京都大学霊長類研究所　＞ニホンザル野外観察施設・メンバー　＞室山泰之　＞原著論文要旨

原著論文要旨

Chimpanzees' choices of prey between two sympatric species of Macrotermes in the Campo Animal Reserve, Cameroon

Muroyama, Y.

Details are presented relating to chimpanzees' choices between two sympatric species of termites, Macrotermes lillijeborgi and M.vitrialatus, as food in the Campo Animal Reserve, southwest Cameroon, West Africa. An attempt was made to determine the various factors that affected such choices. The two species of termites seemed to have almost the same value in terms of ecological factors. However, chimpanzees fed almost exclusively on M. lillijeborgi, using digging sticks and fishing probes, during the study period which extended from the end of August to the middle of January, with their feeding activity showing peak at the beginning of the rainy season. By contrast, M. vitrialatus was rarely eaten in spite of the ease with which such prey could be obtained, namely, by destruction of termite mounds by hand, without the need for tools. The reason that the chimpanzees discriminated between the two species of termites cannot be explained in terms of ecological factors such as size of prey, seasonal differences in termite activity, etc. Sticks used as tools were fairly uniform in size and character, mainly because of physical constraints related to the structure of termite mounds, and the brush-like ends of sticks seemed to be incidental by products of the chimpanzee’s choice of plant species. Ecological factors could provide chimpanzees with a basis for the use of some kind of tool and help them modify it, while other factors, for example, something akin to leisure or the chimpanzee’s interest in use of a tool, could provide an opportunity for inventing some tool-using behavior or for maintaining such behavior. These different factors, not being exclusive of one another, might affect the invention and maintenance of tool using-behavior at different phases. It is possible that chimpanzee’s choice of prey may not always be the most efficient or appropriate in a given ecological situation.

Human Evolution, 6(2): 143-151, 1991

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Mutual reciprocity of grooming in female Japanese macaques (Macaca fuscata)

Muroyama, Y.

Grooming interactions among female Japanese macaques (Macaca fuscata) were observed and compared between affiliated and unaffiliated non-related pairs, mother and adult female offspring pairs, and mother and immature offspring pairs. Unaffiliated (rarely interacting) members of pairs were likely to approach and then groom the other, in contrast to affiliated (frequently interacting) pairs, who more often approached and then solicited grooming from the other. The return receipt of a benefit just given, in the form of reciprocation of grooming, was immediate in non-related pairs. The brief interval between the occurrence of reciprocation facilitated the estimation of receiving as much benefit as was given in the case of rare grooming. However, such was not the case for related pairs. Adult female offspring solicited grooming from mothers more than immature offspring. The findings are discussed with reference to previous theories about the evolution of altruistic behaviour.

Behaviour, 119(3-4): 161-170, 1991

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Exchange of grooming for allomothering in female patas monkeys

Muroyama, Y.

The question is asked whether grooming is exchanged for allomothering in patas monkeys (Erythrocebus patas). Six adult females in one group were observed during the non-birth season (no infants) and the birth season when three females had given birth to an infant. During the non-birth season the exchange of grooming and soliciting for it indicated reciprocity between non-kin. During the birth season, however, non-mothers groomed mothers much more than vice versa, and soliciting was shown more by mothers. This is in accord with the hypothesis that grooming is offered in order to be permitted to allomother. In addition, allomothering was often preceded and followed by grooming. Investment and reciprocity by unaffiliated (rarely grooming) non-kin females tended to occur most promptly. This is in accord with the hypothesis that fairness of reciprocity can be easier assessed if reciprocal acts occur immediately. Effects were less in affiliated non-kin pairs (frequently grooming), and least between kin.

Behaviour, 128(1-2): 103-119, 1994

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Developmental changes in mother-offspring grooming in Japanese macaques

Muroyama, Y.

A cross-sectional analysis was made of developmental changes in mother-offspring grooming in Japanese macaques, Macaca fuscata. When offspring were immature, time spent grooming by their mothers decreased with offspring age. Soliciting by offspring increased steadily with age, in contrast to their successful soliciting, which decreased gradually until early adolescence. This is in accord with the hypothesis that grooming is one form of post-weaning maternal investment, which may entail behavioral conflict between mothers and immature offspring. On the other hand, mothers spent much more time for grooming of their adult female offspring than for their adolescent male and female offspring. It is argued that grooming by mothers may shift from a form of maternal investment in their offspring to a benefit to be exchanged reciprocally with them.

American Journal of Primatology, 37: 57-64, 1995

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Fatal attack on an infant by an adult female Tonkean macaque

Muroyama, Y. & Thierry, B.

We describe a fatal attack on a 10-month-old female infant by an adult female Tonkean macaque (Macaca tonkeana) in a semi-free-ranging group. During an intense conflict involving many group members, an adult female, the second most dominant in the group, attacked the infant of a lower-ranking female. The attacker remained near the victim for approximately 20 min, grabbing and biting it repeatedly, until the mother retrieved the infant. She died 2 days later. An autopsy revealed no lethal injury; the main cause of death was starvation or dehydration or both. We discuss social conditions under which a fatal attack by an adult female might occur.

