@article{oai:ir.soken.ac.jp:00003831,
 author = {長谷川, 眞理子 and HIRAI-HASEGAWA, Mariko and HASEGAWA, Toshikazu and NISHIDA, Toshisada},
 issue = {4},
 journal = {Primates, Primates},
 month = {Oct},
 note = {Long-term demographic observations on a large-sized unit-group of chimpanzees in the Mahale Mountains, Tanzania, are summarized. The unit-group, the M group, contains over 100 individuals, which makes it the largest unit-group ever reported. The age-sex composition, natality, mortality and transfers of the M group are analyzed. An attempt is made to illustrate an age-sex pyramid of the group by estimating the ages of all the individuals in the group. The results reveal that: (1) the mortality rate of the male infants within 1 year almost doubled that of female infant; (2) adult male to adult female ratio of the M group is considerably higher than any other unit-groups elsewhere; and (3) the M group contains a relatively large number of old animals over 40 years of age, suggesting that the longevity of wild chimpanzees might be greater than estimated so far.},
 pages = {401--413},
 title = {Demographic study of a large-sized unit-group of chimpanzees in the mahale mountains, Tanzania: A preliminary report},
 volume = {25},
 year = {1984}
}