Sexual segregation in vertebrates: proximate and ultimate causes

Area of Science:

• Zoology
• Ecology
• Ethology

Background:

• Sexual segregation is prevalent in group-living vertebrates, particularly ungulates.
• Males and females often form separate groups, utilize distinct home ranges, and habitats outside the breeding season.
• Sexual dimorphism in body size contributes to ecological and behavioral differences between sexes.

Purpose of the Study:

• To review proximate and ultimate causes of sexual segregation in social species, with a focus on ungulates.
• To understand the evolution of sociality, sexual dimorphism, and mating systems by examining sexual segregation.
• To differentiate between hypotheses explaining social and habitat segregation and propose integrated models.

Main Methods:

• Comparative review of studies on ruminants and other vertebrates.
• Analysis of hypotheses including predation risk, forage selection, activity budget, and social factors.
• Preliminary experimental study on the activity-budget hypothesis in three-spine sticklebacks.

Main Results:

• Sexual segregation is widespread, with males and females often exhibiting different ecological niches and behaviors.
• Predation risk, forage selection, and activity budgets are key factors influencing segregation.
• A single factor is unlikely to explain sexual segregation; integrated models are needed.

Conclusions:

• Distinguishing between social and habitat segregation is crucial for understanding its causes.
• Experiments and model systems, like shoaling fish, can elucidate underlying mechanisms.
• A comprehensive model integrating multiple factors and levels of segregation is likely necessary to explain sexual segregation.