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Pollinator Week Special Edition: Honey Bee Personalities and a Q&A with a Bee Scientist

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This week is Pollinator Week! To celebrate I thought I’d feature a really cool research study on personality in honey bees. I’ve also added a Q&A with one of the scientists behind the research. Let’s dive in!

The word “personality” in the title of the research paper caught my eye. It’s not a word often associated with bees, because it may seem like honey bees are just little robots doing their chores. After all, there are tens of thousands of honey bees in a honey bee hive, and lots of work needs to be done to keep the hive clean, to feed everyone, and to make sure all of the baby bees grow into strong adults. The bees split up the labour: younger bees feed the larvae (baby bees) and do “housekeeping” chores, whereas older bees tend to guard the nest and go outside to collect food (pollen and nectar). The entire colony is a well-oiled machine, with every bee doing her part. Could there be any room for honey bees to show individual differences?

A honey bee. Does she have her own personality? Photo source: iNaturalist.

Bumble bee colonies are quite similar, in that there are housekeeping bees and food-gatherers and even undertaker bees. During my many hours of watching bumble bees when I was in university, I could often tell bees apart based on what I liked to think of as their “personality.” Each bee had a numbered, coloured, plastic disc that I had glued to their back so I could tell them apart. But each bee behaved a little differently. For instance, Green#6 was always hopping at the door to get out and start foraging (yes, she actually jumped up and down). Yellow#2 was always a little slow to start but once she began foraging she was a little workhorse. And Red#10 always flew around our flight cage for a little while before landing on a flower, instead of just flying straight to a blossom like the other foragers. I wondered whether bees actually did have their own little personalities. And how would we determine that scientifically? Turns out I wasn’t the only scientist who wondered about this.

I am also excited to feature this particular research article because one of the authors is Dr. Amy Toth, who I feature in my upcoming book, The Beekeepers. She does amazing research on honey bees, bumble bees, and wasps. The other author is Dr. Alexander Walton, who very kindly chatted with me about their experiments and what it was like working with the bees (more on this soon).

So, first off, what do Drs. Walton and Toth mean when they talk about “personality”? They think of personality as having three parts. One is consistency over time: a bee acts in a specific way throughout its life. Another is that no matter what situation the bee finds herself in, she behaves in a similar way. This is called consistency over contexts. And finally, the individual shows consistent, related clusters of behaviours. Somehow Drs. Walton and Toth had to test for these three things in honeybees. How did they do it?

Drs. Walton and Toth designed two experiments. In the first experiment, they placed small groups of newly-hatched honey bees into small Plexiglas cages. This allowed them to watch their behaviour much more easily (remember: there are thousands of honey bees in a hive!). On each bee they glued a coloured, numbered plastic tag to the thorax (the bee’s back or middle section).

Small cages with groups of labelled honey bees that Drs. Walton and Toth used in their first experiment. Photo source: Dr. Alex Walton.
Some labelled honey bees in a plastic tub before the experiments began. Photo source: Dr. Alex Walton.

In their first experiment, Drs. Walton and Toth presented the bees with three different situations and watched how the bees reacted. These situations were based on natural events that the honey bees would experience in their hive. One situation was presenting the bees a microscope slide that had queen mandibular pheromone smeared on it. Queen mandibular pheromone is a chemical that the queen bee gives off when she wants to be fed, and it causes worker bees to touch the queen with their antennae and feed her with their proboscis (tongue). (You can buy synthetic queen mandibular pheromone. I had no idea!)

Another situation was presenting the bees a microscope slide with honey bee alarm pheromone smeared on it. They got alarm pheromone from crushed bee stingers and venom sacs. Alarm pheromone is a chemical that guard bees give off when the hive is being attacked, and it causes worker bees to assemble and help defend the hive.

Finally, Drs. Walton and Toth presented the caged bees with an intruder bee from another colony. They actually tied a piece of fishing line around the middle of a honey bee, placed her in the cage, and then after the caged bees reacted, they pulled the harnessed bee out. Pretty clever! (They chilled the intruder bees a bit to slow them down so that they could tie the fishing line around them. The bee then woke up after they were tied. They did the same thing when labelling the bees: they chilled them for a bit first so they would be still during the labelling process. They bees eventually woke up and went back to normal.)

