Figure 5: Model simulation results.

Results from a stochastic model of emigrating colonies choosing between two identical nests, which they could visit prior to emigration. Results are shown for parameter values estimated from a previous empirical dataset³⁰ (see Methods), but are qualitatively similar over a broad range of parameter values (Supplementary File 2). By definition, nest1 corresponds to the nest previously visited by a majority of informed workers. Simulations were run until all scouts were committed to a nest. Heatmaps show the outcome of emigrations, averaged over 10000 simulations for each combination of parameter values a_i (average probability of informed workers independently accepting the nest they know of) and w_d (relative likelihood of informed workers discovering the nest they know of rather than the other nest). The top row shows the preference for nest1, ranging from 0 (full preference for nest2) to 1 (full preference for nest1). The middle row shows colony cohesion, ranging from 0 (colonies equally split between both nests) to 1 (consensus for a single nest). The bottom row shows the decision time, expressed as simulation time steps. Results are shown for p₁ (proportion of informed workers that visited nest1) ranging from 0.5 (left; as many informed workers for both nests) to 1 (right; choice between familiar nest1 and unfamiliar nest2). Within each panel, the left-most column corresponds to colonies using a fixed quorum rule, i.e. where all informed workers have the same low probability of independent acceptance as uninformed workers (a_u); the framed bottom left corner corresponds to naïve colonies (a_i = a_u and w_d = 1), and the black cross corresponds to the values of a_i and w_d estimated from the empirical dataset³⁰. Note that we assigned different values of a to different groups of informed workers according to the graded ‘copy-when-uncertain’ strategy, and that a_i represents the average of these values across all informed workers. Preference for the majority nest (nest1) and emigration speed (1/decision time) consistently increased as a_i increased. By contrast, an increase in a_i resulted in decreasing colony cohesion for p₁ ≤ 0.75, but increasing colony cohesion for p₁ = 0.875 (provided w_d is high enough) and for p₁ = 1.