Growth and threshold weaning weights among captive rhesus macaques

Area of Science:

• Primate reproductive ecology
• Mammalian growth dynamics
• Behavioral endocrinology

Background:

• Interspecific studies reveal a consistent weaning weight threshold (approx. 4x neonate weight) across species.
• Understanding intraspecific variation in this threshold is crucial for reproductive success.

Purpose of the Study:

• To investigate intraspecific variation in infant rhesus macaque growth and attainment of a threshold weaning weight.
• To determine the influence of maternal and offspring factors on growth patterns and subsequent reproduction.

Main Methods:

• Studied 31 captive infant rhesus macaques, measuring growth from birth to maternal reconception.
• Collected data on maternal size, weight, social status, and offspring sex.
• Analyzed correlations between infant growth, maternal characteristics, and future reproductive outcomes.

Main Results:

• A threshold weaning weight of approximately 1,335 g was observed.
• Infant birth weight correlated with maternal size and social rank (alpha mothers had larger neonates).
• Postnatal growth rate was independent of maternal condition but influenced by offspring sex and reconception probability.

Conclusions:

• Maternal investment decisions balance current offspring growth with future reproductive potential.
• Slower infant growth, particularly in males, was associated with earlier maternal reconception.
• Growth patterns reflect a trade-off between maternal resource allocation and reproductive strategy.