Ask Sam: Do Hummingbirds Sleep and Other Questions

Another edition of Ask Sam, where Sam answers listener questions about the natural world. This time, questions about hugging trees, bumpy roads, objects stuck on power lines, and epic hummingbird battles.

Featuring special guests Maddie Sofia, host of NPR's Short Wave, and Kendra Pierre-Louis, climate journalist with Gimlet's How to Save a Planet.

Do Trees Notice When I Hug Them?

An anonymous listener in Vermont asks: “I walk everyday, and there are lots of trees in Vermont, and I’m a tree hugger, and I mean, literally a tree hugger. And so I hug them and I always feel a sense of calm and I’m wondering if there’s anything that makes that happen? Do the trees notice when I hug them?”

The first part of the question is fairly easy: why might you feel calm while hugging a tree? It is likely for some of the same reasons that going outside generally make us feel calm. At this point there are heaps of studies about the mental benefits of being outside. A hypothesis for why that might be that has come into vogue in recent years is that attention is a limited resource and we’ve only got so much of it to expend each day.

So being outside means “your attention is able to drift much more naturally, in a much more relaxed way from moment to moment,” explains science journalist Ferris Jabr. “You might be looking at the surface of a lake, watching the ripples, the leaves are falling from a tree, a bird flies by — and that can replenish our mental resources.”

But on to the second part of the question, which is the real reason we reached out to Jabr.

This question came shortly after he wrote a feature-length article for the New York Times Magazine about the research of Dr. Suzanne Simard. You may have heard of her work because she discovered something that pop cultural has come to call the Wood Wide Web. This is the idea that trees in forests share nutrients, water, even carbon — the physical, chemical building blocks of trees — between each other, through a symbiotic underground fungal network.

However, in Jabr’s profile, there’s a moment in which he and Doctor Simard are walking through a forest and she says, “I’m really interested in whether they perceive us.”

If your first response is to snort that this is new-age nonsense, that’s because you haven’t been keeping up with the latest in botany.

“In fact there is research showing that trees and other plants can pick up on things like the wing-beats of a visiting insect. Some flowering plants will sweeten their nectar when they pick up on the wing-beats of a bee,” Jabr says. “There are some studies showing that the roots of plants can pick up on the sound of running water and will grow towards that sound.”

One of the more famous examples of this is the ways that trees defend themselves from insect attacks. When pests like caterpillars start munching on the leaves of a tree, there are now dozens of studies that have confirmed that nearby trees will start to ramp up their production of chemicals that defend them against insects. It’s thought that they are somehow perceiving the volatile compounds that the chewed up leaves release into the air.

There is also fairly robust evidence that plant cells can perceive and respond to pressure waves, like the kind that are generated by sound in the environment and touch — like, say someone walking up to a tree and hugging it.

We don’t know for sure if that tree knows you’re hugging it. The careful way of putting this is that it’s a very reasonable hypothesis that someone could test. We also could answer the question: “So for sure, you like hugging trees, but do the trees like being hugged?”

What Makes A Washboard Road?

CREDIT FLICKR CREATIVE COMMONS | THIRTEEN OF CLUBS

Sheila from Greenfield asks: "What makes a washboard? For decades I’ve driven over New Hampshire dirt roads, and jiggled and jostled all over the place and have never been able to suss out what makes a washboard."

Many people have theories about what causes a washboard. Many of those theories are wrong.

That includes the gentleman we found to answer this question: Stephen Morris, a physicist at the University of Toronto. “I thought, as many people do, that the suspension might have something to do with it. It’s one of the common but incorrect reasons that people come up with for washboard,” he said.

Over a decade ago, he and some co-authors designed an experiment to figure out what it took to form a washboard. They built a circular sandbox filled with road material and ran various wheels and plows around the sandbox until a washboard began to form.

Morris says that, essentially, a washboard is formed by the same forces that cause stones to skip.

Get more Outside/In in your inbox. Sign up for our newsletter!

“When you’re driving on the road and you hit a tiny bump, no matter how small, it will throw the car up in the air an amount that depends on how fast you’re going. And if you’re going fast enough you’ll come down and deform the road a little bit behind the bump,” he says. “And that little divot that you put in the road will throw up the next car and so on.”

Washboard is mostly a dry road phenomenon. When the road bed is really wet, you tend to get potholes instead. And if it’s a really bad spot, you can get this kind of repeating pattern of potholes.

The frequency of the washboard is a function of the average speed of the cars that drive along a stretch of road. Because cars all tend to drive the same speed on the same stretch of road, which in a bit of chicken-and-egg feedback loop, is determined “partly because of the washboard of course,” Morris explains.

And a bit of trivia: train rails also develop washboard, which leads to a sound called “roaring rails.” Train rails have to be periodically ground down to eliminate the noise.

Many drivers who spend a lot of time driving on gravel roads will tell you the best thing to do is to drive fast. Morris (and dear reader, we, too) would like you to consider *why* this works. “If you drive really fast your tire will bounce from peak to peak of the washboard and you will not feel it, and that works except you’re in the air about half the time.”

