Animals & nature · 2014
Can insecticide doses that do not kill honeybees still make it harder for them to find home?
Yes. In a catch-and-release experiment, honeybees given non-lethal doses of the three insecticides tested were less likely to return to their hive than comparison bees. The bees had learned to visit a feeder and were released at a remote site 1.5 hours after treatment. This shows impaired navigation under the experimental conditions, but exactly how their navigation memory was affected remains uncertain.
Details
Researchers tested imidacloprid, clothianidin and thiacloprid. They caught honeybees as they arrived at a feeder they had learned to visit, treated each bee with one of the insecticides, and later released them at a remote site. Radar tracked individual flight paths.
The later, homeward phase of flight was more disrupted than the initial phase guided by recently learned navigation information. Treated bees had a lower rate of successful return, were less likely to turn correctly at a prominent landscape feature, and showed less directed flight during the homeward phase. The initial phase was less affected, not necessarily unaffected.
The researchers interpreted the pattern as suggesting that treatment either blocked access to navigation memories formed during earlier exploratory flights or altered those memories. The experiment did not establish which explanation was correct. The abstract does not give dose amounts, sample sizes or the size of the drop in return success, so it does not establish how large the effect would be under ordinary field exposure.
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