PREY SIZE REVERSES THE OUTCOME OF INTERFERENCE INTERACTIONS OF SCAVENGER ANTS

In the guild of scavenger ants in the Mediterranean habitats studied, there was a separation of prey on the basis of size: small species too k small food items, and large ants collected large items. Nevertheless , some species enlarged their range of prey sizes through social mecha nisms: Aphaenogaster senilis through recruitment in relatively small r etrieval groups and subsequent cooperative carrying, and the small dom inant species (Pheidole pallidula, Tapinoma nigerrimum, Tetramorium se milaeve) through mass recruitment and subsequent prey dissection. Indi vidually foraging and group-recruiting species were more likely to suf fer prey interference and loss when grey were larger, whereas mass-rec ruiting species showed the opposite pattern, losing fewer prey to oppo rtunistic species as prey size increased. These small ants recruited l arge numbers of workers on very large prey and dominated them before t he other species could dissect and carry them to their nests. Each spe cies displayed only one of these strategies, and, thus, prey size was the main factor determining the success of each strategy. Large subord inate species increased exploitation of very large prey by foraging wh en the three mass-recruiting species were not active, whereas the thre e small dominant species increased the exploitation of medium-sized an d large items by foraging at night, when the diurnal large species wer e absent. These dominant mass-recruiting species, however, did not dif fer from each other in respect to prey size and activity period.