Predation risk places a pressure on animals to adopt mechanisms by which they reduce their individual risk of being preyed on. However, a consensus on methods of determining predation risk has yet to be reached. One of the most widespread ways in which animals respond to predation risk is by living in groups. Minimum permissible group size is the smallest group size that animals are able to live in, given the habitat-specific predation risk they face. We explore ways in which predation risk can be measured and analyse its effect on minimum observed group size in baboons. Using data on predator density, habitat composition and baboon body size, we investigate the impact of the components of predation risk on baboon group size, and derive an equation that best predicts minimum group size. Minimum group size in baboons is related to predator density and female body mass. Both of these elements can, in turn, be estimated from environmental variables. These findings present support for the argument that group living in primates is a response to predation risk and offer potentially new ways of investigating carnivore and primate ecology.

Adamczak VG, Dunbar RIM (2008). Variation in the mating system of oribi and its ecological determinants. African Journal of Ecology 46: 197–206.
Aldrich-Blake F, Bunn T, Dunbar R, Headley P (1971). Observations on baboons (Papio anubis) in an arid region in Ethiopia. Folia Primatologica 15: 1–35.
Altmann J, Altmann S, Hausfater G, Mccuskey S (1977). Life history of yellow baboons: physical development, reproductive parameters, and infant mortality. Primates 18: 315–330.
Altmann SA, Altmann J (1970). Baboon Ecology. Chicago, Chicago University Press.
Anderson C (1981a). Subtrooping in a chacma baboon (Papio ursinus) population. Primates 22: 445–458.
Anderson C (1981b). Intertroop relations of chacma baboon (Papio ursinus). International Journal of Primatology 2: 285–310.
Anderson C (1986). Predation and primate evolution. Primates 27: 15–39.
Balme G, Hunter L, Slotow R (2007). Feeding habitat selection by hunting leopards Panthera pardus in a woodland savanna: prey catchability versus abundance. Animal Behaviour 74: 589–598.
Barrett L, Henzi S, Weingrill T, Lycett J, Hill R (1999). Market forces predict grooming reciprocity in female baboons. Proceedings of the Royal Society B: Biological Sciences 266: 665–670.
Barton R (1989). Foraging Strategies, Diet and Competition in Olive Baboons. PhD Thesis, University of St. Andrews.
Bauer H, Van der Merwe S (2004). Inventory of free-ranging lions Panthera leo in Africa. Oryx 38: 26–31.
Bentley-Condit V, Smith EO (1997). Female reproductive parameters of Tana River yellow baboons. International Journal of Primatology 18: 581.
Berger ME (1972). Live-weights and body measurements of olive baboons (Papio anubis) in the Laikipia District of Kenya. Journal of Mammalogy 53: 404–407.
Bettridge CM (2010). Reconstructing Australopithecine Socioecology: Strategic Modeling Based on Modern Primates. PhD thesis, University of Oxford.
Bettridge CM, Dunbar RIM (2010). Trade-offs between time, predation risk and life history, and their implications for biogeography: a systems modelling approach with a primate case study. Ecological Modelling 221: 777–790.
Boesch C, Boesch H (1989). Hunting behavior of wild chimpanzees in the Tai National Park. American Journal of Physical Anthropology 78: 547–573.
Bothma J, Leriche E (1986). Prey preference and hunting efficiency of the Kalahari Desert leopard. In Cats of the World: Biology, Conservation, and Management (Miller SD, Everett DD, eds.), pp 389–414. Washington, National Wildlife Federation.
Bronikowski AM, Altmann J (1996). Foraging in a variable environment: weather patterns and the behavioral ecology of baboons. Behavioral Ecology and Sociobiology 39: 11.
Busse C (1980). Leopard and lion predation upon chacma baboons living in the Moremi Wildlife Reserve. Botswana Notes and Records 12: 15–21.
Celesia GG, Townsend Peterson A, Kerbis Peterhans JC, Gnoske TP (2010). Climate and landscape correlates of African lion (Panthera leo) demography. African Journal of Ecology 48: 58–71.
Cheney DL, Wrangham RW (1987). Predation. In Primate Societies (Smuts BB, Cheney DL, Seyfarth RW, Wrangham RW, Struhsaker TT, eds.). Chicago, University of Chicago Press.
