Spatial and temporal foraging overlaps in a Chacoan ground-foraging ant assemblage

In arid habitats ant temporal foraging results from a set of trade-offs between species food discovery and food domination ability and between species thermal tolerance and behavioral dominance. We investigated how this set of trade-offs structures the spatial co-occurrence of ants during foraging, hence focusing on interspecific competition. The consequences of food type on the spatio-temporal foraging structure were also studied because food preferences were expected to optimize the restricted foraging time and space of thermophilic species. The food partitioning between 24 species attracted to protein or carbohydrate baits was studied in a dry forest of the Paraguayan Chaco. Baits were spaced at one meter intervals and inspected every 15 min over 90-min sessions conducted during mornings and afternoons. Null model analyses revealed a temporal food partitioning during afternoon sessions and a spatial partitioning, influenced by both thermal conditions and interspecific competition. Bait type did not influence the spatio-temporal foraging. Unexpectedly, evidence of interspecific competition was scarce and avoidance rather than overt conflicts appeared to be the rule of thumb. Overall, the spatio-temporal food exploitation at a small scale was affected by temperature and stochastic processes. This demonstrates that chance structures ant foraging even in constraining arid environments.