Body weights of wild chimpanzees (Pan troglodytes schweinfurthii) of the Mahale Mountains National Park Tanzania.код для вставкиСкачать
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 723155321 119871 Body Weights of Wild Chimpanzees (Pantroglodytes schweinfurthii) of the Mahale Mountains National Park, Tanzania SHIGEO UEHARA AND TOSHISADA NISHIDA Faculty of General Education, Sapporo Uniuersity, Sapporo 062, Japan 6. U.) and Department ofAnthropology, The University of Tokyo, Tokyo 113, Japan (TN.) KEY WORDS Pan troglodytes schweinfurthii, Body weight, I n t r a subspecific variation ABSTRACT Ten male and nine female habituated chimpanzees (Pan t r e glodytes schweinfurthii) in the Kasoje area of the Mahale Mountains National Park, Tanzania, were weighed intermittently between December 1973 and March 1980 by luring them up a rope hung on a spring balance: six adult males averaged 42.0 k g and eight adult females 35.2 kg. Seasonal change in body weight was recognized at least partially; body weights tended to decrease in the later part of the wet season presumably because of food shortage in the middle of the wet season. Comparison of body weight among three populations of the same subspecies suggests that adult female chimpanzees of Mahale appear to be heavier than those of the Gombe National Park, Tanzania, and that they seem to be similar to the forest-living counterparts of eastern Zaire. On the other hand, body weights of adult male chimpanzees from the three populations do not show significant differences. Perhaps feeding competition among adult females in a small, isolated habitat is more severe than that among adult males, which may result in the body weight reduction among adult female chimpanzees at Gombe. Among various chimpanzee populations studied in the wild, only eastern or longhaired chimpanzees in the Gombe National Park, Tanzania, have been weighed systematically with minimal disturbance; they have been habituated enough with attractive food to be induced to climb a rope hung on a spring balance (Wrangham, 1975; Pusey, 1978; Wrangham and Smuts, 1980). Another systematic data set on body weight of the same subspecies in eastern Zaire is available (Rahm, 19679, but the measurements were taken when unhabituated individuals were captured for laboratory research. Jungers and Susman (1984) point out that the differences observed among subspecies of Pan troglodytes may turn out to be as important and instructive to our understanding of chimpanzee evolution as are those differences seen between pygmy chimpanzees and the various subspecies of common chimpanzees. However, intra-subspecific variation should be clarified before inter-subspecific 0 1987 ALAN R. LISS, INC and inter-specific comparisons are undertaken. This report describes newly compiled body weight data, collected in the wild by the same method as that at Gombe, on a third population of the same subspecies (Z? t. schweinfurthii) in the Mahale Mountains National Park, Tanzania, and discusses the intra-subspecific variation in body weight observed among the three populations. SUBJECT AND METHOD Wild chimpanzees of K- and M-groups in the Kasoje area of the Mahale Mountains National Park, Tanzania, were weighed between December 1973 and March 1980. Although the chimpanzees of K- and M-groups have been habituated and provisioned with sugarcane and bananas since 1966, the amount of food given to the chimpanzees was reduced from 1975 onwards. Also, data on KReceived August 18, 1986; revision accepted October 16, 1986. 