Increased Exploration Capacity Promotes Group Fission in Gregarious Foraging Herbivores

Abstract

Many gregarious species display rapid fission-fusion dynamics with individuals frequently leaving their groups to reunite or to form new ones soon after. The adaptive value of such ephemeral associations might reflect a frequent tilt in the balance between the costs and benefits of maintaining group cohesion. The lack of information on the short-term advantages of group fission, however, hampers our understanding of group dynamics. We investigated the effect of group fission on area-restricted search, a search tactic that is commonly used when food distribution is spatially autocorrelated. Specifically, we determine if roe deer (Capreolus capreolus) improve key aspects of their extensive search mode immediately after fission. We found that groups indeed moved faster and farther over time immediately after than before fission. This gain was highest for the smallest group that resulted from fission, which was more likely to include the fission’s initiator. Sex of group members further mediated the immediate gain in search capacity, as post-fission groups moved away at farthest rate when they were only comprised of males. Our study suggests that social conflicts during the extensive search mode can promote group fission and, as such, can be a key determinant of group fission-fusion dynamics that are commonly observed in gregarious herbivores.

Density-Dependent Foraging Behaviors on Sympatric Winter Ranges in a Partially Migratory Elk Population

“…Individuals are expected to return when patch resources recover or depletion in other patches increases the value of the patch (Barraquand and Benhamou, 2008;Van Moorter et al, 2009;Seidel and Boyce, 2015). Concomitantly, in gregarious species, high rates of interaction and conflicts of direction in movement of individuals may limit group speeds (Fortin et al, 2009;Pays et al, 2012;Sigaud et al, 2017), which in turn may put constraints on exploring the environment, reducing foraging intake, or result in group fission (Lardy et al, 2016). Herbivores make compromises between foraging and safety (Lima and Dill, 1990;Verdolin, 2006;Visscher et al, 2017), leading to the generality that risky foraging decreases (Abrams, 1993;Brown, 1999).…”

Individual exploration and selective social learning: Balancing exploration-exploitation trade-offs in collective foraging

“…fusion) into subgroups and benefit from social foraging while avoiding many of the associated costs (e.g., intra-group competition) (Couzin, 2009;Grove et al, 2012b;Grove, 2012;Kummer, 2017;Garg et al, 2021). Our results predict that increased exploration after a fusion event can promote fission and increase foraging efficiency (Lardy et al, 2016). Moreover, our findings provide support to previous hypotheses about the importance of energetically-efficient exploration strategies (such as bipedalism) in promoting extensive fission-fusion and social foraging in early humans under scarce and patchy environmental conditions (Grove et al, 2012a;Isbell and Young, 1996;Kurland and Beckerman, 1985).…”