Portrait of Dr Nicholas E. Newton-Fisher

Dr Nicholas E. Newton-Fisher

Reader in Primate Behaviour and Ecology


Dr Nicholas Newton-Fisher is a primate behavioural ecologist and expert in wild chimpanzee behaviour. He has conducted fieldwork mostly in Uganda, but has also tracked chimpanzees in Tanzania. He conducted the first detailed study of the Sonso community in the Budongo Forest, Uganda, for his PhD research at the University of Cambridge, following a BSc (Hons) in Zoology from the University of Bristol, in which he specialised in mammalian ecology and behaviour. Prior to coming to Kent, Nicholas worked as assistant director of the Budongo Forest Project (now BCFS) in Uganda, and at Washington State University. 

His research interests span a variety of topics, but Nicholas is particularly interested in social behaviour and socioecology.  Current interests include aggression, reciprocity, sexual coercion, home-range use and social foraging, evolution of complex cognition, and non-material culture. The majority of his work has focused on non-human primates, but he is interested in these topics in other (particularly mammalian) taxa. 

Research interests

Dr Nicholas Newton-Fisher is particularly interested is the individual in complex (eg fission–fusion) societies: the evolution and ecology of behavioural strategies. Specific topics include association patterns, grooming, aggression, dominance and status, the evolution of intelligence; also hunting, foraging patterns, ranging, and territoriality. His research focuses on chimpanzees and has added important findings for the understanding of chimpanzee society, seeking always to test and challenge existing theories.


Dr Newton-Fisher’s modules contribute to multiple undergraduate programmes, including the BSc in AnthropologyBSc in Biological AnthropologyBSc in Wildlife Conservation and the BSc in Biology, as well as the MSc in Evolution & Human Behaviour and the MSc in Conservation & Primate Behaviour.


  • SE302: Foundations of Biological Anthropology
  • SE567: Methodology in Anthropological Science
  • SE580: Primate Behaviour and Ecology (module convenor)
  • SE582: Comparative Perspectives in Primate Biology  (module convenor)


SE993: Advanced Topics in Primate Behaviour (module convenor)


Dr Newton-Fisher supervises research projects for the BSc and MSc programmes:

  • SE533: Project in Anthropological Science
  • SE855: Research Project (Evolution & Human Behaviour)

He can offer supervision of PhD and MSc research within any of his areas of interest, broadly behaviour and ecology of primates and other large mammals, with a particular focus on chimpanzees. This can lead to qualifications in either Anthropology or Biodiversity Management.

Current students

  • Juliette Berthier: The role of emotions in the communication of black crested macaques (Macaca nigra)
  • Hella Péter: The effects of water shortage on female chimpanzee social behaviour in the Budongo forest


  • Caroline Howlett: Expression of the 2D:4D digit ratio across the Primate Order (second supervisor)
  • Adriana Lowe: Maternal strategies in wild Ugandan chimpanzees
  • Jakob Villioth: Aggressive interactions in wild chimpanzees Pan troglodytes - demographic and ecological causes and consequences


Dr Newton-Fisher is interested in increasing public understanding of science. He has given numerous interviews for press and broadcast media and is available to provide topical comment or in-depth discussion of topics related to chimpanzees, primatology, and human evolution and behaviour. He has also provided expertise in primatology and chimpanzee behaviour as a consultant for Channel 5/National Geographic, BBC Science Television, Lever Fabergé, Granada Media Television, BBC Science Online, Survival Anglia Television and the Discovery Channel Online.


Showing 50 of 72 total publications in the Kent Academic Repository. View all publications.


  • Lowe, A., Hobaiter, C., Asiimwe, C., Zuberbuhler, K. and Newton-Fisher, N. (2019). Intra‐community infanticide in wild, eastern chimpanzees: a 24‐year review. Primates [Online]. Available at: http://dx.doi.org/10.1007/s10329-019-00730-3.
    Infanticide is well documented in chimpanzees and various hypotheses have been proposed to explain this behavior. However, since infanticide by chimpanzees is relatively rare, it has thus far not been possible to thoroughly test these hypotheses. Here we present an analysis of the largest dataset of infanticides from a single community of chimpanzees, a full record of all intra- community infanticides and failed attempts at infanticide over a 24-year period for the Sonso community of chimpanzees in the Budongo Forest, Uganda. We use these data to test four hypotheses for this behavior: the sexual selection hypothesis, male mating competition, resource competition, and meat acquisition. Our dataset consisted of 33 attacks on 30 victims, 11 of which were ‘definite’ infanticides, four of which ‘almost certain’, and nine were ‘suspected’, while nine were ‘attempted’ infanticides. The majority of attacks where the perpetrators were known (23) had only male attackers and victims were disproportionately young (two-thirds of victims with known ages were under 1 week old). Our data best support the sexual selection hypothesis for infanticide. Cannibalism was infrequent and partial, suggesting meat acquisition was a by-product of infanticide, and there was no evidence to suggest that infanticide was part of a male strategy to eliminate future competi- tors. Infanticide by females was rare, but we suggest sexual selection, operating through intra-sexual competition, may also be responsible for infanticide by females.
  • Lowe, A., Hobaiter, C. and Newton-Fisher, N. (2019). Countering infanticide: Chimpanzee mothers are sensitive to the relative risks posed by males on differing rank trajectories. American Journal of Physical Anthropology [Online] 168:3-9. Available at: https://doi.org/10.1002/ajpa.23723.
    Objectives: Infanticide by males is common in mammals. According to the sexual selection hypothesis, the risk is inversely related to infant age because the older the infant, the less infan- ticide can shorten lactational amenorrhea; risk is also predicted to increase when an infanticidal male's chance of siring the replacement infant is high. Infanticide occurs in chimpanzees (Pan troglodytes), a species in which male dominance rank predicts paternity skew. Infanticidal male chimpanzees (if low-ranking) are unlikely to kill their own offspring, whereas those who are cur- rently rising in rank, particularly when this rise is dramatic, have an increased likelihood of fathering potential future infants relative to any existing ones. Given that mothers should behave in ways that reduce infanticide risk, we predicted that female chimpanzees, and specifi- cally those with younger, more vulnerable infants, would attempt to adjust the exposure of their infants to potentially infanticidal males. Specifically, mothers of young infants should reduce their association with adult males in general, and to a greater extent, with both low-ranking males and those rising in rank from a position where paternity of current infants was unlikely, to a rank where the probability of siring the next infant is significantly higher. We also investigated the alternative possibility that rather than avoiding all adult males, mothers would increase association with males of stable high rank on the basis that such males could offer protection against infanticide.