3 16 S. UEHARA AND T. NISHIDA TABLE 1. Body weights of adult chimpanzees at Mahale Condition' Males KM KS KN SB LU MU Mean Females WB WW WT WS CH WL GW ND Body weight (kg) Mean Range No. of days2 Prime: K-group Prime: K-group Prime: K-group Prime: K-group Prime: M-group Prime: M-group 34.3 49.6 46.1 42.9 38.8 40.3 42.0 30.3-38.0 47.5-52.0 44.3-49.0 38.0-48.0 38.0-39.5 37.0-44.0 39.2-45.1 Past prime: K-group Past prime: K-group Past prime: K-group Prime: K-group Prime: K- or Mgroup Prime (nulliparous): K-group Prime (nulliparous): K- or M-group Young prime: Mgroup 30.5 38.3 36.2 33.8 41.8 36.0-40.5 33.5-40.5 32.5-35.0 35.5-45.5 1 (Aug. '77) 2 (Aug. '75) 6 (Jan. '74-Seat. '78) 2 (Aug. '75-J;ly '78) 27 (Dec. '73-Mar. '80) 35.3 32.5-38.0 2 (Mar.-Jun. '78) 35.5 33.5-37.5 2 (Nov. '77-Apr. '78) Mean 30.0 35.2 30 (Jan. '74-Mar. '80) 5 (Aug. '75-Feb. '76) 4 (Jan. '74) 40 (Jan. '74-Oct. '78) 2 (Sept. '75-July '78) 3 (Sept. '75-Sept. '78) 1 (Aug. '75) 33.0-37.2 'Condition when measurements were taken *On which measurements were taken. group between 1973 and 1974 were collected that individual on that day. This was done when the chimpanzees of this group were because values obtained in such cases during already fed only a small amount of food. the early days of measurement fluctuated Thus, the effect of artificial feeding on the from one occasion to another. The measurechimpanzee body weight seems to have been ments became easier and more stable as both reduced to a minimum (Nishida, 1981). To- the chimpanzees and the observers got used pography, vegetation, and climate of the to the system. Two spring balances were used study area and outlines of the two chimpan- simultaneously in Myako Camp between Oczee unit-groups are described elsewhere tober 1977 and June 1978 in order to enhance (Nishida, 1968, 1972, 1979; Uehara, 1982; the reliability of data. Hiraiwa-Hasegawa, Hasegawa, and Nishida, Male subjects consisted of six prime adults 1984; Nishida et al., 1985; Collins and Mc- (KM, KS, KN, SB, LU, and MU), two adolesGrew, 1985). cents (LJ and MS), one juvenile-infant (KB), Chimpanzees were weighed in camps and one infant (ML). Female subjects con(Myako and Kansyana) by luring them up a sisted of three past prime adults (WW, WT, rope attached to a spring balance; a banana and WB), five prime adults (WS, WI, CH, or a piece of sugarcane hanging on a second WL, and GW) and one young prime adult thin rope was fixed to the top of the main (ND). ML always clung to his mother (WI) rope, a method basically the same as that when she was weighed, while KB (son of CH) used at Gombe (Wrangham, 1975; Pusey, began to climb the rope by himself after he was 1978). Ten males and nine females climbed 2 314 years old. the rope, but most individuals of M-group refused to do so. The scale was read with RESULTS AND DISCUSSION binoculars while the chimpanzee ate or took Body weights of chimpanzees of Mahale away the food a t the top. A reading was taken Body weights of 14 adult chimpanzees are when the subject remained rather still for several seconds. If one chimpanzee was shown in Table 1. Mean body weights were weighed more than once on the same day, calculated for the individuals whose meathe median was used as the body weight of surements were taken on more than one day. Feb. '76 July '77 Aug.-Oct. '77 Nov. '77Jan. '78 Feb.-Apr. '78 May-July '78 Sept.-Oct. '78 Feb.-Mar. '80 L.W. E.D. L.D. E.W. L.W. n = 30 (n = 1) 34.8 34.6 f 0.9 (n = 5) 36.1 f 1.0 (n = 4) 37.2 -f 0.6 (n = 3) 31.8 f 0.9 (n = 4) 31.2 f 0.6 (n = 7) 38.0 (n = 114 36.3 f 1.2 (n = 5) KM = 1) n =5 50.3 (n = 1) (n + 49.2 2.5 (n = 3) 50.0 KS 'E.W., early wet; L.W., late wet; E.D., early dry; L.D., late dry. *In which measurements were taken. 3Year of birth (Dresumed vear in Darentheses). 4Number of dais on which measdrements were taken (sample size). Total number of davs L.D. E.D. L.W. L.D. E.W. Period2 Dec. '73Jan. '74 Aug.- Sept. '75 Jan. '76 E.W. Season' n = 4 46.1 f 2.1 (n = 4) KN n = 40 44.5 -f 2.2 (n = 5) 45.0 i 0.0 (n = 3) 47.0 (n = 1) 46.0 f 1.4 (n = 2) 43.8 f 1.1 (n = 4) 44.8 f 0.4 (n = 2) 41.8 f 0.4 (n = 2) 39.8 f 1.3 (n = 9) 42.0 f 0.5 (n = 7) 43.5 f 0.6 (n = 5) SB n=2 39.5 (n = 1) 38.0 (n = 1) LU n = 3 44.0 (n = 1) 38.5 f 2.1 (n = 2) MU n = l 21.0 (n = 1) LJ (196413 8.5 f 0.0 (n = 2) KB 19743 30.5 (n = 1) 26.5 -f 1.4 7.5 i 0.0 (n = 3) (n = 2) 29.0 8.0 f 0.4 (n = 7) (n = 1) 8.5 f 0.0 31.0 (n = 2) (n = 1) 32.5 12.3 -f 0.1 (n = 2) (n = 1) n = 7 = 16 -n 18.5 (n = 1) MS 19663 TABLE 2. Mean body weights (kg f SD)of male chimpanzees at Mahale between December 1973 and March 1980 Feb. '76 July '77 Apg.