Estimating the Diet of a Sluggish Predator from Field Observations

Abstract

Predation often occurs slowly, so that observing a sufficiently large sample of entire predation episodes represents an inconvenient means of quantitatively estimating the predator's diet. Fortunately, related data are usually available specifying the proportions of predators found feeding on each prey type. We demonstrate how dividing the observed proportion of all predators found feeding on a given prey type by the average contact time required to consume a single item of that prey type produces an estimate of the relative frequency of the prey in the predator's diet. The analogous procedure, when based upon residence times in the gut, serves to derive a quantitative estimate of diet from numerical data on gut contents. Key words: dietary analysis, feeding frequencies, stomach contents, predator–prey contact times