Kleptoparasitism and Scavenging Can Stabilize Ecosystem Dynamics.

Abstract

Scavenging is ubiquitous in nature, but its implications have rarely been investigated. We used camera traps on wolf kills to investigate the role of scavenging on predator and multiprey dynamics in a northern Apennine system in Italy. In contrast to North American systems, the omnivorous wild boar successfully competes with wolves for the meat of their kills. We developed a deterministic, multitrophic web model (wolf, vegetation, deer, and wild boar), tunable through a parameter that governs the impact of prey sharing between wolves and wild boar. When prey sharing is scarce, populations oscillate, but above a threshold value the trophic web is stabilized, with the regime solution becoming a fixed, stable point. Both deer and wild boar then increase as a function of prey sharing, and the impact of herbivores on the vegetation increases. When prey sharing exceeds another threshold, the system collapses due to the extinction of both wolves and wild boar. Our analysis shows that scavenging is crucial for the dynamics of this ecosystem, and thus it should not be overlooked in food web modeling. The exploitation of wolf kills by wild boar may allow juveniles and yearlings to obtain high-quality resources that are not usually available, helping the wild boar to compensate for losses caused by hunting. This is likely to make them even more invasive and difficult to control.