Cheney D, Seyfarth R, Fischer J, Beehner J, Bergman T, Johnson S, Kitchen D, Palombit R, Rendall D, Silk J (2004). Factors affecting reproduction and mortality among baboons in the Okavango Delta, Botswana. International Journal of Primatology 25: 401–428.
Cowlishaw G (1993). Trade-offs between Foraging and Predation in Baboons. PhD thesis, University College London.
Cowlishaw G (1994). Vulnerability to predation in baboon populations. Behaviour 131: 293–304.
Cowlishaw G (1997a). Trade-offs between foraging and predation risk determine habitat use in a desert baboon population. Animal Behaviour 53: 667–686.
Cowlishaw G (1997b). Refuge use and predation risk in a desert baboon population. Animal Behaviour 54: 241–253.
Creel S, Christianson D (2008). Relationships between direct predation and risk effects. Trends in Ecology and Evolution 23: 194–201.
Creel S, Creel N (2002). The African Wild Dog: Behavior, Ecology and Conservation. Princeton, Princeton University Press.
Davidge C (1978a). Ecology of baboons (Papio ursinus) at Cape Point. Zoologica Africana 13: 329–350.
Davidge C (1978b). Activity patterns of chacma baboons (Papio ursinus) at Cape Point. Zoologica Africana 13: 143–155.
De Fries R, Hansen M, Townshend JRG, Janetos AC, Loveland TR (2000). Continuous Fields 1 km Tree Cover. College Park, The Global Land Cover Facility.
Depew LA (1983). Ecology and Behaviour of Baboons (Papio anubis) in the Shai Hills Game Production Reserve, Ghana. MSc Thesis, Cape Coast University.
Devore I, Hall K (1965). Baboon ecology. In Primate Behavior: Field Studies of Monkeys and Apes (Devore I, ed.), pp 20–52. New York, Holt, Rinehart & Winston.
Dunbar RIM (1980). Determinants and evolutionary consequences of dominance among female gelada baboons. Behavioural Ecology and Sociobiology 7: 253–265.
Dunbar RIM (1988). Primate Social Systems. London, Chapman & Hall.
Dunbar RIM (1989). Reproductive strategies of female gelada baboons. In Sociobiology of Sexual and Reproductive Strategies (Rasa A, Vogel C, Voland E, eds.), pp 74–92. London, Chapman & Hall.
Dunbar RIM (1990). Environmental and social determinants of fecundity in primates. In Fertility and Resources (Landers J, Reynolds V, eds.). Cambridge, Cambridge University Press.
Dunbar RIM (1996). Determinants of group size in primates: a general model. Proceedings of the National Academy of Sciences 88: 33–57.
Dunbar RIM, Dunbar E (1974). Ecological relations and niche separation between sympatric terrestrial primates in Ethiopia. Folia Primatologica 21: 36–60.
Dunbar RIM, Nathan M (1972). Social organization of the Guinea baboon, Papio papio. Folia Primatologica 17: 321–334.
Dunbar RIM, Korstjens AH, Lehmann J (2009). Time as an ecological constraint. Biological Reviews 84: 413–429.
Eley RM, Strum SC, Muchemi G, Reid GDF (1989). Nutrition, body condition, activity patterns, and parasitism of free-ranging troops of olive baboons (Papio anubis) in Kenya. American Journal of Primatology 18: 209–219.
Fitzgibbon C, Lazarus J (1995). Antipredator behavior of Serengeti ungulates: individual differences and population consequences. In Serengeti II: Dynamics, Management, and Conservation of an Ecosystem (Sinclair ARE, Arcese P, eds.), pp 274–296. Chicago, University of Chicago Press.
Frid A, Dill L (2002). Human-caused disturbance stimuli as a form of predation risk. Conservation Ecology 6: 11.
Gautier-Hion A, Quris R, Gautier J (1983). Monospecific vs polyspecific life: a comparative study of foraging and antipredatory tactics in a community of Cercopithecus monkeys. Behavioral Ecology and Sociobiology 12: 325–335.
