: increased movement and reduced resting in summer, increased feeding and reduced social activity in winter for females.

Conclusions:

• High-altitude primates like Rhinopithecus bieti exhibit distinct phases of body mass loss, with greater loss during the mating season due to reproductive costs.
• These monkeys demonstrate flexible energy allocation to balance survival and reproduction in challenging high-altitude habitats.
• Findings provide insights into the resilience of seasonal energy allocation in provisioned high-altitude environments.