    Materials and methods: We examined data on female association patterns collected from the Budongo Forest, Uganda, during a period encompassing both relative stability in the male hierar- chy and a period of instability with a mid-ranking male rising rapidly in rank.
    Results: Using linear mixed models, we found that mothers reduced their association with the rank-rising male, contingent on infant age, during the period of instability. We also found evi- dence that females preferentially associated with a potential protector male during the high-risk period.

    Discussion: Our results support the sexually selected hypothesis for infanticide and demon- strate that female chimpanzees are sensitive to the relative risks posed by adult males.
  • Newton-Fisher, N. and Kaburu, S. (2017). Grooming decisions under structural despotism: the impact of social rank & bystanders among wild male chimpanzees. Animal Behaviour [Online] 128:153-164. Available at: http://dx.doi.org/10.1016/j.anbehav.2017.04.012.
    Understanding the evolution of cooperation remains a central concern in studies of animal behaviour, with fundamental issues being how individuals avoid being cheated, or ‘short-changed’, and how partners are chosen. Economic decisions made during social interactions should depend upon the availability of potential partners nearby, as these bystanders generate temptations to defect from the current partner. The influence of bystanders is highlighted in two theoretical approaches, biological markets theory and parcelling, both economic models of behaviour. Here, we tested predictions of these models using the grooming behaviour of wild male chimpanzees, Pan troglodytes, living under strong structural despotism, where grooming is exchanged both for agonistic support and for itself, and so we provide the first investigation of both presence and value of bystanders on chimpanzees' grooming decisions. We found that male chimpanzees took into account the relative value (rank) of bystanders compared to that of their current partner, with this more important than bystander numbers. Highranking bystanders appeared to generate incentives to defect from a potentially cooperative interaction and we found that grooming effort was parcelled into discrete episodes, with smaller parcels used when a bystander outranked the current partner. The number of bystanders also generated a temptation to defect, as bidirectional (reciprocated) bouts were more likely to occur with fewer bystanders. Such bouts were more likely with smaller rank distances between groomer and recipient. We found no influence of grooming relationship on initial investment: groomers did not appear to trust that they would receive grooming in return, even from those with whom they had a history of strongly reciprocal grooming. Our findings are consistent with an economic-benefits, markets-based approach, but not a relationship model paradigm. Our work highlights the importance of considering the immediate social context (number and quality of bystanders) in studies of cooperation.
  • Newton-Fisher, N. (2017). Modeling Social Dominance: Elo-Ratings, Prior History, and the Intensity of Aggression. International Journal of Primatology [Online]. Available at: http://doi.org/10.1007/s10764-017-9952-2.
    Among studies of social species, it is common practice to rank individuals using dyadic social dominance relationships. The Elo-rating method for achieving this is powerful and increasingly popular, particularly among studies of nonhuman primates, but suffers from two deficiencies that hamper its usefulness: an initial burn-in period during which the model is unreliable and an assumption that all win–loss interactions are equivalent in their influence on rank trajectories. Here, I present R code that addresses these deficiencies by incorporating two modifications to a previ- ously published function, testing this with data from a 9-mo observational study of social interactions among wild male chimpanzees (Pan troglodytes) in Uganda. I found that, unmodified, the R function failed to resolve a hierarchy, with the burn-in period spanning much of the study. Using the modified function, I incorporated both prior knowledge of dominance ranks and varying intensities of aggression. This effectively eliminated the burn-in period, generating rank trajectories that were consistent with the direction of pant-grunt vocalizations (an unambiguous demonstration of subordinacy) and field observations, as well as showing a clear relationship between rank and mating success. This function is likely to be particularly useful in studies that are short relative to the frequency of aggressive interactions, for longer-term data sets disrupted by periods of lower quality or missing data, and for projects investigating the relative importance of differing behaviors in driving changes in social dominance. This study highlights the need for caution when using Elo-ratings to model social dominance in nonhuman primates and other species.
  • Kaburu, S. and Newton-Fisher, N. (2016). Markets misinterpreted? A comment on Sanchez-Amaro and Amici (2015). Animal Behaviour [Online] 119:e1-e5. Available at: http://dx.doi.org/10.1016/j.anbehav.2016.02.011.
    In a recent essay, Sanchez-Amaro and Amici (2015) reviewed evidence in support of biological market theory (BMT) in primates. Since the pioneering work by Noe (1990, 1992; Noe, van Schaik, & van Hoof, 1991), and Barrett and colleagues (Barrett, Gaynor, & Henzi, 2002; Barrett, Henzi, Weingrill, Lycett, & Hill, 1999), several studies have looked for and found evidence of BMT in a variety of primate species, from lemurs (Norscia, Antonacci, & Palagi, 2009; Port, Clough, & Kappeler, 2009) to monkeys (Fruteau, Lemoine, Hellard, van Damme, & Noe, 2011; Gumert, 2007; Tiddi, Aureli, & Schino, 2012) and apes (Kaburu & NewtonFisher, 2015a, 2015b; Koyama, Caws, & Aureli, 2012; NewtonFisher & Lee, 2011). With an increasingly large number of studies, a review such as the one by Sanchez-Amaro and Amici (2015) would be warmly welcome as a timely summary of the evidence for BMT, and an indication of future directions. The authors identify four areas of interest and usefully highlight some potential issues with BMT, for example where free trading is compromised by extortion or the need for comparable methods across studies. However, while their aims may be laudable, we feel there are particular flaws in some of their arguments and some misrepresentation of cited literature that we would like to correct.
  • Kaburu, S. and Newton-Fisher, N. (2016). Bystanders, parcelling, and an absence of trust in the grooming interactions of wild male chimpanzees. Scientific Reports [Online] 6:20634. Available at: http:/dx.doi.org/10.1038/srep20634.
