The understanding of the motion of animal groups, such as birds, fish and insects, has been greatly advanced by applying principles of self-organisation – the emergence of global patterns from simple, local, interactions between individuals. The desert locust, Schistocerca gregaria, provides a useful model system for the experimental study of collective behaviour. During plague years, the desert locust can form aggregations extending over hundreds of km. Before developing wings, juvenile locusts form marching ‘bands’ which can maintain group cohesion as they migrate over large distances. In this thesis I investigate locust aggregation, group motion and individual interactions. I also apply the same principles to a study of human behaviour. In Chapter 2, I describe the automated tracking methods that I developed and used to collect the data for the rest of the thesis. In the experiments described in Chapter 3, the relative strengths of the attraction to conspecifics and environmental heterogeneities were explored by presenting groups of locusts with two aggregation sites. I found that locusts had a preference to enter the site with the higher population. The locusts formed dynamic aggregations on the sites; no site was consistently more populated than the other, but individuals were significantly more attracted to the site with the higher current population. In Chapter 4, I consider the effect of marching experience on locust behaviour. Groups of locusts that had experience of directed marching, followed by a sudden reduction in density, behaved indistinguishably from those that had only experienced the lower density throughout, indicating a lack of hysteresis effects in collective responses to change in local population density. In Chapter 5, I investigate a locust’s response to its nearest neighbour. I quantified a locust’s propensity to start or stop moving according to the relative position, orientation and movement of its nearest neighbour. In Chapter 6 the techniques developed studying the locusts were applied to human groups. The response of people to different sized groups was quantified, replicating an earlier study in New York. The response was weaker in Oxford but had the same characteristics of the previous study, showing an initially linear response which saturated. The spatial distribution of gaze copying was anisotropic, tending to occur behind the group.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:494402 |
| Date | January 2008 |
| Creators | Hale, Joseph J. |
| Contributors | Simpson, S. J. ; Sumpter, D. J. T. ; Couzin, I. D. ; Taylor, G. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:041ae2be-cc9d-4cda-9e3c-36f2709853db |
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