Boffins tail bees with tiny radio tags

How long is a beeline?

Bees with radio tags glued onto their backs have been busily demonstrating just how long it takes them to get home, and how much easier it is to travel west.

The tags are 13.75MHz RFID tags – very small ones – and were glued to individual bees by researchers Mario Pahl and ShaoWu Zhang. Once properly tagged, the bees were released from various locations and an RFID reader on the hive noted their eventual arrival. That data then enabled the apicultural boffins to deduce that nearby mountains were used for navigation, and the speed of journey was heavily influenced by landmark availability.

Bee with tag on back

One of the test subjects poses for a close-up

About 1km to the west of the test hive was a distinctive mountain, which (the researchers conclude) guided the bees who were released to the east, enabling them to make their way home from as far as 11km away. Those poor bees released as little as 6km to the west were, sadly, never seen again.

The tags used are 1x1.6mm and weigh 2.4 milligrams. Given that a bee can collect 35 milligrams of nectar that's not a big deal, though having the thing glued to their backs can't help the aerodynamics much. RFID Journal has the technical details of the tags, while the results of the study appeared in the PLoS ONE Journal.

Apparently bees like to circle the hive during their formative days, looking into the distance for landmarks that might help them find their way home. But despite that, and a flying speed of 15km/h, some of the bees took several days to make it back. In the tests the slowest journeys came from the south: a 3km trip took 78 minutes travelling west, compared to 280 minutes travelling north.

Those worried about such things might like to know that the bee will have to refuel every 25 minutes or so, which obviously slows things down.

What the boffins didn't see was bees dropping dead from radio waves, or being confused by having to enter the hive through a tunnel containing a radio signal strong enough to bounce a unique ID off their backpack-mounted tags, which is nice to report. ®

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