    The evolution of cooperation remains a central issue in socio-biology with the fundamental problem of how individuals minimize the risks of being short-changed (‘cheated’) should their behavioural investment in another not be returned. Economic decisions that individuals make during interactions may depend upon the presence of potential partners nearby, which o ers co operators a temptation to defect from the current partner. The parcelling model posits that donors subdivide services into parcels to force cooperation, and that this is contingent on opportunities for defection; that is, the presence of bystanders. Here we test this model and the e ect of bystander presence using grooming interactions of wild chimpanzees. We found that with more bystanders, initiators gave less grooming at the beginning of the bout and were more likely to abandon a grooming bout, while bouts were less likely to be reciprocated. We also found that the groomer’s initial investment was not higher among frequent groomers or stronger reciprocators, suggesting that contrary to current assumptions, grooming decisions are not based on trust, or bonds, within dyads. Our work highlights the importance of considering immediate social context and the in uence of bystanders for understanding the evolution of the behavioural strategies that produce cooperation.
  • Reynolds, V., Lloyd, A., English, C., Lyons, P., Dodd, H., Hobaiter, C., Newton-Fisher, N., Mullins, C., Lamon, N., Marijke Schel, A. and Fallon, B. (2015). Mineral Acquisition from Clay by Budongo Forest Chimpanzees. PLoS ONE [Online] 10:e0134075. Available at: http://www.dx.doi.org/10.1371/journal.pone.0134075.
    Chimpanzees of the Sonso community, Budongo Forest, Uganda were observed eating clay and drinking clay-water from waterholes. We show that clay, clay-rich water, and clay obtained with leaf sponges, provide a range of minerals in different concentrations. The presence of aluminium in the clay consumed indicates that it takes the form of kaolinite. We discuss the contribution of clay geophagy to the mineral intake of the Sonso chimpanzees and show that clay eaten using leaf sponges is particularly rich in minerals. We show that termite mound soil, also regularly consumed, is rich in minerals. We discuss the frequency of clay and termite soil geophagy in the context of the disappearance from Budongo Forest of a formerly rich source of minerals, the decaying pith of Raphia farinifera palms.
  • Kaburu, S. and Newton-Fisher, N. (2015). Trading or coercion? Variation in male mating strategies between two communities of East African chimpanzees. Behavioral Ecology and Sociobiology [Online] 69:1039-1052. Available at: http://dx.doi.org/10.1007/s00265-015-1917-x.
    Across taxa, males employ a variety of mating strategies, including sexual coercion and the provision, or trading, of resources. Biological Market theory (BMT) predicts that trading of commodities for mating opportunities should exist only when males cannot monopolise access to females and/or obtain mating by force, in situations where power differentials between males are low; both coercion and trading have been reported for chimpanzees (Pan troglodytes). Here, we investigate whether the choice of strategy depends on the variation in male power differentials, using data from two wild communities of East African chimpanzees (P.t. schweinfurthii): the structurally despotic Sonso community (Budongo, Uganda) and the structurally egalitarian M-group (Mahale, Tanzania). We found evidence of sexual coercion by male Sonso chimpanzees, and of trading—of grooming for mating—by M-group males; females traded sex for neither meat nor protection from male aggression. Our results suggest that the despotism–egalitarian axis influences strategy choice: male chimpanzees appear to pursue sexual coercion when power differentials are large and trading when power differentials are small and coercion consequently ineffective. Our findings demonstrate that trading and coercive strategies are not restricted to particular chimpanzee subspecies; instead, their occurrence is consistent with BMT predictions. Our study raises interesting, and as yet unanswered, questions regarding female chimpanzees’ willingness to trade sex for grooming, if doing so represents a compromise to their fundamentally promiscuous mating strategy. It highlights the importance of within-species cross-group comparisons and the need for further study of the relationship between mating strategy and dominance steepness.
  • Kaburu, S. and Newton-Fisher, N. (2015). Egalitarian despots: hierarchy steepness, reciprocity and the grooming-trade model in wild chimpanzees (Pan troglodytes). Animal Behaviour [Online] 99:61-71. Available at: http://dx.doi.org/10.1016/j.anbehav.2014.10.018.
    Biological-markets theory models the action of natural selection as a marketplace in which animals are viewed as traders with commodities to offer and exchange. Studies of female Old World monkeys have suggested that grooming might be employed as a commodity to be reciprocated or traded for alternative services, yet previous tests of this grooming-trade model in wild adult male chimpanzees (Pan troglodytes) have yielded mixed results. Here we provide the strongest test of the model to date for male chimpanzees: we use data drawn from two social groups (communities) of chimpanzees from different populations, and give explicit consideration to variation in dominance hierarchy steepness as such variation results in differing conditions for biological markets. First, analysis of data from published accounts of other chimpanzee communities, together with our own data, showed that hierarchy steepness varied considerably within and across communities and that the number of adult males in a community aged 20-30 years predicted hierarchy steepness. The two communities in which we tested predictions of the grooming-trade model lay at opposite extremes of this distribution. Second, in accord with the grooming-trade model, we found evidence that male chimpanzees trade grooming for agonistic support where hierarchies are steep (despotic) and consequent effective support is a rank-related commodity, but not where hierarchies are shallow (egalitarian). However, we also found that grooming was reciprocated regardless of hierarchy steepness. Our findings also hint at the possibility of agonistic competition, or at least exclusion, in relation to grooming opportunities compromising the free market envisioned by Biological Markets theory. Our results build on previous findings across chimpanzee communities to emphasise the importance of reciprocal grooming exchanges among adult male chimpanzees, which can be understood in a biological markets framework if grooming by or with particular individuals is a valuable commodity.
  • Newton-Fisher, N. (2014). Roving females and patient males: a new perspective on the mating strategies of chimpanzees. Biological Reviews [Online] 89:356-374. Available at: http://dx.doi.org/10.1111/brv.12058.
