Foraging by Cave Beetles: Spatial and Temporal Heterogeneity of Prey

Abstract

This study assesses the effect of temporal and spatial heterogeneity of preferred prey on the foraging strategies of two carabid cave beetles, Neaphaenops tellkampfii and Pseudanophthalmus menetriesii. Neaphaenops tellkampfii prefers the eggs and nymphs of the common cave cricket (Hadenoecus subterraneus) which are patchy in time but not in space. Cave cricket eggs are laid in sandy habitats which support few alternate prey. As a result N. tellkampfii is forced to switch diet, habitat, and foraging mode in the fall when cricket eggs and nymphs become rare. Pseudanophthalmus menetriesii preys on collembola that are confined to habitats with organic matter. These items are patchily distributed but continuously available. In sand or mud habitats collembola are rare and P. menetriesii appears to incur higher foraging costs in these habitats than in litter areas. As a result P. menetriesii shows restricted habitat preference and tracks its prey between various organic patches.