Koyama Naoki, Nakamichi Masayuki, Ichino Shinichiro, Takahata Yukio
The Center for African Area Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
Primates. 2002 Oct;43(4):291-314. doi: 10.1007/BF02629604.
In the present study, we recorded all births, immigrations, deaths, and emigrations for a population of ring-tailed lemurs at Berenty Reserve, Madagascar, between September 1989 and August 1999. In September 1989, three troops (C, B, and T) inhabited the study area of 14.2 ha. During the 10-year period, eight troop divisions, six evictions of females, and three troop takeovers of ranges by other troops occurred in and around the study area. Consequently, in August 1999, the number of troops in the same area increased to six (CX, C1, C2A, C2B, T1, and T2). The number of lemurs aged > 1 year increased from 63 to 82, which resulted from 204 births, 58 immigrations, 125 deaths, and 118 emigrations. Of the 204 newborn lemurs during the study period, 103 died, 44 emigrated outside the study area, and 57 remained within the study area. The total number of lemurs that emigrated from natal troops was 69 (54 males and 15 females). Natal males left their troops around the age of 3. Non-natal males changed troops after a tenure varying from 1 to 7 years. Survival curves showed a fall in survival rates of both sexes to < 0.5 between the ages of 2 and 3. For females, the survival rate gradually decreased to < 0.2 at the age of 9. On the other hand, due to emigration, the survival rate of males could not be determined after the age of 5 yr. Since some males attained high-rank at the age of 6 - 10 yr, the prime age for male ring-tailed lemurs is thought to be around 7 - 10 yr. Ring-tailed lemurs are essentially female philopatric, because all cases of females leaving natal troops resulted from troop divisions or forced evictions. Such social changes may have resulted from competition among females. All cases of troop divisions or evictions occurred in larger troops consisting of >or=20 lemurs, and only a few females could rejoin their troops. When males joined such a female-group, a new troop was formed. Although promoted by an increase in population, frequent emigrations of females from original troops are the characteristics of ring-tailed lemurs at Berenty.
在本研究中，我们记录了1989年9月至1999年8月期间马达加斯加贝伦蒂保护区一群环尾狐猴的所有出生、迁入、死亡和迁出情况。1989年9月，三个群体（C、B和T）栖息在面积为14.2公顷的研究区域。在这10年期间，研究区域内及周边发生了8次群体分裂、6次雌性驱逐以及3次其他群体对领地的接管。因此，到1999年8月，同一区域的群体数量增加到了6个（CX、C1、C2A、C2B、T1和T2）。年龄大于1岁的狐猴数量从63只增加到了82只，这是204次出生、58次迁入、125次死亡和118次迁出的结果。在研究期间出生的204只新生狐猴中，103只死亡，44只迁出研究区域，57只留在了研究区域内。从出生群体迁出的狐猴总数为69只（54只雄性和15只雌性）。出生的雄性在3岁左右离开它们的群体。非出生的雄性在1至7年的任期后更换群体。生存曲线显示，两性在2至3岁之间的生存率下降至<0.5。对于雌性来说，生存率在9岁时逐渐下降至<0.2。另一方面，由于迁出，5岁以后雄性的生存率无法确定。由于一些雄性在6至10岁时获得了高等级，环尾狐猴雄性的黄金年龄被认为在7至10岁左右。环尾狐猴基本上是雌性留居型的，因为所有雌性离开出生群体的情况都是由于群体分裂或被迫驱逐。这种社会变化可能是雌性之间竞争的结果。所有群体分裂或驱逐的情况都发生在由≥20只狐猴组成的较大群体中，只有少数雌性能够重新加入它们的群体。当雄性加入这样的雌性群体时，就会形成一个新的群体。尽管种群数量增加起到了推动作用，但雌性频繁从原群体迁出是贝伦蒂环尾狐猴的特征。