    Mating strategies are sets of decisions aimed at maximizing reproductive success. For male animals, the fundamental problem that these strategies address is attaining mating access to females in a manner that maximizes their chances of achieving paternity. For chimpanzees (Pan troglodytes), despite substantial interest in mating strategies, very little attention has been paid to the most fundamental problem that mating strategies need to solve: finding mates. Only a single model, Dunbar’s general model of male mating strategies, exists to explain mate-searching behaviour in chimpanzees. Under this model, males in most populations are regarded as pursuing a ‘roving’ strategy, searching for and sequestering fertile females who are essentially passive with respect to mate searching. The roving mating strategy is an assumption deeply embedded in the way chimpanzee behaviour is considered; it is implicit in the conventional model for chimpanzee social structure, which posits that male ranging functions both to monitor female reproductive state and to ward these females from other groups of males through collective territoriality: essentially, ranging as mating effort. This perspective is, however, increasingly at odds with observations of chimpanzee behaviour. Herein, I review the logic and evidence for the roving-male mating strategy and propose a novel alternative, a theoretical framework in which roving is a strategy pursued by female chimpanzees in order to engage successfully in promiscuous mating. Males, unable to thwart this female strategy, instead maximise the number of reproductive opportunities encountered by focusing their behaviour on countering threats to health, fertility and reproductive career. Their prolonged grooming bouts are seen, in consequence, as functioning to mitigate the negative impacts of socially induced physiological stress. In this new framework, the roving-male strategy becomes, at best, a ‘best of a bad job’ alternative for low-ranking males when faced with high levels of competition for mating access. Male chimpanzees do not search for mates, but for one another, for food, and, at times, for rivals in other communities. To the extent that female promiscuity functions to counter infanticide risk, mate searching by female chimpanzees—and any associated costs—can be seen as an unavoidable consequence of male sexual coercion. This novel framework is a better fit to the available data than is the conventional account. This review highlights the desperate need for additional work in an area of chimpanzee biology that has been somewhat neglected, perhaps in part because assumptions of roving males have remained unquestioned for too long. It also highlights the need, across taxa, to revisit and revise theory, and to test old assumptions, when faced with contrary data.
  • Kaburu, S. and Newton-Fisher, N. (2013). Social instability raises the stakes during social grooming among wild male chimpanzees. Animal Behaviour [Online] 86:519-527. Available at: http://dx.doi.org/10.1016/j.anbehav.2013.06.003.
    Explaining cooperative behaviour is a fundamental issue for evolutionary biology. The challenge for any cooperative strategy is to minimize the risks of nonreciprocation (cheating) in interactions with im- mediate costs and delayed benefits. One of a variety of proposed strategies, the raise-the-stakes (RTS) strategy, posits that individuals establish cooperation by increasing investment across interactions from an initial interaction. This model has received little quantitative support, however, probably because individuals of many social species engage in repeated interactions from a young age. In some situations, however, such as following conflicts, after prolonged absences or during social instability, established relationships may become unreliable predictors of future behaviour, creating an environment for RTS. We investigated grooming interactions among wild male chimpanzees, Pan troglodytes, testing RTS in these specific contexts. We found evidence to support the view that male chimpanzees employed RTS during social instability, but not under the other conditions. However, we also found that the duration of episodes (discrete parcels) of grooming was negatively related to aggression risk and in consequence suggest that the patterning of grooming interactions indicative of RTS was less to do with preventing cheating, and more to do with avoiding the elevated risks of intramale aggression during the period of social instability. We interpret the apparent support for RTS in our data as a by-product of the way chimpanzees cope with fluctuating (here, elevated then diminishing) risks of aggression. We suggest that social instability raises the stakes for grooming by creating a more hazardous marketplace in which to trade.
  • Kaburu, S., Inoue, S. and Newton-Fisher, N. (2013). Death of the Alpha: Within?Community Lethal Violence Among Chimpanzees of the Mahale Mountains National Park. American Journal of Primatology [Online] 75:789-797. Available at: http://dx.doi.org/10.1002/ajp.22135.
    Chimpanzees (Pan troglodytes) are capable of extreme violence. They engage in inter?group, sometimes lethal, aggression that provides the winners with an opportunity to enlarge their territory, increase their food supply and, potentially, attract more mates. Lethal violence between adult males also occurs within groups but this is rare; to date, only four cases (three observed and one inferred) have been recorded despite decades of observation. In consequence, the reasons for within?group lethal violence in chimpanzees remain unclear. Such aggression may be rare due to the importance of coalitions between males during inter?group encounters; cooperation between males is also thought to be key in the defense or advancement of social rank within the group. Previous accounts of within?group lethal violence concern victims who were low?ranking males; here we provide the first account of the killing of an incumbent alpha male by a coalition of adult males from the same community. We found no clear evidence that the alpha male’s position was under threat during the months before the lethal attack: the male dominance hierarchy was highly stable, with low rates of male–male aggression, and there were no significant changes in social interactions (i.e. grooming and aggression) between the alpha male and the other adult males. Two of the four attackers were former alpha males and were the individuals with whom the victim appeared, in the period preceding his death, to be most strongly affiliated: his most frequent grooming partners and those with whom he spent most time in proximity. The lethal attack triggered a period of instability in the male hierarchy and was likely an opportunistic attempt to seize alpha status by the third?ranking male.
  • Johns, S., Hargrave, L. and Newton-Fisher, N. (2012). Red Is Not a Proxy Signal for Female Genitalia in Humans. PLoS ONE [Online] 7:e34669. Available at: http://dx.doi.org/10.1371/journal.pone.0034669.
