Refuse dumps of leaf‐cutting ants as a deterrent for ant herbivory: does refuse age matter?

Abstract

AbstractLeaf‐cutting ants often avoid contact with their waste because it harbors microorganisms that are dangerous to the ants and their symbiotic fungus. Therefore, the use of ant waste (i.e., refuse dumps) has been proposed as a deterrent method against leafcutter attack. We tested experimentally whether the age of the refuse dump (fresh vs. old) affects the herbivory‐deterrent effect against the leaf‐cutting ant Acromyrmex lobicornis Emery (Hymenoptera: Formicidae). Refuse placed around seedlings significantly delayed the initiation attacks of leaf‐cutting ants, and this deterrent effect decreased gradually over a period of 30 days. The initial strength of this decrease was the same for newly‐discarded ( ‘new’) refuse and refuse from the bottom of the ants’ waste pile (‘old’ refuse). However, the loss of deterrent effect over time was more rapid for new than old refuse. A further experimental manipulation, replacement of refuse every 3 days, had no effect on the deterrent effect for old refuse, but increased this effect for new refuse, although the amount of this increase gradually weakened over the course of the 30‐day experiment. We speculate on the possible causes of these effects, their consequences for the hygienic behavior of leaf‐cutting ants, and on the use of ant debris as short‐term control method against leaf‐cutting ants.