Large-range movements of neotropical orchid bees observed via radio telemetry

Abstract

Neotropical orchid bees (Euglossini) are often cited as classic examples of trapline-foragers with potentially extensive foraging ranges. If long-distance movements are habitual, rare plants in widely scattered locations may benefit from euglossine pollination services. Here we report the first successful use of micro radio telemetry to track the movement of an insect pollinator in a complex and forested environment. Our results indicate that individual male orchid bees (Exaerete frontalis) habitually use large rainforest areas (at least 42-115 ha) on a daily basis. Aerial telemetry located individuals up to 5 km away from their core areas, and bees were often stationary, for variable periods, between flights to successive localities. These data suggest a higher degree of site fidelity than what may be expected in a free living male bee, and has implications for our understanding of biological activity patterns and the evolution of forest pollinators.

Figure 1. Attachment of a micro-radio transmitter to a male orchid bee Exaerete frontalis.

Transmitters (300mg) were attached to the bee's thorax by the battery, using eyelash adhesive inside, and minute amounts of superglue around the outside of the battery. The angle at which the transmitter stuck off the bee was somewhat variable and usually lower than in this picture, i.e., the transmitter was closer to the bee's abdomen. Picture by Christian Ziegler.

Figure 2. Home ranges of 11 orchid bees on Barro Colorado Island.

While some home ranges are small and centred around the capture sites situated in the NE of the island. Others use very large ranges, with one even including a site off the island on the other side of the Panama canal. These data are available at www.movebank.org.

Figure 3. Flight trajectories of 7 orchid bees.

The different colors indicate different flights of orchid bees, with lines connecting consecutive locations (dots). Bees were stationary for variable lengths of time and then flew to a new site where again they remained stationary.

Figure 4. Radio tracking sampling effort on Barro Colorado Island.

The outline of the island is shown, as well as the total area in which a micro-transmitter would have been detected. Under worst-case conditions (e.g., bee in a tree hole), a transmitter can only be observed for 100 metres. Usually, detection range is ca. 300 metres even in dense forest understory.