    Red is a colour that induces physiological and psychological effects in humans, affecting competitive and sporting success, signalling and enhancing male social dominance. The colour is also associated with increased sexual attractiveness, such that women associated with red objects or contexts are regarded as more desirable. It has been proposed that human males have a biological predisposition towards the colour red such that it is ‘sexually salient’. This hypothesis argues that women use the colour red to announce impending ovulation and sexual proceptivity, with this functioning as a proxy signal for genital colour, and that men show increased attraction in consequence. In the first test of this hypothesis, we show that contrary to the hypothesis, heterosexual men did not prefer redder female genitalia and, by extension, that red is not a proxy signal for genital colour. We found a relative preference for pinker genital images with redder genitalia rated significantly less sexually attractive. This effect was independent of raters' prior sexual experience and variation in female genital morphology. Our results refute the hypothesis that men's attraction to red is linked to an implied relationship to genital colour and women's signalling of fertility and sexual proceptivity.
  • Birkett, L. and Newton-Fisher, N. (2011). How abnormal is the behaviour of captive, zoo-living, chimpanzees?. PLoS ONE [Online] 6:e20101. Available at: http://dx.doi.org/10.1371/journal.pone.0020101.
    Background. Many captive chimpanzees (Pan troglodytes) show a variety of serious behavioural abnormalities, some of which have been considered as possible signs of compromised mental health. The provision of environmental enrichments aimed at reducing the performance of abnormal behaviours is increasing the norm, with the housing of individuals in (semi-)natural social groups thought to be the most successful of these. Only a few quantitative studies of abnormal behaviour have been conducted, however, particularly for the captive population held in zoological collections. Consequently, a clear picture of the level of abnormal behaviour in zoo-living chimpanzees is lacking.
    Methods. We present preliminary findings from a detailed observational study of the behaviour of 40 socially-housed zoo-living chimpanzees from six collections in the United States of America and the United Kingdom. We determined the prevalence, diversity, frequency, and duration of abnormal behaviour from 1200 hours of continuous behavioural data collected by focal animal sampling.
    Results, conclusion, and significance. Our overall finding was that abnormal behaviour was present in all sampled individuals across six independent groups of zoo-living chimpanzees, despite the differences between these groups in size, composition, housing, etc. We found substantial variation between individuals in the frequency and duration of abnormal behaviour, but all individuals engaged in at least some abnormal behaviour and variation across individuals could not be explained by sex, age, rearing history or background (defined as prior housing conditions). Our data support a conclusion that, while most behaviour of zoo-living chimpanzees is ‘normal’ in that it is typical of their wild counterparts, abnormal behaviour is endemic in this population despite enrichment efforts. We suggest there is an urgent need to understand how the chimpanzee mind copes with captivity, an issue with both scientific and welfare implications.
  • Newton-Fisher, N. and Lee, P. (2011). Grooming Reciprocity in Wild Male Chimpanzees. Animal Behaviour [Online] 81:439-446. Available at: http://dx.doi.org/10.1016/j.anbehav.2010.11.015.
    Understanding cooperation between unrelated individuals remains a central problem in animal behaviour; evolutionary mechanisms are debated, and the importance of reciprocity has been questioned. Biological-markets theory makes specific predictions about the occurrence of reciprocity in social groups; applied to the social grooming of mammals, it predicts reciprocity in the absence of other benefits for which grooming can be exchanged. Considerable effort has been made to test this grooming-trade model in non-human primates; such studies show mixed results, but may be confounded by kin-effects. We examined patterns of reciprocity within and across bouts, and tested predictions of the grooming-trade model, among wild male chimpanzees (Pan troglodytes); a system with negligible kin effects. In accord with the model’s expectations, we found that some grooming was directed by lower to higher ranked individuals, and that higher ranked individuals, on average, groomed more reciprocally. We found no support, however, for a prediction that more reciprocity should occur between individuals close in social rank. For most dyads, reciprocity of effort occurred through unbalanced participation in grooming bouts but reciprocity varied considerably between dyads and only a small proportion showed strongly reciprocal grooming. Despite this, each male had at least one reciprocal grooming relationship. In bouts where both individuals groomed, effort was matched through mutual grooming, not alternating roles. Our results provide mixed support for the current grooming-trade biological markets model, and suggest that it needs to incorporate risks of currency inflation and cheating for species where reciprocity can be achieved through repeated dyadic interactions.
  • Newton-Fisher, N., Emery Thompson, M., Reynolds, V., Boesch, C. and Vigilant, L. (2010). Paternity and Social Rank in Wild Chimpanzees (Pan troglodytes) from the Budongo Forest, Uganda. American Journal of Physical Anthropology [Online] 142:417-428. Available at: http://dx.doi.org/10.1002/ajpa.21241.
    We analyzed patterns of paternity and male dominance rank in the Sonso community of wild East African chimpanzees (Pan troglodytes schweinfurthii) in the Budongo Forest, Uganda. Our major objective was to determine whether and how social rank influenced paternity success. We successfully genotyped 52 individuals at up to nine microsatellite loci, using DNA extracted from fecal samples. Of 24 offspring analyzed, we identified sires for 21. Paternity success was significantly correlated with social rank, with alpha males siring a disproportionate number of offspring. However, both middle- and low-ranking males also fathered offspring, and the priority-of-access model provided a relatively poor prediction of which males would be successful and under what circumstances. The concentration of paternities among only 7 males and the tendency for high-ranking males to sire offspring of multiparous females suggest that both individual variation in male quality and the resource value of particular females may be mediating factors. In comparison with other chimpanzee studies, our results support the hypothesis that larger male cohort size reduces the ability of the alpha male to monopolize females, though within our study, male number did not affect the success of the alpha. Successful sires were not necessarily those who achieved the highest mating success with the females whose offspring they sired, but were those who demonstrated higher investment by spending significantly more time in association with these females. Finally, we estimate extra-group paternity at 0-5%, supporting other evidence that the community serves as the primary reproductive unit in chimpanzees. Am J Phys Anthropol 142:417-428, 2010. (C) 2009 Wiley-Liss, Inc.
  • Newton-Fisher, N. (2010). Dr Nicholas Newton-Fisher: I watched as an adult male tore an infant chimp to pieces. The Independent [Online]. Available at: http://www.independent.co.uk/voices/commentators/dr-nicholas-newtonfisher-i-watched-as-an-adult-male-tore-an-infant-chimp-to-pieces-2006830.html.
