Capped langurs of Madhupur. Review of The Capped Langur in Bangladesh Behavioral Ecology and Reproductive Tactics by Craig B. Stanford. Basel Karger 1991 XVII + 179 pp 53 fig. 30 tab. 4 plates $98код для вставкиСкачать
American Journal of Primatology 28299-302 (1992) BOOK REVIEWS Capped Langurs of Madhupur Review of The Capped Langur in Bangladesh: Behavioral Ecology and Reproductive Tactics, by Craig B. Stanford. Basel, Karger, 1991, XVll 179 pp, 53 fig., 30 tab., 4 plates, $98.50, hardcover. + After over 30 years of field investigations, the behavioral ecology of a t least one population has now been well-documented for many primate species. This has provided a scattered but invaluable database on ranging behavior, activity budgets, dispersal patterns, and social behavior of individuals, from which synthetic hypotheses in primate socioecology are being formulated. Early attempts to explain variation in primate behavior focused on classifying broad types of groupings [e.g., Crook & Gartlan, 1966; Eisenberg et al., 19721. As more information has become available, hypotheses have become more refined. More recent hypotheses have addressed very specific issues, such as the nature of relationships between individuals within and between groups [Wrangham, 1980; van Schaik, 1989; Isbell, 19911 and patterns of dispersal [Wrangham, 1980; Clutton-Brock, 19891. Testing these hypotheses necessitates renewed efforts to gather data on the behavior and ecology of species not yet studied. We still have embarrassingly little data on the natural history of forest primates, i.e., most New World monkeys, guenons, and langurs. For this reason, Craig Stanford's study of the behavior and ecology of capped langurs (Presbytis pzleata) is a helpful contribution to primatology. He collected data in Madhupur National Park, Bangladesh over 15 months on various aspects of their behavioral ecology, including ranging behavior (chapter 3 in the monograph), activity patterns (chapter 4), feeding ecology (chapter 5), and social behavior (chapters 6 and 7). The following is a brief summary of Stanford's findings: capped langurs at Madhupur are leaf-eaters that also feed heavily on fruits a t certain times of the year. They live in single-male, multi-female groups containing about five adult females. Females have poorly defined dominance hierarchies within groups because they rarely interact aggressively toward one another. The main study group ranged over an area of about 22 hectares that overlapped extensively with the home ranges of other groups. Interactions between females of different groups are non-aggressive. In contrast, resident males can be aggressive toward males of other groups, particularly if those males are unfamiliar. During intergroup encounters, the resident male typically places himself between his group and other males, and acts aggressively toward females in his group if they attempt to approach or appear to be attracted to other males. Males presumably disperse from their natal groups at sexual maturity, and move about by themselves Lynne A. Isbell is now at Department of Anthropology, Rutgers University, P.O. Box 270, Douglass Campus, New Brunswick, NJ 08903. 0 1992 Wiley-Liss, Inc. 300 I Isbell or in all-male bands. Females may also leave their natal groups but female dispersal appears to be less common than male dispersal. The intent of this monograph was to provide a descriptive account of the natural history of capped langurs and to incorporate this information into an examination of some of the central issues and hypotheses in primate socioecology. Unfortunately, the monograph was not carefully edited and it contains a large number of errors that make it difficult to read. Some of the errors are sufficiently serious that uncritical readers might be led to the wrong conclusions (e.g., in Fig. 5.10 it is stated that P > .05 when it is clear from the graphics that this is incorrect; the text mentions a P value of < .001; also, Tables 5.3 and 5.4 are particularly intriguing). Fortunately, some parts of the monograph have been published with fewer errors and with arguments that he developed more clearly in peer-reviewed journals. On the other hand, the monograph contains more discussion of the conceptual arguments, which I found interesting, even if sometimes difficult to follow. Despite the editing (or lack thereof), the monograph addresses some of the more fundamental issues in primate socioecology. Among these issues are the functional significance of female transfer and the validity of Wrangham’s [19801 model of female-bonded vs. non-female-bonded primate species. When Stanford went into the field in 1986, Wrangham’s was the only model that attempted to explain the ecological determinants of variation in female relationships within and between groups. As more studies are conducted, however, it is becoming clear that there is more variation in female relationships than is accounted for by Wrangham’s model. Stanford is correct in recognizing this for his study species. He points out that capped langurs are non-female-bondedin that females have poorly defined dominance hierarchies within groups, they are not aggressive between groups, and sometimes transfer to other groups. However, they also direct group movements, a characteristic predicted for female-bonded species. In the last few years, newer models [van Schaik, 1989; Isbell, 19911 have come into existence that do attempt to account for this kind of variation, apparently after this monograph went to press. It is still unclear just how much variation among primate species does exist, and why, mainly because of the shortage of studies such as Stanford‘s on the behavioral ecology of forest primates. Stanford’s discussion of variation in female transfer is timely and informative. He documented a t least three transfers of adult females into five study groups during his 15 months of study. Accounting for variation in patterns of female transfer is a relatively young issue in primate socioecology.Again, as more natural history studies are conducted, it is becoming apparent that dispersal patterns are more variable than previously believed. In many species, females typically remain in their natal groups throughout