Optimizing sampling protocols: is it feasible to collect predatory beetles (Coleoptera: Staphylinidae and Carabidae) using dung beetle (Scarabaeinae) traps in soybean fields and native vegetation areas in Brazil?

Abstract

Optimizing sampling protocols can improve data reliability while reducing sampling effort. As sampling methods for dung beetles are well established, testing their efficiency for other key beetle groups, such as Carabidae and Staphylinidae, may help refine sampling approaches. Both groups are widely distributed, sensitive to environmental changes, and effective bioindicators that can be readily sampled using pitfall traps. Although optimal sampling protocols have been proposed, particularly for Carabidae, the effectiveness of baited traps remains uncertain. This study evaluated the richness, abundance, and composition of predatory beetles captured in pitfall traps with and without human-feces bait in native vegetation and soybean croplands. Sampling was conducted at 44 points across farms in Mato Grosso, Brazil. At each point, two transects were established with baited and unbaited pitfall traps. We found differences in richness, abundance, and community composition between trap types, with more staphylinid species captured in baited traps and more carabid species in unbaited traps. Bait use may enhance Staphylinidae capture, whereas unbaited traps may favor Carabidae. These findings highlight the importance of taxon-specific sampling protocols for beetle diversity assessments and environmental monitoring.