"Cleverness comes at a cost"
The plight of the brainy bumble bee
Scientists at Plant & Food Research, Royal Holloway University of London and the University of Guelph have been studying how the learning ability of individual bumble bees (Bombus terrestris) influences their foraging performance and contribution to the colony.
What they found was that the fast-learning bumble bees had 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,” says Plant & Food Research scientist Dr Lisa Evans.
“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 bumble bees 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 reveal that slower learning bumble bees 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. They learn which flowers provide the most rewards, when and where to find them – often in habitats containing dozens of flower species,” says Professor Nigel Raine from the University of Guelph.
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. Foraging is energy demanding, but so is learning. This may explain the significantly shorter foraging lifespan of fast-learning bumble bees,” says Dr Evans.
The findings raise the question as to why fast-learning is still an attribute found in bumble bee 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,” says Professor Raine.
“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.
The research has been published in the journal Scientific Reports (www.nature.com/articles/s41598-017-00389-0)
Source: Plant & Food Research