Territoriality in Drosophila melanogaster as a conditional strategy

Abstract

Factors affecting the establishment of territories and incidence of territorial defence in Drosophila melanogaster males were examined, as well as their influence on the relative mating success of territorial and non-territorial males. Males were more likely to establish territories when females or recently eclosed males were present. Territorial defence was not influenced by female age and reproductive state and was more likely on food areas of 20 mm than on either larger or smaller ones. Very large food areas were not defended at all. Territorial males defending large food areas did not have a mating advantage. Males were more likely to defend resources that were attractive to females for oviposition. Sex ratio did not influence the tendency of males to establish territories and territorial males had a mating advantage even when females were twice as common as males. Males were less likely to establish and defend territories when more than 12 males were present with only one food area. This coincided with the absence of a mating advantage for territorial males at a high male density. The findings suggest that D. melanogaster males are more likely to express territorial behaviour when territory defence is associated with a mating advantage.