And having your tires in the air is real bad for steering. REAL BAD.

How Do Power Lines Grow Through Trees?

CREDIT FLICKR CREATIVE COMMONS | MATTHEW PROSSER

Zach from Maryland asks: "I was riding my bike recently along the Anacostia River, and I noticed big pieces of wood through which the power lines were growing. How does this happen? How do power lines grow through pieces of trees - that are then presumably cut off so you just have these pieces of trees hanging there?

So the shortest answer here is that the wire is insulated!

There are places where electric lines are totally bare, which means nothing can touch them. That’s usually true in more rural areas where running a lot of insulated wire would be really expensive. Big transmission lines tend to be bare as well.

If a branch so much as rested on a bare line, it could spark or catch fire.

But in more densely populated places (like where Zach lives, outside Washington, D.C.) the lines probably have some sort of shielding. Which means wood can touch them, even slowly grow around them, without causing a short.

But underneath that insulation, live wires can still be dangerous. Greg Bruton, a senior electrical engineer at National Grid and board member of the Boston chapter of the American Association of Blacks in Energy says that when people are called in to deal with tree issues, they tend to keep their distance.

“You send a guy up the line who typically cuts down trees for a living, he’s not really keen about taking a chainsaw to something that could potentially kill him,” explains Bruton.

So often, the safest and easiest thing to do is just leave a bit of wood dangling there.

If we want to get technical, it's also possible that Zach may not have been looking at a power line. Utility poles carry all sorts of different lines. Back in ye olden days, Greg Bruton says, crews would sometimes mix up which was which.

"You’d have people receiving a phone call and instantly getting electrocuted because they ran power to the phone line.”

Eek! Thankfully, it has all been standardized now.

Up at the top is what’s called the primary: usually three wires, held up by an arm at the very top of the pole. The expression "three-phase-power" (for the energy geeks out there) refers to all three of those together.

Below the primary is the secondary. That's the wire that carries electricity to our homes and businesses after a transformer (it's the grey cylindrical box you see at the top) lowers the voltage.

Everything else below the secondary isn’t actually electricity: it’s our phone, TV or internet.

Those don't carry the same risks as the powerlines higher up - so it's possible Zach saw a chunk of wood that had grown over one of those lines instead.

Do Hummingbirds Sleep?

Debbie Beauvair from Deerfield, N.H., asks: "I have a question about hummingbirds. We’ve noticed in the last 3 weeks or so that the number of hummingbirds have increased and the fights are off the charts. Our feeders are socially distanced by humminbird standards — at least 20 feet apart — but they’re swooping and chasing all over the place. What’s going on?"

Now for the first time ever, we’re actually going to do a two-fer, because relatedly, Sue in Bradford emailed to ask: “Do hummingbirds sleep and if so, where? I can't see any nests.”

And while it might not be obvious at first, we will show that these questions are indeed related.

So our hummingbird expert is Anusha Shankar who is doing a post-doc at the Cornell Lab of Ornithology.

"They always fight, that's what they do, that's how they exist," Shankar says.

She says the reason that our caller is seeing more hummingbirds is straightforward: fall migration has begun, and all of the ruby-throated hummingbirds — which is the only species that you’ll commonly see in the entire eastern United States — are headed south to Central America where they accordion in to a tiny overwintering ground, all together.

And Shankar says they fight because they really, really, really need the food sources that they find.

"They don’t have much of an energy store as a backup if they dont’ feed all the time," she explains, "So they feed every 15 minutes sometimes, and they could die if they don’t feed for like two hours. They’re operating on a really, really thin edge … like a very tight energy budget."

Hummingbirds are just constantly burning calories. Shankar's research shows they spend as much as 80 percent of their days flying or hovering. And one hummingbird scientist calculated that if we wanted to do the equivalent work and consume the equivalent amount of sugar to power it relative to our body size, you’d have to drink a can of soda every minute to keep up.

Now this gets us to the connection between the fighting question and the sleep question. They fight all the time because they need to eat all the time. They also need to sleep, which is tricky when you need to eat all the time so every night, they sleep HARD. They enter a state called torpor.

"If you were actually torpid and I shook you, you wouldn’t be able to to do anything for it for 20 or 30 minutes, because so many functions in your body would be just switched off, and you wouldn’t be able to respond to outside stimuli," Shankar says.

During torpor, the heartbeat of the ruby throated hummingbird drops from 600 beats per minute to less than 50 per minute - worse than your teenagers.

And just to round out these absolutely BANANAS hummingbird facts: hummingbird females do make nests. They are tiny, adorable little jobs, which the females make by gathering SPIDERWEBS to hold together all the little nest bits. How about that?

Credits

Outside/In was produced this week by Sam Evans-Brown, with Taylor Quimby and Justine Paradis

Erika Janik is our executive producer.

Our theme music is by Breakmaster Cylinder.

Ask Sam theme by Taylor Quimby.

If you’ve got a question for our Ask Sam hotline, give us a call! We’re always looking for rabbit holes to dive down into. Leave us a voicemail at: 1-844-GO-OTTER (844-466-8837). Don’t forget to leave a number so we can call you back.