Picky about their pollen

I like grocery shopping. There is something about the variety of foods and all the options available for the choosing. Lots of micro- and macro-decisions to make about what will go into our mouths and fuel our bodies.

There are variety and options in the quality of the foods, too. Do you choose the pasta sauce with sugar listed as the second ingredient, or do you pick a sauce that sticks more to the basics of tomatoes and spices (and is thus better for you)?

 When bees leave the nest to forage (find food), they are on a kind of grocery-shopping-expedition of sorts. Which flowers should the bee choose to land on? What kind of nectar and pollen should the bee bring back to the nest? 

Nectar is the primary source of energy for adult bees. It is made up of mostly carbohydrates (sugar). Pollen, on the other hand, is mainly for the larvae (baby bees) and the queen. Pollen is mostly protein which is important for development and egg production. Pollen also has a bit of fat and other nutrients. It turns out that not all pollen is created equal: the nutrient composition of pollen can vary from plant to plant. So one theory is that bees are more healthy if they can forage from a variety of plants rather than getting all their food from one source. Thus, a colony of bumblebees that forages from a field of wild flowers might be better off compared to a colony that only forages from a big farmer’s crop of blueberries, for example. Healthy bees are much more resistant to viruses and diseases and other nasty stuff.

Can bumblebees tell the difference between high-quality and low-quality pollen? If they can, can they also adjust their foraging so that they gather only the good stuff?

A group of researchers gave bumblebees the choice of pure pollen (high quality) and diluted pollen (low quality). The pollen was offered on petri dishes and the researchers weighed the dishes both before and after the bumblebees were allowed to forage. The low-quality pollen was diluted with cellulose, which bumblebees can’t detect by smell or sight. So from the bees’ point of view both types of pollen appeared the same. But the bees could taste the difference, and they consistently chose to collect the high quality pollen over the low quality pollen.

Then the researchers gave bumblebees the choice between apple pollen or diluted almond pollen. The bumblebees predictably gathered only the apple pollen, since it was of higher quality than the diluted almond pollen. But then the researchers offered apple pollen and regular ol’ almond pollen that was not diluted. Bumblebees quickly started to gather equal amounts of almond and apple pollen. This suggests that bumblebees monitor the quality of pollen at the source; i.e., at the flower. 

Pretty cool. It’s kind of like they read the ingredients before deciding to put the food in their cart.

I suddenly have a vision of a human-sized bumblebee, marching down the aisle of the grocery store, turning up her nose (er, antennae) at crappy, processed foods and instead heads toward the organic, locally-grown section…

 

bumblebee-pollen
This awesome photo of a bee covered in pollen grains is courtesy of Scholastic.

References

Ruedenauer, F. A., Spaethe, J., & Leonhardt, S. D. (2016). Hungry for quality–individual bumblebees forage flexibly to collect high-quality pollen. Behavioral Ecology & Sociobiology, 70, 1209-1217. DOI: 10.1007/s00265-016-2129-8.

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