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The postejaculatory copulations of cactus mice are demonstrated to function in facilitating neuroendocrine responses necessary for pregnancy. Whereas estrous cycles were altered after just 10 percent of the tests terminated after one ejaculatory series, females became either pregnant or pseudopregnant after 80 percent of tests continued at least to sexual satiety (30 minutes with no copulations).

The copulatory behavior and nest building behavior of wild house mice (Mus musculus) were examined in an attempt to study the effects of domestication on these behaviors. In the first experiment, 17 male and 17 female wild house mice were observed on a total of 68 tests of copulatory behavior, each carried to a satiety criterion of 90 min with no intromissions. The basic copulatory pattern was found to be identical to that of domesticated strains of house .mice. However, the wild house mice appeared more extreme in certain of the quantitative aspects of copulatory behavior than most inbred strains. In the second experiment, 9 male and 10 female wild house mice and 10 male and 10 female C57BL/6J inbred house mice were tested for nest building behavior for 28 consecutive days. The nest building of wild house mice appeared similar to that of most domesticated house mice, although wild house mice used less cotton in building nests than did domesticated animals.Interest in the effects of domestication on behavior has generated a number of recent studies of wild rodents and comparisons with their domesticated counterparts

The purpose of this study was to compare the sexual performance of rams that differed in age (maturation) and sexual experience. Twenty-four ram lambs (8 mo of age) and 21 rams (20 mo of age) were individually exposed to four females in hormonally induced estrus for 30 min on five occasions, 7 d apart. Half (12) the ram lambs and nine of the yearlings were sexually naive at the start of testing (had been denied access to females since weaning); the remaining males were sexually experienced. The sexual performance of the virgin rams was poorer during the initial exposure to females than in subsequent tests, whereas the sexual behavior of the sexually experienced males did not change over the days of testing. Sexually naive ram lambs and rams exhibited an improvement in sexual performance between Tests 1 and 2; during Test 3 to 5 the sexual performance (ejaculations per test) of sexually naive and experienced rams was similar. The only effects of age (maturation) on sexual performance during the last three test days were a higher frequency of mounts without ejaculation plus mount attempts (P less than .03) and a greater number of mount interactions per ejaculation (P less than .02) by ram lambs. In conclusion, one or two relatively brief exposures to estrous females can bring the sexual performance of virgin rams up to levels comparable to that of experienced males. Also, ram lambs in good condition exhibit acceptable levels of sexual performance.

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