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of the commons [50, 51], where selfish actions that provide an individual short-term benefit lead to a decrease in overall group fitness. 

## Tragedy of the commons in heterogeneous groups 

To explore this apparent tragedy of the commons scenario further, we directly compare vigilance and fitness values from the forced and optional grouping experiments alongside a third experiment where we force the population to forage and survive as individuals. Figure 4 shows that when given the choice to group in the homogeneous treatments, prey behavior closely mirrors the behavior observed when forced to forage in a group. This observation confirms the previous suggestion that collective vigilance in homogeneous groups provides a fitness benefit that positively selects for gregarious foraging behaviors. 

In contrast to the homogeneous populations, heterogeneous populations are much less likely to evolve gregarious foraging behaviors. Heterogeneous/iteroparous populations never 

