Group mating among Norway rats II. The social dynamics of copulation: Competition,cooperation, and mate choice |
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Authors: | Martha K McClintock Joseph J Anisko Norman T Adler |
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Institution: | 2. Department of Behavioral Sciences, The University of Chicago, 5730 Woodlawn Ave., Chicago IL 60637 USA;3. Department of Psychology, University of Pennsylvania, Philadelphia, PA USA |
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Abstract: | The social interactions within groups of Norway rats (Rattus norvegicus) had a strong impact on the individual pattern of copulation which, in turn, affects sperm precedence and the probability of implantation in this species. Males alternated uninterrupted ejaculatory series, augmenting each others' copulatory investment. Females took turns mating after receiving an intromission, collectively potentiating the males' copulatory behaviour; increasing the number of oestrous females increased the number of intromissions and ejaculations achieved by each male but did not affect the amount of copulation experienced by each female. These turn-taking patterns within each sex provided the opportunity to change partners and permitted the emergence of different sex-typical patterns of copulation. Furthermore, the dominant male contributed more intromissions and tended to give each female more ejaculations than the subordinates did. Dominant males were also more likely to inhibit the subordinates' sperm transport. Females competed among themselves for the opportunity to mate with a male as he approached ejaculation and were likely to protect more of the dominant male's sperm transport than the subordinate male's. |
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Keywords: | Address reprint requests to M K M the University of Chicago |
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