Temperature and body size underpin metabolic rates which, in turn, dictate consumer feeding rates across the biosphere. Despite limited data, generalising consumer feeding rates from metabolic theory has advanced our understanding of food web topology and stability. However, I argue that an excessive focus on metabolic theory has stymied our search for others. This is well-exemplified by the recent discovery that the dimensionality of consumer search space systematically alters the scaling of feeding rates. Additionally, the notion that habitat structural complexity affects consumer-resource interactions is practically as old as ecology but, again, there has been scant focus on systematic generalisations. In an attempt to address some of these gaps, I experimentally measured interactions between a large size range of aquatic predators (4–6400 mg over 1347 feeding trials) and a shared prey (Chelicorophium curvispinum) that transitions among habitats: from the water column (3D interactions) to simple and complex benthic substrates (2D interactions).
Results/Conclusions
Capture rates were generally highest in the open 3D context, and were unimodally associated with consumer-resource size ratios. Simple and complex 2D substrates mediated successive reductions in capture rates–particularly around the unimodal optimum–such that on complex substrates modality was lost and capture rates instead scaled as a shallow power law. A simple consumer-resource model parameterised with these data suggest that the dampening of capture rates resulting from habitat structure promotes stability across a wider range of consumer-resource size ratios. One post hoc explanation for these empirical patterns posits that the relative velocity of consumer–resource pairs and the size of consumer detection regions combine to mediate capture rates. Thus, the complexity and dimensionality of consumer search space might mediate capture rates, in part, by the same mechanism: through the modification of detection region size. Many consumer–resource systems transition between 2D and 3D interactions, and along complexity gradients. Thus, the Context-Dependent Scaling (CDS) of feeding interactions could represent an unrecognised aspect of food webs. A new focus on quantifying the extent of CDS and other hypothesised generalisations could enhance predictive ecology.