Effects of group composition on agonistic behavior of captive pigtail macaques Macaca nemestrina.код для вставкиСкачать
Effects of Group Composition on Agonistic Behavior of Captive Pigtail Macaques, Macaca nemestrina J. DAZEY, K. KUYK, hi. OSWALD, J MARTENSON AND J. E R W I N ~ Aegionul Primate Researrh Center Field Station, University of Wmhington, Medical Lakc, Washington 9902% KEY WORDS Pigtail macaque . Macaca nemestrina . Agonistic behavior * Aggression . Control role. ABSTRACT We surveyed agonistic behaviors of 20 captive groups of pigtail macaques fMacaca nemestrina) housed under identical spatial conditions. Fifteen groups contained one male each; the other five groups contained no adult males. Groups included six to twelve adult females, some of which had infants with them. We found no relationship between social density of groups and incidence of agonistic behavior, but significantly more contact aggression (grab, hit, push, bite) and noncontact aggression (chase, open-mouth “threat,” bark vocalization) occurred among females in groups containing no males than in those containing one male each. Apparently, males played an important role in the inhibition of intragroup conflict.We also found that females in groups containing males exhibited less noncontact aggression if infants were present than if no infants resided in their groups. Thus, competition of females over infants must not have been an important constituent of intragroup conflict under the conditions of this survey. Destructive violence, observed in freeranging primates, is frequently intensified under captive conditions (Rowell, ’67). Nagel and Kummer (’74) suggested the following reasons for higher rates of agonistic behavior among captive groups of cercopithecoid primates: (A) Social factors such as competition over females, conflict over infants, and disturbance of social order, and (A) Ecological factors such as competition over food or space, absence of cover, excess time to engage in social behavior (time spent foraging by nonprovisioned animals), reduction of ecological functions of alpha males, and incompatible composition of groups. Maintenance and breeding of nonhuman primates in captivity has become vital to assure a supply of research subjects for domestic biomedical use and to avoid further depletion of wild populations; yet, little research on the effects of captive conditions on the behavior and physiology of AM. J , PHYS. ANTHROP., 46: 73-76. nonhuman primates has been reported, and trauma sustained in aggressive interactions continues to be a problem in captive groups. We instituted a series of research projects designed to assess the factors contributing to violence and its control in captive groups of pigtail macaques to find ways of minimizing the destructive consequences of aggression. While our primary goal is increased efficiency and self-sufficiency in primate production, we also anticipate finding useful analogues of human aggressive motivation. In the project reported here we studied influences of group ’ Ihib research was supported b y NIHiCSPHS grant RHO0166 to the Regional Primate Research Center at University of‘Washington and by an intramural grant from the Fund for Instructional Developmrnt and Innovation, University of Washington. J , Erwin r w r i v e d partial siipport under NICBHD-08633 during the period in which this project WRY done. l h e authors gratefully acknowledge the cuoperation or the staff‘of the Primate Field Station. * Rrquestt\ for reprints of this paper should b e addressed to J. Erwin, c/o Regional Primate Heseai-ch Center, Univrrsity of Washington, Seattle, Washington 98195. 73 74 DAZE”, KUYK, OSWALD, MAHTEMON AKD ERWIN composition (primarily the presence or absence of adult males) on the expression of agonistic behavior by adult females. METHODS Subjects The subjects for this survey were 203 pigtail macaques (15 adult males, 166 adult females, and 22 infants less than six months old) housed in 20 groups at the Regional Primate Research Center Field Station, Medical Lake, Washington. Fifteen groups contained one male each while five groups included no adult males. Ten groups contained no infants; the other groups contained one to three infants. The number of adult females per group ranged from 6 to 12. All groups were housed indoors under identical spatial conditions. Each group had access to two adjoining rooms with access between rooms provided by a small shuttle door. A detailed description of the facility is contained in Blakley et al. (‘721. Procedure Two pairs of experienced observers