Prey killing without consumption: Does Macrolophus pygmaeus show adaptive foraging behaviour?

Several predators exhibit a killing behaviour that might not result in prey consumption after prey death. This behaviour includes partial prey consumption and/or killing without consumption. This study was undertaken to elucidate the factors that may influence consumptive and non-consumptive prey mortality in a predator–prey system. The hypotheses tested included whether or not the predatory behaviour of Macrolophus pygmaeus is affected by the density or size of prey. As prey, the nymphal instars of the aphid Myzus persicae were used. Additionally, to determine if this behaviour was constrained by temperature, the experiments were conducted at three different temperatures. Data was obtained showing that the frequency of non-consumptive mortality was higher with larger and overall less preferred prey instars. Predators that foraged at low temperatures appeared to be less selective, killed more frequently, and left more prey unconsumed. Killing behaviour, however, was not found to increase with prey density. Instead, non-consumptive prey mortality was associated with intermediate prey densities and was dependent on temperature and the prey instar. We conclude that the factors leading to non-consumptive prey killing behaviour are affected by internal and external elements. Additionally, we believe that this behaviour corresponds to a foraging predator’s strategy for optimal exploitation of the available prey.