Rats are gregarious and promiscuous and when a female enters the behavioral estrous, two or more males copulate alternately (mount, intromission or ejaculation are performed by any of them). This circumstance promotes male-male competition that in turns influences the copulatory behavior. Thus, olfactory and visual cues of rivals, in laboratory conditions, shorten the ejaculation latency. Other studies focusing in the presence of a rival found the increment in the sperm number. Until now it is unknown if the simultaneous presence of two males simultaneously influences the copulatory performance and seminal characteristics. Thus, the aim of the present work was to evaluate if sexual competition modifies the copulatory behavior, the sperm number and seminal plug. Sexually experienced Wistar rats were tested in two different copulatory contexts. Non-competitive mating (one male-one female), and competitive mating (two males-one female). The copulatory (mounts, intromissions and ejaculation) and seminal parameters (sperm count and copulatory plug) were analyzed. We found that under competition, there was a shortening of the ejaculation latency due to the reduction in the inter-intromission interval and in the number of intromissions. Respect to the ejaculate, the sperm number increased drastically but the seminal plug maintain its size and weight characteristics. Therefore, sexual competition in male rats affects copulatory behavior and sperm count but not the seminal plug.

中文翻译：

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大鼠在竞争交配期间过早射精并增加精子输出

大鼠是群居的和混杂的，当雌性进入行为发情时，两只或更多雄性交替交配（坐骑、插入或射精由其中任何一个进行）。这种情况会促进雄性竞争，进而影响交配行为。因此，在实验室条件下，对手的嗅觉和视觉线索会缩短射精潜伏期。其他在竞争对手存在的情况下进行的研究发现精子数量增加。到目前为止，尚不清楚同时存在两只雄性是否会同时影响交配性能和精液特征。因此，目前工作的目的是评估性竞争是否会改变交配行为、精子数量和精液栓。性经验丰富的 Wistar 大鼠在两种不同的交配环境中进行了测试。非竞争性交配（一雄一雌）和竞争性交配（两雄一雌）。分析了交配（坐骑、插入和射精）和精液参数（精子计数和交配栓）。我们发现，在竞争中，由于插入间隔和插入次数的减少，射精潜伏期缩短。就射精而言，精子数量急剧增加，但精液塞保持其大小和重量特征。因此，雄性大鼠的性竞争影响交配行为和精子数量，但不影响精塞。我们发现，在竞争中，由于插入间隔和插入次数的减少，射精潜伏期缩短。就射精而言，精子数量急剧增加，但精液塞保持其大小和重量特征。因此，雄性大鼠的性竞争影响交配行为和精子数量，但不影响精塞。我们发现，在竞争中，由于插入间隔和插入次数的减少，射精潜伏期缩短。就射精而言，精子数量急剧增加，但精液塞保持其大小和重量特征。因此，雄性大鼠的性竞争影响交配行为和精子数量，但不影响精塞。