Methods to identify the prey of invertebrate predators in terrestrial field studies

Abstract

Predation is an interaction during which an organism kills and feeds on another organism. Past and current interest in studying predation in terrestrial habitats has yielded a number of methods to assess invertebrate predation events in terrestrial ecosystems. We provide a decision tree to select appropriate methods for individual studies. For each method, we then present a short introduction, key examples for applications, advantages and disadvantages, and an outlook to future refinements. Video and, to a lesser extent, live observations are recommended in studies that address behavioral aspects of predator–prey interactions or focus on per capita predation rates. Cage studies are only appropriate for small predator species, but often suffer from a bias via cage effects. The use of prey baits or analyses of prey remains are cheaper than other methods and have the potential to provide per capita predation estimates. These advantages often come at the cost of low taxonomic specificity. Molecular methods provide reliable estimates at a fine level of taxonomic resolution and are free of observer bias for predator species of any size. However, the current PCR‐based methods lack the ability to estimate predation rates for individual predators and are more expensive than other methods. Molecular and stable isotope analyses are best suited to address systems that include a range of predator and prey species. Our review of methods strongly suggests that while in many cases individual methods are sufficient to study specific questions, combinations of methods hold a high potential to provide more holistic insights into predation events. This review presents an overview of methods to researchers that are new to the field or to particular aspects of predation ecology and provides recommendations toward the subset of suitable methods to identify the prey of invertebrate predators in terrestrial field research.

Organic farming at local and landscape scales fosters biological pest control in vineyards

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Combined effects of agrochemicals and ecosystem services on crop yield across Europe

“…It should be noted that inherent problems in measuring biocontrol using cage experiment and open control call for caution when interpreting absolute values of BCI (Birkhofer et al . ).…”

Predation‐mediated ecosystem services and disservices in agricultural landscapes

“…However, we argue that seed and invertebrate sentinels often represent the most reliable estimate for services and disservices, in particular if multiple services and disservices are assessed (Birkhofer et al. ).…”

“…), predation experiments generally only assess snapshots in time and our current evidence base relies mainly on studies performed during the main vegetation period (Birkhofer et al. ). Yet, predation on weed seeds and pest prey early in the season or after crop harvest may be important for biological control due to a depletion of the seed bank or reduction of overwintering pest populations (Pfiffner and Luka , Harrison et al.…”