Biology / Biomedical Sciences
School of Environmental Sciences / Life Sciences

Evolutionary Biology Group

Dr Lesley Morrell's research


Department of Biological Sciences

  • Teaching
  • Research
  • Key Publications
  • Additional


1. Evolution of aggregation behaviour

Mechanisms for aggregation in animals

Aggregation in Animals

When many animals are frightened, perhaps because they detect a predator, they tend to bunch together tightly. This has been called the 'Selfish Herd' because each animal tries to reduce its chance of being captured by the predator by moving in between other individuals, and the best place to be is in the middle (which is selfish because it pushes others to the edge, where they are more vulnerable). But how can animals achieve this? Several 'movement rules' have been suggested. For example, one rule suggests each animal should move towards its nearest neighbour, while other rules suggest that animals should take notice of many others, and how far away they are, before deciding in which direction to move. By modelling these different rules, we have shown that ecological variables (such as group size and density), the time at which predators attack, and the position of an individual within the group all influence the optimal movement rule for an individual.

Funding: NERC (2006-2010)

Collaborators: Dick James (Bath), Bill Romey (SUNY Potsdam), Ben Hirsch (Smithsonian)

Balancing conflicting selection pressures in social decisions

It is well known that individuals associate with others on the basis of species, size, parasite load, colour, familiarity (recent experience with particular individuals) and shared recent environments. Associating by such factors is thought to reduce predation risk by reducing phenotypic oddity (predators are known to preferentially target phenotypically distinct individuals within a group), as well as minimising competition. However, it is likely that animal groups may differ in more than one of these factors, and so animals may have to prioritise the cues that they use when making social decisions. Furthermore, such trade-offs may be influenced by individual state (e.g. the body condition of an individual) or environmental factors (e.g. predation risk, visibility and temperature).

Funding: BBSRC (2007-2011)


2. Environment and behaviour


This research theme aims to understand how the physical and social environment can interact to affect behaviour, using guppies (Poecilia reticulata) and sticklebacks (Gasterosteus aculeatus as model systems. Projects under this theme include:

·Effects of flow, turbidity and prey distribution on prey detection by visual and olfactory predators (with PhD student Freya Johannesen)

·The role of early experience in the development of behaviour (with former PhD student Ben Chapman)

·The effect of environmental and social cues on behaviour

Funding: Faroese Research Council (2010-2013), University of Leeds (2006-2009), The Leverhulme Trust (2005-2006), Association for the Study of Animal Behaviour (2005)

Collaborators: Ben Chapman (Lund), Jens Krause (IGB Berlin), Darren Croft (Exeter)

Colour and behaviour


This theme links strongly into our research into the evolution of aggregation as an anti-predator response. Projects include:

·The role of natural variation in colour pattern in mediating shoaling decisions in rainbowfish (Melanotaenia australis)

·The influence of facultative colour change on patterns of social assortment in both rainbowfish and guppies (Poecilia reticulata)

·Nest ornamentation in three-spined sticklebacks.

Funding: Royal Society (2006-2007 & 2010-2011), Company of Biologists (2006-2007), British Ecological Society (2006-2007),

Collaborators: Jennifer Kelley (UWA)

Ownership conflicts and their resolution

Ownership conflicts and their resolution

My PhD research (University of Glasgow, 2001-2004) focused on the resolution of animal conflicts. I used modelling approaches to investigate two general themes: the division of space, and the allocation of time to different activities. Firstly, I investigated how animals can divide previously unoccupied space to create territories, and on the stability of so-called 'paradoxical' strategies in such situations. Secondly, I have investigated optimal time allocation strategies as a trade-off between two or more mutually incompatible behaviours.

I also studied the assessment rules that individuals use during a conflict, and investigated the applicability of game-theory models of animal conflict to contests in Australian fiddler crabs (Uca mjoebergi) in the field. I also looked at how animals can use visual landmarks to reduce the costs associated with establishing boundaries, and investigated this question empirically using sticklebacks (Gasterosteus aculeatus) and Kribensis dwarf cichlids (Pelvicachromis pulcher).

Funding: NERC (2001-2004), Academy of Finland

Collaborators: Hanna Kokko (Helsinki), Neil Metcalfe (Glasgow), Pat Backwell (ANU), Graeme Ruxton (Glasgow), Jan Lindstrom (Glasgow)


Our research falls into three interlinked themes. Firstly, we are interested in the evolution of social behaviour, specifically the evolution of group-living in response to selection pressures such predation risk. We are also interested in how animals respond to the environment in which they live: this might be the physical environment, such the distribution of resources, or water flow and turbidity, or it might be the social environment – the other individuals around them and how they are behaving. A final, more minor theme, linking particularly with our work on social behaviour, is the role of colour in animal behaviour. We use a combination of theoretical models, controlled empirical studies in the laboratory, and field research to investigate these questions.

I welcome informal applications (by email) from researchers at both postdoctoral and postgraduate levels who are interested in joining my research group and are able to attract their own funding (eg. EU fellowships, international Ph.D. scholarships, visiting researchers).

