Sex differences in energy expenditure in non-human primates

Area of Science:

• Evolutionary biology
• Primate ecology
• Bioenergetics

Background:

• Female mammals incur energetic costs during gestation and lactation.
• Intrasexual competition in males can also lead to substantial energetic expenditure.
• Body size dimorphism is a key factor influencing sex-based energetic costs.

Purpose of the Study:

• To investigate the relationship between male and female energetic costs in non-human primates.
• To determine the short-term (daily energy expenditure) and long-term (per-offspring) energetic costs for both sexes.
• To identify the primary drivers of sex differences in energetic expenditure.

Main Methods:

• Analysis of data from 19 non-human primate species.
• Comparison of daily energy expenditure between males and females.
• Assessment of the energetic cost of producing a single offspring for each sex.

Main Results:

• Body size dimorphism is the principal determinant of sex differences in energetic costs.
• Females often incur greater long-term energetic costs, but this can reverse in highly dimorphic species.
• When male body size exceeds female body size by 60% or more, male energetic costs surpass female costs.

Conclusions:

• In highly sexually dimorphic primate species, male energetic costs of maintaining large body size can equal female costs of gestation and lactation.
• Sexual dimorphism significantly influences the energetic trade-offs between sexes in reproduction and competition.
• Understanding these energetic differences is crucial for evolutionary and ecological studies of primates.