O efeito de formigas (Formicidae) predadoras no decaimento da massa de carcaças de pequenos vertebrados

Abstract

Vertebrate carcasses account for a significant portion of the matter and energy that flow within ecosystems, and attract a wide range of decomposers, scavengers, and predators. Among these, necrophagous flies are one of the main insect groups that remove decomposing animal matter. They use carcasses as development sites for their larvae, which rapidly consume carrion. Other insects, such as ants, are also virtually ubiquitous on vertebrate carcasses in terrestrial ecosystems, but little is known about their effects on carrion decay. Several ant species have been recorded preying on necrophagous fly larvae and adults. However, the effects of only a few predatory ant species have been quantitatively tested, and there are conflicting results in the literature. In this study, we tested the effects of four predatory ant species on carcass mass loss and the mass of fly larvae developing in the carcasses. We conducted an experiment in which we deployed carcasses of Rattus norvegicus near colonies of the ant species Ectatomma brunneum, Pheidole oxyops, Solenopsis geminata, and Solenopsis substituta, as well as carcasses from which ants were excluded. We compared carcass mass loss and fly larval mass over a 96-hour period between carcasses exposed to ants and those in the ant-exclusion treatment. With the exception of S. geminata, the ant species studied did not significantly alter remaining carrion mass, larval mass, or the patterns of decay relative to the ant exclusion. Workers of S. geminata covered carcasses with soil and monopolized them, which resulted in lower larval mass and slower decay. In conclusion, the effect of ants on carcass removal varies strongly among species, even when they share feeding habits and similar recruitment strategies. Their effects may be determined by a combination of factors, including behavioral traits.