Bee (Hymenoptera: Apoidea: Anthophila) roadkill across Texas, United States of America, compared with other studies

Roadkill is an often-overlooked contributor to wild bee declines and additional surveys are needed to better understand population impacts, especially for vanishing species. Comparative studies are also needed to appreciate effects of roadkill sampling methodologies. We sampled hundreds of 100 m roadside transects across Texas, USA during spring and autumn 2020 and spring 2021, identifying roadkill bees, mapping roadkill distributions, hotspots, and hot-moments, and estimating regional roadkill and community metrics. We compared our results with data newly extracted from other bee roadkill studies, including a Utah vehicle-mounted sticky trap survey and a Tennessee year-round single roadside transect study. We correlated and compared bee genera median body lengths and their relative abundance among Texas and Utah bee roadkill surveys and iNaturalist occurrence data. Roadkill was highly to moderately skewed towards hotspots/hot-moments. Approximately 4.1–11.7 million bees were killed on Texas roads in 2020, based on boot strapped accelerated bias-corrected 95% CI. These included mean estimates of 336,213 Bombus pensylvanicus and 45,847 B. sonorus , both species of conservation concern. Non-lethal roadside transect methods commonly detected larger-bodied Bombus and Xylocopa bees absent in lethal Utah vehicle-mounted sticky trap surveys. Conversely, Utah sticky trap surveys detected abundant smaller-sized Perdita and Lasioglossum bees rare or absent from roadside transect studies. Roadkill hotspots/hot-moments for bees of conservation concern can be better identified through combining multi-seasonal roadside transect replicates with data from vehicle-mounted foam-backed sticky traps or quasi-lethal vehicular bee sweepers. Accounting for the adjacent habitat and bee community can facilitate identifying and mitigating bee roadkill susceptibility.