Bumblebees under the midnight sun - Monitoring circadian rhythms of bumblebees under continuous daylight, using radio frequency identification (RFID)

• Published in: Nature Precedings
• Main Authors: Ralph J. Stelzer, Lars Chittka
• Format: Still Image
• Language: unknown
• Published: 2008
• Subjects: Ecology; Arctic; midnight sun
• Online Access: http://precedings.nature.com/documents/1719/version/1; https://doi.org/10.1038/npre.2008.1719.1

Circadian rhythms enable organisms to anticipate and to prepare for predictable changes in their environment. Most previous studies on circadian rhythms focused on solitary animals. However, in social insects, the colony as a superorganism has a foraging rhythm aligned to the patterns of resource availability. Within this colony rhythm, the activity patterns of individuals are embedded. In temperate regions bumblebee foragers show strong circadian rhythms that adjust their foraging activity to the changing light conditions in the course of the day. But what about circadian foraging patterns under continuous daylight? One would assume that the colony as a whole extends its foraging activity over the whole 24 hours of a day under such light conditions to maximise colony growth. To answer this question four colonies of _Bombus terrestris terrestris_ have been set up in north-western Finland (Kilpisjärvi Biological Station, 270km north of the Arctic Circle) between 20/06/07 and 18/07/07. During that time period the sun is always above the horizon in that area. Each worker of each colony was fitted with a small RFID tag, allowing to continuously monitor the foraging activity of each individual worker for the whole duration of the experiment. Against the hypothesis the foragers still showed strong circadian rhythms and ceased their activity from about 0000h until about 0600h each day.