It’s been a while since I posted about bees. My post about Costa Rican bumblebees gets quite a few reads, and apparently it’s pollinator week! So I thought I’d go to an extreme place to find bees this time and post about Bombus polaris, an Arctic bumblebee.
I had a hard time finding anything on this cutie. I’m guessing it’s at least partly because research in the Arctic is expensive and it’s hard to get up there. Plus, I’m sure the Arctic is not the first place people think of when it comes to bumblebees and pollination!
However, I did find one study done in the ’70s on pollination of Arctic flowers at Ellesmere Island, Canada. Bombus polaris was one of the main pollinators of a number of plants such as the Arctic willow (Salix arctica) and the Arctic lousewort (Pedicularis arctica). But the main pollinators of Arctic flora? Flies!
Bombus polaris lives in a unique area of the world where the growing season is very short, there’s 24-hour sunlight, and temperatures might only rise to 10 degrees Celsius in the summer. To adjust to this cooler climate, Bombus polaris is fuzzier than temperate bumblebees and as a higher body temperature.
Recently there was a New York Times story on Arctic bumblebees. Perhaps with increasing interest in pollinators and effects of climate change, there will be more to report on this fuzzy critter in the near future! References
Heinrich, B., & Vogt, F. D. (1993). Abdominal temperature regulation by Arctic bumblebees. Physiological and Biochemical Zoology, 66(2), 257-269.
Kevan, P. G. (1972). Insect pollination of high arctic flowers. The Journal of Ecology, pp. 831-847.
How cool would it be to follow a bumblebee for a day or two? To see where is flies, to see what it does in the nest…
Turns out scientists are beginning to do just that, thanks to advances in technology!
I stumbled across a paper that reports how a group of scientists attached tiny radar tracking devices to four bumblebees, and then followed them for their whole life! Here is a picture of what the radar tracking device looked like:
The device was a small metal pole about 16 mm in length, sticking straight up from where it had been superglued to a plastic disc that had been glued to the bee’s thorax. Apparently these transponders attached to the bees weighed about 15 mg.
Is this heavy for the bee?
To put it into perspective, worker bumblebees weigh between 175-200 mg, so the transponder is only 8-10% of the bee’s mass. As the authors of the study point out, worker bumblebees can carry pollen loads of up to 90% of their body mass. So the transponder is small potatoes to the bee!
The bumblebee nests were beside a large field of mostly thistles. The researchers tracked the four bumblebees until death or until they did not return to the nest for 48 hours, by which time they were presumed dead.
What did they find?
Here is a handy-dandy table that summarizes the “lives” of the four bumblebees:
Note: Exploitation flights were flights that were a single loop, with a stop where the bee had stopped in the past. Since bumblebees tend to return to flowers from which they gathered nectar and pollen, exploitation flights were assumed to be trips where the bees collected food. All other flights were categorized as exploration.
Four (out of many) Things to Notice from the Table Above:
There is so much variability between the four bumblebees! Bumblebees are not just little clones when it comes to their flight and foraging behaviour. They don’t all do the same thing when they fly out of the nest.
There were occasions when Bees 1, 2, and 3 did not return to the nest in the evening, but returned the next morning. What did they do all night?! They likely found a nice place to hide, as bees can’t fly in the dark.
Bee 1 was a little superstar: She had way more exploitation flights and more flights in general. She also had the least number of exploration flights before exploitation flights. I wonder why the other bumblebees were not as diligent?
Poor Bee 2. She lived for only 6 days.
With such differences across bumblebees, can I dare say bumblebees might have different personalities? After all, there’s some evidence that they might have emotions.
Julie, a chimpanzee, decided one day to stick a piece of long grass into her ear.
Apparently she would do this quite often. Then she would carry on with her day-to-day activities: grooming, playing, resting…with a big piece of grass hanging out of her ear.
Was it some strange kind of fashion statement? What would possess a chimpanzee to stick a piece of grass into their ear?
What first came to my mind was how my son loves to have his ear cleaned out with a Q-tip. He says it “feels nice.” Maybe it feels nice to have a big piece of grass stuck in your ear?
The amazing thing was that some of the other chimpanzees who lived in the sanctuary with Julie started to stick grass in their ears, too.