Gaynor D (1994). Foraging and Feeding Behaviour of Chacma Baboons in a Woodland Habitat. PhD thesis, University of Natal, South Africa.
Gillespie T, Chapman C (2001). Determinants of group size in the red colobus monkey (Procolobus badius): an evaluation of the generality of the ecological-constraints model. Behavioral Ecology and Sociobiology 50: 329–338.
Hall KRL (1963). Variations in the ecology of the chacma baboon, Papio ursinus. Symposia Zoological Society London 10: 1–28.
Hall KRL (1965). Behaviour and ecology of baboons, patas and vervet monkeys in Uganda. In The Baboon in Medical Research (Vagtborg H, ed). San Antonio, University of Texas Press.
Hamilton WD (1971). Geometry for the selfish herd. Journal of Theoretical Biology 31: 295–311.
Hamilton W, Buskirk RE, Buskirk W (1975). Chacma baboon tactics during intertroop encounters. Journal of Mammalogy 56: 857–870.
Hamilton WJI, Buskirk RE, Buskirk WH (1976). Defense of space and resources by chacma (Papio ursinus) baboon troops in an African desert and swamp. Ecology 57: 1264–1272.
Harding R (1976). Ranging patterns of a troop of baboons (Papio anubis) in Kenya. Folia Primatologica 25: 143–185.
Heithaus MR, Wirsing AJ, Burkholder D, Thomson K, Dill LM (2009). Towards a predictive framework for predator risk effects: the interaction of landscape features and prey escape tactics. Journal of Animal Ecology 78: 556–562.
Henzi SP, Lycett JE, Piper SE (1997). Fission and troop size in a mountain baboon population. Animal Behaviour 53: 525–535.
Hill RA (1999). Ecological and Demographic Determinants of Time Budgets in Baboons: Implications for Cross-Populational Models of Baboon Socioecology. PhD thesis, University of Liverpool.
Hill RA, Dunbar RIM (1998). An evaluation of the roles of predation rate and predation risk as selective pressures on primate grouping behaviour. Behaviour 135: 411.
Hill RA, Lee PC (1998). Predation risk as an influence on group size in cercopithecoid primates: implications for social structure. Journal of Zoology 245: 447–456.
Isbell LA (1994). Predation on primates: ecological patterns and evolutionary consequences. Evolutionary Anthropology: Issues, News and Reviews 3: 61–71.
Janson CH (2003). Puzzles, predation, and primates: using life history to understand selection pressures. In Primate Life Histories and Socioecology (Kappeler PM, Pereira ME, eds.). Chicago, University of Chicago Press.
Janson CH, Goldsmith ML (1995). Predicting group size in primates: foraging costs and predation risks. Behavioural Ecology 6: 326–336.
Jolly CJ (1972). The Evolution of Primate Behavior. New York, Macmillan Co.
Kenyatta CG (1995). Ecological and Social Constraints on Maternal Investment Strategies. PhD thesis, University College London.
Lima SL (1987). Vigilance while feeding and its relation to the risk of predation. Journal of Theoretical Biology 124: 303–316.
Lima SL (1995). Back to the basics of anti-predatory vigilance: the group-size effect. Animal Behaviour 49: 11–20.
Lima S, Zollner P (1996). Anti-predatory vigilance and the limits to collective detection: visual and spatial separation between foragers. Behavioral Ecology and Sociobiology 38: 355–363.
Maxim PE, Beuthner-Samuel J (1963). A field study of the Kenya baboon. American Journal of Physical Anthropology 21: 165–180.
Nagel U (1973). A comparison of anubis baboons, hamadryas baboons and their hybrids at a species border in Ethiopia. Folia Primatologica 19: 104–165.
Oliveira LC, Dietz JM (2011). Predation risk and the interspecific association of two Brazilian Atlantic forest primates in Cabruca agroforest. American Journal of Primatology 73: 852–860.
Patterson JD (1973). Ecologically differentiated patterns of aggressive and sexual behavior in two troops of Ugandan baboons, Papio anubis. American Journal of Physical Anthropology 38: 641–647.
Patterson JD (1976). Variations in the Ecology and Adaptation of Ugandan Baboons Papio cynocephalus anubis. PhD thesis, University of Calgary.
