Male bumblebees seek mates on the hills
Bumblebee males head for the hills to find mates, according to scientists in Scotland.
Researchers made the discovery while investigating how bees are distributed across their habitat.
The behaviour, called "hilltopping", has been observed in butterflies in the past, but not in bees.
Little is known about how bumblebees find their mates and mating itself is rarely observed.
Professor Dave Goulson from the University of Stirling became interested in the distribution of bumblebees when he encountered so many in his local area.
On a regular run with co-workers in the hills next to the campus, Prof Goulson noticed an abundance of the large, fuzzy pollinators.
This casual observation led to a scientific investigation into what he thought was an unusual distribution of bees in the windswept, flowerless habitat.
End Quote Professor Dave Goulson University of Stirling
It's quite a neat, simple 'dating' mechanism for butterflies but nobody knew that bees did it”
The study, published in the journal Ecological Entomology, revealed that it was male bumblebees from four species that were most frequently found on hilltops.
"Male bumblebees are essentially lazy," explained Prof Goulson.
"You can see gangs of them sitting around on flowers in July and August and, in between drinking, they go looking for mates."
With a reduced amount of plants suitable for foraging at the top of the hill, Prof Goulson proposed that the bees favoured location was solely a mating strategy.
The bumblebee expert compared his findings to those of previous studies on hilltopping behaviour in butterflies, flies, and wasps.
Scientists studying these insects found that males and females seeking mates flew to the tops of hills to improve their chances of reproducing.
"It's quite a neat, simple 'dating' mechanism for butterflies but nobody knew that bees did it," said Prof Goulson.Secretive sex lives
For bumblebees it seems that only the males make the effort to be seen.
- Some of the cleverest members of the insect world, bumblebees are able to navigate the most efficient route from flower to flower and back to their nest.
- Honeybees' brains have evolved to make the insects better at learning new odours in the morning. This seems to help the insects sniff out flowering plants and forage for nectar more efficiently.
- Some ant species may give bees a run for their money in the brain stakes. When the fragile nest of the tiny house-hunting ant is damaged beyond repair, knowledgable ants that have explored the area guide their nest-mates to a new site.
- African Camponotus fellah ants form long-term memories via the same basic process as us. The insects' brains make new proteins that "consolidate knowledge". In a test, they learned to associate a scent with food. When presented with the same scent three days later, the ants moved their mouthparts in expectation of food.
Although his results showed males congregating on hill tops, Prof Goulson did not record any females taking advantage of the gathering.
The striking insects are surprisingly mysterious and their behaviour, and particularly their reproductive strategies have been the subject of study for many years.
In the late 19th Century, Charles Darwin studied the flight paths of male bumblebees in his garden and found that they left pheromone markers along a regularly patrolled circuit.
But no observations have since been made of females reacting to these signals.
"There are some well-known things that male bumblebees do that have always been assumed to be something to do with how they find mates," Prof Goulson told BBC Nature.
"But none of them are terribly well understood because you almost never see [the bees] actually mating."