title: Demography, female life history, and reproductive profiles among the chimpanzees of Mahale.
abstract: 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 (x = 72 mo) tended to be longer than that after the birth of a daughter (x = 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.
authors.affiliation: Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto, Japan. nishida@jinrui.zool.kyoto-u.ac.jp
authors.forename: Toshisada
authors.initials: T
authors.lastname: Nishida
authors.forename: Nadia
authors.initials: N
authors.lastname: Corp
authors.forename: Miya
authors.initials: M
authors.lastname: Hamai
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Mariko
authors.initials: M
authors.lastname: Hiraiwa-Hasegawa
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Hosaka
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Hunt
authors.forename: Noriko
authors.initials: N
authors.lastname: Itoh
authors.forename: Kenji
authors.initials: K
authors.lastname: Kawanaka
authors.forename: Akiko
authors.initials: A
authors.lastname: Matsumoto-Oda
authors.forename: John C
authors.initials: JC
authors.lastname: Mitani
authors.forename: Michio
authors.initials: M
authors.lastname: Nakamura
authors.forename: Koshi
authors.initials: K
authors.lastname: Norikoshi
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sakamaki
authors.forename: Linda
authors.initials: L
authors.lastname: Turner
authors.forename: Shigeo
authors.initials: S
authors.lastname: Uehara
authors.forename: Koichiro
authors.initials: K
authors.lastname: Zamma
mesh_terms: D000367:Age Factors; D000818:Animals; D001721:Birth Intervals; D003247:Conservation of Natural Resources; D003710:Demography; D004971:Estrus; D005260:Female; D015993:Life Tables; D008297:Male; D009026:Mortality; D002679:Pan troglodytes / Q000254:growth & development / Q000502:physiology*; D011247:Pregnancy; D012098:Reproduction / Q000502:physiology*; D012930:Social Dominance; D013636:Tanzania