In short-lived animals, the birth date during the breeding season can lead to differences in life history and corresponding behavioral traits. We studied the link between birth date and personality in the bush Karoo rat, a seasonally-breeding and short-lived rodent which relies on a limited resource, stick lodges, essential to survive in a harsh semi-desert environment. Individuals born later in the season were more active, bolder and more explorative; these traits likely help them to successfully compete for stick lodges during the late breeding season when population density and thus competition is high. Earlyborn females, which can potentially start reproducing within their season of birth, showed no personality differences regardless of their reproductive status, suggesting that resource availability rather than reproduction opportunity may underly the emergence of seasonal personality differences in this species.