Multi-trophic interactions in anthropogenic landscapes: the devil is in the detail.

Dorresteijn et al. [1] recently addressed the question what influence humans have on predator–prey interactions in human-modified landscapes. Their study follows increasing evidence from relatively natural landscapes that large carnivores are central drivers of ecosystem structure and functioning through density-mediated and behaviourally mediated effects on their prey [2]. A key question is whether large carnivores will have similar ecological effects in human-dominated landscapes [3]. This is particularly relevant in the light of the carnivore recolonization of European landscapes [4]. We applaud Dorresteijn et al. [1] for highlighting that ecological effects of large carnivores may be quite different in human-modified landscapes. Unfortunately, we feel that there are crucial flaws with their study design, analyses and interpretation. These flaws seriously undermine the strong conclusions that they draw about the role of topdown and bottom-up processes in anthropogenic landscapes. Our main concerns include (i) lack of relevant bottom-up data, (ii) a camera trap design unsuitable for testing their hypotheses regarding community structure, and (iii) top-down and bottom-up processes that are studied at an inappropriate spatial scale.