Predicting primate responses to "Stochastic" demographic events

Area of Science:

• Primate Behavioral Ecology
• Demography
• Conservation Biology

Background:

• Primate responses to ecological changes are complex, involving individual, group, and population dynamics.
• Understanding demographic processes is key to interpreting primate behavioral ecology.

Purpose of the Study:

• Examine demographic and life history factors influencing reproductive seasonality and infant sex ratios in muriquis (Brachyteles arachnoides).
• Investigate the impact of maternal parity on offspring sex ratios.

Main Methods:

• Long-term data analysis (1982-1998) from an expanding muriqui group in Brazil.
• Statistical examination of birth cohort size, birth distribution, and infant sex ratios in relation to maternal parity.

Main Results:

• Annual birth cohort size positively correlates with the annual distribution of births, highlighting the role of reproductive females.
• A female-biased infant sex ratio was observed, exclusively among multiparous mothers.
• Primiparous mothers had balanced sex ratios, while multiparous mothers showed an increasing tendency for daughters.

Conclusions:

• Reproductive seasonality in muriquis is influenced by the number of reproductive females.
• Maternal parity is a critical factor in determining offspring sex ratios.
• Differential sensitivity to resource competition across maternal life stages may explain the observed female-biased sex ratio.