Detection and occupancy estimates for bumble bee species in urban and rural habitats of eastern Wisconsin

Bumble bees (Hymenoptera: Apidae: Bombus) are a pollinator group of global conservation concern, given documented population declines and changes in community composition. Prior research has highlighted threats faced by bumble bee species and communities, including habitat loss and degradation. Given the many threats faced by bumble bees, robust monitoring is necessary to assess current trends in populations and communities and to evaluate recovery goals for federally listed species (e.g., Bombus affinis Cresson). Understanding the factors that influence the collection of monitoring data and subsequent inferences derived from the data is paramount to bumble bee conservation. Contemporary bumble bee records are often disproportionately biased towards urban areas, as there are more people and thus greater effort. Our work seeks to assess differences in detection and occupancy estimates for multiple bumble bee species, including Bombus affinis, in urban and rural habitats of eastern Wisconsin. Across two years, we collected data from 28 pairs of rural and urban sites, resulting in a total of 190 standard-effort survey events. We recorded a total of 8681 individuals, including individuals from 13 distinct species and 1 species complex. From this data, we provide estimates of detection and occupancy probabilities for common and rare bumble bee species within the study area. These results will help inform subsequent conservation and monitoring efforts for bumble bee species and communities.