collective vigilance? In the presence of even a small penalty for foraging in groups, we observe that only prey in homogeneous groups with a semelparous reproductive strategy are capable of evolving gregarious foraging behavior (Figure 6). This finding suggests that, in the absence of un- limited food resources or extreme predation rates, collective vigilance (i.e., the many eyes hypothesis) is insufficient to select for gregarious foraging. However, there may be impor- tant aspects of natural systems that select for gregarious foraging that we did not model here. For example, predators have been observed to preferentially attack non-vigilant prey in groups [55], which would require prey to be vigilant even without the benefit of collec- tive vigilance. Thus, it would be informative in future work to model such a preference for non-vigilant prey and observe the evolution of gregarious foraging under those conditions. The experimental platform presented here enables a plethora of hypotheses to be studied in future work. Given that there is considerable evidence suggesting that foraging and vig- ilance behaviors are not mutually exclusive in some species [56–58], it would be instructive to relax that assumption in this model and make foraging only a “reduced vigilance” state. Furthermore, we assume here that prey cannot detect the size of their group; a useful exten- sion would be to allow prey to detect their group’s size and study collective vigilance in prey that evolved in varying group sizes. We also assume here that prey always communicate the presence of the predator to their group members. Given that it may not always be evolu- tionarily advantageous to aid other group members, another informative extension would be to allow prey to optionally make their alarm signals upon detection of the predator. Finally, there are several hypotheses other than the many eyes hypothesis that could be explored with a model similar to the one presented here, such as the predator confusion hypothesis [20] and the selfish herd hypothesis [13, 14]. Once all of these hypotheses have been studied in isolation, we can then combine them into a single model to study their relative importance and separate the adaptive benefits (those that select for the evolution of grouping) from the chance side effects of grouping. Such experiments will be invaluable for understanding how 19