Some researchers wrote an article about Julie and her fancy ear accoutrements in the journal Animal Cognition. They had over 700 hours of video footage of Julie and her chimp colleagues, and they watched for this grass-in-ear-behaviour. Julie did it most often, followed by Kathy, Val, and Julie’s son, Jack. The researchers call the grass-in-ear behaviour a “spontaneously emerged tradition.”
Julie has since passed away, but apparently her ear grass-fashion lives on. Reference
Van Leeuwen, E. J. C., Cronin, K. A., & Haun, D. B. M. (2014). A group-specific arbitrary tradition in chimpanzees (Pan troglodytes). Animal Cognition, 17(6), 1421-1425. DOI: 10.1007/s10071-014-0766-8.
After my visit to the Cambridge Butterfly Conservatory yesterday, I started thinking about what might be going on in the little brains of those creatures. Like bumblebees, butterflies and moths drink nectar from flowers. They have to decide where to land to get food: what is a flower and what isn’t? They have to expend energy probing flowers with their long tongues (proboscis), so they have to be choosy about there they “stick it.” It really fascinated me how the Owl Butterfly on my arm was licking my red sweater. Like bumblebees, do butterflies and moths have unlearned preferences for certain colours, like red? Or did it lick me because I smelled good? Or was it a combination of both, or something else?
I did an online search to see if any interesting nuggets are out there about butterfly and moth cognition. I found an uber cool one about moths retaining memories they made as caterpillars!
Caterpillars turn into butterflies or moths in a process called metamorphosis. Given how different a butterfly or moth looks and behaves compared to a caterpillar, it is thought that the entire caterpillar must be broken down inside the cocoon and re-arranged to form a butterfly or moth. But if butterflies and moths can remember what they learned as caterpillars, then this suggests that at least some of their neutrons (brain cells) remain intact during metamorphosis. Their bodies might have been scrambled up, but maybe at least a portion of their nervous system remains the same?
The researchers in the study I found focused on tobacco hornworm caterpillars, which transform into tobacco hornworm moths. The researchers exposed the caterpillars to a particular odour followed by a mild electrical shock. They repeated the odour-shock pairing until the caterpillars learned to avoid the odour (i.e., they would crawl away from it). Then, after the caterpillars built a cocoon and transformed into a moth, the newly emerged moths were placed one at a time in a Y-maze. A Y-maze looks exactly like it sounds: It is a big tube in the shape of a Y. The moth was placed in the vertical part in the bottom. Unscented air was piped into one arm of the Y and air scented with the odour encountered as a caterpillar was piped into the other arm. The researchers watched to see which arm of the Y-maze the moth crawled into: the unscented arm or the odour arm.
Moths chose the unscented arm significantly more often than the scented arm, suggesting they were avoiding the scented arm; i.e., avoiding the odour that brought them shocks as caterpillars.
A very cool nuance in the experiment: Butterflies and moths smell with their antennae, and there are brain structures called “mushroom bodies” that receive information directly from the antennae. The researchers gave the odour-shock pairing to caterpillars of different ages, whose mushroom bodies would be at different stages of development. During the test as moths, those moths who had been exposed to the odour-shock pairing as caterpillars before their mushroom bodies would have been developed did not show avoidance of the odour. However, moths who had been exposed to the odour-shock pairing at an age when their mushroom bodies would have been developed did show avoidance of the odour. So this suggests that a particular brain structure–or at least the synapses within them–remain intact during metamorphosis.
As Brandon Keim writes in his article in Wired, “wouldn’t it be poetic if scientists ended up developing treatments for dementia based on the persistence of butterfly memories?”
Food for thought, for sure.
Blackiston, D. J., Casey, E. S., & Weiss, M. (2008). Retention of memory through metamorphosis: Can a moth remember what it learned as a caterpillar? PLoS ONE, 3(3): e1736. DOI: 10.1371/journal.pone.0001736.
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…
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.
An absolutely amazing study was recently published about bumblebees learning how to pull a string to get food. And not only that, bumblebees learned how to do it from other bumblebees. (Yay, bees!)
The set-up: Sugar water (food) was available in a blue plastic “flower.” Bumblebees learned to drink the sugar water from the flower, and then the flower was placed more and more underneath a Plexiglas “table.” There was a string attached to the flower so that the bees simply had to pull the string with their front legs or mandibles (mouthparts) to slide the flower out from under the table.
