Much of my research focuses on understanding how group-living animals regulate their social relationships. Investigating how individuals manage their social relationships in response to environmental and social factors contributes to our understanding of the evolutionary basis of sociality. I conduct investigations both in the wild and in captivity.


Past research has addressed the factors influencing the maintenance of social relationships in macaques and chimpanzees. Studies have included how individuals manage aggressive conflict within the context of their various relationships, how individual’s affective state influences post-conflict behaviour, the long-term effects of post-conflict reconciliation, individuals’ integration within their social networks and network changes over time. I have explored how individuals maintain their cooperative relationships through reciprocation and interchange of valuable social services and the flexibility within these strategies.

You can browse a list of publications below and on ResearchGate.

  • Dealing with conflict and competition
  • Social integration within networks
  • Reciprocity and interchange
  • Behavioural strategies for coping with stress/tension.

I currently supervise students at several field sites (South Africa/Indonesia) working on

  • behavioural ecology and anthropogenic disturbance in vervet monkeys
  • behavioural ecology of samango monkeys
  • stress and behaviour in savannah elephants
  • intergroup conflict in crested macaques


  • Prof. F. Aureli, University of Veracruz
  • Prof. R. Hill, University of Durham
  • Prof. C. Downs, University of Kwazulu Natal
  • Dr Y. Pretorius, University of Pretoria
  • Prof. A. Ganswindt, University of Pretoria
  • Dr L. Swanepoel, University of Venda
  • Chester Zoo, U.K.
  • Lajuma Research Centre, South Africa

Thatcher, H.R., Downs, C.T. & Koyama, N.F. (in press) Understanding foraging flexibility in urban vervet monkeys, Chlorocebus pygerythrus, for the benefit of human-wildlife coexistence. Urban Ecosystems.

Stringer, S.D., Hill R.A., Swanepoel, L., Dalrymple, S.E., Linden, B. & Koyama, N.F. (in press). Assessing the role of a mammalian frugivorous species on seed germination potential depends on study design: A case study using wild samango monkeys. Acta Oecologica 106, 103584.

Parker E., Hill R.A., Allan A.T.L., Howlett C., Koyama N.F. (2020) Influence of food availability, plant productivity and indigenous forest use on ranging behavior of the endangered samango monkey (Cercopithecus albogularis schwarzi), in the Soutpansberg Mountains, South Africa. Integrative Zoology. doi: 10.1111/1749-4877.12438

Stringer S., Hill R.A., Swanepoel L., Koyama N.F. (in press) Adapting methodology used on captive subjects for estimating gut passage time in wild monkeys. Folia Primatologica 91(4): 417-432.

Szott, I., Pretorius, Y., Ganswindt, A. & Koyama, N.F. (2020). Normalized Difference Vegetation Index, temperature, and age affect faecal thyroid hormone concentrations in free-ranging African elephants. Conservation Physiology 8(1): 1-13. 

Nyssen, P. & Koyama, N.F. (2020). Chimpanzee raiding. In: Encyclopedia of Evolutionary Psychological Science, edited by T. K. Shackelford and V. Weekes-Shackelford. Springer.

Szott, I., Pretorius, Y., Ganswindt, A. & Koyama, N.F. (2019) Physiological stress response of African elephants to wildlife tourism in Madikwe Game Reserve, South Africa. Wildlife Research.

Thatcher, H., Downs, C. and Koyama, N.F. (2019) Positive and negative interactions with humans concurrently affect vervet monkey, Chlorocebus pygerythrus, ranging behavior. International Journal of Primatology.

Szott, I., Pretorius, Y. & Koyama, N.F. (2019) Behavioural changes in African elephants in response to wildlife tourism. Journal of Zoology.

Thatcher, H., Downs, C. & Koyama, N.F. (2019) Anthropogenic influences on the time budgets of urban vervet monkeys. Landscape and Urban Planning 181: 38-44. DOI: 10.1016/j.landurbplan.2018.09.014

Koyama, N.F. & Aureli, F. (2019) Social network changes during space restriction in zoo chimpanzees. Primates 60(3): 203-211. DOI: 10.1007/s10329-018-0675-6

Thatcher, H., Downs, C. & Koyama, N.F. (2018) Using parasitic load to measure the effect of anthropogenic disturbance on vervet monkeys. Ecohealth. DOI: 10.1007/s10393-018-1349-y

Koyama N.F., Ronkainen K., Aureli F. (2017) Durability and flexibility of chimpanzee grooming patterns during a period of dominance instability. American Journal of Primatology, 79. DOI: 10.1002/ajp.22713   Read the online version here

Koyama, N.F. (2016) ‘R = Coefficient Of Relatedness’. In: Encyclopedia of Evolutionary Psychological Science, edited by T. K. Shackelford and V. Weekes-Shackelford. Springer. DOI: 10.1007/978-3-319-16999-6_1479-1

