The influence of stable fly invasion on the behavior of captive black rhinoceros (Diceros bicornis)

Abstract

To determine the effect of stable fly invasion on the state of captive animals, we investigated the fly abundance and related behavioral responses of captive black rhinoceroses before and after the use of pesticide. Two black rhinoceroses in the Kamine Zoo were used as the subjects. We compared the number of stable flies on their bodies, repelling behavior, and maintenance behavior under normal husbandry conditions (control) and after pesticide application (debug). The number of stable flies decreased by nearly 80% under the debug condition compared with the control. Stable flies were observed most frequently on the bellies of the rhinoceroses, and the largest decrease in the number of flies after pesticide application was observed on the animals' backs. The frequency of the rhinoceroses’ repelling responses also decreased, by an average of nearly 60%, after the debug treatment compared with the control. Time allocation to the maintenance behaviors of standing rest and lying rest increased significantly, by 5%-10%, under the debug condition for both rhinoceroses. On the other hand, the time allocation to walking decreased significantly, by approximately 9%-13%, in both rhinoceroses with pesticide application. These results suggest that fly invasion drastically disrupted rhinoceros behavior, and that it likely poses a severe burden in zoo animals during the fly season.