Abstract
The occurrence and consequences of nest-raiding behaviours of male three-spined sticklebacks (Gasterosteus aculeatus L., forma leiura) were studied in an enclosed section of a small stream of the Tsuya River, Gifu Prefecture Central Japan. The observations were made almost daily on 99 males which were individually marked and the 189 nests built by them during the breeding season, March to mid July 1988. About 10% of the nests were subjected to raiding which included egg cannibalism, egg stealing and sneaking fertilizations. Most raidings were done by single territorial males. The probability of nest raiding was related to the degree of cover around the nest: nests in dense vegetation were most prone to raiders. The probability of raiding was further related to the stage of the nest: nests with eggs were most liable, those with fry least liable to raiding actions. Males that performed raiding behaviour could have nests in every stage, but most likely had no eggs in their nests. The probability of being raided was thus positively related to the number of neighbouring nests without eggs. Males that raided had a significantly duller overall nuptial coloration during the egg collecting phase than non-raiders. Body size and territory size did not differ between raiders and non-raiders. Raiders may thus be less attractive to ripe females. By egg stealing they may increase the attractiveness of their otherwise empty nest to spawning. Indeed, nests of raiders produced significantly more often young than those of non-raiders, but the number of young produced in successful nests was not different between the two categories of males. Nest-raiding was detrimental to the victims of raiding actions: raided nests produced less offspring early in the breeding season.
Published Version
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