World Bee Day: Bees Working Together

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May 20th is World Bee Day! I found a really cool research article that features both honey bees and bumble bees, and I thought I’d share it to help celebrate.

By far, honey bees are the more well-known of the pollinators. These are the bees that beekeepers take care of in tall, wooden hives in a field or in their backyard. Commercial beekeepers rent their honey bee hives to farmers to pollinate food crops, as opposed to hobby beekeepers, who just let their beehives stay put and harvest honey every once in a while. Although commercial beekeepers collect and sell honey, too.

The ever-popular European or Western honey bee, Apis mellifera. Photo source: iNaturalist.
A group of honey bee hives. Photo source: Wikipedia.
Beekeepers inspecting a honey bee hive. Photo source: mnn.com.

The reason why wooden honey bee hives are so tall is because there are thousands of honey bees in a honey bee colony. They need lots of room to move around, raise baby bees into adults, and store their honey. Honey bees are used to pollinate food crops because there are many bee mouths to feed, so lots of honey bees in a hive go out to collect nectar (which the adult bees drink for energy) and pollen (which has the protein needed by baby bees to grow).

What is pollination, anyway? Pollination happens when pollen grains are moved from one part of the flower to another. When this happens, the flower can turn into fruit and create seeds, and the seeds allow new plants to grow. When a honey bee visits a flower, pollen grains stick to her, and as she moves around they can rub off onto the part of the flower that receives pollen. So in a way, bees pollinate flowers by accident!

But honey bees are not the only pollinators. Flies, butterflies, bats, hummingbirds, beetles, and moths also pollinate flowers. Some plants are even pollinated by the wind! But there are also thousands of other species of bees besides honey bees that are pollinators. One type of bee that pollinates flowers happens to be my favourite type of bee: the bumble bee!

Bombus terrestris, or the buff-tailed bumble bee, which is found in many parts of Europe. There are hundreds of species of bumble bees with different fur colours and patterns. Photo source: iNaturalist.

Why are bumble bees my favourite? Besides looking like little winged teddy bears, they are quite tough little workers. Thanks to their fuzzy coats, they can go out and forage (collect food) when it is cooler outside, and because of their bigger size they can withstand stronger winds compared to honey bees. I remember doing some research in a blueberry field and the weather turned rather chilly and windy…a storm was coming. When I looked around, all of the honey bees had hurried on home but bumble bees were still out in force, collecting food, until the first few drops of rain arrived.

If bumble bees are such good little workers, why don’t farmers use them to pollinate their crops? Well, some do. There are companies that breed bumble bees and sell them to farmers, particularly to pollinate greenhouse tomatoes (honey bees don’t pollinate tomatoes). However, the colonies of bumble bees that come from these companies often have disease, due to the factory-like conditions that they are bred in. But that’s a story for another day. (I talk more about this in my upcoming book, The Beekeepers, to be released in March 2021.) But bumble bee colonies are quite small compared to honey bee colonies: a family of bumble bees is usually around 100-200 worker bees, plus the queen. Because there are so fewer mouths to feed, only a handful of bumble bees go out to forage at any one time. So a LOT of bumble bee colonies are needed to pollinate the vast fields of food crops that exist today. And, quite simply, people have used honey bees for hundreds of years to pollinate crops, whether or not there exist better native animals out there that can do a better job.

ANYWAY…all of this is to say that even though people use honey bees to pollinate their crops, there exist multitudes of native, wild critters, such as bumble bees, that pollinate the crops, too. Like in the blueberry field I was in: the farmer was using honey bee hives, yet bumble bees that naturally lived in the area were taking advantage of the bounty, too. (Honey bees are not native to North America. They were imported from Europe hundreds of years ago.)

Which brings me to the research study: could naturally-occurring bumble bees actually help honey bees do a better job at pollinating plants?

