Mating success of resident versus non-resident males in a territorial butterfly.
Male-male competition over territorial ownership suggests that winning is associated with considerable benefits. In the speckled wood butterfly, Pararge aegeria, males fight over sunspot territories on the forest floor; winners gain sole residency of a sunspot, whereas losers patrol the forest in search of females. It is currently not known whether residents experience greater mating success than non-residents, or whether mating success is contingent on environmental conditions. Here we performed an experiment in which virgin females of P. aegeria were allowed to choose between a resident and a non-resident male in a large enclosure containing one territorial sunspot. Resident males achieved approximately twice as many matings as non-residents, primarily because matings were most often preceded by a female being discovered when flying through a sunspot. There was no evidence that territorial residents were more attractive per se, with females seen to reject them as often as non-residents. Furthermore, in the cases where females were discovered outside of the sunspot, they were just as likely to mate with non-residents as residents. We hypothesize that the proximate advantage of territory ownership is that light conditions in a large sunspot greatly increase the male's ability to detect and intercept passing receptive females.
Bergman
Martin
M
Department of Zoology, Stockholm University, Stockholm, Sweden. martin.bergman@zoologi.su.se
Gotthard
Karl
K
Berger
David
D
Olofsson
Martin
M
Kemp
Darrell J
DJ
Wiklund
Christer
C
D000818:Animals; D002080:Butterflies / Q000502:physiology*; D003163:Competitive Behavior / Q000502:physiology*; D005260:Female; D008297:Male; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013472:Sunlight; D013548:Sweden; D013731:Territoriality