Neonicotinoid Exposed Bumblebees Get Heavier Loads From Fewer Flowers

Summary: Neonicotinoid exposed bumblebees get heavier pollen loads from the first flower that they find while unexposed bumblebees load up lighter from more flowers.

Bird's foot trefoil (Lotus comiculatus), native to temperate Eurasian and North African grasslands, is favored by neonicotinoid exposed bumblebees: Fredrik Lähnn, Public Domain, via Wikimedia Commons

Neonicotinoid exposed bumblebees are collecting more pollen and flying to fewer plants than nevertheless more efficient bumblebees lacking chronic exposure, according to a study published online March 14, 2016, in Functional Ecology.

Researchers at Royal Holloway University in London, England, and University of Guelph in Ontario, Canada, base their findings upon one pesticide, two flowers and 10 colonies. The buff-tailed bumblebee (Bombus terrestris audax) colonies can be divided into recipients of acetone and sucrose solution with or without 10 parts per billion (ppb) thiamethoxam. A “bright but shaded outdoor” 78 x 52 x 100-centimeter (30.71 x 20.47 x 39.37-inch) flight area drew bumblebees to one of two favorite forage plants.

The 131 florets of two bird’s-foot trefoils (Lotus corniculatus) elicited more visits from neonicotinoid exposed bumblebees than one white clover (Trifolium repens) with 11 flowering inflorescences.

Bumblebees generally “forage in the environment to collect nectar and pollen, both to feed themselves but also to provision their colonies and feed their developing brood.”

The study’s 160 bumblebees got foraging flights in for nectar and pollen between June 23, 2014, and July 3, 2014, from 10:30 a.m. to 4:00 p.m. They had to coordinate multiple clues of color, fragrance and structure to “locate flowers, assess their profitability and how to manipulate them to extract their rewards.” Research indicated tendencies to “forage even when they themselves are satisfied” even though “foraging for pollen can be a more challenging task than foraging for nectar.”

The study’s neonicotinoid exposed bumblebees joined unexposed bumblebees in tending toward nectar-only forages while a total of 23, selected from both groups, foraged only for pollen.

Professors Nigel E. Raine in Canada and Dara A. Stanley in the United Kingdom kept track of the size of the loads that their bumblebees carried. Seven neonicotinoid exposed bumblebees left with “medium” sized loads, and 11 with “small,” while making many more visits to the first flowering plant that they saw.

The co-researchers’ previous research makes it clear that “the pollination services provided were not affected suggesting that this increased activity did not deliver improved pollination quality.” They noted that unexposed bumblebees learn “manipulation behaviour” for nectar-collecting and pollen-gathering by emphasizing accuracy in “speed-accuracy trade-offs” and “investing more time and/or energy in learning.”

The two co-researchers observed that other, similar studies with the neonicotinoid imidacloprid suggest that foraging abilities decline or stabilize, but do not improve, with pesticide exposure.

Bird's-foot trefoil produces more nectar while white clover provides a "more nutritious forage source," with "twice the total sugar content and higher concentrations of amino acids."

More qualifies as less since trefoil quenches thirst less efficiently than clover and neonicotinoid exposed bees quit learning to "manipulate a greater number of flower types." Downward-curving or flat-lined learning and memory curves for such a "cognitively challenging" task potentially result in "negative impacts on pollination service delivery" and wild seed set. Neonicotinoid exposed bumblebees potentially "scent mark flowers without proper visitation thereby discouraging other bees from visiting them" and show floral preferences that stress their colony's survival.

Thwarted forages on "real wildflowers with complex morphology even in a relatively unchallenging scenario" threatens "augmented" impacts under "more challenging conditions in a wild, fully-outdoor setting."

Neonicotinoid exposure affects bumblebee foraging: Nigel Raine @NigelERaine via Twitter March 14, 2016

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Lotus corniculatus: Fredrik Lähnn, Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Lotus_corniculatus10.JPG

Neonicotinoid exposure affects bumblebee foraging: Nigel Raine @NigelERaine via Twitter March 14, 2016, @ https://twitter.com/NigelERaine/status/709418986077757440

For further information:

“Bee Flower Choices Altered by Exposure to Pesticides.” Phys.Org > Biology > Plants & Animals > March 14, 2016.
Available @ http://phys.org/news/2016-03-bee-choices-exposure-pesticides.html

“Bee Flower Choices Altered by Pesticide Exposure.” Biotechnology and Biological Sciences Research Council > News, Events and Publications > Food Security News > 2016.
Available @ http://www.bbsrc.ac.uk/news/food-security/2016/160314-pr-bee-flower-choices-altered-by-pesticide-exposure/

Gilmour, Kara. 15 March 2016. “Bumblebees Pesticides: Study Raises Serious Concerns about Exposure That Can Harm Food Supply.” NewsOxy > Science.
Available @ http://www.newsoxy.com/science/bumblebees-pesticides-189988.html

Hazen, Shelley. 15 March 2016. “Pesticides Damage Bumblebees’ Pollinating Skills – And That Spells Trouble for Our Food.” Inquisitr > Science.
Available @ http://www.inquisitr.com/2890308/pesticides-damage-bumblebees-pollinating-skills-and-that-spells-trouble-for-our-food/

Montgomery, Garrett. 15 March 2016. “Bumblebees & Pesticides: Bees Affected by Exposure Face Problems.” The Spreadit > Tech.
Available @ http://www.thespreadit.com/bumblebees-pesticides-exposure-70611/

Nigel Raine @NigelERaine. 14 March 2016. "Bee flower choices altered by #neonicotinoid pesticide exposure @DaraStanley @FunEcology." Twitter.
Available @ https://twitter.com/NigelERaine/status/709418986077757440

PAN Europe. 2 February 2015. "How Neonicotinoids Kill Bees." YouTube.
Available @ https://www.youtube.com/watch?v=CLuX5TjRDdg

Stanley, Dara A.; and Raine, Nigel E. 14 March 2016. “Chronic Exposure to a Neonicotinoid Pesticide Alters the Interactions between Bumblebees and Wild Plants.” Functional Ecology. DOI: 10.1111/1365-2435.12644
Available @ http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12644/full

Wheaton, J. 15 March 2016. “Bumblebees and Pesticides Study: Chemicals Can Affect Insects’ Learning.” NewsMax > The Wire.
Available @ http://www.newsmax.com/TheWire/bumblebees-pesticides-study-pollen/2016/03/15/id/719154/