International Journal of Primatology, 17(2): 219-227, 1996

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Decision making in grooming by Japanese macaques (Macaca fuscata)

Muroyama, Y.

I analyzed the temporal organization of individual Japanese macaques’ (Macaca fuscata) grooming sequences in 14 mothers and 13 offspring of different age/sex classes and 4 nonkin females. I hypothesized that preceding grooming affects subsequent grooming by the same individual. Grooming bouts were likely to be terminated as the bouts became longer when females groomed nonrelatives. Moreover, the duration of first bouts was longer than that of following bouts. These effects were also seen in grooming of mothers by their offspring > 1 year old and that of adult and adolescent female offspring by their mothers. In contrast, neither the duration of first bouts nor the number of preceding bouts had much effect on the occurrence or duration of subsequent bouts in any subject.

International Journal of Primatology, 17(5): 817-830, 1996

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Species differences of male loud calls and their perception in Sulawesi macaques

Muroyama, Y. & Thierry, B.

Playback experiments were conducted to investigate interspecific discrimination of male loud calls in Sulawesi macaques. Loud calls of four macaque species living in Sulawesi (Macaca tonkeana, M. maurus, M. hecki, and M. nigrescens) and a control stimulus (an 8-sec frequency modulated sound) were played back to semi-free-ranging Tonkean macaques (M. tonkeana). A preliminary acoustic analysis indicated that the calls of these four species differ in some spectral and temporal features. In the playback experiments, Tonkean macaques responded in a similar manner to conspecific calls and calls of two other species, M. maurus and M. hecki. In contract, animals responded more weakly to the call of M. nigrescens and the control stimulus. Males responded more strongly than females to all stimuli, while females appeared to be more discriminating for species differences than males. Analyses on the acoustic features of loud calls suggested that high frequency, wide frequency range, and repetition of sound units at a high rate elicit quick responses form animals.

Primates, 39(2): 115-126, 1998

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Radio tracking of a male Japanese macaque emigrated from its group

Muroyama, Y., Imae, H. & Okuda, K.

A male Japanese macaque’s ranging behavior before and after emigration from its group was investigated by using radiotelemetry techniques. The male’s locations before leaving the troop were regarded as those of the troop, while those after leaving were regarded as those of a solitary male. Monthly home range sizes of the male with the troop were larger than those of the male moving alone, while the whole home range of the male with the troop for three months was much smaller than that of the male moving alone for five months. Overlaps between the male’s home ranges with the troop between months were much greater than those between the ranges of the male moving alone. One neighboring troop’s home range overlapped the male’s range in August and September, and another neighboring troop’s range overlapped the male’s in October. The mean travel distance and speed of the male with the troop per day did not differ significantly from those of the male moving alone. The results suggest that emigrated males of Japanese macaques may visit home ranges of some troops and stay for a while without interacting troop monkeys before they decide to visit or join the troops.

Primates, 41(3): 349-354, 2000

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Monitoring the reproduction status of Japanese monkeys (Macaca fuscata) by measurement of the steroid hormones in fecal samples

Yoshida, T., Matsumuro, M., Miyamoto, S., Muroyama, Y., Tashiro, Y., Takenoshita, Y., & Sankai, T.

The menstrual cycles as well as the pregnancy in female Japanese monkeys (Macaca fuscata) were monitored by measuring the fecal estradiol concentrations and relative amounts of fecal progesterone. Steroids from fecal samples were extracted by using a previously developed simplified two-step method and then measured by radioimmunoassay. We successfully demonstrated that the two-step method is effective and convenient for monitoring the reproductive status of Japanese monkeys.

Primates, 42(4):367-373, 2001

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Life-history parameters of a wild group of West African patas monkeys (Erythrocebus patas patas)

Nakagawa, N., Ohsawa, H. & Muroyama, Y.

Based on long-term, although intermittent, observations (2 years 4 months of 14 years), we present data on birth seasonality, age at first birth, interbirth intervals, mortality rates, age at first emigration, and population change of a wild population of West African patas monkeys (Etythrocebus patas patas) in northern Cameroon. Birth season was from the end of December until the middle of February, corresponding to the mid-dry season. In spite of large body size, the patas females had the earliest age at first birth (36.5 monthsold) and the shortest interbirth intervals (12 months) compared to the closely related wild forest guenons. Age at first emigration of the males was considered to occur between 2.5 and 4.5 years. The group size of the focal group drastically decreased between 1984 and 1987, and steadily increased until 1994, then decreased again in 1997. The neighboring group also showed a similar trend in group size. The population decreases were likely to be caused by drought over 3 years. Annual crude adult mortality rate was 4% during population increase periods (PIP) between 1987 and 1994. It rose to 22% during all the periods (AP), including drought over 3 years. Despite their smaller body size, the rate of the wild forest guenons (Cercopithecus mitis) (4%) was the same and much lower than those of the patas during PIP and AP, respectively. The annual average juvenile mortality rate was 13% during PIP and it also rose to 37% during AP. That of wild forest guenons (C. ascanius) (10-12%) was a little lower and much lower than those of the patas during PIP and AP, respectively. These findings were consistent with Charnov’s theoretical model of mammalian life-history evolution in that patas with high adult and juvenile mortality showed early and frequent reproduction in spite of large body size. Charnov also considered high adult mortality as a selective force and high juvenile mortality as a density-dependent consequence of high fecundity. Our results support the former but not the latter research findings.