Popp J (1978). Male Baboons and Evolutionary Principles. PhD thesis, Harvard University, Cambridge.
Popp J (1983). Ecological determinism in the life histories of baboons. Primates 24: 198–210.
Ransom TW (1981). Beach Troop of the Gombe. Lewisberg, Bucknell University Press.
Rasmussen DR (1978). Environmental and Behavioural Correlates of Changes in Range Use in a Troop of Yellow (Papio cynocephalus) and a Troop of Olive (Papio anubis) Baboons. PhD thesis, University of California, San Francisco.
Rasmussen DR (1983). Correlates of patterns of range use of a troop of yellow baboons (Papio cynocephalus). II. Spatial structure, cover density, food gathering, and individual behaviour patterns. Animal Behaviour 31: 834–856.
Rowell T (1969). Long-term changes in a population of Ugandan baboons. Folia Primatologica 11: 241–254.
Saayman GS (1971). Behaviour of the adult males in a troop of free-ranging chacma baboons (Papio ursinus). Folia Primatologica 15: 36–57.
Schmitz OJ (2007). Predator diversity and trophic interactions. Ecology 88: 2415–2426.
Shultz S, Noe R, McGraw WS, Dunbar RIM (2004). A community-level evaluation of the impact of prey behavioural and ecological characteristics on predator diet composition. Proceedings of the Royal Society B: Biological Sciences 271: 725–732.
Sigg H, Stolba A, Abegglen J, Dasser V (1982). Life history of hamadryas baboons: physical development, infant mortality, reproductive parameters and family relationships. Primates 23: 473–487.
Stacey P (1986). Group size and foraging efficiency in yellow baboons. Behavioral Ecology and Sociobiology 18: 175–187.
Stanford C (1995). The influence of chimpanzee predation on group size and anti-predator behaviour in red colobus monkeys. Animal Behaviour 49: 577–587.
Stanford C (1998). Predation and male bonds in primate societies. Behaviour 135: 513–533.
Stoltz L, Saayman G (1970). Ecology and behaviour of baboons in the northern Transvaal. Annals of the Transvaal Museum 26: 99–143.
Struhsaker T (1981). Polyspecific associations among tropical rain-forest primates. Zeitschrift Tierpsychologie 57: 268–304.
Swedell L (2000). Social Behavior and Reproductive Strategies of Female Hamadryas Baboons, Papio hamadryas hamadryas, Ethiopia. Dissertation, Columbia University, New York.
Treves A (1999). Has predation shaped the social systems of arboreal primates? International Journal of Primatology 20: 35–67.
Van Orsdol K (1984). Foraging behaviour and hunting success of lions in Queen Elizabeth National Park, Uganda. African Journal of Ecology 22: 79–99.
van Schaik CP (1983). Why are diurnal primates living in groups? Behaviour 87: 120–144.
Warren Y (2003). Olive Baboons (Papio cynocephalus anubis): Behaviour, Ecology and Human Conflict in Gashaka Gumti National Park, Nigeria. PhD thesis, University of Surrey, Roehampton.
Whiten A, Byrne RW, Barton RA, Waterman PG, Henzi SP, Hawkes K, Widdowson EM, Altmann SA, Milton K, Dunbar RIM (1991). Dietary and foraging strategies of baboons [and discussion]. Philosophical Transactions: Biological Sciences 334: 187–197.
Whiten A, Byrne R, Henzi S (1987). The behavioral ecology of mountain baboons. International Journal of Primatology 8: 367–388.
Willems EP, Hill RA (2009). Predator-specific landscapes of fear and resource distribution: effects on spatial range use. Ecology 90: 546–555.
Willmott CJ, Feddema JJ (1992). A more rational climate moisture index. The Professional Geographer 44: 84–88.
Willmott CJ, Matsuura K (2001). Terrestrial air temperature and precipitation: monthly and annual climatologies (version 3.02).
Wrangham RW (1980). An ecological model of female-bonded primate groups. Behaviour 75: 262–300.
Zinner D, Peláez F, Torkler F (2001). Group composition and adult sex-ratio of hamadryas baboons (Papio hamadryas hamadryas) in Central Eritrea. International Journal of Primatology 22: 415–430.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.