Bumble Bee (Hymenoptera: Apidae) Foraging Distance and Colony Density Associated With a Late-Season Mass Flowering Crop

Foraging behaviors of bumble bee workers have been examined in natural habitats, whereas agricultural landscapes, which can provide insights on ßight distances to fragmented patches of bloom,have received limited attention. Inparticular, informationonworkerßightdistances to crops blooming several months after nests have been established is invaluable. Here, we examined foraging patterns of Bombus vosnesenskii Radoszkowski in late-season blooming clover in the agriculturaldominatedWillamette Valley in Oregon. Workers from 10 Þelds collected over 2 yr were assigned to full sibling families (colonies) by using eightmicrosatellite loci.With estimation of numbers of unseen species, we inferred the presence of 189 colonies from 433 bees genotyped in year 1, and 144 from 296 genotyped the next year. Worker foraging distance was estimated to be at least 11.6 km, half the distance between the most remote Þelds visited by the same colonies. Numbers of nests contributing workers to each Þeld ranged from 15 to 163. Overall, 165 (50%) colonies foraged in two ormore Þelds, and thus used common resources within the landscape. Estimates of average nest densities in the landscape each year ranged from 0.76/km to 22.16/km, and highlighted the inßuences of various study parameters incorporated into the calculation including sample size, distances between sites, and analytical tools used to estimate unsampled individuals. Based on the results, bumble bees can ßy long distances, and this could facilitate their survival in fragmented agricultural landscapes. This has important implications for the scale of habitat management in bumble bee conservation programs.