Original Article

The foraging strategy of Formica sanguinea (Hymenoptera: Formicidae), a facultative slave-maker

Ślipiński, P., Markó, B., Włodarczyk, T. & Czechowski, W.

Abstract: There are almost no hard data on the competitive status of Formica sanguinea, and previous studies focus mainly on its spectacular lifestyle as a slave-maker. It is usually described as an aggressive and territorial species, the latter due to its raiding behaviour and morphological resemblance to species of the subgenus Formica s. str. (typical territorial species and top dominants). A series of field observations using baits was carried out across the longitudinal extent of F. sanguinea’s range in Europe, from Finland through Poland to Romania. The main objective of the present study was to determine the competitive abilities of F. sanguinea and its status in the interspecific ant hierarchy. We also investi gated the changes in the competitive abilities of F. sanguinea along the meridional axis of the species’ range. Based on our results, the distribution of F. sanguinea foragers around the nest showed a distance dependent pattern, with fewer individuals present in distant arenas and at distant baits. While in the absence of baits, other ant species were seemingly not influenced by the abundance of F. sanguinea, this changed in the presence of baits, showing that F. sanguinea has a negative effect on other species. Still, many baits were exploited by other ant species around the studied nests. There were also clear differences among the study regions in terms of bait utilisation, with Finnish colonies exploiting most of baits, while Romanian colonies mostly neglecting them. In light of the present study and due to the complexity of the competitive strategy of the species, we believe that F. sanguinea does not fall into the conventionally arranged three level hierarchy of interspecific ant competition. In addition, F. sanguinea’s competitive ability may depend on local ecological conditions as revealed by the comparison of different populations across Europe.