Newswise – Bumblebees forage to gather the most sugar from flowers in the shortest amount of time – even if it means using more energy in the process – for an immediate energy boost for the colony, research shows.
New research investigating the nectar drinking of one of the UK's most common bumblebees. ground bumblebee found that when foraging they maximize the amount of nectar sugar they bring back to the colony every minute.
To make a choice, bumblebees trade off the time spent collecting nectar against the energy content of that nectar. This means they will forage to collect hard-to-find nectar – but only if the sugar content of that nectar makes them worth doing.
This big and fast approach contrasts with bee foraging: bees make decisions by optimizing their individual energy expenditure for whatever nectar they collect. This more measured approach should extend the working life of the bee.
“When they forage, bumblebees make decisions about which nectar sources will bring the greatest energetic payoff, rather than optimizing the energy efficiency of their foraging,” said Dr. Jonathan Patrick, joint first author of the report, who began the research when the University of Cambridge's Department of Plant Sciences .
Patrick, now based at the University of Oxford, added: “Our results allow us to make predictions about the flowers that bumblebees are likely to visit, which can inform which flowers to plant in field fields to support these important pollinators. . It is also relevant for crop breeders who want to produce ‘better' varieties for bumblebees.”
The results are Published today in the magazine iScience.
Over six months, the researchers made 60,000 behavioral observations of the bumblebees, which allowed them to accurately estimate the feeding energy of the bumblebees. It was time-consuming work: each study bumblebee was watched for up to eight hours a day without a break.
The team used vertically and horizontally oriented artificial flowers with surfaces that were slippery and difficult for bumblebees to grip.
A personal computer program allowed the team to measure the split-second time that the bumblebees flew between the artificial flowers and foraged from them. This meant the team could track how much energy the bumblebees spent flying, as well as how much they gathered while drinking, and determine how the bumblebees decided whether to spend the extra time and energy collecting sugary nectar from slippery flowers, or the easier option. Collecting low sugar nectar from flowers they could land on.
“It's amazing that even with brains smaller than a sesame seed, bumblebees can make such complex decisions,” said Dr. Hamish Symington at the University of Cambridge's Department of Plant Sciences and first author of the report.
He added: “It's clear that bumblebee foraging isn't based on a simple ‘the more sugar in the nectar, the better' idea – it's much more sophisticated than that. And it underscores that there is still much to learn about insect behavior. “
Individual bumblebees were subjected to one of three tests. In the first test, the nectar on both vertical and horizontal artificial flowers had the same amount of sugar, and the bumblebees made a clear choice to forage on the horizontal flowers rather than spend the extra time and energy on the vertical flowers. In the second test, nectar on vertical flowers was much more sugary than nectar on horizontal flowers, and bumblebees chose to drink almost exclusively from vertical flowers.
In a third test, vertical flowers offered nectar that was only slightly more sugary than horizontal flowers. This created a situation where bumblebees had to trade off the time and energy they spent foraging and the energy in the nectar they drank—and they switched to feeding from horizontal flowers.
The results show that bumblebees may choose to spend extra time and energy foraging for food from hard-to-reach nectar sources—but only if the reward is worth it.
Bumblebees drink nectar from flowers, then drop it into the nest – with regurgitation – For use with other bumblebees in the nest. Unlike honey, bumblebees store only a small amount of nectar in their nests, so they must make the most of every foraging opportunity.