  • Brosnan, S., Newton-Fisher, N. and Van Vugt, M. (2009). A melding of the minds: when primatology meets personality and social psychology. Personality and Social Psychology Review [Online] 13:129-147. Available at: http://dx.doi.org/10.1177/1088868309335127.
    Social/personality psychology and behavioral primatology both enjoy long histories of research aimed at uncovering the proximate and ultimate determinants of primate--human and nonhuman--social behavior. Although they share research themes, methodologies and theories, and their studied species are closely related, there is currently very little interaction between the fields. This separation means that researchers in these disciplines miss out on opportunities to advance understanding by combining insights from both fields. Social/personality psychologists additionally miss the opportunity for a phylogenetic analysis. The time has come to integrate perspectives on primate social psychology. Here we provide a historical background and document the main similarities and differences in approaches. Next we present some examples of research programs that may benefit from an integrated primate perspective. Finally, we propose a framework for developing a social psychology inclusive of all primates. Such a melding of minds promises to greatly benefit those who undertake the challenge.
  • Emery Thompson, M., Newton-Fisher, N. and Reynolds, V. (2006). Probable community transfer of parous adult female chimpanzees in the Budongo Forest, Uganda. International Journal of Primatology [Online] 27:1601-1617. Available at: http://dx.doi.org/10.1007/s10764-006-9098-0.
    Female chimpanzees with dependent offspring generally avoid border areas of their community's home range because they risk aggression and infanticide from extracommunity males. Typically, only nulliparous females risk crossing the boundary areas to transfer between communities; while immigration of parous females occurs, it is extremely rare and dangerous for the females and their offspring. In the Budongo Forest, Uganda, where researchers have continuously studied the Sonso community since 1990, our field data provide strong indications that >= 5 adult females with offspring have immigrated into the community. If the interpretation is correct, then it has fundamental implications for our understanding of female chimpanzee social strategies and dispersal patterns. Further, the identification of such a large number of new individuals within a short time frame is remarkable and suggests a major event, such as the breakup of a neighboring community or major habitat disturbance. We explore the evidence that points to the events as immigrations and discuss the implications for understanding the chimpanzee social system.
  • Newton-Fisher, N. (2006). Female coalitions against male aggression in wild chimpanzees of the Budongo Forest. International Journal of Primatology [Online] 27:1589-1599. Available at: http://dx.doi.org/10.1007/s10764-006-9087-3.
    In the wild, female chimpanzees (Pan troglodytes) are subject to male aggression that at times can be prolonged or particularly violent. Cooperatively retaliating to such aggression, a strategy observed in the con-generic Pan paniscus, has not been reported from the wild despite more than four decades of detailed behavioral study across a number of populations and reports of such behavior among captive female chimpanzees. If the reports from captivity represent an inherent capacity, then the absence of similar reports from wild populations suggests that female may only be able to form coalitions under appropriate ecological and demographic conditions. During a study of aggression of male and female aggressive interactions among chimpanzees of the Budongo Forest, Uganda, wild adult female chimpanzees sometimes formed coalitions with one-another to retaliate against male aggression. This may be possible because these females tend to be more gregarious than those in other populations of East African chimpanzees, as has been suggested by other studies of the same population. These observations suggest that the extent and variation of female chimpanzee social strategies need reconsideration, and strengthens the argument that at least some of the differences between chimpanzees and bonobos may be more of degree than of kind.
  • Slocombe, K. and Newton-Fisher, N. (2005). Fruit sharing between wild adult chimpanzees (Pan troglodytes schweinfurthii): a socially significant event?. American Journal of Primatology [Online] 65:385-391. Available at: http://dx.doi.org/10.1002/ajp.20123.
    Food-sharing is a habitual aspect of chimpanzee (Pan troglodytes) life, although sharing of plant foods between unrelated adults is rare. Observations of such behaviour have typically been interpreted as the outcome of a process by which individuals, unable to otherwise gain access to the food, manage to obtain a nutritional benefit. Here we present behavioural details and acoustic analysis from an observation of food sharing between unrelated adult wild chimpanzees that we suggest cannot be explained using traditional nutrition-based models. Instead we propose the exchange is only understandable as a socially important event and we cite two further observations from the same population that support this suggestion.
  • Newton-Fisher, N. (2004). Hierarchy and social status in Budongo chimpanzees. Primates [Online] 45:81-87. Available at: http://dx.doi.org/10.1007/s10329-003-0064-6.
    The status hierarchy is fundamental in the lives of male chimpanzees. This study describes the dominance interactions and social status among adult male chimpanzees of the Sonso community in the Budongo Forest Reserve, Uganda, during the period that they were first studied (1994 & 1995). Social dominance is typically measured using the behaviour of either the subordinate or the dominant individual, but as a relationship is dependent on the behaviour of both parties and this study explicitly used both subordinate and dominant behaviours to investigate the status hierarchy. Among adult males of the Sonso community, agonistic interactions occurring at a low rate and pant-grunts were rare, but males could be ranked into separate hierarchies of agonistic dominance and pant-grunting (labelled ‘respect’) using ratios of behaviour performed / behaviour received. These hierarchies were combined to form a single hierarchy of social status that divided the males among five distinct status levels. The highest status level was held by an alliance between two males who replaced the previous alpha male during the first part of the study. Neither male in this alliance partnership pant-grunted to the other, although the reason for cooperative behaviour was unclear. Although the nominally beta male was treated as such by other adult males, he achieved surprisingly little mating success. Budongo Forest chimpanzees do not warrant the sometimes-expressed view that they are non-aggressive and peaceable and the broad pattern of their status interactions matches with that seen in other chimpanzee populations.

