Age-related site fidelity in the territorial butterfly Hypolimnas bolina (L.) (Lepidoptera: Nymphalidae)

The males of many territorial animals exhibit significant interindividual variation in site fidelity. A general prediction from theoretical models is that site fidelity should increase as a function of male age. In this study, I investigated the relationship between age and site fidelity in the territorial nymphalid butterfly Hypolimnas bolina (L.). A total of 144 males from a population in tropical Australia were captured and marked over two seasonal rounds in 1998. Sampling of the subsequent fidelity of these marked individuals provided two related lines of evidence in support of the age-based prediction. First, older males were more likely to be resighted at their territories on at least one occasion following their capture and marking. Second, the subsequent site fidelity of the group of males that was resighted at least once was related to age, with older males showing greater average fidelity. Both results were consistent across seasons. Taken in concert, these findings strongly support the hypothesis that fidelity is linked to age in this territorial butterfly. At this stage it is not possible to distinguish between increased competitive ability and increased motivation for fidelity as the underlying cause of this relationship.