Owl pellets, a useful method to study epigean tenebrionid beetles in arid lands

Abstract

Owl pellets, regurgitates formed by the undigested parts of owls? prey, have been used since the sixties to estimate relative species abundances and community diversity of small mammals in the field. Although insects are important food sources for raptors, the usefulness of owl pellets as a collecting method for entomological studies remains practically unexplored. Many terrestrial arthropods have fragile bodies that degrade during the raptor´s digestive process; however, darkling beetles (Tenebrionidae) resist this process. These organisms are abundant, rich in species, and play significant roles in food and nutrient soil cycles in arid regions. Moreover, darkling beetles are well known and represent up to 52% of prey abundances in Bubo magellanicus (Lesson), one of the most common owls in arid Patagonia. The aim of this work is to evaluate the suitability of B. magellanicus pellets as a research tool for studies of tenebrionid beetle biodiversity assessments in arid Patagonia. Thus, we compare tenebrionid relative species abundances, species richness, and their species assemblage estimated from the diet of B. magellanicus with those identified simultaneously by conventional trapping (pitfall trapping and hand collecting) using multivariate techniques and the Fisher´s Exact Test. Mitragenius araneiformis Curtis, Patagonogenius quadricollis Fairmaire and Emmallodera crenaticostata crenaticostata Blanchard were the most abundant tenebrionid species. Relative abundances of almost all species, the estimation of species richness and tenebrionid assemblage from both collecting methodologies were similar. Therefore, we propose the owl pellets analysis as a useful sampling tool for rapid estimations of the tenebrionid assemblage structure in arid Patagonia.