Book section

  • Newton-Fisher, N. (2015). The Hunting Behavior and Carnivory of Wild Chimpanzees. In: Handbook of Paleoanthropology. Springer, pp. 1661-1691. Available at: http://dx.doi.org/10.1007/978-3-642-39979-4_42.
    The pursuit, capture and consumption of small- and medium-sized vertebrates appear to be typical of all chimpanzee (Pan troglodytes) populations, although large variation exists. Red colobus monkeys (Piliocolobus sp.) appear to be the preferred prey, but intensity and frequency of hunting varies from month to month and among populations. Hunting is a predominately male activity and is typically opportunistic, although there is some evidence of searching for prey. The degree of cooperation during hunting, as well as prey selection, varies between East and West African populations and may be related to the way the kill is divided: in West Africa, hunters often collaborate, with kills tending to be shared according to participation, whereas in East Africa, cooperation in hunting is more limited and the kill is typically consumed selfishly, or divided in response to harassment (begging) by others. In some cases it may be shared tactically, trading meat with other males to strengthen alliances. The adaptive function of chimpanzee hunting is not well understood and a variety of hypotheses have been proposed. Ideas that chimpanzees hunt to make up for nutritional shortfalls, or to acquire meat to trade for sex, have failed to find empirical support, while recent work favors nutritional benefits of some kind. Nevertheless, cross-population studies evaluating multiple hypotheses are in their infancy, and there is much to be learned. In particular, very little is known about hunting of non-primates, particularly ungulates, or the impact that variation in levels of hunting, and of carcasses to share and consume, has on patterns of chimpanzee behavior. If one goal of studying this topic is to shed light on the behavioral ecology of hominins, then efforts to understand the diversity of hunting and carnivory in wild chimpanzees are needed.
  • Humle, T. and Newton-Fisher, N. (2013). Culture in Non-human Primates: Definitions and Evidence. In: Ellen, R. F., Lycett, S. J. and Johns, S. E. eds. Understanding Cultural Transmission in Anthropology: A Critical Synthesis. Berghahn Books.
    The attribution of culture to non-human animals has been controversial and continues to fuel much heated debate, much of which hinges on how culture is defined. We illustrate how definitions have become less human-centric as observations from wild primates have led to a new discipline – cultural primatology – and challenged the idea of culture as uniquely human. Although cultural primatology has it roots in field studies of wild primates, the weight of captive studies across a variety of species has resulted in a comparative view of culture which emphasises the mechanism of transmission. We argue that, while this has broadened the species and behaviours that have been considered ‘cultural’, it weakens the usefulness of comparative studies in understanding the evolutionary origins of human culture. We prefer a definition that centres on the concept of culture as an array of behaviour patterns across multiple domains that vary between groups or populations due to differing histories of social transmission. We argue for the necessity of field studies of wild primates in the comparative study of culture, providing examples of how such studies allow both the identification of cultures across non-human primate social groups and the mechanisms by which behaviours are transmitted both within and between groups. Such studies are essential for an ecologically valid understanding of culture, and to investigate how social dynamics, ecology and demographics shape culture and the diffusion and dissemination of socially learned behaviours.
  • Newton-Fisher, N. and Emery Thompson, M. (2012). Comparative evolutionary perspectives on violence. In: Shackleford, T. K. and Weekes-Shackelford, V. A. eds. The Oxford Handbook of Evolutionary Perspectives on Violence, Homicide, and War. Oxford University Press. Available at: http://ukcatalogue.oup.com/product/9780199738403.do.
    Perhaps more than for any other human behavior, the evolutionary heritage of violence has been the subject of vigorous debate: whether shared patterns of intra-specific aggression between humans and other species doom us to a bloody existence. This chapter reviews intra-specific aggression and violence among mammalian species, focusing on primates. It highlights three themes: aggression is a part of everyday life for most social animals; the vast majority of conflicts in animal societies are of low intensity; there are extraordinary examples within the broad spectrum of aggressive behaviors seen in nonhumans that conform to even the most anthropocentric definitions of violence. To illustrate the latter, the chapter reviews violence in chimpanzees, the extant species most closely related to humans and which, next to humans, exhibits the most spectacularly gruesome and varied aggressive repertoire in mammals.
  • Newton-Fisher, N. (2007). Chimpanzee hunting behavior. In: Henke, W. and Tattersall, I. eds. Handbook of Paleoanthropology. New York: Springer-Verlag, pp. 1295-1320.
    The pursuit, capture and consumption of small-and medium-sized vertebrates, appears to be typical of all chimpanzee (Pan troglodytes) populations, although large variation exists. Red colobus monkeys (Piliocolobus sp.) appear to be the preferred prey but intensity and frequency of hunting varies from month to month and between populations. Hunting is a predominately male activity and is typically opportunistic, although there is some evidence of searching for prey. The degree of cooperation during hunting, as well as prey selection, varies between East and West African populations and may be related to the way the kill is divided: in West Africa, hunters often collaborate, with kills tending to be shared according to participation, whereas in East Africa, the kill is typically divided tactically by the male in possession of the carcass, trading meat with females in return for sex or with other males to strengthen alliances, and cooperation in hunting is more limited. The adaptive function of chimpanzee hunting is not well understood, although it appears that it may be both a means to acquire a nutritionally valuable commodity that can then be traded and as a means for males to display their prowess and reliability to one another.
  • Okecha, A. and Newton-Fisher, N. (2006). The diet of olive baboons (Papio anubis) in the Budongo Forest Reserve, Uganda. In: Newton-Fisher, N. E., Notman, H., Paterson, J. D. and Reynolds, V. eds. Primates of Western Uganda. New York: Springer, pp. 61-73.
    Baboons (genus Papio) are large-bodied, semi-terrestrial monkeys that occupy a diversity of habitats. Across populations, they show wide variation in dietary composition and in their foraging behaviour. Early studies concluded that baboons were generalist feeders, but it is now clear that baboons selectively exploit their environment. The baboon foraging adaptation, in general terms, may be to selectively exploit a wide array of plant foods to satisfy energetic and nutritional needs when faced with a shifting mosaic of possibilities.The variation in diet between baboon populations has been used to investigate the influence of ecology on both diet and foraging behavior, but few such quantitative data have been published for forest- dwelling baboons. Savannah and forest habitats present different ecological conditions and resources to foraging baboons: Tropical forests typically show less dramatic seasonality in comparison with savannah habitats, and so forest-living baboons should experience a wider and potentially more consistent resource base, which may influence both dietary composition and feeding time.
    Such data will also be useful for interspecific comparisons. Forest- living baboons may be significant competitors with sympatric chimpanzees (Pan troglodytes) despite contrasts in foraging strategies. While baboons follow a selective–generalist strategy, chimpanzees typically show a reliance on ripe fruit. Baboons may have the advantage in scramble competition where the two species target fruit of the same plant species, as they are better able to digest unripe fruit. There are few data available to test whether such competition occurs. Here, as a preliminary step in investigating potential feeding competition and to broaden the knowledge of baboon foraging strategies, we describe the diet of forest-living olive baboons (Papio anubis) from the Sonso region of the Budongo Forest Reserve, where they live sympatrically with chimpanzees (P. t. schweinfurthii). The diet of these chimpanzees has been well studied, but comparable data for baboons have not been collected.

