  Individual resource intake rates are known to depend on both individual body
size and resource availability. Here, we have developed a model to integrate
these two drivers, accounting explicitly for the scaling of perceived resource
availability with individual body size. The model merges a Kleiber-like scaling
law with Holling functional responses into a single mathematical framework,
involving both body-size the density of resources.
  When the availability of resources is held constant the model predicts a
relationship between resource intake rates and body sizes whose log-log graph
is a concave curve. The significant deviation from a power law accounts for the
body size dependency of resource limitations. The model results are consistent
with data from both a laboratory experiment on benthic macro-invertebrates and
the available literature.

Populations and Evolution