Here is an awesome picture of what this set-up looked like. I LOVE the picture because it is so clear and you can even see the label that was glued onto the bumblebee’s thorax! This bee must have been Yellow #5 or Yellow #15 (I can’t quite see if it’s one or the other).
Here is a diagram showing the steps the bumblebees needed to learn the task:
With training like this, most bumblebees learned how to pull the string to get at the flower. When you think about it, this is pretty amazing behaviour for bumblebees because they don’t need to do anything like string-pulling in nature to get at nectar in flowers.
And if that wasn’t cool enough, the researchers found that bumblebees never exposed to the string-pulling task learned how to pull the string to get the food by watching other bumblebees do it! Social learning! In bumblebees! (BOOM! Mind blown!).
During graduate school with my own bumblebee experiments, I sometimes wondered if bumblebees could learn from other bumblebees–what is called social learning. When bumblebees were drinking from my own artificial flowers I would often see bumblebees who had never been to the flowers before make a “bee-line” to the flowers and start to drink (or, if a bee was already there, crash into it, knock it out of the way, and then start to drink!). I wondered if the bumblebees could recognize other bumblebees and learn what the other bumblebees were doing.
These little critters sure are impressive. Just think: they have a brain the size of a sesame seed, but can learn a complex task like pulling a string…even learn it from other bumblebees. Quite the cognitive toolkit that is packed into a brain that’s so much smaller than ours! Gives me a whole new appreciation for the animal kingdom and nature in general.
Here is a great video where you can see the experiments in action.
Alem, S., Perry, C. J., Zhu, X., Loukola, O. J., Ingraham, T., Søvik, E., & Chittka, L. (2016). Associative mechanisms allow for social learning and cultural transmission of string pulling in an insect. PLoS Biology, 14(10): e1002564. doi: 10.1371/journal.pbio.1002564.
I came across a recently published study that I simply MUST share and comment on:
“Unexpected rewards induce dopamine-dependent positive emotion-like state changes in bumblebees.”
Wait–emotions and bumblebees in the same title?!
When I worked with bumblebees I certainly saw what could be interpreted as emotion-like behaviour. For instance, I would allow bumblebees to forage for nectar from articifical flowers I had in a flight cage (a screened-in, gazebo-like structure). The bumblebee “nest,” which was a wooden or plastic box, was connected to the flight cage via a tunnel with a gate I could control. I was literally the “gatekeeper” for which bumblebees could enter the flight cage. Soon I was able to identify which bumblebees were the keen foragers: they would race down the tunnel, fly directly to the flowers, eat, fly directly back to the tunnel, and scurry home. They were all business. If I saw these bees come out of the nest and I put the gate down so they couldn’t enter the flight cage, they would buzz and buzz and literally hop up and down repeatedly right in front of the gate until I opened it.
These bumblebees were certainly showing something. Frustration? Excitement? Murderous rage?
But these are human interpretations of behaviour. What were the bumblebees experiencing, if anything? That’s the key question.
Let’s have a look at the published study. What did they do to show that bumblebees exhibit emotion-like behaviour?
It’s pretty clever.
All of the experiments with the bumblebees were based on this one, dare I say, fact: When humans eat something sweet, they experience positive emotions. (Mmmm…pumpkin pie!)
Before bumblebees were given a test, the researchers gave them a bit of sugar water. Would the bumblebees show behaviour that is consistent with a positive emotion state?
(Another thing to keep in mind: Positive emotion states often result in biased decision-making: there is a tendency (for example, after eating a piece of pumpkin pie) to respond positively to ambiguous stimuli, and to react less negatively to aversive things.)
In the first experiment, bumblebees were trained to land on blue artificial flowers but not green ones. Then they were given an ambiguous situation where they were presented with a flower that was blue-green in colour. Before the blue-green test some bumblebees were given a droplet of sugar water. The bumblebees who got the sugar water took less time to land on the blue-green flower compared to bumblebees who did not get any “sweet snack.” In other words, the sweet snack lead to a positive response to an ambiguous stimuli, which is consistent with positive emotions.
(I should note that the researchers did some extra tests to rule out the possibilities that the sweet snack simply made the bees “expect” more sugar water, or made the bees more excited or active, and were thus more likely to explore the new blue-green colour. I’ll save you the gory details. But they are convincing.)
