A global citizen science effort via iNaturalist reveals food webs of large predatory rove beetles

The behavior of organisms is very difficult to observe and document, especially direct interactions such as predation. As a result, there are few systematic studies of such phenomena on a large scale and the food webs of organisms that are formed by fleeting and opportunistic interactions are largely unknown. Understanding food webs is essential for addressing the Eltonian shortfall in biodiversity knowledge and revealing ecosystem dynamics. The rise of citizen science in recent years offers unique opportunities to study food webs on a global scale, which has been demonstrated for larger animals but not for small ones like insects. Here we explore the potential of iNaturalist as a cost-effective citizen science platform to obtain data about the prey choices of predatory rove beetles (family Staphylinidae) from the subtribe Staphylinina, as an alternative to traditional, labor-intense laboratory studies. We manually mined the dietary evidence of Staphylinina worldwide through over 48,000 observations on iNaturalist and 159 records of predation were found. Our findings show that citizen science data not only supports the published studies, but also provides direct and novel field-based evidence of rove beetle prey specialization with numbers of observations that exceed the amount of previously available data by an order of magnitude. We confirmed that some Staphylinina are generalist predators and discovered that some genera and species exhibit specific prey preferences, as documented by iNaturalist. This approach demonstrates that citizen science platforms offer an innovative, scalable, and cost-effective solution to filling global biodiversity knowledge gaps.