JUANA SUMMERS, HOST:
From NPR News, this is ALL THINGS CONSIDERED. I'm Juana Summers.
SCOTT DETROW, HOST:
I'm Scott Detrow, and I am joined by Emily Kwong and Berly McCoy of NPR's science podcast Short Wave for our science news roundup. Hey there.
EMILY KWONG, BYLINE: Hi.
BERLY MCCOY, BYLINE: Hi, Scott.
DETROW: You have, as you often do, brought us three stories that caught your attention this week. Let's hear what they are.
MCCOY: A galaxy cluster so hot, it shocked researchers.
KWONG: How elephants' trunks lead them to food.
MCCOY: And a big discovery in butterfly migration.
DETROW: When I have the option of starting with a hot galaxy cluster, it's always going to be that.
KWONG: Wow.
DETROW: Let's start off. What would you say a galaxy cluster is, though? Let's start there.
KWONG: Exactly what it sounds like. It is a collection of galaxies, but kind of like a city, where each galaxy is a different building. Our galaxy, the Milky Way, is part of a cluster called the Local Group, for example. But the galaxy cluster we want to talk about, which is the subject of a new paper in Nature, was formed about 12 billion years ago, and the universe itself is only about 13.8 billion years old.
DETROW: So that's just a fast billion years, like, a snap of the fingers in galaxy terms. Like, we're talking about - this was a baby in galactic years.
MCCOY: Exactly. And current theories say that younger galaxy clusters should be relatively cool. But this one is very hot, like, hotter than the surface of the sun. We talked to Jorge Moreno, an astrophysicist who didn't work on the paper, and he made an analogy to U.S. history. He said, if you go back a few centuries, you expect to see little buildings and horses and carriages, not a modern metropolis.
JORGE MORENO: Like, it's late 1700s and a city looks like Las Vegas.
KWONG: This galaxy cluster is popping. And it's far hotter than scientists expected to find at this early point in the universe.
DETROW: Do researchers have any idea why it's so hot?
KWONG: We don't know why yet. But one of the study authors, Dazhi Zhou, says it is the first time a galaxy cluster this hot has been detected at such a young age.
MCCOY: And this cluster also contains active galaxies. Three of them have supermassive black holes at the center, which is also surprising given the cluster's age.
DAZHI ZHOU: So this forces us to rethink our current understanding of how these large structures form and evolve in the universe.
KWONG: Although, Scott, it is possible that this cluster is an extreme case, so we need more data.
DETROW: I have a lot of other questions that I will keep googling, but for now, we are going to move forward to another topic though 'cause we got a lot to talk about. And we got to talk about elephants (imitating elephant trumpet). Like...
MCCOY: That was really good.
DETROW: Yeah. Thank you. Listeners don't see that I flared my hand...
(LAUGHTER)
DETROW: ...Like a trunk. But the trunks are what we're talking about, right?
MCCOY: Yes, big time. At the very tip of an elephant trunk are two nostrils powered by nearly 2,000 olfactory genes, which is five times more than a human has and over twice as many as dogs.
DETROW: Which makes me think if you need to sniff something out, hire an elephant, not a dog.
MCCOY: True.
KWONG: Yeah. And if you do, pay them fairly in what they love - grass, leaves - because elephants eat hundreds of pounds of plants a day. They are constantly making food decisions about whether to stay foraging in a patch or travel in search of a better one. And Adrian Shrader at the University of Pretoria wanted to know how their noses guide them in the wild.
ADRIAN SHRADER: Animals don't just randomly walk across the landscape and hope to find food. And so our question really was an idea of, well, do they use the amount of food as a cue?
MCCOY: Yeah. And to test this, Adrian's team built a giant maze for elephants shaped like a Y with walls over 7 feet tall. So picture one entrance, two paths with different quantities of food at either end.
DETROW: So it's like choosing almost between, like, two different Las Vegas buffets but not being able to see which one was bigger.
KWONG: Exactly. Four captive elephants took on this challenge. From the maze entrance, the food was about 30 feet away, so way beyond the reach of their trunks. They couldn't see 'cause the walls were so tall. And every time, they chose the path with more food, unless the quantity difference was less than 600 grams, which is about six to 10 trunk loads of grass, and then they tended to pick either route, which suggests they couldn't smell the difference or they just didn't care. These results were published in the journal Biology Letters.
MCCOY: And Alvaro Lopez Caicoya, who was not part of the study, found the elephants' ability to discriminate food quantities remarkable, though he points out there are a lot more smells in the wild than in the preserve, where these captive elephants lived.
DETROW: This is really interesting. And I'm curious. Like, what is useful about this research?
KWONG: Well, elephants, while adorable, can damage their environments. They stomp on farmers' crops. They can knock down endangered trees. But if researchers understand elephants' use of smell, maybe they can cover plants with bad odors to protect them from hungry elephants.
DETROW: All right, so let's go from a very large animal to a very small one. Let's talk butterflies, specifically butterfly migration. What's surprising about it?
MCCOY: Yeah. So this is a migration in painted lady butterflies. They have similar coloring to monarchs, but they're smaller. They're super widespread, and they have the longest migration of any butterfly. And scientists found something striking in that migration - that depending on if they live in the Northern or Southern Hemisphere, they follow completely opposite migration paths. Essentially, the equator is acting as a migration barrier for these two isolated populations.
DETROW: OK. I'm going to be honest here. This doesn't particularly surprise me, right? The seasons are opposite. This makes sense. Why is it a big deal?
KWONG: Fair, but this is the first time a migration barrier has been described for any insect. And to study this, researchers collected more than 300 butterflies from 38 countries across the Northern and Southern Hemispheres.
MCCOY: We talked to Aurora García-Berro from the Botanical Institute of Barcelona, and she says their team looked at the butterflies' genes for months, searching for clues about what made these two populations distinct. And then one day, she found something really weird.
AURORA GARCÍA-BERRO: And I actually thought it was an artifact, but then I showed it to my colleague. And they were, like, completely surprised. Like, you don't know? This is so exciting.
DETROW: And this schematic (ph) - what was it?
KWONG: Yeah. They found that a large chunk of DNA in the Southern Hemisphere butterflies was completely flipped. It was oriented the other way than the same DNA chunk in the Northern Hemisphere butterflies. And this chunk contains genes involved in migration.
DETROW: Whoa.
MCCOY: So what they think they're seeing is one species that separated into two populations, and now their genetics are diverging, too, because of these different migration pathways. And this is sort of a lens into how a single species might split into two across a migration barrier. And it might explain why we see closely related species in different hemispheres. They published the results in the journal Nature Communications.
DETROW: That is really interesting. What is the thinking on the larger significance of this?
KWONG: Well, painted lady butterflies, while small, make up a huge biomass. In 2017, a 70-mile stretch of these butterflies blocked weather radar in Colorado. They can affect agriculture, pollination and the health of other species. So Aurora says identifying how animals migrate is important to understanding the health of that species, yes, but also the health of all the places that species travels.
DETROW: That was Emily Kwong along with Berly McCoy from NPR's science podcast Short Wave, which you can follow on the NPR app or other podcasting apps for new scientific discoveries. Thanks to you both.
KWONG: Thank you, Scott.
MCCOY: Thanks.
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