During grooming, primates remove harmful ectoparasites, such as ticks and lice, and there is direct evidence for a health benefit of tick removal. Grooming behaviors differ among primates with respect to age and sex. Moreover, the number of ectoparasite may exhibit seasonal variation. Therefore the number of ectoparasites on a host may vary with effects, host age and sex, and season. However, these effects have not been a focus of louse infestation studies of primates. Grooming in Japanese macaques is related to sex and age, with developmental changes in behavior corresponding to the timing of tooth eruption. Moreover, behavioral data for Japanese macaques suggest that lice load may differ with the season. Thus, we examined whether the number of louse eggs varies according to host macaque sex, age, and season, and whether it changes in response to tooth eruption. We counted unhatched and hatched eggs attached to the hair on six 1-cm2 areas on the left wrist skin of culled macaques, using a stereoscopic microscope. We sampled five winter coats and three summer coats for each age class: infant, juvenile, adolescent, and adult. The number of unhatched and hatched eggs was related to age, but not to sex and season. There were significant differences in the number of unhatched eggs between infants and adults, juveniles and adults, and adolescents and adults. There were also significant differences in the number of hatched eggs between infants and adults, juveniles and adults, adolescents and adults. Tooth eruption did not influence the number of louse eggs. These results suggest that researchers should consider the age of host animals when assessing the relationship between grooming and ectoparasites.

中文翻译：

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野生日本猕猴 (Macaca fuscata) 上的虱卵数量随年龄变化，但与性别或季节无关


在梳理毛发的过程中，灵长类动物会清除有害的体外寄生虫，例如蜱虫和虱子，并且有直接证据表明清除蜱虫对健康有益。灵长类动物的梳理行为因年龄和性别而异。此外，体外寄生虫的数量可能表现出季节性变化。因此，宿主体内的体外寄生虫数量可能会因影响、宿主年龄、性别以及季节而异。然而，这些影响并不是灵长类虱子感染研究的焦点。日本猕猴的梳理行为与性别和年龄有关，行为的发育变化与牙齿萌出的时间相对应。此外，日本猕猴的行为数据表明，虱子数量可能随季节而变化。因此，我们研究了虱子卵的数量是否会根据宿主猕猴的性别、年龄和季节而变化，以及是否会随着牙齿萌出而变化。我们使用立体显微镜对被宰杀的猕猴左手腕皮肤上六个 1 平方厘米区域的毛发上附着的未孵化和孵化的蛋进行了计数。我们针对每个年龄段（婴儿、青少年、青少年和成人）抽取了五件冬季外套和三件夏季外套。未孵化和已孵化蛋的数量与年龄有关，但与性别和季节无关。婴儿与成人、青少年与成人、青少年与成人之间未孵化蛋的数量存在显着差异。婴儿与成人、青少年与成人、青少年与成人之间的孵化蛋数量也存在显着差异。牙齿萌出并不影响虱子卵的数量。这些结果表明，研究人员在评估梳理行为和体外寄生虫之间的关系时应考虑宿主动物的年龄。