Migrating giant honey bees (Apis dorsata) congregate annually at stopover site in Thailand

Abstract

Giant honey bees (Apis dorsata) of southern Asia are vital honey producers and pollinators of cultivated crops and wild plants. They are known to migrate seasonally up to 200 km. It has been assumed their migrations occur stepwise, with stops for rest and foraging, but bivouacking bees have rarely been seen by scientists. Here I report discovery of a site in northern Thailand where bivouacs appeared in large congregations during the wet seasons of 2009 and 2010. The bivouac congregation stopover site is a small mango orchard along the Pai River. Bivouacs rested in branches of mango and other tree species in the immediate vicinity. Departures were preceded by dances indicating approximate direction and apparently, distance of flights. Such consistent stopover sites likely occur throughout southern Asia and may support critical, vulnerable stages in the life history of giant honey bees that must be conserved for populations of the species to survive.

Figure 1. Study site map to scale, with bivouac locations marked for 2009 (purple dots) and 2010 (yellow dots).

Note concentration of bivouacs in riverside mango trees. In 2010 one other bivouac was seen, 1 km NE of study site, along transect road. A  =  airstrip; C  =  assorted vegetable crops; F  =  forest; M  =  mango orchards; Ma  =  macadamia orchard; OMA  =  old mango trees; P  =  pomelo orchard; PS  =  passion fruit; R  =  road; U  =  undergrowth.

Figure 2. Cumulative rainfall, Mae Hong Son, July-November 2009 and 2010.

Source: Air Force Datsav3 Weather Station 483000, call sign VTCH.

Figure 3. Timeline chart of bivouac arrival and departure, 2009 and 2010.

Bars followed by a question mark represent bivouacs still on site at conclusion of 2010 study.

Figure 4. The smallest bivouac at the study site.

Figure 5. One of the largest bivouacs at the study site.

Figure 6. Compass plots depicting flight directions indicated by dancers and following flights.

(A) observations from 2009, (B, C) observations from 2010. Dances of each worker were numerous; directions and distances indicated were unanimous for all dancers in each bivouac. Each color represents dances and flight of a single bivouac. Each concentric ring represents either 3 s of dancing (zigzag lines)–waggle runs only for dances of >3 s duration, complete circuits for dances of <3 s–or 30 m of flight (straight lines). Most flights exceeded 150 m and disappeared from view, as indicated by broken lines. At periphery are identification numbers of bivouacs. N  =  maximum number of workers simultaneously dancing within 30 min before flight.

Figure 7. A. dorsata folragers in high density on Eucalyptus flowers.