Primates, 44: 281-290, 2003

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Seasonal variation and sex differences in the nutritional status in two local populations of wild Japanese macaques.

Muroyama, Y., Kanamori, H., and Kitahara, E. (2006)

Seasonal variation and sex differences in the nutritional status in two local populations of wild Japanese macaques (Macaca fuscata fuscata) were examined. It was hypothesized that ecological condition and/or reproductive strategies of each sex determine nutritional condition and their seasonal fluctuation in each sex. Morphometric measures such as body mass, thoracic and femoris circumferences, skinfold thickness in four places (triceps, biceps femoris, subscapular, and abdomen), and wet mass of mesenteric and omental fat were used for comparisons between sexes, seasons, and populations. Animals of the Shimane population were larger than those of the Boso in most morphometric measures, abdominal skinfold, and mesenteric and omental fat mass, suggesting environmental and/or genetic differences in the two populations. Females of both populations had larger skinfolds and mesenteric and omental fat mass than males, indicating that females had more fat than males. Females showed seasonality in most measures, having two peaks of body mass, thoracic and femoris circumferences, abdominal skinfold, and mesenteric and omental fat mass in early spring and late autumn. In contrast, males exhibited no clear seasonal variations in most measures, except for biceps femoris and subscapular skinfolds, which showed peaks in summer. Most morphometric measures were significantly correlated to each other, particularly in females, but most skinfolds had no correlations with other measures. These findings suggest that sexual dimorphism in body composition and its fluctuation may be affected by different the reproductive strategies of males and females.

Primates, in press.

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Seasonal variations of fecal testosterone levels in free-ranging male Japanese macaques.

Muroyama, Y., Shimizu, K., and Sugiura, H.

Seasonal variation in fecal testosterone levels in free-ranging male Japanese macaques (Macaca fuscata) was examined with reference to their dominance rank and age class. Six adult (>=7 years old, 3 higher-ranking and 3 lower-ranking) and 4 adolescent (5-6 years old, 2 higher-ranking and 2 lower-ranking) males were selected as target animals. Fecal samples of these males were collected during the first 3-5 days of each month, and analyzed by the method developed by Barrett et al. [2002b]. Testosterone levels varied significantly across the 12 months, being highest in the early and middle part of the mating season, i. e. October and November. Higher-ranking adult males were found to have the peak of testosterone level in October, whereas lower-ranking adults had no clear peak in the mating season. Such a difference of testosterone peak in males could enable higher-ranking males to have more opportunity to fertilize females at first ovulation in a mating season than lower-ranking males.

American Journal of Primatology, in press.

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総説 (学術雑誌・紀要等：^*査読付)要旨

The social repertoire of Sulawesi macaques

Thierry, B., Bynum, E.L., Baker, S., Kinnaird, M.F., Matsumura, S., Muroyama, Y., O’Brien, T.G., Petit, O. & Watanabe, K.

The social repertoire of Sulawesi macaques is presented, based upon data recorded both in the wild and from captive populations. The repertoire describes behaviors observed in social contexts, including communication patterns, movement patterns, sexual patterns, infant-related and play behaviors, and triadic interactions. Most of these behavior patterns are shared by all known Sulawesi taxa. The form or function of certain patterns depart significantly from what has been reported in other macaques, while particular similarities may be linked to phylogenetic relationships within the genus Macaca.

霊長類研究　Primate Research, 16: 203-226, 2000

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著書(論文集・分担執筆・翻訳含む)要旨

Grooming relationships in two species of chimpanzees

Muroyama, Y. & Sugiyama, Y.

The grooming behavior between same- and opposite-sex members of chimpanzee groups differed from grooming behavior in bonobo groups. In all of the chimpanzee groups except the one at Bossou, grooming frequencies between males were higher, numbers of male-male grooming partners were larger, and male-male grooming durations were longer than in any other sex combination. By contrast, in all studies of the bonobo groups except the one at Wamba, grooming interactions between males and females were more frequent and longer than in any other sex combination.

Diversity of grooming between different study populations and different periods was greater in chimpanzees than in bonobos. Grooming frequencies between chimpanzee males correlated negatively with those between females, whereas grooming frequencies between bonobo males correlated negatively with those between males and females. Differences in grooming patterns between chimpanzees and bonobos were discussed in relation to cooperation between males, female-female kin relationships, and kin relations between males and females.

Chimpanzee Cultures (edited by Richard W. Wrangham, W.C. McGrew, Frans B.M. de Waal & Paul G. Heltne with assistance from Linda A. Marquardt), pp.169-180, Harvard University Press, London, 1994.

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