Method of handling affects post-capture encounter probabilities in male Hypolimnas bolina (L.) (Nymphalidae)

Mark-recapture studies of butterfly populations are often plagued by low recapture rates, which make population estimation problematic. One reason for low recaptures is that the handling process of capture, marking and release contributes to low and unequal catchability of marked individuals. Here we report the results of an experiment conducted to evaluate the hypothesis that cooling individuals prior to release minimizes handling effects. The post-capture difference in site fidelity of territorial male Hypolimnas bolina (L.) (Lepidoptera: Nymphalidae) was compared among three groups: (1) males handled normally, (2) males chilled prior to release, and (3) uncaught controls. Unchilled males showed significantly reduced site fidelity compared to both control and chilled butterflies. Furthermore, chilled butterflies resumed activity after capture in a manner similar to uncaught controls. These results indicate that chilling has the potential to minimize the adverse effects of handling on subsequent butterfly catchability. Since 'equal catchability' of caught and uncaught individuals is a critical assumption of mark-release-recapture programs, this method has the potential to greatly increase the accuracy of subsequent population estimates. On this basis, in population studies on butterflies, the precise method of handling may prove a more meaningful consideration than the question of whether or not to handle.