The impact of prey behaviour and prey density on the foraging ecology of Ranatra montezuma (Heteroptera): a serological examination

Serological techniques were used to examine the seasonal and diel diets of Ranatra montezuma (Heteroptera) in the fishless, thermally constant environment of Montezuma Well, Arizona. Although alternative invertebrate prey were diverse and abundant, copepods were the primary food of first-instar R. montezuma, while the endemic amphipod Hyalella montezuma was the preferred food of adults. Laboratory predation experiments and serological diet analyses from field collections suggest that R. montezuma feeds more actively at night when prey densities in Montezuma Well are elevated in the littoral vegetation. Prey behaviour is very important in the foraging ecology of R. montezuma. Hyalella montezuma, which swim in the littoral vegetation, were captured more frequently than more sedentary damselfly larvae (Telebasis salva). Prey-choice experiments and in situ serological diet analyses suggest that the high standing crop of R. montezuma is dependent upon the presence of high densities of actively swimming H. montezuma.