their lives and only rarely transfer, e.g., most macaques, baboons, and guenons [Pusey & Packer 19871. In other species, e.g., gorillas [Gorilla gorilla: Harcourt, 19781 and red colobus [Colobus badius: Struhsaker, 19751, females commonly transfer to other groups. In still other species, female transfer is not common but does occur occasionally. Stanford is correct in pointing out that female transfer is a puzzle in capped langurs. Unlike red colobus, in which only females typically leave their natal groups, both male and female capped langurs leave. In species such as capped langurs, in which both sexes emigrate, it becomes more difficult to explain female transfer as a way to avoid inbreeding. Stanford suggests that females may assess their opportunities for successful reproduction both in their current group and in other groups and leave when better opportunities arise [see also Harcourt, 1978; Marsh, 19791. What determines whether a female will remain in or leave her natal group? Stanford was not able to determine exactly what females might be assessing. Capped Langurs I 301 Wrangham [19801 suggested that females would remain when they benefit from cooperation with relatives in defense of food resources. However, given that movement out of natal groups or natal home ranges entails known costs [Johnson & Gaines 19901, we might expect females to remain philopatric regardless of the positive benefits of remaining philopatric. Dispersal is likely to be costly when animals either disperse into an unfamiliar home range (locational dispersal), or interact with unfriendly, unfamiliar conspecifics (social dispersal), or both. The decision to disperse or stay will probably depend on the number of potential costs that are faced by each individual, weighed against the potential benefits. In most primate species, the cost of aggression from unfamiliar neighbors appears to be sufficient to prevent most females from transferring into new groups. The capped langurs of Madhupur are an example of species in which there is no female aggression and female transfer does occur a t least occasionally, in common with several other colobine species. There are also species in which groups of females are aggressive toward one another and females nonetheless still occasionally transfer. This suggests that other costs prevent such females from leaving their natal groups. The most obvious cost is that of moving into an unfamiliar area. Female transfer tends to occur at low levels in more species with extensive (as opposed to minimal) home range overlap. In fact, those species in which female transfer occurs occasionally despite intergroup aggression often have extensive home range overlap in which one might expect greater familiarity with the home ranges of new groups Ce.g., brown capuchins, Cebus apella: Robinson & Janson 1987; rhesus macaques, Mucuca mulatta: Hausfater 19721. Because, as Stanford shows, female capped langurs are not aggressive toward one another and have extensive home range overlap, they may not suffer either social or locational costs of dispersal. The distinction between dispersal into an unfamiliar area and dispersal into an unfamiliar social environment has not been made explicitly in the literature, and should be helpful for understanding variation in female dispersal patterns among primates. Because dispersal in group-living animals may include any combination of social and locational dispersal, group-living animals may face different combinations of costs based on their particular situations. Stanford's study provides a good example of a system that would benefit from such analysis. Indeed, with transfer occurring a t least occasionally, most langurs (Hanuman langurs, P. e n t e l h , are an exception) should be an ideal group of species with which to compare the situations faced by those who disperse and those who stay behind. At close to $100.00, this monograph is more likely to be found in libraries than on personal bookshelves. Nonetheless, it is another in a series of natural histories that are valuable in elucidating issues in socioecology such as those Stanford and others are now addressing. Such studies always make lasting contributions to primatology. Lynne A. Isbell Department of Anthropology University of California Davis REFERENCES Clutton-Brock,T.H. Female transfer and inbreeding avoidance in social mammals. NATURE 337:70-72, 1989. Crook, J.H.; Gartlan, J.S. Evolution of primate societies. NATURE 210:1200-1203, 1966. Eisenberg, J.F.; Muckenhirn, N.A.; Rudran, R. The relation between ecology and social structure in primates. SCIENCE 176:863874, 1972. Harcourt, A.H. Strategies of emigration and transfer by primates with particular refer- 302 / Isbell ence to gorillas. ZEITSCHRIFT FUR TIERPSYCHOLOGIE 48~401-420,1978. Hausfater, G. Intergroup behavior of freeranging rhesus monkeys (Mucucu mulutta). FOLIA PRIMATOLOGICA 18:78-107, 1972. Isbell, L.A. Contest and scramble competition among primates: variation in female aggression and ranging behavior. BEHAVIORAL ECOLOGY 2~143-155,1991. Johnson, M.L; Gaines, M.S. Evolution of dispersal: theoretical models and empirical tests using birds and mammals. ANNUAL REVIEW OF ECOLOGY AND SYSTEMATICS 21~449-480,1990. Marsh, C.W. Female transference and mate choice among Tana River red colobus. NATURE 281568-569,1979. Pusey, A.E.; Packer, C. Dispersal and philopatry. Pp. 250-266 in PRIMATE SOCIETIES. B.B Smuts; D.L. Cheney; R.M. Seyfarth; R.W. Wrangham; T.T. Struhsaker, eds. Chicago, University of Chicago Press, 1987. Robinson, J.G.; Janson, C.H. Capuchins, squirrel monkeys, and atelines: socioecological convergence with Old World primates. Pp. 69-82 in PRIMATE SOCIETIES. B.B. Smuts; D.L. Cheney; R.M. Seyfarth; R.W. Wrangham; T.T. Struhsaker, eds. Chicago, University of Chicago Press, 1987. Struhsaker, T.T. THE RED COLOBUS MONKEY. Chicago, University of Chicago Press, 1975. van Schaik, C.P. The ecology of social relationships amongst female primates. Pp. 195-218 in COMPARATIVE SOCIOECOLOGY: THE BEHAVIOURAL ECOLOGY OF HUMANS AND OTHER MAMMALS. V. Standen; R.A. Foley, eds. Oxford, Blackwell Scientific Publications, 1989. Wrangham, R.W. An ecological model of female-bonded primate groups. BEHAVIOUR 75262-300,1980.