Male reproductive status affects contest outcome during nidification in Canthon cyanellus cyanellus LeConte (Coleoptera: Scarabaeidae)

Abstract

Contests between male dung roller beetles for the possession of food balls and females have been well documented. However, the factors that determine contest success between resource owners and intruders trying to appropriate it, have received considerably less attention. We analyzed how the reproductive status of males influenced the outcome of contests between owners and intruders during the nidification of pairs in Canthon cyanellus cyanellus . When mated owners were attacked by unmated intruders, the mated owners won more contests than when they were attacked by mated intruders. Unmated owners had the same likelihood of defeating intruders, regardless of the reproductive status of the intruding male. Another factor influencing contest outcome was the stage of nidification during which the pair was attacked. If the pair was just beginning a nest, the male was more successful at defending than when the pair had finished making the brood balls and most of the eggs had been fertilized. Larger males had a greater likelihood of winning a combat than smaller ones. Males of similar size and reproductive status, as well as large unmated male owners that fight with small mated intruders, did not tend to fight, in lieu they divided the food for reproduction.