Emergence of huddling, aggregation, pup flow, and thermoregulation in an agent-based model of rodent huddling.

Abstract

<p>An agent-based model of rodent thermoregulatory huddling was simulated through a range of ambient temperatures. In this model, rodents are represented as circles moving in a large circular arena, which exchange heat when they make contact, and turn to minimize the discrepancy between <i>T</i>_<i>B</i> and <i>T</i>_<i>P</i>. Plots show averages from twenty simulations run at each ambient temperature. <b>A</b> Huddling is defined in the agent-based model in terms of the proportion of the surface area of each agent that is exposed, i.e., the length around its circumference that is not overlapping with other agents in the arena. <b>B</b> Agents that are in contact in the arena are labelled as belonging to the same group, and the number of groups and the huddling metric again provide complementary profiles of the phase transition. <b>C</b> Pup flow in the agent-based model is defined as the absolute value of the time derivative of the exposed surface area of the agents, and like the thermodynamic model is shown here to predict a peak in pup flow at the critical temperature of the phase transition. <b>D</b> At lower ambient temperatures, the average body temperature is maintained above baseline due to heat exchange via huddling interactions. Data are comparable with equivalent figures generated by [<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1005378#pcbi.1005378.ref009" target="_blank">9</a>], which describes the agent-based model in full, and results should be compared to the corresponding panels in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1005378#pcbi.1005378.g001" target="_blank">Fig 1</a> obtained from the new thermodynamic huddling model. Error bars show the standard deviation for huddling, group size, and body temperature metrics, and standard error for pup flow.</p