-Oct. 77 Nov. '77Jan. '78 Feb.-Apr. '78 May- July E.W. L.W. E.D. L.D. '78 Sept.-Oct. n = l 30.5 (n = 1) WB n=2 38.3 5 3.2 (n = 2) ww WT n=6 34.5 (n = 1) 33.8 & 0.6 (n = 3) 40.5 f 0.0 (n = 2)4 'E.W., early wet; L.W., late wet; E.D., early dry; L.D., late dry. 'In which measurements were taken. 'Year of birth. 4Number of days on which measurements were taken (sample size). 'Weighed with KB. Feh.-Mar. '80 Total number of davs L.W. L.D. E.D. L.W. E.W. '78 .- Aug.-Sept '75 Jan. '76 L.D. L.W. Dec. '73Jan. '74 Feh. '74 Period' E.W. Season' n = 2 32.5 (n = 1) 35.0 (n = 1) ws n=6 41.8 k 1.3 (n = 5) 40.3 (n = 1) WI-ML (male) 19723 44.6 k 1.0 (n = 6) 45.0 (n = 1) 40.0 (n = 115 47.0 (n = 1P 42.5 (n = 115 41.5 (n = 1) 42.6 f 0.8 (n = 3) 40.0 (n = 1) 37.1 k 1.2 (n = 5) 42.2 k 0.9 (n = 8) 41.5 (n = 1) 42.5 (n = 1) n = 27 + 35 CH n=2 32.5 (n = 1) 38.0 (n = 1) WL GW n = 2 33.5 (n = 1) 37.5 (n = 1) TABLE 3. Mean body weights (kg & SD) of female chimpanzees at Mahale between December 1973 and March 1980 n = l 30.0 (n = 1) ND 319 BODY WEIGHT OF WILD CHIMPANZEES TABLE 4.Mean body weights (kg k SD)o f adult common chimpanzees (Pan troglodytes schweinfurthii) from three nonulotinna Adult female/ adult male Pooulation Mahale Gombe Eastern Zaire Average of the three Adult males' Adult females2 42.0 k 5.4 (n = 6) Range: 34.3 -49.63 30.3-52.04 39.5 4.5 (n = 9) Range: 33.6-47.33 31.8-49.54 42.3 (n = llI7 35.2 f 3.9 (n = 8) Range: 30.0-41.83 30.0-45.54 29.8 k 2.2 (n = 6) Range: 26.4-32.33 22.7-35.Ei4 30.0 (n = 7)7 42.8 f 2.8 (n = 3) Range: 41.0-46.0 40.9 4.6 (n = 18) Range: 33.6-49.6 34.3 f 5.6 (n = 9) Range: 27.6-46.0 33.4 k 4.7 (n = 23) Range: 26.4-46.0 + + (%) Source 83.8 This study (Dec. 1973Mar. 198015 75.4 Wrangham and Smuts (1980)6 (1970-1973)5 70.9 Pusey (1978)(July 1970Dec . 197iY5 Rahm (1967)(1963-1966)5 80.1 81.7 nonulationn 'Differences between the respective means are not significant. 'Differences between the means for Mahale and Gombe and for Gombe and eastern Zaire are significant (Mahale vs. Gombe, t = 3.041, d.f. = 12, p < 0.05; Gomhe vs. eastern Zaire, t = 3.513, d.f. = 13, p < 0.01). Difference between the means for Mahale and eastern Zaire is not significant. 'Individual mean body weight. 4All measurements. 5Period in which measurements were taken. 'Statistical analysis of the present paper is based on the data from Wrangham and Smuts (1980). 7Means were calculated taking the second heaviest weight far each individual. Six adult males averaged 42.0 kg and eight adult females (excluding WI) 35.2 kg. Judging by the external appearance, however, KM seemed to be the smallest among the adult males of K- and M-groups. The mean body weight for all adult males (more than 25 individuals recorded so far in the two groups) may thus be higher to some extent than 42 kg. Our personal impressions do not suggest such a bias for the female data. Data on body weight of all individuals are combined in three-month blocks in order to see the body weight development and/or the seasonal variation: November-January (early wet season), February-April (late wet season), May-July (early dry season), and August-October (late dry season plus the beginning of the wet season) (Tables 2 and 3). No clear-cut picture can be drawn for the body weight development of four immature chimpanzees or for the seasonal variation in body weight of the other individuals because the data were incomplete. However, it must be pointed out that, except for GW, all chimpanzees including the two developing immatures (MS and KB) weighed between July 1977 and October 1978 showed