recorded absolute frequencies of agonistic encounters in the groups. We measured the incidence of contact aggression (grab, push, hit, bite), non-contact aggression (chase, openmouth “threat,” bark vocalization), and fear/submission (grimace, screech, crouch). Agonistic encounters were identified according to perpetrator and recipient: adult male, adult female, or infant. Two of us observed each group for 15minutes, one watching each room of the suite; then the other pair did so. We balanced the order of observation and did not give the second pair of observers access to the data gathered by the first pair; thus, the survey included a blind replication. We evaluated differences between male-present and male-absent conditions and infant-present and infant-absent conditions using the Mann-Whitney U test for differences between means of unequalsized samples. RESULTS As table 1 shows, females exhibited significantly less contact aggression, non-contact aggression, and total agonistic behavior toward each other in groups containing one male than in those containing no males. The differences were statistically significant for the initial session and the replication. Total non-contact aggression in groups containing males was significantly less frequent if infants were present (mean = 0.554; S.D. = 0.519) than if no infants were present (mean = 1.070; S.D. = 0.587) (Mann-Whitney U = 5; P < 0.01). Social density (number of animals per group) exerted no detectable influence on agonistic behavior. Fear/submission behaviors occurred infrequently; we detected no relationship between group composition and any behavior involving males or infants. DISCUSSION The influence of males on agonistic interactions was the most consistent effect we detected in this survey. Bernstein (’64) and Smith (’74) have documented active interference of male macaques in intragroup agonistic encounters. Erwin (’76) and Tokuda and Jensen (’68)have reported that short-term removal of males from groups of pigtail monkeys resulted in increased aggression among females, and reinstatement of males restored peace among females. The survey reported here and a smaller one done previously by Sackett et al. (’75)provides clear evidence that the mere presence of an adult male in a group of female pigtail monkeys inhibits aggressivity. We noted that most interference by males was in the form of very mild “threatened” aggression, often no more than a brief stare toward the perpetrating female. The incidence and effcctiveness of such interference varied inversely with the distance between the male and the interacting females. Most attacks that occurred near the male consisted of a (0-11-3) (0- 9-11 (0- 9-01 (0- 8-1) (0- 6-01 (0-43-5) 1- 12- 3) 1- 10- 3) 1- 9- 3) 1- 9- 2) 1- 9- 2) 1- 9- 0 ) 1- 8- 0) 1- 8- 0) 1- 8- 0) 1- 8- 0) 1- 7- 3) 1- 7- 0) 1- 7- 0) 1- 6- 1) 1- 6- 0) (15-123-17) ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( Males-fernalea inf. Composition Total Mean S.D. Differences between harern and all-female groups .Mariri-Whitriey U Probability x XIX XVI XVII XVlII (h u p a 1V V \'I VII \'Ill IX X XI XI1 XI11 XlV XV Total Mean S.D. All -female 111 I 11 Harem Groups Gronp No. I < 0.05 11 0.273 0.556 1.667 2.125 0.333 4.954 0.991 0.849 0.250 0.500 0.000 0.111 0.222 0.778 0.125 0.125 0.125 0.500 0.286 1.000 0.000 0.500 0.333 4.855 0.324 0.286 1st 011s. 10 < 0,05 9 < 0.05 1.182 1.000 4.000 3.500 0.500 10.182 2.036 I594 0.346 0.667 0.500 0.222 0.111 0.889 0.889 0.375 0.125 0.37s 1.125 0.286 1.000 0.143 0.833 0.333 7.873 0.525 Total 0.909 0.444 2.333 1.375 0.167 3.228 1.046 0.854 0.417 0.000 0.222 0.000 0.667 0.111 0.250 0.000 0.250 0.625 0.000 0.000 0.143 0.333 0.000 3.018 0.201 0.227 2nd obs. Contac? aggression 9 < 0.05 0.273 2.000 2.889 1.250 2 500 8.912 1.782 1.043 0.250 0.200 0.444 0.333 0.222 1.111 0.125 0.500 0.625 0.000 0.143 1.143 0.286 0.667 1.167 7.216 0.481 0.387 1st ohs. Otis. 5.5 < 0.01 1.364 2.556 2.778 3.000 0.333 10.031 2.006 1.129 0.083 0 200 0.222 0.111 0.000 0.333 1.250 0.000 1.375 0.500 0.000 0.143 0.000 1.000 0.000 5.217 0.348 0.473 2nd 2 < 0.01 5.667 4.250 2.833 18.942 3.788 1.571 4.556 1.636 0.333 0.400 0.667 0.444 0.222 1.444 1.375 0.500 2.000 0.500 0.143 1.286 0.286 1.667 1.167 12.434 0.829 0.599 Total Nnrr-contact aggre\\ion ns. n.s. 0.091 0.333 0.333 0.000 0.000 0.737 0.151 0.170 0.000 0.167 0.000 0.778 0.052 0.106 0.ODO 0.000 0.000 0.000 0.000 0.375 0.125 0.000 0.000 0.111 0.000 0.000 2nd obs. 0.000 0.111 0.000 0.000 0.000 0.111 0.022 0.050 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.125 0.000 0.000 0.000 0.000 0.000 0.125 0.008 0.032 1st olis. Ft.ar/srd)mission Agoriistic hehucior amongfemcrle Macaca rierncstriria in captive groups (frequency per cupitu) 'I'r\HL.E 11,s. - 0.091 0.444 0.333 0.000 0.000 0.868 0.174 0.203 0.000 0.000 0.111 0.000 0.000 0.000 0.000 0.375 0.125 0.125 0.000 0.000 0.000 0.167 0.000 0.903 0.060 0.106 Total 0 < 0.01 2.909 6.000 10.000 7.750 3.333 29.992 5.998 2.989 1.000 0.900 1.000 0.356 1.11I 2.333 1.7.50 1.000 2.300 1.750 0.429 2.000 0.429 2.667 I .so0 20.925 1.395 0.742 Total agonistic 76 DAZEY, KUYK, OSW.