Ants are among the insects involved in cadaveric decomposition processes, as they exhibit predatory and necrophagous behavior. Red ants exhibit an aggressive behavior, which impacts carcass colonization, accelerates or delays the decomposition rates and potentially confounds interpretation of the post-mortem interval. Here, we estimated the effects of Solenopsis saevissima (Smith) activity on the decomposition rate in domestic pig carcasses. We placed two pig carcasses close to S. saevissima nests, and two other pig carcasses (controls) in other locations 50 m away from the nest. Decomposition processes were delayed by at least three days for carcasses on the nest compared to those without direct exposure to ants. Our results showed that predatory activity of S. saevissima interfered with carcass colonization by scavenger insects, functioning as an ecological barrier to the establishment of immature Diptera. Such results highlight the importance of considering ecological processes that may interfere with mechanisms determining post-mortem intervals.