Optimal foraging can drive emergent initiator-follower dynamics in social groups

Deciding when and where to move is a challenge for group-living animals as
differences in preferences must be resolved for the group to maintain
cohesion. In many species, consensus is reached through shared
decisions-making, whereby group members initiate group movements by
stopping foraging and making directed movements away from a feeding
source. Yet, despite being widespread, it is unclear how this initiation
process has emerged in animal groups, and theory has yet to resolve the
paradox of why some individuals forego foraging to instigate collective
movements. By applying theoretical predictions from the marginal value
theorem to heterogeneous foraging groups, we show that (i) movement
initiations can reduce subsequent within-group conflict over when to
depart, (ii) habitat heterogeneity and within-group differences in
foraging rate shape who initiates, and (iii) different forms of collective
decision-making can emerge under different environmental conditions. These
results demonstrate that optimal foraging theory can resolve outstanding
questions about leadership in collective movements of animal groups.