Koyama, N.F. (2016) ‘C < Rb’. In: Encyclopedia of Evolutionary Psychological Science, edited by T. K. Shackelford and V. Weekes-Shackelford. Springer. DOI: 10.1007/978-3-319-16999-6_1479-1

Farooqi, S. & Koyama , N.F. (2016) The occurrence of post-conflict skills in captive immature chimpanzees. International Journal of Primatology 37:185-199. DOI: 10.1007/s10764-016-9893-1

Bethell, E. J. & Koyama, N.F. (2015) Happy hamsters? Enrichment induces positive judgement bias for mildly (but not truly) ambiguous cues to reward and punishment in Mesocricetus auratus. Royal Society Open Science 2.7: 140399. DOI: 10.1098/rsos.140399

Lawson, J., James, C., Jannson, A., Koyama N.F. & Hill, R. (2014) A comparison of heterosexual and homosexual mating preferences in personal advertisements. Evolution & Human Behaviour 35:408-414. DOI: 10.1016/j.evolhumbehav.2014.05.006

Koyama, N.F., Caws, C. & Aureli, F. (2012) Supply and demand predict male grooming of swollen females in captive chimpanzees, Pan troglodytes. Animal Behaviour 84(6):1419-1425. DOI: 10.1016/j.anbehav.2012.09.007

Majolo, B., Ventura, R. & Koyama, N.F. (2009) Anxiety level predicts post-conflict behaviour in wild Japanese macaques (Macaca fuscata yakui). Ethology 115 (10): 986-995. DOI: 10.1111/j.1439-0310.2009.01685.x

Majolo, B., Ventura, R. & Koyama, N.F. (2009) A statistical modeling approach to the occurrence and timing of reconciliation in wild Japanese macaques. Ethology 115(2):152-166. DOI: 10.1111/j.1439-0310.2008.01591.x

Majolo, B., Ventura, R., Koyama, N.F., Hardie, S.M., Jones, B.M., Knapp, L.A. & Schino. (2009) Analysing the effects of group size and food competition on Japanese macaque social relationships. Behaviour 146:113-137. DOI: 10.1163/156853908X390959

Koyama, N.F. & Palagi, E. (2006) Managing conflict: Evidence from wild and captive primates. International Journal of Primatology Special Issue 27(5):1235-1240. DOI: 10.1007/s10764-006-9073-9

Koyama, N.F., Caws, C. & Aureli, F. (2006) Interchange of grooming and agonistic support in chimpanzees. International Journal of Primatology 27(5): 1293-1309. DOI: 10.1007/s10764-006-9074-8

Majolo, B., & Koyama, N.F. (2006) Seasonal effects on reconciliation in wild female Japanese macaques (Macaca fuscata). International Journal of Primatology 27(5):1383-1397. DOI: 10.1007/s10764-006-9079-3

Ventura, R., Majolo, B., Koyama, N.F., Hardie, S. & Schino, G. (2006) Reciprocation and interchange in wild Japanese macaques: grooming, co-feeding and agonistic support. American Journal of Primatology 68:1-12. DOI: 10.1002/ajp.20314

Hill, R.A., Donovan, S. & Koyama, N.F. (2005) Female Sexual Advertisement Reflects Resource Availability in Humans. Human Nature 16: 266-277DOI: 10.1007/s12110-005-1010-7

Majolo, B., Ventura, R & Koyama, N. (2005) Sex, rank and age differences in the Japanese macaque (Macaca fuscata yakui) participation in inter-group encounters. Ethology 111:455-468. DOI: 10.1111/j.1439-0310.2005.01087.x

Majolo, B., Ventura, R & Koyama, N. (2005) Post-conflict behaviour among male Japanese macaques (Macaca fuscata yakui). International Journal of Primatology 26(2): 321-336.DOI: 10.1007/s10764-005-2927-8

Koyama, N.F., McGain, A & Hill, R.A. (2004) Self-reported mate preferences and feminist attitudes regarding marital relations. Evolution & Human Behavior  25(5):327-335. DOI: 10.1016/j.evolhumbehav.2004.06.004

Koyama, N.F. (2003) Matrilineal cohesion and social networks in Macaca fuscataInternational Journal of Primatology 24(4):797-811. DOI: 10.1023/A:1024676705433

Koyama, N.F. (2001) The long-term effects of reconciliation in Japanese macaques (Macaca fuscata).  Ethology 107: 975-987. DOI: 10.1046/j.1439-0310.2001.00731.x

Koyama, N.F. (2000) Conflict-reduction mechanisms before feeding. In: Natural Conflict Resolution, (F. Aureli & F.B.M. de Waal eds.), pp.130-132. University of California Press, Berkley, California.

Koyama, N.F. & Dunbar, R.I.M. (1996). Anticipation of conflict in chimpanzees. Primates 37(1):79-86. DOI: 10.1007/BF02382923