Primate Research
Online ISSN : 1880-2117
Print ISSN : 0912-4047
ISSN-L : 0912-4047
Volume 27, Issue 2
Displaying 1-7 of 7 articles from this issue
Review
  • Ikki MATSUDA
    2011 Volume 27 Issue 2 Pages 75-93
    Published: December 20, 2011
    Released on J-STAGE: January 19, 2012
    JOURNAL FREE ACCESS
    Proboscis monkeys (Nasalis larvatus) belong to the colobines and are a large, sexually dimorphic and primarily arboreal species. These monkeys are endemic to Borneo Island, inhabiting areas by rivers in mangroves, peat swamps or riverine forests, and their typical social unit is a one-male group consisting of an adult male and several adult females with their offspring. Since some of their favorite habitats are swampy, observation and tracking of the monkeys in inland forests is difficult, and hence, knowledge about the ecology and the social system of proboscis monkeys is incomplete. However, by a lot of efforts of researchers, our knowledge of the monkeys has greatly expanded in these days. In this paper, I highlighted novel findings on proboscis monkey ecology and social system, comparing to those in other colobine species.
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  • Shinya YAMAMOTO
    2011 Volume 27 Issue 2 Pages 95-109
    Published: December 20, 2011
    Released on J-STAGE: January 19, 2012
    JOURNAL FREE ACCESS
    How did humans evolve to such an altruistic and cooperative animal? This review paper discusses the primate origin of altruism and cooperation from the viewpoints of cognitive mechanisms and adaptation to social systems. Our previous studies have revealed three characteristics of chimpanzees' altruistic helping behavior: 1) helping upon request, but seldom voluntarily; 2) understanding others' goals by visually assessing the situations; and 3) understanding of others' goals does not automatically lead to voluntary helping. It is suggested that the mechanism in chimpanzees' helping is different from that in human helping, which is often solicited by only witnessing others in trouble. This difference in spontaneity in helping might be a result of their different social systems. In human societies, where indirect reciprocity works, individuals who behave altruistically can gain good reputations. In such societies, voluntary helping is favored and rewarded. Meanwhile, institutions and social sanctions exist in human societies: selfish individuals can be punished by third-party group members. This system also maintains altruism and cooperation. In contrast, there has been no empirical evidence for existence of reputation and social sanction in chimpanzees, which might explain their lack of voluntary helping. Instead of indirect reciprocity, fission-fusion dynamics might be an alternative system for maintaining altruism and cooperation in chimpanzee societies. It is possible that an ecological environment influences a social system, which in turn determines behavior and its mechanism. This emphasizes the importance of empirical studies with broad perspectives. Comparative studies with humans, chimpanzees and bonobos both in the wild and under experimental conditions are expected to deepen our understanding of the evolution of altruism and cooperation, and accordingly to reveal multiple dimensions of human evolution from the viewpoints of cognition, behavior, society, and ecology.
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Research Report
  • Naofumi NAKAGAWA, Masayuki NAKAMICHI, Kazunori YAMADA
    2011 Volume 27 Issue 2 Pages 111-125
    Published: 2011
    Released on J-STAGE: January 19, 2012
    Advance online publication: November 30, 2011
    JOURNAL FREE ACCESS
    Questionnaire on infrequently-observed behaviors (IOBs) in Japanese macaques (Macaca fuscata) were given to primatologists. This survey aimed to provide basic information on the degree of rarity of each behavior. The questionnaire consisted of questions for respondents themselves, (e.g., name, research carrier, daily observation time), focal group (name of group and local population, captive, provisioned free-ranging, crop-raiding or purely wild), and IOBs. Experience of direct observation of 36 candidates of IOBs was also requested to answer by yes, no, or impossible to answer because of ambiguous memory or unawareness of its behavior. In total, 39 answer sheets were obtained from 32 respondents. The top 10 IOBs and the number of those answering "yes" in parenthesis are as follows: mating interruption by juveniles (1), simultaneously nursing different-aged offspring (1), tool-use (1), single mount ejaculation (2), transporting the older offspring (2), nursing the older offspring (2), simultaneously transporting different-aged offspring (3), pulling the hair of female chin as a courtship behavior by male (4), twin birth (4), and (diurnal) birth (6). Some of IOBs, such as mating interruption by juveniles, seem to be due to ambiguous memory or unawareness of its behavior. Apparent inter-population differences in the percentage of respondents answering "yes" to the all the respondents giving definite answers were found in some behaviors, such as embrace-rocking behaviors, mating behaviors in birth season, stone-handling, and feeding on vertebrates. Some of them, like the latter two, seem to have something to do with provisioning. With the modification of three categories by Nakamichi et al. (2009), we proposed the following five categories of IOBs: I) behaviors which are difficult to be observed despite its common occurrence; II) behaviors which rarely occur in every population: III) behaviors which rarely occur in some populations, but frequently occur in the others; IV) behaviors which are difficult to identify and memorize despite its common occurrence; V) behaviors which rarely occur during the most of the time but temporally occur.
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Review
  • Masaki SHIMADA
    2011 Volume 27 Issue 2 Pages 127-139
    Published: 2011
    Released on J-STAGE: January 19, 2012
    Advance online publication: September 05, 2011
    JOURNAL FREE ACCESS
    Previous studies have used some verbs or nouns in ordinary language to describe, count, or analyze different types of animal behavior. However, the concept of "play" is problematic for ethological analysis. Although ethological analysis should be based on well-defined concepts, play is an ill-defined concept because the various meanings of the term necessarily make the boundary of the concept ambiguous and because the phenomena of play do not form discrete categories. Considering these difficulties, the ethological study of play should posit the argument that the concept of play is characterized by prototypeness. Consequently, the question "What is play?" is divided into the following three sub-types: (1) The question on our own cognition of play, "What type of phenomena do I (we) call play?"; (2) the question on the objective features of play, "What are the ethological features of the phenomena that we call play?"; and (3) the question on the animal cognition of play, "How do target animals recognize the phenomena that we call play?" By integrating prototype theory and the ethological study of play, we can establish various important and positive research agendas with respect to these three questions.
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  • Yoko SATTA
    2011 Volume 27 Issue 2 Pages 141-152
    Published: 2011
    Released on J-STAGE: January 19, 2012
    Advance online publication: November 30, 2011
    JOURNAL FREE ACCESS
    As genomic studies have progressed, it has become easier to get the nucleotide sequences at several nuclear loci from many species. Molecular phylogenetic studies have provided the branching (diverging) order and divergence time of many primates. Recent phylogenetic studies have revealed that the most closely related species to humans is the chimpanzee, not the gorilla or orangutan. However, there remain arguments about the time of divergence of many species, including the hominoids. In fact, estimates of the divergence time show a large variation among different loci and this may be due to a large extent on ancestral polymorphism. In this article we present the method to estimate the effective size of an ancestral population and the divergence time simultaneously. We showed both estimates in the lineage leading to extant humans. We will discuss the biological meaning and problems of estimating effective sizes of an ancestral population and divergence times in primate evolution.
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