Several intruder honey bees tied to fishing line before being presented to the caged bees. Photo source: Dr. Alex Walton.

So, in each of the small cages, newly-hatched honey bees were presented with three things to react to: (1) a chemical signal that said, The queen is hungry! Feed her! (2) a chemical signal that said, The hive is under attack! and (3) an actual stranger honey bee invading the cage. Remember that to show personality, the caged bees would have to react similarly over time and across all three situations. Drs. Walton and Toth presented these three situations to the caged bees multiple times over 17 days. (That was how long the bees lived for before they died. Honey bee works have relatively short lives!) What kinds of behaviours did Drs. Walton and Toth look for? They wrote down whether the caged bees did any of the following: trophallaxing with a cage-mate (exchanging food tongue-to-tongue); attacking a cage-mate; using their antennae to touch the microscope slide with queen mandibular pheromone; using their antennae to touch the microscope slide with alarm pheromone; attacking the intruder bee. In all, they had 35 small cages with 171 honey bees to watch. What did they find?

For the first dimension of personality, that bees needed to show similar behaviour over time, they found that yes, honey bees tended to repeat their behaviour over the 17 days of the experiment. Hooray! The first requirement of personality was met!

For the second dimension of personality, that bees needed to show similar behaviours across different situations, they found evidence for this, too! Caged honey bees that were aggressive toward a cage mate when presented with a microscope slide with alarm pheromone were more likely to be aggressive toward cage mates when in the presence of queen mandibular pheromone as well. In other words, some caged honey bees seemed to have a more aggressive personality compared to other caged bees. Also, caged bees that showed trophallaxis as a reaction to queen mandibular pheromone were more likely to show trophallaxis in the other two contexts as well (that is, alarm pheromone and intruder). Trophallaxis is thought to be used not only to feed other bees, but also to exchange queen and forager pheromones, to inform other bees about the food needs of the colony, and to exchange information about the quality of nectar a forager collected. So maybe bees that show trophallaxis across situations have a “communicator” personality?

Now for the second experiment. For this one, Drs. Walton and Toth focused on the third part of personality: behaviours that tend to cluster together. After they noticed that some caged bees showed trophallaxis across situations, they wondered whether some honey bees are more “interactive” with other bees. So, they figured out a list of behaviours that bees would need to show to be considered “interactive bees”:

  • Grooming other bees
  • Caring for baby bees
  • Waggle dancing
  • Following another bee who is waggle dancing
  • Guarding the hive
  • Feeding the queen or touching her with their antennae
  • Trophallaxis

They distinguished interactive bees from “non-interactive” bees. Non-interactive bees were bees that spent most of their time:

  • Cleaning cells in the hive
  • Fanning their wings to help keep the temperature steady in the hive
  • Going outside of the hive to forage for nectar
  • Going outside of the hive to forage for pollen
  • Processing pollen
  • Processing nectar
  • Grooming themselves
  • Washboarding: scraping her legs and mouthparts across wooden surfaces of the hive (we’re not sure why they do this…)
  • Working the wax in the hive

This time, instead of watching small groups of honey bees in tiny cages, Drs. Walton and Toth watched bees in a full colony, so they could look for all of the behaviours that are listed above. They had special hives built that had Plexiglas walls so they could watch the bees without disturbing them. They labelled and watched over 1000 honey bees in 4 Plexiglas hives. That’s a lot of bees to watch! This experiment was a biggie.

Dr. Alex Walton watching honey bees in a specially-made observation hive. Photo source: Dr. Alex Walton.

After many, many hours of watching the bees, was there evidence of clustering of interactive and non-interactive behaviours? Although honey bees did not show a perfect distinction between interactive and non-interactive behaviours (that is, individual bees sometimes showed both), non-interactive behaviours tended to cluster together. The strongest relationship was between washboarding and wax work: honey bees that performed one of these behaviours tended to perform the other as well. Even though Drs. Walton and Toth spent oodles of time watching over a thousand bees, more experiments will need to be done to give us a clearer idea about whether some bees are more interactive than others.

