Invertebrate by-catch from vertebrate pitfall traps can be useful for documenting patterns of invertebrate diversity

There is a pressing need to develop simplified sampling protocols that allow invertebrates to be routinely incorporated into terrestrial faunal surveys for informing conservation planning. This study assesses the usefulness of sampling invertebrate by-catch from standard vertebrate bucket pitfall traps for documenting spatial patterns of terrestrial invertebrates. We compare among-site (N = 78) patterns of species richness and composition of ten invertebrate families (comprising ants, beetles and spiders) captured in vertebrate bucket traps with those captured in two different arrays of invertebrate-specific pitfall traps. For three families (Formicidae, Carabidae and Lycosidae) patterns of richness and composition captured in the vertebrate traps were comparable with those captured in the invertebrate-specific trap arrays. Thus, in some cases, vertebrate traps appeared to be as useful in detecting patterns of invertebrate diversity as were invertebrate-specific traps. Our findings show that sampling invertebrate by-catch from vertebrate bucket traps can be a reliable and robust simplified protocol for documenting biodiversity patterns for some key groups of terrestrial invertebrates. This simplified protocol can take terrestrial invertebrates out of the ‘too-hard basket’ for biodiversity assessment and monitoring, breaking the positive-feedback loop that currently maintains ignorance of invertebrate diversity and distribution and that prevents their inclusion in conservation planning.