Comparison of solitary and collective foraging strategies of Caenorhabditis elegans in patchy food distributions

The benefits of social behaviour in insects and vertebrates are well-documented in terms of mating success and predator avoidance. Social foraging has also been shown to benefit organisms in environments where food is patchily distributed, but whether this is true in the case where organisms do not rely on long-range communications to coordinate their social behaviour has been understudied. To address this question, we use the tractable laboratory model organism Caenorhabditis elegans, where a social strain (npr-1 mutant) and a solitary strain (N2) are available for direct comparison of foraging strategies. We first develop an on-lattice minimal model for comparing social and solitary feeding strategies, finding that social agents benefit from feeding faster and more efficiently simply due to group formation. To compare these simulation results with real experimental data, we modify our minimal model to incorporate the specific feeding behaviours of the npr-1 and N2 strains. Surprisingly, the resultant strain-specific model predicts that the solitary strain performs better than the social one in all food distribution environments that we tested, which we confirm with lab experiments. Additional computational experiments identify the N2 strain9s higher feeding rate to be the key factor underlying its advantage over npr-1 worms. Our work highlights the difficulties in addressing questions of optimal behaviour, and the valuable role of modelling as a guiding principle.