marked body weight reduction in the period of FebruaryApril 1978 (Tables 2 and 3) when no apparent sign of disturbance was observed. According to Wrangham (19751, wet season body weights at Gombe are generally higher than dry season, but not always. This finding is clearly affected by the inter-annual fluctuation in food production or availability (Wrangham, 1977; Uehara, 1982; Nishida and Uehara, 19831, although the middle of the wet season is often one of the lean seasons for fruits (Nishida, 1976). Comparison of adult body weight among three populations Data sets on adult body weight from three different populations are now available within the same subspecies of wild common chimpanzees (P t. schweinfurthii): Mahale (6" S , 29" 40'E: this study), Gombe (4'403, 29'40'E: Pusey, 1978;Wrangham and Smuts, 1980), and eastern Zaire (1"30'-1"50'S, 28"28'30'E: Rahm, 1967) (Table 4).Adult male data from the three populations show similar tendencies, although the sample from eastern Zaire is represented only by three individuals. By contrast, adult female data are not similar to one another. Not only is the mean value of Gombe significantly lower than Mahale and eastern Zaire, but the range of the former population apparently differs from the latter two populations (Table 4).No significant difference in adult female body 320 S. UEHARA AND T. NISHIDA weight exists between Mahale and eastern Zaire. With the current information, it is difficult to draw a definite conclusion regarding the factors causing the intra-subspecific variation in body weight described above. However, the following speculations are worth testing in future studies. Geographically, both Mahale and Gombe are situated on the eastern shore of lake Tanganyika and consist of grassland, open woodland, thicket woodland, and gallery forest (Collins and McGrew, 1985), while Rahm’s study site (1967) is located in the lowland rain forest of eastern Zaire. Physical features, climate, and vegetation at Mahale are basically similar to those at Gombe, although some characters such as the rainfall and vegetation indicate that Mahale is wetter than Gombe (Collins and McGrew, 1985). Therefore, it is not expected that the intrasubspecific variation in female body weight is explained solely on the basis of the environmental gradient. Comparing the distribution of the three populations, however, a conspicuous aspect of Gombe emerges. The chimpanzees at Gombe seem to have been confined to a relatively small, isolated habitat owing to human disturbance, although in 1960 there were pockets and strips of forest connecting the Gombe chimpanzee with the chimpanzee population outside the national park (Goodall, 1983). At least in the main study unitgroups a t Gombe (Kasakela and Kahama communities), immigrant females have exceeded emigrant females in number (Goodall, 1983). The effect of artificial feeding is often thought to be the only cause for such a n imbalance, but this does not seem to be the case (Goodall, 1983: 51-52). Although it is not certain, there remains a possibility that the population density at Gombe is increasing. Core areas of female chimpanzees are much narrower than those of male counterparts (Wrangham, 1975, 1979; Hasegawa, unpublished data). Therefore, female chimpanzees may be expected to be subject to more severe feeding competition than are male chimpanzees. This situation may be exaggerated when the habitat is small and becomes isolated, as in Gombe. (In such a situation, overt competition among groups of adult males may also become stronger.) The body weight reduction among adult female chimpanzees a t Gombe may be explained in this context. ACKNOWLEDGMENTS The field work was financed by the Ministry of Education, Science, and Culture, Japan, between 1973 and 1974 and in 1977 (Grants-in-Aid for Overseas Scientific Research to J. Itani and to T. Kano), and by the Japan International