So, after all this work, did honey bees show evidence of personality? Yes, they did! Individual bees tended to show individual differences in their behaviour across time and different situations, and some honey bees were more non-interactive than others.

What I find so cool about this research is the clever methods used to investigate whether or not honey bees show evidence of personality. It is amazing to think that even though honey bees are “programmed” to switch tasks as they age, moving from inside-hive chores to more outside-hive chores, we now have evidence that they can still show individual differences as well. Like all good experiments, the ones featured here lead to more questions: What causes honey bees to differ in personality, as it is defined here? Why are some bees different from others? What benefit would different personalities be to bees and their survival? Do other insects show signs of personality?

I also had questions about what it was like to carry out these experiments, and Dr. Walton very kindly gave me answers!

Q&A with Dr. Alex Walton

Dana: What did you like doing most in this research study?

Alex: It is really rewarding to just sit and watch the inner workings of a hive of bees. There are so many individuals doing so many things, and so many bizarre behaviours. You constantly find yourself thinking, “Why is she doing that? What does that signal to that other bee?”

Dana: Were there any challenges in doing this research?

Alex: The study was very challenging because it required keeping track of hundreds of bees. I would slowly scan the observation hives from the top left to the bottom right, looking for marked bees and then writing down what behaviour they were performing. It was extremely tedious!

Dana: Can you talk a bit more about tying honey bees to fishing line? That must have been difficult!

Alex: The reason I tied them to the fishing line was so that I could easily retrieve them once the observation period was over. Trying to get a loose bee out of the cage (as she is being chased and attacked by other bees ) without accidentally letting any of the other bees out would not have been an easy task! I know from experience, as one of my tied bees did manage to wriggle free of her binding once in the cage and retrieving her was no easy task. However, tying a fishing line to a bee is no easy task either, as it really requires 2 hands (one to hold the bee down with forceps, and two to place the line around the bee and tighten). As I was not blessed with 3 hands, I would first chill the bee in the fridge to slow her down, then gently place a loop of fishing line around her waist.

Dana: Did anything about your results surprise you?

Alex: One of the main findings of the study is that honey bee workers have consistent behavioural differences throughout their lives. This was surprising because we know that honey bees have stereotyped behavioural transitions as they get older. They will switch from nursing tasks (feeding larvae, or baby bees) to outside tasks (foraging), and pretty much all of them do this. So, the fact that they still have distinct behavioural differences even as they shift behavioural repertoires was very surprising!

Dana: What advice do you have for kids who want to study bees or other animals?

Alex: Take some time (or a lot of time) to sit and watch animals: at a bird feeder or bird bath, follow a trail of ants to their anthill, watch the squirrels at the park interact with each other. Then, start asking yourself questions about what you observe, and write those questions in a notebook (it isn’t real science unless you write it down!): Why is that bird splashing around in the water? Why are those ants attacking that other ant? Are those squirrels playing or fighting? Try to come up with your own explanations for your questions, and then fact-check them by looking online or in a book. The first skills a scientist needs to develop are a keen eye for observing nature and an inquisitive mind that is always asking questions. For kids who want to study bees in particular: 1) go to a flower patch and watch the bees visiting flowers. See if you can follow one bee’s path: how many flowers does she visit? Are they all the same kind?  2) Visit with a beekeeper who will open up a hive and show you what the bee home life is like, and 3) Don’t be afraid to get stung! Yes, getting stung is not fun but it’s not the most painful thing in the world. For every bee scientist, the first thing they had to do was get confident around bees.

Dana: What are you studying now?

Alex: Currently, I am studying the evolution of cooperative behaviour in paper wasps.

That sounds like a great topic for a future blog post! Happy Pollinator Week!

Reference

Walton, A., & Toth, A. L. (2016). Variation in individual worker honey bee behavior shows hallmarks of personality. Behavioral Ecology & Sociobiology, 70, 999-1010. DOI: 10.1007/s00265-016-2084-4

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Animals

World Bee Day: Bees Working Together

By Posted on 7 min read 473 views

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

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