Takahashi Hiroyuki
Primate Research Institute, Kyoto University, Aichi, Japan.
Am J Primatol. 2004 Jun;63(2):95-102. doi: 10.1002/ajp.20042.
This study was designed to test the hypothesis that male primates in multi-male/multi-female social groups with a clear male dominance hierarchy have a better chance of mating when the number of estrous females is equal to or greater than, as opposed to less than, the males' ordinal rank. I studied a Japanese macaque (Macaca fuscata fuscata) troop during mating seasons from 1992 to 1995. The mean daily operational sex ratio (OSR; the number of estrous females per troop male), which was calculated on observation days, was 0.21, 1.9, 0.48, and 3.1 in 1992-1995, respectively. Overall, focal animal sampling of males yielded 118 male-day records. The male-day records for each male were divided into the two estrous female number conditions: 1) the male-day records when the number of estrous females was equal to or greater than the male's ordinal rank, and 2) the male-day records when the number of estrous females was less than the male's ordinal rank. In the 1993 and 1995 mating seasons, when the number of estrous females was equal to or greater than the ordinal rank of each male, all of the males were observed mating. Conversely, when the number of estrous females was less than the ordinal rank of some male, they were not observed mating in the 1992 and 1994 mating seasons. The percentage for each male across each male's total mating opportunity was <20% when the number of estrous females was less than the male's ordinal rank. By contrast, the percentage for each male across each male's total mating opportunity exceeded 45% when the number of estrous females was equal to or greater than the male's ordinal rank, except for one male. Of all the male-day records for males observed mating with ejaculation, 41 were obtained when the number of estrous females was equal to or greater than the male's rank; conversely, only three records were obtained when the number of estrous females was less than the male's ordinal rank. Therefore, it appears that males have a better chance of mating when the number of estrous females is equal to or greater than the males' ordinal rank, as opposed to when the number is less than their ordinal rank.
在具有明确雄性优势等级制度的多雄多雌社会群体中，当处于发情期的雌性数量等于或大于（而非小于）雄性的等级位次时，雄性灵长类动物交配的机会更大。我在1992年至1995年的交配季节研究了一群日本猕猴（Macaca fuscata fuscata）。在观察日计算得出的平均每日实际性比（OSR；即每只雄性猕猴对应的处于发情期的雌性数量）在1992年至1995年分别为0.21、1.9、0.48和3.1。总体而言，对雄性猕猴进行焦点动物取样得到了118个雄性日记录。每个雄性的雄性日记录被分为两种处于发情期的雌性数量情况：1）处于发情期的雌性数量等于或大于该雄性等级位次时的雄性日记录；2）处于发情期的雌性数量小于该雄性等级位次时的雄性日记录。在1993年和1995年的交配季节，当处于发情期的雌性数量等于或大于每只雄性的等级位次时，观察到所有雄性都有交配行为。相反，在1992年和1994年的交配季节，当处于发情期的雌性数量小于某些雄性的等级位次时，未观察到它们进行交配。当处于发情期的雌性数量小于雄性的等级位次时，每个雄性在其总的交配机会中所占的百分比小于20%。相比之下，当处于发情期的雌性数量等于或大于雄性的等级位次时，每个雄性在其总的交配机会中所占的百分比超过45%，只有一只雄性除外。在所有观察到有射精交配行为的雄性日记录中，41个是在处于发情期的雌性数量等于或大于雄性等级时获得的；相反，当处于发情期的雌性数量小于雄性的等级位次时，仅获得了3个记录。因此，似乎当处于发情期的雌性数量等于或大于雄性的等级位次时，雄性交配的机会更大，而当数量小于其等级位次时则不然。
