DNA-based analysis of regurgitates: a noninvasive approach to examine the diet of invertebrate consumers

DNA-based gut content analysis has become an important tool for unravelling feeding interactions in invertebrate communities under natural conditions. It usually implies killing of the consumer and extracting the DNA from its food, using either the whole animal or its dissected gut. This post-mortem approach, however, is not suitable for investigating the diet of rare or protected species and also prohibits tracking individual dietary preferences as each consumer can provide trophic information only once. Moreover, removing large numbers of consumers from a habitat for analysis might critically change population densities and affect species interactions. Here, we present DNA-based analysis of invertebrate regurgitates, a novel approach to overcome these limitations. Conducting feeding experiments where adult Poecilus cupreus (Coleoptera: Carabidae) were fed with larvae of Amphimallon solstitiale (Coleoptera: Scarabaeidae), we show that detection success in regurgitates compared to samples prepared from whole beetles was similar or significantly enhanced for small/medium and large prey DNA fragments, respectively. Prey DNA detection success remained high in regurgitates stored in ethanol for 21 months at room temperature prior to DNA extraction. We conclude that in those invertebrates where regurgitates can be obtained, examination of food DNA in regurgitates offers many advantages over conventional post-mortem gut content analysis.