Role of prolonged copulatory behavior in facilitating reproductive success in a competitive mating situation in laboratory rats

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Results of 3 experiments (with 50 female F344/MA, 19 male F344, 12 male Long-Evans, 9 male BN/MA, and 9 male MAXX/MA rats) lend support to the hypothesis that the multiple ejaculatory pattern of male rats is of functional significance in that it increases the proportion of offspring sired by a given male when his female partner subsequently mates with a 2nd male, thus establishing conditions for sperm competition. When each male attained just 1 ejaculatory series, there was little effect of mating order (Exp I). Exp II revealed that when the 1st male completed 5 ejaculatory series, he sired a significantly higher porportion of the offspring relative to a 2nd male than when the 1st male attained just 1 ejaculation. The mechanism underlying the advantage of multiple ejaculations appears to lie in the proportion of sperm from each male in the female's tract rather than in either the mere passage of time or the effects of stimulation per se (Exp III). The multiple ejaculation pattern with a single female can be seen not as “wasted activity” but rather as functional in maximizing the reproductive success of individual males. (44 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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