[INTRO]

HANK: Springtime brings, you know, allergies for many of us. But also, it means the return of the cutest of the insects: the bees. They just are, don't at me.

And in this compilation, we're going to share some cool facts about bees and their behavior. From why they stare at flowers—you know, which we do as well—to why some of them... stab plants? Is that what that says? We're going to kick things off, though, with their buzz because bees are not the only insects that do this.

Other critters like beetles and those pesky mosquitoes, they buzz too. But some species of bees have a unique reason to produce that trademark sound. Let me explain.

Plenty of insects buzz when they fly around like beetles and that little [buzzing sound] of a mosquito - I hate that noise so much.

But bees are kind of special. There are more than 20,000 species of bees, all of which buzz when they fly and many of which also do it to communicate. But some bees buzz for a completely different reason that has nothing to do with communication or with flight: they're trying to get pollen out of flowers in what's known as "buzz pollination".

The kind of buzzing we hear when bees fly comes from their wings, which they can flap at up to 230 beats per second. Their quick wing movements cause air vibrations which your ear translates to sound.  The faster the wings beat, the higher the pitch. And if you've ever had the unfortunate experience of disturbing a hive, you've probably seen them buzz a little louder in agitation.

But in buzz pollination, they generate sound energy by vibrating their bodies, not their wings. They use the same muscles they'd normally use to move their wings, but kind of separate their wings from those muscles, so their bodies vibrate instead at about 400 beats per second. This full-body vibration causes the distinct buzzing sound you hear when bees are on a flower, which is a bit louder and higher-pitched than regular flying buzzing - it's actually in the tone of middle C.

That exact middle C buzzing is like a secret passcode that unlocks pollen trapped inside flowers.

But bees don't need to do it for every kind of flower. Most flowers are like a buffet, their pollen is on the outside of the anther - the male part of the flower - and just about anyone can come take it.

But there are some flowers, like the ones on tomato and blueberry plants, that have poricidal anthers. These anthers lock the pollen inside them, with just a small pore for an opening. To get the pollen out, the bees wrap their legs around the flower, bite down on the anther for grip, and buzz.

And when they vibrate at that super high speed, the pollen bounces up and down in the tube, and when in gains enough momentum, a bunch of it explodes out and lands on the bee. Only some bees can do this, like bumblebees and a few kinds of solitary bees. Honeybees can't.

But for the record, you don't really need a bee if you want to get the pollen out. A tuning fork will do. Or if you want to get more high tech, you can get tools to vibrate the plant to the right frequency, which yes do exist, and people actually use them to pollinate their plants; although they are not as efficient as the natural method. Because when it comes to getting up close and personal with a flower, bees are definitely the experts.

So, these bees do some extra buzzing to get pollen out of flowers, but what if there weren't any bees at all to do this shaking. Is it true that we will all spiral into starvation if honeybees go extinct?

Well, here's Stephan with more on that.

STEPHAN: Albert Einstein once said that if the bees dissapeared off the face of the earth, man would only have four years left to live. And that's terrifying. I mean Albert Einstein probably didn't say that, but the idea is terrifying.

And even if you haven't heard that particular quote, you probably heard how the death of honeeybees will lead to some doomsday scenario. Like, no honeybees will mean global starvation because 70% of our crops depend on them.

Or that all the world's flowers will vanish and the planet will become a colorless globe of death and despair.

Is it true? Not really.

Well, maybe a little. Mostly, trying to predict what will happen if honeybees go extinct, reveals just how much we need to care for other insects. Let's start with that 70% of all crops number, since that's the one we hear the most.

It seems to be a mistaken extrapolation. It's true that roughly 70% of flowering plant species are biotically pollinated, which means they need some sort of third party creature to do the pollinating for them. But that includes only around 35% of the world's food crops.

Many of the world's staples, like corn, wheat, and rice, for example, are wind pollinated, while others like tomatoes, lettuce, and beans, are self-pollinated. So tortillas, fried rice, french bread, and pasta would be fine in the advent of a bee-pocalypse. But that leaves a bunch of plants that do require pollinators that we might worry about.

Turns out that of the 100 or so crop species that dominate human diets around the globe, only 13 need pollinators. Though, another 30 are highly dependent on them. But, just because plants are pollinated by animals, doesn't mean that they need honeybees specifically.

