The plight of the brainy bumblebee

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For our hard-working bumblebees, it seems being smart comes at a cost. Photo / Plant & Food Research

By Jamie Morton

For our bumblebees, it seems being smart comes at a cost.

Odd findings just published by Kiwi, UK and Canadian researchers show that bumblebees that learn faster have a much shorter foraging lifespan than their slow-learning co-workers.

They also found that the fast-learning bumblebees collected food at rates comparable to the less cognitively able in the colony and completed a similar number of foraging bouts per day.

"Our results are surprising, because we typically associate enhanced learning performance and cognitive ability with improved fitness, because it is considered beneficial to the survival of an individual or group," said study co-author Dr Lisa Evans, of New Zealand's Plant and Food Research.

"This study provides the first evidence of a learning-associated cost in the wild."

The researchers evaluated the visual learning performance of 85 individual foraging bumblebees across five different colonies - subjecting them to an ecologically realistic colour and reward association task in the laboratory and then monitoring their performance in the wild using radio frequency identification tagging technology.

Observers were also on hand to monitor the quantity of nectar and pollen brought back to the nests.

The results, published in the journal Scientific Reports, reveal that slower learning bumblebees collected more resources for the colony over the course of their foraging career.

"This is particularly interesting because we know that learning is really important for bees," said Professor Nigel Raine, of the University of Guelph in Canada.

"They learn which flowers provide the most rewards, when and where to find them - often in habitats containing dozens of flower species."

According to the researchers, the shorter foraging careers of the fast-learning bumble bees may be due to costs associated with their higher cognitive functioning.

"Neural tissue is metabolically expensive to produce and maintain," Evans explained.

"Foraging is energy demanding, but so is learning. This may explain the significantly shorter foraging lifespan of fast-learning bumblebees."

The findings raise the question as to why fast-learning is still an attribute found in bumblebee colonies rather than having been bred out of the population over time.

"This may relate to the range of environments a colony could find itself in. We conducted our research in an environment where the ability to learn quickly may not confer an advantage," Raine said.

"In a more complex or changeable environment, these enhanced learning abilities may be vital to ensure colony resilience.

"Then it could pay to have some smart heads in the room."

The findings go some way to support research into the conservation of pollinators that assist with the production of commercial crops.

Determining how pollinators are adapted to their environment can provide insights into aspects that are important for colony success, which contributes to habitat and pollinator conservation.

Bumblebees make great pollinators as they perform "buzz pollination", an effective technique used to free pollen from anthers, and can forage in poor weather conditions that keep honeybees indoors.

Further, their large size and hairy bodies mean they can collect larger quantities of pollen - it's estimated a single bumblebee can do the work of 50 honey bees - and they visit a wider diversity of flowers, increasing pollination.

Plant and Food Research pollination scientists are now using them in trials to investigate whether they could play a larger role in orchards around the country.

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