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Bumblebees choose immediate rewards over energy efficiency

Researchers have discovered that bumblebees make complex decisions when foraging for nectar, and they prioritize immediate rewards over energy efficiency.

While observing bumblebees’ interactions with slippery artificial flowers, the experts found that they make choices to maximize the rate of energy return, or the amount of sugar collected each minute.

Focus of the study 

“Bumblebees can make decisions ‘on the fly’ about which nectar sources are the most energetically economical,” said study first author Jonathan Pattrick. 

“By training bumblebees to visit artificial slippery flowers and using different ‘nectars’ with high, medium or low amounts of sugar, we found that they could make a trade-off between the energy content of the nectar and how difficult it was to access.”

Distinct lifestyles 

This behavioral pattern stands in contrast to honeybees, which have been found to prioritize energy efficiency in their foraging. Pattrick suggests that the distinct lifestyles of bumblebees and honeybees might be responsible for this variance. 

“Bumblebees have a different lifestyle to honeybees: they only store a small amount of nectar in the nest and so have to make the most of every available opportunity to forage,” Pattrick said. 

“This difference between species may be why the bumblebees adopt a strategy such that their foraging is of more immediate benefit to the colony, even if it means they have to work harder, while honeybees take a relatively more measured approach to how hard they work – this should prolong their working lifespan.”

How the research was conducted 

The team, working at the University of Cambridge, UK, used specially designed artificial flowers with slippery surfaces to study this trade-off. These flowers were placed both vertically and horizontally. 

The researchers also used a custom computer program to record the minute behaviors of the bumblebees as they opted to gather high-sugar nectar from the slippery flowers, which necessitated hovering, or chose flowers they could land on with lower sugar concentrations. This rigorous method resulted in a total of 60,000 individual behavioral observations.

What the researchers learned 

The data showed that bumblebees were making decisions based on the rate of energy return. Earlier studies, relying on observing bees in their natural settings, had left some ambiguity regarding their decision-making process.

Study significance 

Pattrick noted the significance of these findings for understanding bee behaviors and their interaction with flowers. 

“Identifying the currency used by nectar-foraging bumblebees helps provide a framework for understanding how bumblebees make foraging decisions,” said Pattrick.

“This information can be used to make predictions about the sorts of flowers the bees are likely to be visiting. In turn, this could inform choices of the flowers to plant in field margins and is also relevant to crop breeders who want to make varieties which are ‘better’ for bumblebees.”

Study implications 

However, this is just the tip of the iceberg. The researchers believe that future studies should delve deeper to determine if bumblebees consistently use this decision-making currency across varied foraging contexts. 

The team also expressed admiration for the bumblebee’s cognitive abilities, with Pattrick stating, “We find it amazing that, even with a relatively simple brain, bumblebees are able to make such complex energetic decisions.”

The study is published in the journal iScience.

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