Bees' flight paths are disturbed by predators

White-tailed bumblebee (c) Dave Goulson Bumblebees do not just journey from A to B

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Foraging bumblebees change their flying patterns to avoid predators, researchers have found.

The animals are known for their straight forward travel: inspiring the phrase "to make a bee-line".

But scientists at Queen Mary, University of London used artificial spiders to test the flight paths of bees collecting nectar.

The bees travelled straight from flower to flower when spiders were absent, but made more turns when faced with them.

Bees often systematically visit multiple flowers in one single area to collect nectar and scientists refer to this method as a "Levy flight", named after French mathematician Paul Pierre Levy.

But the latest study suggests bees respond to the presence of predators in a more complex way than previously thought, says one of its authors, Dr Rainer Klages from Queen Mary's School of Mathematical Sciences.

Bumblebee buzz

  • There are around 250 species of bumblebee around the world, with 24 species found in the UK
  • They can visit flowers up to 2km away from their colonies, to feed on nectar and gather pollen
  • Buff-tailed bumblebees are the UK's largest species
  • Different species have certain flower preferences: The great yellow bumblebee has a long tongue and forages in flowers where nectar is harder to reach
  • Some bumblebee species are "cuckoos", where females take over another nest instead of making their own. The cuckoo evicts or kills the queen and uses the workers to rear its own offspring

Dr Klages says: "In mathematical theory we treat a bumblebee as a randomly moving object hitting randomly distributed targets.

"Bumblebees in the wild are under the constant risk of predators, such as spiders, so the question we wanted to answer is how such a threat might modify their foraging behaviour."

He explains that velocity - speed in a given direction - is the key to how bees stay safe when seeking food.

"The way the velocities change with time during a flight is characteristically different under predation threat," says Dr Klages.

With spiders present, the researchers found that the bees turned more often, deviating from their usually straight paths.

Special set-up

The experiments were carried out in controlled conditions, with "artificial spiders created" in the form of a trapping mechanism that grabbed the bumblebee for two seconds.

Bee on flower Bees were thought to fly mostly very systematically from flower to flower

The 3D flight trajectories of 30 bumblebees were tracked by two high frame-rate cameras.

"The bumblebee flies in a small box, going in one side and there are artificial flowers where the bee can search for food," says PhD student and study author Friedrich Lenz.

"What we look at is the data from the two cameras in there, and how the bee's behaviour changes when artificial spiders were introduced."

Friedrich Lenz says the team hope to look at bumblebees in the wild as well and compare the results.

"We are in a very special set-up, and the problem is it's much harder to do it outside," he says.

The sensory perception, memory, and individuality of the bees may also be factors that could change the outcomes of foraging theories, the research found.

Dr Klages says it's a very important discovery for other mathematical foraging studies.

"In previous foraging theories, the mathematical model was more abstract. We found you do really have to incorporate the interaction."

The research was part of a cross-disciplinary study with other departments at the university.

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