Between-gender differences in vigilance do not necessarily lead to differences in foraging-vigilance tradeoffs

Area of Science:

• Behavioral Ecology
• Zoology
• Wildlife Biology

Background:

• Herbivore foraging behavior is influenced by time constraints and differing ecological pressures on males and females.
• Sexual dimorphism can lead to varied vigilance strategies and foraging costs, but this is less pronounced in monomorphic species.
• Understanding trade-offs between vigilance and intake rate is crucial for sexually monomorphic herbivores with similar energy needs.

Purpose of the Study:

• To investigate how gender, reproductive status, age, group size, predation risk, and food biomass affect vigilance and intake rate in plains zebras (Equus quagga).
• To determine if males and females in a monomorphic species make similar trade-offs between vigilance and food intake.
• To analyze the impact of various ecological factors on vigilance and foraging efficiency in plains zebras.

Main Methods:

• Observational study of plains zebras (Equus quagga) in their natural habitat.
• Quantified vigilance levels (percentage of time spent scanning) and feeding behavior (bite rates, intake rates).
• Analyzed data in relation to factors including gender, reproductive status, group size, predation risk, and food biomass.

Main Results:

• Males exhibited higher vigilance than females; lactating females showed reduced vigilance.
• Vigilance levels were generally low (around 10% of feeding time) with minimal impact on feeding time, bite rates, or intake rates.
• Intake rates increased with group size and were higher in tall grass for adult females; males and females adjusted intake with vigilance similarly.

Conclusions:

• Gender and reproductive status significantly influence vigilance levels in plains zebras.
• Group size and food biomass are key drivers of food intake rates.
• Despite differing vigilance patterns, plains zebras demonstrate similar trade-off strategies between vigilance and intake rate, supporting the hypothesis for monomorphic species.