In another test, bumblebees were trained to drink from a feeder and then they experienced a simulated predator attack (what?!): a sponge pressing gently down on the bee, restraining it from moving for 3 seconds. Before the “predator attack,” some bumblebees got a droplet of sugar water. The bumblebees who received the sugar water took less time to resume foraging from the feeder after the “predator attack” compared to bumblebees who received no sugar water. So, the sweet snack was associated with the bumblebees reacting less negatively to the aversive event, which is consistent with positive emotions.
Finally, the last experiment is where things are really cool. The title of the research study has the word “dopamine” in it, which refers to a chemical (neurotransmitter) in the brain that is involved in the reward system. In other words, dopamine is one of the key neurotransmitters that is active in your brain (and in other species’s brains) when you are experiencing something positive. (Like pumpkin pie!)
The researchers subjected some new bumblebees to the “predator attack” experiment. This time all bumblebees received a drop of sugar water before the attack. Some bumblebees, though, were treated with a chemical that blocks dopamine. (There isn’t much detail in plain English about what this treatment was exactly, other than it was “topical.” So I guess it was some kind of liquid/substance that they rubbed onto the bees’ bodies?? Or sprayed on them??)
Anyway, the bumblebees that were treated with the dopamine-blocker took the longest to resume foraging after the predator attack. Thus, the dopamine-blocker prevented a positive emotion-state, which resulted in the bees taking longer to recover after the predator attack.
The researchers also repeated the blue-green test with new bumblebees: this time all bumblebees received sugar water before the test, but some bees got the dopamine blocker. The bees with the dopamine blocker took longer to land on the blue-green flower. Less dopamine, less positive emotion-state, less likely to respond positively to ambiguous things.
So, in a nutshell:
Like humans, giving bumblebees a sweet treat can result in behaviour that is associated with a positive emotion-state: a bias to respond positively to ambiguous things, and an ability to recover more quickly after aversive events.
The sweet treat does not simply give the bees more energy, or simply make them behave in a way that suggests they expect more treats.
Blocking a brain chemical in bumblebees that is involved in positive emotion states also blocks behaviour that is associated with positive emotion states.
Whew! That was a long post. Probably the longest post I’ve written about a research study. But emotions are complex, especially when it comes to other animals. Especially invertebrates!
Are you convinced that bumblebees have emotion-like states? I think it’s pretty convincing.
But no experiment is perfect.
Like I mentioned earlier, we can’t know what the bumblebees experienced. Did they experience a mental state that is associated with positive emotions? Were they in sugar-water-bliss? Or did the sugar water have no mental effect at all, and only altered their observable behaviour?
Something to ponder about over a piece of pumpkin pie.
Perry, C. J., Baciadonna, L., & Chittka, L. (2016). Unexpected rewards induce dopamine-dependent positive emotion-like state changes in bumblebees. Science, 353(6307), 1529-1531.
I admit I am sucked in by interesting titles. I came across this one in the journal Animal Cognition: “Affective forecasting in an orangutan: Predicting the hedonic outcome of novel juice mixes.”
I’ve never heard of “affective forecasting” before. This and “hedonic outcome” combined with “juice mixes”? I gotta read it!
Turns out this was a research study to determine whether an orangutan, along with some humans, could choose which juice combinations they would like based on their liking of the individual juices.
(Affective forecasting = predicting how you will feel.)
(Hedonic outcome = whether a result is pleasant or not.)
Specifically, they offered cherry juice, rhubarb juice, lemon juice, and diluted apple cider vinegar in little cups. The juices were coloured and the humans were not told what they were. The juices were presented two at a time, and the participant could taste them and choose which one they liked best.
The participants were ten humans and one orangutan: Naong, a male orangutan who was 21 years old. To indicate his choices of juice, Naong would point with his finger or point with a straw that he held between his lips (which is quite hilarious if you ask me).
So once Naong and the humans chose which juices they liked best, then they were shown three cups with a different juice in each. They watched as the experimenter poured one of the juices into another. The participant could then choose whether to drink the combination or the plain juice.
The participant was shown a cup of cherry juice, a cup of lemon juice, and a cup of apple cider vinegar.