\LD, MAKTENSOS AND EKWlN single aggressive act, usually a grab or hite; we seldom saw any reciprocation. Thus, it appears that remaining near a male allows females the freedom to attack other females briefly without fear of retaliation while affording them protection from sustained attacks by other feniales. Under the conditions of this survey, feniales spent most of their time in the same room a s the male even though they had access to an adjoining room. We found in an earlier study that less aggression occurred among females confined to one room than when given access to both rooms of their suites (Anderson et al., '76). Apparently; aggression is inhibited more effectively undcr conditions of forced proximity than under relatively less crowded conditions. One of the sources of intragroup conflict suggested by Nagel and Kummer ('74) was competition over infants. Under the conditions of this survey, this was clearly not an important contributor to intragroup conflict because the only general effect of presence of infants in groups was reduced non-contact aggression. All infants involved in this survey were less than sixmonths-old, and no juvenile or adolescent animals were present in groups. While females are retentive and protective of young infants, infants exhibit little social involvement during their fist half-year relative to their second half-year of life (cf. Jensen et al., '68; Kuyk et al., '76). Our failure to find a relationship between social density (number of animals per group) and aggression was rather surprising in view of previous evidence (Anderson et al., '76; Erwin and Erwin, '76) that contact aggression was positively related to social density. Research on agonistic behavior of captive groups of nonhuman primates can be of practical value by providing evidence helpful in establishing and maintaining self-sufficient domestic colonies for the production of biomedical subjects, but it can also generate hypotheses useful in the analysis of social organization in groups. Elucidation of the dynamics of social processes in natural groups of primates contributes substantially to the understanding of primate evolution. LITERATURE CITED Anderson, B., N. Erwin, I).Flynn, I,. Lewis and J. Erwin 1976 Effects of short-term crowding on aggression in captive groups of' pigtail monkey.; (LMacac.a nemestrina). 8ggrt:ssive Behavior, in press. Bernstein, I. 1964 Group social pattcms a s influenced b y removal and later reiritroduction o f the dominant male rhesus. Psychol. Rep., 14: 3-10. Rlakley, G.. W. Morton arid 0.Sriiith 1972 Husbandry and breeding of &fucacanemestrina. In: Medicnl Primatology 1972, Part I. S. Karger, Basel, pp. 61-72. Erwin, J. 1976 Aggressive lichavior of captive pigtail macaques: spatial conditions a n d social cmtrolh. Lahoratory Primatc. Newsletter, 15 (2): 1-10 Eruin, N.. and J . Erwin 1976 Social density and aggression in captivc. groups of pigtail Inonkey (macacn nemesfrina). Applied Animal Ethology, in press. Jcnsen, G., R. Bobliitt and B. Gordon 1968 Sex differences in the development of independence of infant monkeys. Behaviour, 30: 1-14. Kriyk, K., J. Dazey and J. Erwin 1976 Play patterns of pigtail nionkey infants: effects of age and peer presence. Journal of Biological Psychology, in press. Nagel, U., arid H. Krimmer 1974 Variation in cercopithecoid aggressive behavior. In: Primate aggrcssion, Territoriality. and Xcnoptiot)ia: a Coniparative Perspective. R. Holloway, ecl. Academic Press. New York, pp. 159-184. Howelli T. 1967 4 quantitative cornparison of t h e b e haviour of a wild and a caged 1)aI)oongroup. ,hima1 Behaviour, 15: 499-509. Sackett, D., M. Oswald and J. Erwin 1975 Aggression among captive female pigtail monkeys in all-fefziale and harem groups. Journal of' Iliological Psychology, 17 (21: 17-20. Smith, E. 1973 A fiirthcr description of the control role in pigtail macaques, Macnca raemestrha. Primates, 14: 413-419. Tokuda, K., and G. Jellsen 1968 ' I l ~ eleader's role in controlling aggressive hehavior in a monkey- group. Primates, 9: 319-322.