Seasonal Aggregation Behaviour in a Mixed Population of Legless Lizards, Delma australis and D. fraseri

Abstract

Large numbers of Delma australis Kluge and D. fraseri Gray aggregate at a site near Esperance, Western Australia during the winter months. With the onset of spring they disperse over a much larger area returning to the aggregation site in the following autumn. Maximum concentration/aggregation occurs in June for both species. Total dispersion occurs from December to March in D. australis and November to January in D. fraseri. The dispersion is not random but involves a westerly drift by most of the population to an alternative habitat which is suitable for summer occupation. It is suggested that this seasonal migration is behaviour of recent origin caused by the changes to the habitat that occurred when this area was largely cleared for agricultural use.