The honeybee is just 1 of 20,000 or so species of bee, and bees aren't the only pollinators either. In fact there are close to 200,000 different species worldwide that act as pollinators, which include butterflies, flies, moths, beetles, birds, and even mammals like bats. So what would actually happen if honeybees went extinct?

Well, there would be some changes. You see the honeybee is the main human-managed pollinator. We've grown to rely on it because it's easy for us to house, transport, and control.

But it's not native to most of the places that depend on it now. Honeybees probably originated in asia around 300,000 years ago; from there they spread throughout africa and europe mostly by human hands, arriving in north america sometime in the 17th century. You could even think of them as an invasive species in some areas, because while honeybees are good for agriculture, they're not necessarily good ecologically.

They sometimes outcompete native bees which puts those other species at risk. They can also spread diseases to native bee populations, and in some places honeybees are the sole pollinator of invasive weeds; helping ensure those invaders stick around where they aren't wanted.

They can also spread diseases to native bee populations, and in some places, Honey bees are the sole pollinator of invasive weeds, helping ensure those invaders stick around where they aren't wanted.

If honey bees disappear tomorrow, some crops would be just fine. Most US alfalfa, for example, is now pollinated by a solitary Leafcutter bee.

And when researchers at the Cornell University Iticha apple orchard recently ditched their Honey bee hives, they found they still got a full crop of apples thanks to native wild bees. Other experiments have also suggested wild bees could pollinate crops in the absence of Honey bees. In Florida, Bumblebees could replace honey bees on blueberry farms.

And the solitary Blue Orchard Bee, which occurs throughout most of the United States and as far north as Canada, could pollinate peaches, cherries and almonds. And the Alkali bee, another solitary species that's native to the western and south western United States could pollinate onions. As a bonus, these wild bees aren't vulnerable to colony collapse disorder.

So in many cases if Honey bees disappeared, it's likely other species could step up.  But that doesn't mean we can stop worrying about the Honey bees. Without the Honey bee some foods would become more expensive, because for many crops Honey bees are still the most important pollinator. Coffee for example doesn't need Honey bees, but their presence can significantly boost yield.

And higher yield means less expensive coffee. There are also a handful of fruit, seed, and nut crops that would have much lower yields without Honey bees. For instance Macadamia Nut Trees are up to ten times more productive when visited by Honey bees.

And it's not like we could just go like 'well the Honey bees are gone now so lets move in the Bubmblebees!' There would be a lot of logistical hurdles to get over. For starters, there's concern that native bees could be in trouble too. Because they are also vulnerable to things like climate change and pesticides.

So we have to be just as proactive about protecting native bees as we're trying to be about protecting the Honeybee. And there are other challenges too. For example, it's more difficult and expensive to maintain commercial Bumblebee hives.

In part, that's because Bumblebees don't make honey, and honey sales are important for offsetting the expense of maintaining a hive. And Bubmlebee colonies are smaller than Honeybee colonies. They average around 200 to 400 bees, while Honeybee colonies can have as many as 50,000 individuals.

But, more to the point, the average bumblebee colony only lasts three to five months, while honeybee hives can last basically indefinitely when given the right conditions. 

Other native bees present challenges, too.  Solitary bees like the Blue Orchard bee don't multiply as rapidly as honeybees do, and farmers would have to provide nesting sites for them, which is a lot more labor-intensive than simply renting a few hives. 

Native bees also don't handle transport as well as honeybees do, so you can't just shuttle them around to the places they're needed.  And all the usual problems with introducing non-native species would still apply.

So the good news is that there's no doomsday scenario to losing honeybees, but perhaps it's not such a bad idea to lessen our dependence on them anyway.  Supporting biodiversity and native species is never a bad thing, and there's even some evidence that crops benefit from having a variety of pollinators.  For example, recent research in blueberry fields has shown that pollinator diversity leads to fatter blueberries, and who doesn't want that? 

The real issue is that, even without colony collapse disorder, native bees and other pollinators are struggling.  So, maybe we should worry a little bit less about honeybees and a little bit more about all the other species that are buzzing around us.

*end of video*

[Hank]  So, yeah, we might not need to worry about, like a 'doomsday scenario.'  But should we be worrying about the bees that spend a whole lot of their time staring at flowers?  Like are flowers the bees' secret mirrors or are they just deciding if it 'sparks joy'?  

Well let me clear that one up.

*next video: "Why Do These Bees Just Keep Staring at Flowers?"*

[Hank]  If you ever watch a bumblebee really closely, you will notice that some of them do something kind of odd when they're leaving a flower: They'll turn around mid-flight and just stare at it, like they're a little drone taking footage, like they're like "That was a really beautiful flower, I wanna get another look at it."

