Long-term Changes in Age-Sex Groups of the Captors and Developmental Stages of the Prey in the Red Colobus Hunting Behavior by the Chimpanzees of Mahale, Tanzania

We analyzed the long-term changes in the age-sex of chimpanzee captors and the developmental stages (estimated by body size) of the colobus prey. We also analyzed whether any specific male chimpanzees disproportionately contributed to the red colobus hunting over time. The data were obtained from a 46-year observation at Mahale Mountains National Park, Tanzania. In the early stages of this long-term study, only mature and adolescent male chimpanzees hunted red colobus, and these hunts were mostly single-kill episodes. But over time, mature and adolescent female chimpanzees began to participate in red colobus hunts as well, and the number of multiple-kill episodes increased. The developmental stages of the red colobus taken as prey also diversified over time. In particular, the rate of infant prey increased, which suggests that chimpanzees may have developed hunting tactics to counter the antipredator tactics of female colobus that have dependent offspring. Thus, the spread of red colobus hunting appears to have increased the diversity of the age-sex classes of chimpanzees acting as hunters and the range of developmental stages of red colobus taken as prey. No consistent tendency was observed that specific male chimpanzees contributed in red colobus hunting more than others continuously over the years. Nevertheless, male chimpanzees tended to kill the red colobus more frequently when they had the alpha status

The diet and feeding behavior of the black-and-white colobus (Colobus guereza) in the Kalinzu Forest, Uganda

One of the goals for primate feeding ecology is to understand the factors that affect inter- and intra-specific variations. Therefore, a detailed description of basic feeding ecology in as many populations as possible is necessary and warrants further understanding. The black-and-white colobus (Colobus guereza) or guereza is widely distributed in Africa and is one of the well-studied colobines in terms of their feeding; they demonstrate considerable variation in their diets in response to local conditions. We studied the diet of a group of guerezas in the Kalinzu Forest, Uganda, for over 30 consecutive months using behavioral observation (4308 h in total), phenology, and vegetation surveys. A total of 31 plant species were consumed by the study group. This study group was predominantly folivorous; the majority of their feeding time was involved in feeding on young leaves (87%). However, during certain times of the year, fruits and seeds accounted for 45% of monthly feeding time. Young leaves of Celtis durandii were by far the most important food, which constituted 58% of the total feeding records. There was a significant increase in the consumption of fruits and flowers once young leaf availability was low, but their consumption of fruits did not significantly increase even when fruit availability was high. Their monthly dietary diversity increased as the number of available plants with young leaves declined, suggesting that much of the dietary diversity in the study group may be attributable to the young leaf portion of their diet. Our findings may help contribute to a better understanding of the dietary adaptations and feeding ecology of guerezas in response to local environmental conditions

The Diurnal Primate Fauna and Population Densities of Tschego Chimpanzees in Southwestern Congo

An extensive two-part survey on the diurnal primate fauna and population densities of tschego chimpanzees (Pan t. troglodytes) was carried out in southwestern Congo from November 1992 to February 1993. The first half of the survey was conducted in the Regions of Niari and Lekoumou. In this area, the occurrence of Pan t. troglodytes and Cercopithecus pogonias was confirmed by direct observations. The occurrence of Gorilla g. gorilla, Mandrillus sphinx, Cercopithecus cephus and C. nictitans was confirmed by the indirect evidence. Local people informed me of the presence of Cercocebus albigena, C. torquatus and Miopithecus talapoin, although they were not confirmed directly. The second half of the survey was carried out at Dimonika in the Region of Kouilou. Pan t. troglodytes and Cercopithecus cephus were directly observed. Feer (1991) has reported the occurrence of Gorilla g. gorilla, Mandrillus sphinx, Cercocebus albigena, Cercopithecus pogonias and C. nictitans, but no evidence was obtained for their presence. The chimpanzee population densities, calculated from nest counts in the survey, were higher near the border of Gabon and in the eastern part of the Region of Lekoumou than other areas. This difference in population densities seemed to be due to differences in hunting pressure by humans. The overall population density of chimpanzees in southwestern Congo was lower than that in the Nouabale-Ndoki National Park in northern Congo, but roughly the same as in Equatorial Guinea, and in Gabon

ザイール共和国ワンバにおける野生ボノボのオス間関係

要旨ファイルの氏名は"五保部 裕京都大学0048新制・課程博士博士(理学)甲第4881号理博第1338号新制||理||746(附属図書館)UT51-91-S4京都大学大学院理学研究科霊長類学専攻(主査)教授 加納 隆至, 教授 杉山 幸丸, 教授 西田 利貞学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA

<Note>Male chimpanzee age affects red colobus monkey hunting success

We used data collected from 1976 to 2010 in Mahale, Tanzania, to explore longitudinal changes in red colobus hunting throughout the life histories of individual male chimpanzees. The relative frequency (z-scores) of successful red colobus hunts by male chimpanzees exhibited an inverted U-shaped distribution with age. Hunting success increases when males are between 8–20 years old. Males in adulthood (20–35 years of age) made the highest number of kills. After 39 years of age, male chimpanzees were not observed to kill red colobus monkeys. These results were discussed in terms of their implications for understanding changes in the social status of male chimpanzees over time

<Note>Seasonal hunting for red colobus monkeys by Mahale chimpanzees

With the spread of red colobus hunting by Mahale chimpanzees after the 1990s, hunting became more concentrated from August to October when the party size of chimpanzees increased. In particular, infant red colobus monkeys seemed to be caught more frequently from July to September compared to other age-group prey