Conference or workshop item

  • Newton-Fisher, N. and Kaburu, S. (2016). Demography and despotism: making sense of inter-community differences in the behaviour of wild male chimpanzees (Pan troglodytes). In: 26th Congress of the International Primatological Society.
    Comparative approaches are fundamental to behavioral ecology, yet differences in methodology and approach limit opportunities for this when studying chimpanzees. We studied two communities, the Sonso community of the Budongo Forest, Uganda, and M-group of the Mahale Mountains National Park, Tanzania using a common set of definitions and protocols focusing on male social interactions. We found striking differences between the two communities. Sonso males were similar to those in other East African communities, showing evidence of effective aggressive coercion of females, the provision of agonistic support and the trading of grooming for rank-restricted commodities. By contrast M-group males were ineffective in their use of aggression to coerce females, and neither seemed to provide nor trade for commodities such as agonistic support or social tolerance. Placing our data in a comparative context, we identified variation in structural despotism and in both membership and age profiles of adult male cliques. In our samples, Sonso males showed a high level of structural despotism while the M-group male fell at the opposite end of the cross-community distribution, being more structurally egalitarian. We discuss how demography, through aggressive interactions and structural despotism, impacts male social behavior (including both grooming & mating strategies). Our findings also highlight how the degree of structural despotism in a community is labile and not a species-specific characteristic.
  • Lowe, A. and Newton-Fisher, N. (2016). Countering the varying risk of infanticide: chimpanzee mothers adjust their association patterns relative to male rank and infant age. In: British Association for Biological Anthropology and Osteoarchaeology Conference 2016.
    Infanticide by males is common in mammals. According to the sexually-selected infanticide hypothesis, risks increase when males can kill unrelated infants, and when an infanticidal male’s chance of siring the replacement infant is high. Infanticide occurs in chimpanzees, and rank predicts paternity, so infanticidal low-ranking males are unlikely kill their own offspring while males who rise in rank are more likely to father potential future infants than any existing ones. Given that mothers should be selected to reduce infanticide risk, we predicted that they would attempt to adjust the exposure of their infants to potentially-infanticide males: specifically, that they would reduce association with low-ranking and rank-rising males. We examined data on female association patterns collected from the Budongo Forest, Uganda, during a period encompassing both relative stability in the male hierarchy and a period of instability with a mid-ranking male rising rapidly in rank. We found that in the period of instability, mothers with younger infants reduced their association with mid-low ranking males, and particularly the rank-rising male. Our results support the sexually-selected hypothesis for infanticide, and demonstrate that female chimpanzees are sensitive to the relative risks posed by adult males.
  • Newton-Fisher, N. and Medland, K. (2016). Male mating strategies in a fluid social system: Dunbar’s general model of mating strategies revisited. In: 26th Congress of the International Primatological Society.
    Dunbar’s general model of mating strategies provides a useful, but largely ignored approach for understanding the fundamental choice faced by male: to remain with females in order to exploit paternity opportunities when they arise, a social strategy, or to search for these opportunities on an ongoing, roving, basis. The model has been criticized in both its assumptions, and the data used to test it. Using published data from six different communities of chimpanzees, we address three questions: How robust is Dunbar’s original model; how robust is its support for social males in West and roving males in East Africa; and how real are supposed differences in female gregariousness between West and East African chimpanzees? We test the original model against two variants and find that despite quantitative differences, all three generate the same qualitative prediction. Thus for chimpanzees at least, Dunbar’s original model can be regarded as fairly robust. However, this prediction is that chimpanzee males should pursue a ‘roving’ strategy and that this was as true for West as for East African chimpanzees. Furthermore, the comparative data did not support an East/West dichotomy in female gregariousness. This study highlights the importance of the collection and reporting of comparable data, the utility of simple mathematical models, and the similarities in behaviour across subspecies of chimpanzees.
  • Newton-Fisher, N. (2014). Living with wild chimpanzees. In: Discovering Places: Uganda.
  • Market forces predict the distribution of grooming among wild male chimpanzees. (2013). In: Primate Society of Great Britain, Spring Meeting.
  • Johns, S., Hargrave, L. and Newton-Fisher, N. (2013). Red is not a proxy signal for human female genitalia. In: European Human Behaviour and Evolution Association Conference.
  • Kaburu, S. and Newton-Fisher, N. (2012). Grooming reciprocity among wild chimpanzees of the Mahale Mountains National Park. In: 24th Congress of the International Primatological Society.
  • Johns, S., Hargrave, L. and Newton-Fisher, N. (2012). Red is not a proxy signal for human female genitalia. In: 81st Meeting of American Association of Physical Anthropologists.
  • Inoue, S., Kaburu, S. and Newton-Fisher, N. (2012). Reaction to the alpha-male’s dead body after a within-group killing among wild chimpanzees: a case report. In: 28th Congress of the Primate Society of Japan.
  • Newton-Fisher, N. and Lee, P. (2011). Grooming reciprocity in wild male chimpanzees. In: 80th Meeting of American Association of Physical Anthropologists.
  • Newton-Fisher, N. and Lee, P. (2010). Grooming reciprocity in wild male chimpanzees. In: 23rd Congress of the International Primatological Society.
  • Emery Thompson, M., Muller, M., Newton-Fisher, N., Gilby, I., Kahlenberg, S., Machanda, Z., Zuberbuhler, K. and Wrangham, R. (2010). Inter- and Intra-Community Variation in Aggression by Adult Male Chimpanzees. In: 79th Meeting of the American Association of Physical Anthropologists. p. 101.
  • Birkett, L. and Newton-Fisher, N. (2010). Recognising the subjective experience in animals with mental disorders. In: Animals, Research, and Alternatives: PCRM Conference.
  • Birkett, L. and Newton-Fisher, N. (2010). Recognising psychological abnormality in chimpanzees (Pan troglodytes) using human psychiatric principles. In: Animals, Research, and Alternatives: PCRM Conference.
  • Newton-Fisher, N. (2009). Culture in non-human primates: definitions and evidence. In: Interdisciplinary Approaches to Culture.
  • Newton-Fisher, N., Emery Thompson, M., Reynolds, V., Boesch, C. and Vigilant, L. (2008). Paternity and Social Rank in Budongo Forest Chimpanzees. In: 22nd Congress of the International Primatological Society.
  • Newton-Fisher, N. (2006). Living alone or working together? Behavioural responses to male aggression by female chimpanzees in the Budongo Forest, Uganda. In: 21st Congress of the International Primatological Society.
  • Newton-Fisher, N. (2005). Coercive aggression in wild chimpanzees. In: Research in Anthropology.
  • Newton-Fisher, N. (2005). The broader perspective: sociality in primates. In: EAESP Workshop: Understanding the Human Social Animal.
  • Newton-Fisher, N. (2005). Reciprocity, partner choice and the function of chimpanzee intelligence.
  • Newton-Fisher, N. (2004). Data resolution and analysis technique in observational studies of ranging patterns. In: 20th Congress of the International Primatological Society.

Edited book

  • Newton-Fisher, N.E., Notman, H., Paterson, J.D. and Reynolds, V. eds. (2006). Primates of Western Uganda. Chicago: Springer.


  • Newton-Fisher, N. (2012). Animal Behaviour Pro: 1.4.4. [iTunes download]. Available at: https://itunes.apple.com/gb/app/animal-behaviour-pro/id579588319?mt=8.
    iOS App (for iPhone & iPod Touch) that provides a professional-level solution to the logging of animal (including human) behaviour, implementing discipline-standard protocols in a highly flexible structure that will useable across a range of species.
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