A new study from the University of Exeter reveals that large bumblebees go to work earlier in the morning, despite the risks involved. The experts found that the biggest bees, and some of the most experienced foragers, were the most likely to head out in the low light of dawn.
“Foraging on flowers in low light at dusk and dawn comes at an additional cost for insect pollinators with diurnal vision,” explained the study authors.
“Nevertheless, some species are known to be frequently active at these times. To explore how early and under which light levels colonies of bumblebees, Bombus terrestris, initiate their foraging activity, we tracked foragers of different body sizes using RFID over 5 consecutive days during warm periods of the flowering season.”
The researchers noted that bumblebee vision is poor in low light, so flying at dawn or dusk raises the risk of getting lost or being eaten by a predator. At the same time, bumblebees benefit from extra foraging time and fewer competitors for pollen in the early morning.
“Larger bumblebees have bigger eyes than their smaller-sized nest mates and many other bees, and can therefore see better in dim light,” said study lead author Katie Hall.
“We might expect all bumblebee foragers to leave the colony to forage as soon as there is enough light to allow them to fly. In fact, colonies seem to regulate the start of foraging.”
“There is a balance of risks and rewards in low light – and most bees wait for higher light levels when they can see better and fly faster, with less risk from predators or getting lost and running out of energy.”
“Our finding that more experienced bees are more likely to fly in lower light suggests that knowledge of food locations helps them navigate safely.”
The study is published in the journal Ecology and Evolution.
By Chrissy Sexton, Earth.com Staff Writer