Summary: Co-existence of learners and stayers maintains
the advantage of social foraging
Sigrunn Eliassen,* Christian Jørgensen and Jarl Giske
Department of Biology, University of Bergen, PO Box 7800, N-5020 Bergen, Norway
Question: To what extent can learning facilitate group formation in a social forager?
Model features: An individual-based simulation model is used to explore frequency- and
density-dependent interactions between mobile learners and non-selective stayers that forage
in a patchy resource environment.
Key assumption: Foraging efficiency peaks at intermediate group sizes.
Conclusions: Frequency-dependent interplay between mobile learners and sedentary stayers
represents a general mechanism of group formation that maintains the advantage of social
foraging. When rare or at moderate frequencies, learners redistribute and aggregate in groups
of optimal size. This enhances the foraging performance of both learners and stayers. When
the learning strategy dominates in the population, group size dynamics become unstable,
resource intake for learners drops, and stayers do best. The strategies mutually benefit from
each other and may potentially co-exist.
Keywords: frequency dependence, group formation, group size, individual-based model,
learning, optimal foraging theory, social foraging.