Key Publications

  • Morrell, LJ, Ruxton, GD & James, R. (in press) The temporal selfish herd. Proceedings of the Royal Society of London Series B
  • Morrell, LJ, Ruxton, GD & James, R. (2010) Spatial positioning in the selfish herd. Behavioural Ecology 21: 1367-1373
  • Rodgers, GM, Kelley, JL & Morrell, LJ. (2010) Colour change and assortment in the western rainbowfish. Animal Behaviour 79: 1025-1030
  • Chapman, BB, Morrell, LJ & Krause, J. (2010a) Unpredictability in food supply during early life drives the development of boldness in fish. Behavioural Ecology 21: 501-506
  • Chapman, BB, Morrell, LJ, Tosh, C, & Krause, J. (2010b) Behavioural consequences of sensory plasticity in guppies. Proceedings of the Royal Society of London Series B 277: 1395-1401
  • Chapman, BB, Morrell, LJ & Krause, J. (2009) Plasticity in male courtship behaviour as a function of light intensity in guppies. Behavioural Ecology and Sociobiology 63: 1757–1763
  • Ioannou, CC, Morrell, LJ, Ruxton, GD & Krause, J (2009) The effect of prey density on predators: conspicuousness and attack success are sensitive to spatial scale. American Naturalist 173: 499-506
  • Dyer, JRG, Croft, DP, Morrell, LJ & Krause, J (2009) Shoal composition determines foraging success in guppies. Behavioural Ecology 20: 165-171
  • Morrell, LJ & Romey, WL (2008) Optimal individual positions in animal groups. Behavioural Ecology 19: 909-919
  • Botham, MS, Hayward, RK, Morrell, LJ, Croft, DP, Ward JR, Ramnarine, I & Krause, J (2008) Risk sensitive anti-predator behaviour in guppies. Ecology 89: 3174-3185
  • Morrell, LJ, Croft, DP, Dyer, JRG, Chapman, BB, Kelley, JL, Laland, KN & Krause, J (2008) Association patterns and foraging behaviour in natural and artificial guppy shoals. Animal Behaviour 76: 855-864
  • Morrell, LJ & James, R (2008) Mechanisms for aggregation in animals: Rule success depends on ecological variables. Behavioural Ecology 19: 193-201
  • Chapman, BB, Morrell, LJ, Benton, TG & Krause, J (2008) Early interactions with adults mediate the development of predator defences in juvenile guppies Poecilia reticulata. Behavioural Ecology 19: 87-93
  • Dyer, JRG, Ioannou, C, Morrell, LJ, Croft, DP, Couzin, ID, Waters, DA, Wong, Y & Krause, J. (2008) Consensus decision making in human crowds. Animal Behaviour 75: 461-470
  • Thomas, POR, Croft, DP, Morrell, LJ, Davis, A, Faria, JJ, Dyer, JRG, Piyapong, C, Ramnarine, I, Ruxton, GD & Krause, J. (2008) Does defection during predator inspection affect social structure in wild shoals of guppies? Animal Behaviour 75: 43-55
  • Piyapong, C, Morrell, LJ, Croft, DP, Dyer, JRG, Ioannou, C & Krause, J. (2007) A cost of leadership in human groups. Ethology 113: 821–824
  • Morrell, LJ, Hunt, KL, Croft, DP & Krause, J. (2007) Diet, familiarity and shoaling decisions in guppies. Animal Behaviour (74: 311-319)
  • Kokko, H, Gunnarsson, TG, Morrell, LJ & Gill, JA. (2006) Why do female migratory birds arrive later than males? Journal of Animal Ecology 75: 1293-1303
  • Croft, DP, Morrell, LJ, Wade, AS, Piyapong, C, Ioannou, CC, Dyer, JRG, Chapman, BB, Wong, Y & Krause, J. (2006) Predation risk as a driving force for sexual segregation: a cross-population comparison. American Naturalist 167: 867-887
  • Kokko, H, López-Sepulcre, A & Morrell, LJ. (2006) From hawks and doves to self-consistent games of territorial behaviour. American Naturalist 167: 901-912
  • Morrell, LJ, Backwell, PRY & Metcalfe NB (2005) Fighting in fiddler crabs Uca mjoebergi: what determines duration? Animal Behaviour 70: 653-662
  • Morrell, LJ, Lindstrom, J & Ruxton, GD (2005) Why are small males aggressive? Proceedings of the Royal Society of London Series B 272: 1235-1241
  • Kokko, H & Morrell, LJ (2005) Mate guarding, male attractiveness and paternity under social monogamy. Behavioural Ecology 16: 724-731
  • Morrell, LJ & Kokko, H (2005) Bridging the gap between mechanistic and adaptive explanations of territoriality. Behavioural Ecology and Sociobiology 57: 381-390
  • Morrell, LJ (2004) Are behavioural trade-offs all they seem? Counter-intuitive resolution of the conflict between two behaviours. Behavioural Ecology and Sociobiology 56: 539-545
  • Morrell, LJ & Kokko, H (2004) Can too strong female choice deteriorate male ornamentation? Proceedings of the Royal Society of London Series B 271: 1597-1604
  • Morrell, LJ & Kokko, H (2003) Adaptive strategies of territory formation.  Behavioural Ecology and Sociobiology 54: 385-395


Lecturer in Evolutionary Biology

Lesley Morrell

PhD students

Gwen Rodgers

University of Leeds (2007-2011, BBSRC)

PhD project: Colour and oddity in fish social behaviour


Freya Johannesen

University of Leeds (2010-2013, Faroese Research Council)

PhD project: Effects of flow, turbidity and prey distribution on prey detection by visual and olfactory predators

Co-supervisor: Alison Dunn (Leeds)


Jen Miller (2011-2014, NERC)

University of Leeds

PhD project: TBA 

Co-supervisor: Bill Kunin (Leeds)


Masters students

Beatrice Downing

University of Leeds

MRes project: Size and oddity in fish behaviour


Previous group members & associates

Dr Jolyon Faria (PhD, 2006-2010) now a postdoc at Princeton

Project: Collective decision making in animal groups

Dr Ben Chapman (PhD, 2006-2009) now a postdoc at Lund

Project: Early experience and behavioural plasticity in the guppy


Helen Kimbell (MRes, 2009-2010)

Project: Mixed-phenotype grouping

Daniel Sidoli (MRes, 2009-2010)

Project: Familiarity-mediated habitat choice

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