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Caught in a trap: Bumblebees versus robotic crab spiders

4 September 2008

Bumblebees learn to avoid camouflaged predators by sacrificing foraging speed for predator detection, according to scientists from Queen Mary, University of London.

One of the bumblebee's main predators is the crab spider. Crab spiders hunt pollinating insects like bees and butterflies by lying in wait on flowers, and are particularly difficult for their prey to spot because they can change their colour to blend in with their surroundings.

A bumblebee being trapped by a crab spider in the wild

Dr Tom Ings and Professor Lars Chittka from Queen Mary's School of Biological & Chemical Sciences wanted to discover whether bumblebees could learn to avoid these crab spiders. Their study, funded by the Natural Environment Research Council and published in the journal Current Biology, shows how a run in with a spider affected the bees' foraging patterns.

Dr Ings and his team allowed a colony of bumblebees (Bombus terrestris) to forage in a meadow of artificial flowers in a 'flight arena' which contained 'robotic' crab spiders. Some of the spiders were well hidden, others were highly visible. Whenever a bee landed on a flower which contained a robot spider, the spider 'caught' the bee by trapping it briefly between two foam pincers, before then setting it free to continue foraging.

The team used 3D tracking software to follow the bees' movements, and found that the bees which were caught by a camouflaged spider slowed down their subsequent inspection flights. Although they lost valuable foraging time by slowing down, they were more likely to accurately detect whether there was a hidden crab spider present.

In addition, the bees which had already been caught a few times the day before by the hidden spiders behaved as if they saw spiders where there were none i.e. they rejected foraging opportunities on safe flowers, 'just in case' and were more wary than bees which had been caught by the more conspicuous spiders.

Dr Ings commented, "Surprisingly, our findings suggest that there is no apparent benefit to the spider in being camouflaged, at least in terms of prey capture rates. Spider camouflage didn't increase the chances of a bumblebee being captured, or reduce the rate at which the bees learnt to avoid predators. But our results did show that the bees which encountered camouflaged spiders were worse off in terms of reduced foraging efficiency."

Further information

Siân Halkyard
Senior Communications Officer
Queen Mary, University of London
Tel: 020 7882 7454
Mob: 07970 096175

A copy of the paper, high resolution images of the bees and robotic crab spiders, along with video footage of the bees in action, are all available on request. Dr Ings and Professor Chittka are available for interview.

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Notes

1. Speed accuracy tradeoffs and false alarms in bee responses to cryptic predators will be published in the journal Current Biology on 4 September 2008.

2. Queen Mary, University of London is one of the UK's leading research-focused higher education institutions with some 15,000 undergraduate and postgraduate students. Amongst the largest of the colleges of the University of London, Queen Mary's 2,800 staff deliver world class degree programmes and research across 21 academic departments and institutes, within three sectors: Science & Engineering; Humanities, Social Sciences & Laws; and the School of Medicine & Dentistry. Over 80 per cent of Queen Mary's research staff work in departments where research is of international or national excellence (RAE 2001). Queen Mary has an annual turnover of £200m, research income worth £43m, and generates employment and output worth £500m to the UK economy each year.

3. The Natural Environment Research Council funds world-class science, in universities and its own research centres, that increases knowledge and understanding of the natural world. It is tackling major environmental issues such as climate change, biodiversity and natural hazards. NERC receives around £400m a year from the government's science budget, which is used to provide independent research and training in the environmental sciences.

Press release: 49/08