The participant watched as the lemon juice was poured into the cherry juice.
The participant could then choose whether to drink the combination cherry-lemon juice, or the apple cider vinegar.
Below is a handy diagram that was included in the article, showing what was done. The bottom conditions with the covered bottles was to control for the fact that the participants (especially the orangutan) might simply be choosing the bottle with more liquid in it.
Turns out Naong was just as good as the humans in predicting which juice mixes he would like. Which suggests he can put memories together to precise a new outcome. Quite impressive!
Naong also had quite a penchant for cherry juice…as with most of the humans.
Here is a picture of Naong, who lives at a zoo in Sweden:
Saucing, G.-A., et al. (2016). Affective forecasting in an orangutan: Predicting the hedonic outcome of novel juice mixes. Animal Cognition. DOI 10.1007/s10071-016-1015-0.
When I think about pollination I think of flowers and bees.
Wind can also help pollinate flowers, as well as butterflies and bats and a host of other creatures.
What about plants under the water that need to be pollinated? Call me naive but I never thought about this before.
Apparently plants under the water can pollinated by the flow of the water: the pollen from one plant detaches and flows through the water to another plant. Then POOF! Pollination. Technically this is called hydrophilic pollination.
But a new article in Nature Communications suggests that there are little creatures under the water that perform the same function as bees!
They studied Thalassia testudinum, or turtlegrass, which is a type of marine seagrass that forms meadows in sandy or shallow places in the Caribbean Sea and the Gulf of Mexico. (Meadows in the sea? How cool!) Tiny white flowers open up at night that contain sticky stuff containing pollen and sugary substances.
It just so happens that at night, a lot of teeny-tiny marine invertebrate species are active in the water. The researchers witnessed these little creatures feeding off of the flowers and pollen getting stuck to their bodies. The creatures then visited other flowers and voila: pollination! They made a really nice You Tube video of this.
The researchers concluded that turtlegrass has a “mixed pollination syndrome”: hydrophilous (movement of the water) and zoobenthophilous (benthos refers to the community of organisms that live on or near the sea bottom). This is very similar to flowering plants above the water that rely on wind and pollinators to reproduce.
Van Tussenbroek, B. I., et al. (2016). Experimental evidence of pollination in marine flowers by invertebrate fauna. Nature Communications, 7, 12980 doi: 10.1038/ncomms12980.
Wikipedia. (2016). Thalassia testudinum. Retrieved September 29, 2016 from: https://en.wikipedia.org/wiki/Thalassia_testudinum
Wow, combine the word “spider” with “cannibalism” in the title of an article and there’s no way I can’t read it!
The specific title of the article I found is, “Cannibalism in spiderlings is not only about starvation.”
Baby spiders eating each other? What?!
Turns out that after spiders hatch, they tend to congregate for a while in a big group. This is called gregariousness. The baby spiders seem to get a long for a while, but then at some point they start acting aggressive…even eating each other!
The study I read tried to figure out if baby spiders sometimes eat each other simply because they are hungry, or whether they do it for some other reason(s).
The species they studied was Angelenalabyrinthica. (What a poetic name!) They put recently-hatched babies in groups and varied the amount of food (dead flies) they were given. Basically they found that the group that received no food, and would therefore be starving, did NOT cannibalize each other. Cannibalism seemed to be linked to spiders that had moulted (shed their skin). The authors suggest that when moulting occurs, some changes in communication between the spiders happen and it often leads to aggression. (I have visions of Dr. Bruce Banner changing into The Hulk…)
So it appears that cannibalism between spiders, and aggression in general, is more complicated than just being hungry. Spiders communicate things to each other that we are just beginning to find out. Such complexity in such a tiny species really makes me appreciate the whole animal kingdom that much more. Awe is more like it. Who knows what happens in little spider worlds?
A note on the name of the spiders: Why are they named labyrinthica? These spiders apparently spin flat, horizontal webs that are attached to funnel-like “retreat webs” that are like a maze or labyrinth.
Imagine all the cognitive calculations involved in spinning a contraption like that, then navigating within it! Very impressive for a tiny being.
Lessen, P., Trabalon, M., & Jeanson, R. (2016). Cannibalism in spiderlings is not only about starvation. BehaviouralEcology & Sociobiology, 70, 1669-1678.