Remarkable long-distance returns to a forage patch by artificially displaced wild bumble bees (Hymenoptera: Apidae)

Bumble bees are believed to minimize travel distance and time while seeking foraging resources, and to memorize landmarks and return to forage patches visited earlier. Given these abilities, if a worker is displaced, will it switch to a new forage resource close by or will it navigate back to the original forage patch? To address this question we collected 210 Bombus vosnesenskii workers from an ornamental Spirea patch, marked them with numbered tags, transported them in a cooler, and released them at seven distances, from 1.5 km to 16 km, in each of two directions. Each worker that returned to the Spirea patch was recaptured, and re-released at its first release location. Over 8 observation days, 54 workers from 11 release locations returned to the Spirea patch. Of these, 16 were recaptured twice, 13 three times, 5 four times and 1 five times. Nine workers returned from release distances ≥10 km, including one from 16 km, despite the presence of multiple rewarding resources between the release location and the Spirea patch. Returns were rapid—three workers released up to 5 km away were recaptured within 4 h, while a worker from 13 km returned within 30 h of release. Wind direction, wind speed, and release direction had significant (P < 0.05) impacts on release-to-recapture-times. Also, workers returned significantly (P < 0.001) more quickly during subsequent trips compared to their first return. These findings highlight the ability of displaced bumble bee workers to travel long distances, and to navigate back to familiar forage patches.