Cooperation Agency between 1975 and 1980. The Tanzania National Scientific Research Council, the Wildlife Division of the Ministry of Lands, Natural Resources, and Tourism, Tanzania, and the Serengeti Wildlife Research Institute permitted us to conduct the study and to publish this paper. The staff at the Mahale Mountains Wildlife Research Centre (Kasoje Chimpanzee Research Station) supported the research. M. Uehara, K. Kawanaka, T. Hasegawa, and R. Nyundo greatly contributed to the collection of data in the field. H. Takasaki and two anonymous reviewers commented on a n earlier version of this paper. J. Itani and T. Kano encouraged the study. The preparation of this paper was financed in part by a 1986 Research Grant from Sapporo University to S.U. and in part by a Grant-inAid for Special Project Research on Biological Aspects of Optimal Strategy and Social Structure from the Japan Ministry of Education, Science and Culture to T.N. To these people and institutions, we make grateful acknowledgment. LITERATURE CITED Collins, DA and McGrew, WC (1985)Chimpanzees’ (Pun troglodytes) choice of prey among termites (Macrotermitinae) in western Tanzania. Primates 26t375-389. Goodall, J (1983) Population dynamics during a 15 year period in one community of free-living chimpanzees in the Gombe National Park, Tanzania. Z. Tierpsychol. 61: 1-60. Hiraiwa-Hasegawa, M, Hasegawa, T, and Nishida, T (1984) Demographic study of a large-sized unit-group of chimpanzees in the Mahale Mountains, Tanzania: A preliminary report. Primates 25t401-413. Jungers, WL and Susman, RL (1984) Body size and skeletal allometry in African apes. In RL Susman (ed): The Pygmy Chimpanzee: Evolutionary Biology and Behavior. New York: Plenum Press, pp. 131-177. Nishida, T (1968) The social group of wild chimpanzees in the Mahali Mountains. Primates 9:167-224. Nishida, T (1972)A note on the ecology of the red-colobus monkeys (Colobus badius tephrosceles) living in the Mahali Mountains. Primates 13:57-64. Nishida, T (1976) The bark-eating habits in primates, with special reference to their status in the diet of wild chimpanzees. Folia Primatol. 255377-287. Nishida, T (1979) Social structure among wild chimpanzees of the Mahale Mountains. In DA Hamburg and ER McCown (eds): The Great Apes. Menlo Park: Benjamidcummings, pp. 72-121. Nishida, T (1981) The World of Wild Chimpanzees. Tokyo: Chuokoron-sha. (in Japanese) BODY WEIGHT OF WILD CHIMPANZEES Nishida, T, Hiraiwa-Hasegawa, M, Hasegawa, T, and Takahata, Y (1985) Group extinction and female transfer in wild chimpanzees in the Mahale National Park, Tanzania. Z. Tierpsychol. 67:284-301. Nishida, T and Uehara, S (1983) Natural diet of chimpanzees (Pan troglodytes schweinfurthii): Long-term record from the Mahale Mountains, Tanzania. Afr. Stud. Monogr. 3t109-130. Pusey, AE (1978) The physical and social development of wild adolescent chimpanzees (Pan troglodytes schweinfurthii). Unpubl. dissertation. Stanford Univ., California. Rahm, U (1967) Observations during chimpanzee captures in the Congo. In D Starck, R Schneider, and HJ Kuhn (eds): Progress in Primatology. Stuttgart: Fischer, pp. 195-207. Uehara, S (1982) Seasonal changes in the techniques 321 employed by wild chimpanzees in the Mahale Mountains, Tanzania, to feed on termites (Pseudacanthe termes spiniger). Folia Primatol. 37~44-76. Wrangham, RW (1975) The behavioural ecology of chimpanzees in Gombe National Park, Tanzania. Unpubl. dissertation, Univ. of Cambridge, England. Wrangham, RW (1977) Feeding behaviour of chimpanzees in Gombe National Park, Tanzania. In TH Clutton-Brock (ed): Primate Ecology. London: Academic Press, pp. 504-538. Wrangham, RW (1979) On the evolution of ape social systems, Social Science Information 18:335-368. Wrangham, RW and Smuts, BB (1980) Sex differences in the behavioural ecology of chimpanzees in Gombe National Park, Tanzania. J. Reprod. Fert., Suppl. 28:1331.