Creating a buzz: Efforts to seed new yellow-faced bee populations using translocations

Hawaiian yellow-faced bees (Hylaeus spp.) are the only native bees in the Hawiian Islands. Many of the 60+ species comprising this important pollinator group are now extremely rare owing to habitat loss, habitat degradation, and predation and competition from invasive species. In 2016, seven species were formally listed as Endangered, including Hylaeus anthracinus, a species occurring in coastal habitats on several islands. In an effort to increase the number of H. anthracinus populations on Oʻahu, we attempted to translocate this species from existing populations at Marine Corps Base Hawaiʻi and James Campbell National Wildlife Refuge to two new locations within Kaʻena Point State Park and the Kalaeloa Unit of Pearl Harbor National Wildlife Refuge. Approximately 150 bee nests constructed within artificial nest blocks were moved to each translocation site in July and August, 2020. Bees began emerging and constructing local nests within the first week after translocation, indicating successful establishment, at both sites. However, subsequent reproduction was lower at Kalaeloa than at Kaʻena, despite a greater floral resource base, and the Kalaeloa population perished after about five months. In contrast, the Kaʻena population has persisted, at low levels, to the present. Potential causes for the eventual failure of the Kalaeloa population include greater parasitism and a possible shortage of natural nesting habitat. Both translocations provided useful insights into the factors contributing to the success or failure of bee establishment and persistence, and serve as foundations for similar future efforts.