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Demography, female life history, and reproductive profiles among the chimpanzees of Mahale
Author(s) -
Nishida Toshisada,
Corp Nadia,
Hamai Miya,
Hasegawa Toshikazu,
HiraiwaHasegawa Mariko,
Hosaka Kazuhiko,
Hunt Kevin D.,
Itoh Noriko,
Kawanaka Kenji,
MatsumotoOda Akiko,
Mitani John C.,
Nakamura Michio,
Norikoshi Koshi,
Sakamaki Tetsuya,
Turner Linda,
Uehara Shigeo,
Zamma Koichiro
Publication year - 2003
Publication title -
american journal of primatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.988
H-Index - 81
eISSN - 1098-2345
pISSN - 0275-2565
DOI - 10.1002/ajp.10068
Subject(s) - demography , offspring , fecundity , biology , weaning , tanzania , population , geography , pregnancy , zoology , genetics , environmental planning , sociology
Demography provides critical data to increase our understanding of the evolution, ecology, and conservation of primate populations. The chimpanzees of the Mahale Mountains National Park, Tanzania, have been studied for more than 34 yr on the basis of individual identification and standardized attendance records. From this long‐term study, we derived the following demographic data: The major cause of death was disease (48%), followed by senescence (24%) and within‐species aggression (16%). Fifty percent of Mahale chimpanzees died before weaning. The median ages of female life history variables were: first maximal swelling, 10.0 yr (n=5); emigration, 11.0 yr (n=11); and first birth, 13.1 yr (n=5). The median period of adolescent infertility was 2.8 yr (n=4) when calculated from the age at immigration to that at first birth. Female fecundity was highest between 20 and 35 yr of age, with an annual birth rate of 0.2. Twenty‐six females that were observed from a young age (10–13 yr) to death at various ages (15–40 yr) gave birth to an average of 3.9 and weaned an average of 1.4 offspring. Twenty‐five females that were observed from middle age (18–33 yr) to death in older age (31–48) gave birth to an average of 2.7 and weaned an average of 2.0 offspring. The post‐reproductive lifespan for female chimpanzees was defined as the number of years that passed from the year when the last offspring was born to the year when the female died, minus 5. Twenty‐five percent of old females had a post‐reproductive lifespan. The interbirth interval after the birth of a son (x̄ = 72 mo) tended to be longer than that after the birth of a daughter (x̄ = 66 mo). The extent of female transfer, which is a rule in chimpanzees, is influenced by the size and composition of the unit group and size of the overall local community. Am. J. Primatol. 59:99–121, 2003. © 2003 Wiley‐Liss, Inc.