They're not doing it to collect information for their hive mates, although bumblebees do live in colonies, they are solitary foragers.  And also, not every bee does this the same way.  Researchers have found that the biggest bees do it the most.

So, what are they doing?

It seems to have something to do with memory.  This behavior is called "learning flight", and bees do it so they can remember how they got there.

They're taking a mental image of what the flower and the surrounding area look like so they can visit it again. That doesn't explain why the bigger bees would do this more.

That's a question that came up in a 2021 study published in Current Biology. In it, researchers were studying bumblebee learning flights by offering bumblebees fake flowers with fake nectar. And even though the bees didn't seem to notice that the flowers and the nectar were totally fake, they did realize that some of them were more rewarding than others. The nectar in different flowers consisted of either 20 or 50 percent sugar. So some flowers were kinda 'meh' and others were a pretty good score.

What was unexpected was that the bigger bees worked harder to remember the more rewarding flowers. They spent more time facing the flowers while flying away from them on their learning flights. Meanwhile, the smaller bees didn't seem to care; in fact, they treated all flowers equally.  This was surpising becauese if you're a bee and you find a really rewarding flower, it seems you would want to remember it regardless of how big you are, but that doesn't seem to be the case, and it turns out a key variable is carrying capacity.

Smaller bees don't forage that often--they spend more time on tasks around the nest. So when they do forage, they're limited by how far they can travel, so they tend not to be super picky. They dont bother putting all that effort into remembering super potent flowers because, well, they probably couldnt carry that much from them anyway. But larger bees can fly farther and carry more nectar back to the colony. Plus, their size means they can handle the cold better, and they have better eyesight so they can visit flowers in the morning when the light is low, and there's more nectar around. So, it may be worthwhile for them to seek out and memorize the locations of more rewarding flowers.

Overall, it's not totally unexpected to see different bees in the same colony adopting different learning behaviors; but it was surprising to find that these behaviors seem to be based on size. Now the question is: How many other overlooked bumblebee behaviors are there? Because the more we understand them, well, the more we get to marvel at how cool and complex bumblebees are.

[HANK] But also, knowledge like that can help us figure out how to care better to our fuzzy friends.

[TRANSITION]

[Hank] So it's safe to assume the bee's relationship with flowers is really tight. They visit flowers for the necter and help pollinate plants in the process. But what if we add a third wheel to the mix? Maybe something like yeast, because it turns out, they do other things besides making bread rise. Yes, the bee-flower relationship is actually a shocking love triangle. Here's Michael with more. 

[Michael] There are tons of cooperative relationships in nature. And one of the most obvious is between bees and flowers. Bees visit flowers for their tasty pollen and nectar, and they help pollinate the plant as they go. We've known about this for years, and it's so basic that you've probably learned about this in elementary school. But hold on to your juice boxes and kick balls, because this story is more interesting than we thought. In fact, there's a third, much tinier member of this relationship. Yeast. Yeast is a fungus found all over the globe, and the types that live in your garden do a bunch of important jobs. For instance, they help plant matter decompose, and they help roots absorb nutrients and water. Some of them also hang out in nectar, where they feed on it's sugar. So there's obviously some plant-yeast friendliness going on here, but as for how pollinators factor into that, it took a bit to sort out. Because yeast eats the nectar's sugar, pollinators might get less nutrition from yeasty nectar. So maybe they'd avoid it. Then again, a 2018 study showed that yeast can change a nectar;'s scent by altering it's chemistry, and we know scent affects pollinators, too. So maybe that factors into this somehow? Really, there are a lot of variables. So in 2019, a group in Belgium set out to get a better understanding this role yeast actually plays in the pollinator plant relationship. In one experiment, they took buff-tailed bumblebees and introduced them to a field of fake flowers. Some contained a yeast and sugar solution, while others just had sugar water. They had hypothesized that the yeast would negatively impact the bees' behavior and health, except, well, not only did the bees show no adversion to the yeast flowers; the yeast helped their colonies grow. (13:59)

The hives that ate this nectar even had fewer larvae die, which led to more worker bees and an overall healthier colony. We'll need more research to say why, but the authors think this could be because yeast stores nutrients in its cell walls, so even if the nectar has fewer nutrients, the yeast might ultimately help the bees.

