Why do hunting cheetahs prefer male gazelles?

Cheetahs, Acinonyx jubatus, in the Serengeti National Park kill more male Thomson's gazelles, Gazella thomsoni, than expected from the sex ratio of the local population. This paper examines whether behavioural differences between male and female gazelles predispose males to higher rates of predation. Cheetahs hunting groups of Thomson's gazelles preferentially selected individuals that were positioned on the periphery of groups, were further from their nearest neighbours, were in areas of high vegetation, were less vigilant and were either in small groups or on their own. As a result, male Thomson's gazelles, which tended to concentrate on the periphery of groups, had greater nearest-neighbour distances, were less vigilant and were found in smaller groups, were more vulnerable than females and were preferentially selected from groups. There was no evidence that males were more vulnerable because they tended to concentrate in areas of high vegetation. Overall, gazelles in groups were far less vulnerable to predation than solitary individuals and the fact that males spent so much more time alone than females was another factor contributing to their high risk of predation; although solitary males were actually better at escaping once chased by cheetahs than solitary females, the difference in escape ability was not sufficient to offset the high number of attacks experienced by males as a result of their more solitary behaviour.