With some crops such as sunflowers and almonds, there is evidence that when in the presence of bumble bees, honey bees performed better. Specifically, they were more likely to fly to different rows of plants rather than sticking to just one plant or plants that were close together. Flying between distant plants causes what is called cross-pollination: taking pollen from one plant and delivering it to one that is further away tends to result in better fruit. A group of scientists in Belgium decided to study this systematically in sweet cherry orchards, to see if bumble bees do in fact influence honey bees to do a better job.

The scientists chose eight sweet cherry orchards across Belgium that were in full bloom. They made sure that each orchard was surrounded by hedgerows, wildflowers, trees, forests, and/or shrubs so that there would definitely be wild bumble bees living nearby.

Sweet cherry blossoms. Photo source: iNaturalist.

In each orchard they selected blocks that were each roughly 4 metres by 5 metres. In 25-minute intervals, the scientists used a net to catch every honey bee and bumble bee that visited the cherry blossoms. They then put each bee in a tube so they could identify it, and also so that they didn’t count the same bee twice. When 25 minutes were up, they released the bees. This data allowed them to measure bumble bee abundance, which was the number of bumble bees they counted, and bumble bee richness, which was the number of different species of bumble bees they caught. They also measured honey bee abundance (the number of honey bees they caught).

At the same time as bees were being caught and identified, other scientists walked slowly up and down the rows of cherry trees. When they saw a bee visit a cherry blossom, they noted whether it was a honey bee or a bumble bee, and they followed it to see whether its next visit was to a tree in the same row or to a tree in a different row. If a bee visited trees in different rows, this meant that the cherry blossoms were being cross-pollinated, and this should result in better cherries (bigger, juicier, and overall higher quality).

What did the scientists find? It was clear that bumble bees were the superstars! Compared to honey bees, bumble bees visited around twice as many cherry blossoms and changed rows almost twice as often. But the really cool thing? When there were more bumble bees and more types of bumblebees around (that is, high bumble bee abundance and richness), the better the honey bees performed! The honey bees visited more blossoms and changed rows more often when in the presence of bumble bees. Somehow, bumble bees influenced honey bees in a positive way to get more cherry blossoms pollinated.

So, what this research tells us is that it is important to provide places for wild bumble bees to live around food crops, even if the farmers are using honey bees to pollinate their plants. Providing habitat for bumble bees is a win-win situation: the bumble bees can have a home, influencing honeybees to do their best, and in the end, we can harvest better quality food.

But how exactly did the bumble bees influence the honey bees? Were they somehow yelling at the honey bees, “C’mon, sisters! Step it up!” Were they somehow showing the honey bees how to do a better job? That’s another puzzle for another research study!

What Can You Do to Help the Bees?

This post on World Bee Day would not be complete without some tips about what you can do to help bees. Here are some suggestions:

DON’T START KEEPING HONEY BEES! Many people think that by getting a honey bee colony and keeping it in their backyard, they are somehow “helping the bees.” Sorry, but no, you are not. Honey bees are not native to North America, and they take food and space away from native bees, like bumble bees, who are trying to live in the wild. Honey bees can also introduce diseases into the wild, and can make native critters (like bumble bees) sick.

AVOID PESTICIDES. There are tons of research studies that show that pesticides harm and even kill bumble bees, honey bees, and other insects. A well-manicured lawn is a wasteland for bees and other critters anyway.

TRY THE “MESSY LOOK.” Let your yard, or parts of your yard, go wild and see what happens. Many wildflowers and weeds are actually quite pretty. And many wildflowers and weeds provide nectar and pollen for bees. Leaving piles of leaves and branches in your yard also provides a place for the bees to hibernate for the winter or escape bad weather.

TRY TO PLANT NATIVE FLOWERS. Wild bumble bees know best the types of plants that naturally grow in their area. So why not do a bit of research and find out what plants naturally grow where you live? The bees will thank you!

Reference

Eeraerts, M., Smagghe, G., & Meeus, I. (2020). Bumble bee abundance and richness improves honey bee pollination behaviour in sweet cherry. Basic and Applied Ecology, 43, 27-33. https://doi.org/10.1016/j.baae.2019.11.004