Through other tests, the team even discovered that yeasts could suppress the growth of a bumblebee-gut parasite called "Crithidia bombi", which might play a role in the overall decline of honeybees. Again, the team isn't totally sure why, but they suspect the yeast could be out-competing the parasite for food in the bee's gut, which is pretty metal for a single-celled organism.

So based on this, it looks like nectar full of yeast is helpful for bumblebees, and the bees help the yeast, too. As they move from flower to flower, they take the fungi with them and spread them around.

And just to really come full-circle here, that's even good news for the flowers. A study published in 2010 found that yeast gives off heat as it breaks down sugar, so yeast in nectar increased flowers' temperatures by up to 6?C. Then, another study published in 2013 found that bumblebees are more likely to feed from warmer flowers, probably because it makes the nectar less sticky and easier to drink. So, the yeast might be making flowers more appealing to bumblebees, too, and since bumblebees are pollinators, well, it's a happy love triangle for everyone.

[Hank] And speaking of this love triangle, it turns out there might be trouble brewing in the relationship between flowers and bumblebees because scientists have found the bees also like to stab the plants, but not for the reasons you think. Let me explain.

We know a lot about the way bees and other pollinators impact our lives. We have to, because without them we wouldn't have things like almonds and apples and blueberries. Yet there is something that we have completely missed about the humble bumblebee, and it might give them a leg up on weathering climate change.

In a paper published in 2020 in the journal "Science", researchers reported a previously undocumented behavior in bumblebees.

In tough times, when the colony is hungry, bumblebees will use their mouthparts to deliberately damage the leaves of plants that haven't yet flowered, which seems like a bad idea when you need those plants for food. The researchers observed the bees and concluded that they're not consuming pieces of the plant or taking them back to their colonies. Instead, they appear to be damaging leaves because it induces the plant to flower sooner. The researchers found that bee-damaged plants flower up to 30 days earlier than plants that have not been stabbed by bees. What's more, they gave one test colony access to flowering plants and another colony access to flowerless plants. They found that the leaf-damaging behavior was strongly associated with bees who were presented with the flowerless plants. This behavior makes sense, the colony depends on flowers for food, and if you've got a lot of baby bumblebees to feed you can't afford to wait for those slacker plants to 'get their flower on'. What we don't know is how this leaf-stabbing behavior evolved. It seems unlikely that individual bees would have learned that puncturing a leaf causes the plant to flower early, since so much time passes between the behavior and the reward. Neither are they looking for pollen in the wrong places, bumblebees instinctively know better than that. We're also not really sure why the leaf-stabbing behavior works. It could be that the plants interpret the behavior as an attack by actual leaf-eating bugs, so they flower sooner as a survival strategy, but there aren't really any known examples of plants doing this when, say, grasshoppers arrive, so it doesn't seem likely. Neither is early flowering advantageous for the plant, it's more beneficial for plants to flower at the same time as other members of their species, in order to ensure cross-pollination. However, scientists conducting this study did find a bit of a clue by indulging in some leaf-stabbing themselves, and they found that it's not just the physical damage that induces flowering. (18:01)

Plants damaged by actual bees still flowered up to 25 days sooner than plants damaged by researchers.  So, it's got something to do with the bees themselves.  It could be that they're injecting some kind of chemical into the leaf that jump starts flowering, but we'd have to identify that chemical to know for sure, and it could be something totally different.

Ultimately though. this clever strategy might give bumblebees a head start on adjusting for climate change.  As the climate warms, it may become more common for the calendars of plants and pollinators to be out of sync.  That means many pollinators won't be able to find flowers when they need them the most.  But pollinators that can change the flowering schedule of their food source will likely have an advantage over species that have to wait aorund for nature to take its course.

Now if only we humans could figure out how to do the same thing for our tomatoes--I'm tired of waiting!

--end video--

[Hank]  So from stabbing plants to fascinating love triangles, bees are amazing critters.  And if you're worried you're seeing double, well you're not in trouble, because yes, this is our second compilation of bee-related episodes!  You can check out part one if you're looking for something to watch next.

And if you'd like to help us keep making videos, you can check out our pin of the month.  This month we have Mars III, the probe that discovered evidence of Martian lakes and mapped the surface of Phobos.  If you want to take this little probe home, you've gotta be quick and pre-order before the end of the month (May of 2021), because then it will be gone.

The pin is available until the end of May at dftba.com/scischow, and be sure to check back again in June (2021), when we will have a whole new pin waiting for you.

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