The effect of increasing the population density.

<p>In (a-d) we show mean values over 15 simulations. We explore two different parameter combinations: <i>(δ_deplete, δ_disturb) = (0, 0)</i> - white filled circles and <i>(δ_deplete, δ_disturb) = (1, 0.1)</i> - black filled circles (see also legend in panel d). Values for the two different parameter combinations are offset on the x-axis to ensure error bars (+/−1 s.d.) are visible. (a) the size of the largest group in the population normalised by the population size <i>N</i>. Panel (b) shows the angular momentum of the largest group in the population, (c) shows the polarisation and (d) the tortuosity of individual movement. (e,f) movement dynamics and available nutrient field <i>Q</i> for <i>N = 150</i> at the end of a <i>300 second</i> simulation, showing the last second of each individual trajectory. In (e) we show the case when <i>(δ_deplete, δ_disturb) = (0, 0)</i> and in (f) we show log values of the available nutrient field <i>Q</i> for the case <i>(δ_deplete, δ_disturb) = (1, 0.1).</i> Brighter colours indicate higher levels of available nutrients in <i>Q</i>. The colour scales indicating the level of available nutrients differ between (e) and (f), but since individuals do not interact with the nutrient fields in (e) this does not matter. The darker regions in (f) show that the separate groups move slowly through the environment and ‘graze’ the available nutrients. All simulations start from a homogeneous underlying nutrient field <i>U</i>. Other parameters values can be found in the figure or in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0075879#pone-0075879-t001" target="_blank">table 1</a>.