Short Wave - Why These Squirrels Are Eating Meat

Episode Date: December 27, 2024

In pop culture, squirrels are often seen as jerky, excited critters on the hunt for nuts to stuff themselves with and tuck away for later. But squirrels are on the hunt for something a bit meatier in the California Bay Area. Their target: local voles. The entire process — from hunt to kill — was captured on video.Want to hear more biology stories? Let us know by emailing [e-mail]! Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, Shortwavers. Jessica Young here. And Regina Barber. With our biweekly science news roundup featuring the hosts of all things considered. And today we have Juana Summers. Hello, thanks for having me. I hear today we're talking about carnivorous squirrels hunting in California. Yeah.

Yes. And also a new study charting the biodiversity on ancient Earth. And new insights into how humans and dogs became friends. All that on the world. this episode of Shortwave, the science podcast from NPR. Hey, shortwaivers, Emily Kwong here. Believe it or not, the year is almost over. And as we are reflecting on 2024, we're thinking about the hundreds of podcast episodes we've brought you this year. I mean, episodes about big things like climate change, nuclear energy, COVID, and episodes about weird and wonderful things like sea cucumbers, the biology

of memory, the science of skincare trends you see on TikTok, and episodes about stuff we just can't stop obsessing over, I'm looking at you, Naked Mull Rats, Succession War. Now is the time of year when we reflect on all that work and ask you to support it. Maybe you are already an NPR Plus supporter, and if so, I'm sorry to bother you and thank you so much. But if you have never given to public media before or not in a while, please consider doing it right now. NPR Plus is a recurring donation that gets you special perks for more than 25 NPRR. podcasts like sponsor-free listening, bonus episodes, behind-the-scenes content, and even exclusive and discounted items from the NPR shop and the NPR Wine Club, it only takes a few minutes to

sign up. You could do it right now at plus.mpr.org because this year, shortwave turned five years old. Whether you've been with us from the very start or you're listening this week for the first time supporting public media means you're part of a community of people who are curious about the world. We're honestly so proud to have served the public media community these past five years. Let's keep it going, but it can only be done with your help. So join NPR Plus today at plus.mpr.org. Thanks so much. Okay, Juana, where do you want to start? Okay, we got to start off with these squirrels. I thought squirrels ate nuts. Yeah, so a study that was just published in the Journal of Ethology shows a group of California ground squirrels hunting, killing, and eating a vol,

like a little mouse. And I talked with the lead researcher and a behavioral ecologist, Jennifer Smith. She's at the University of Wisconsin-Oclair. We have one squirrel approaching a vole, targeting that vole, biting it at the neck, and taking it down, eventually crunching through the skull and then eating the meat from the bones. Wow, I am suddenly not hungry anymore. Okay, this really sounds like serious predator behavior. Is this a new phenomenon? Well, Jennifer says that if you look through the literature, there are other accounts of this. There's been accumulating evidence of one or two events within a species of a red squirrel taking a sparrow. They tend to try to take chickens. There's also accounts of squirrels eating like roadkill or insects,

but what's new here is that they've documented the whole process from start to finish with video, the hunt, the kill, and then the consumption. And they've shown that this isn't just like a one-off but part of these squirrel's behavior. And where exactly do these fiercely predatory squirrels live. So this study is only looking at two populations of squirrels in a regional park in the Bay Area in California. They actually saw this during the 12th year of a long-term study. Okay, so we're talking about just two sets of squirrels in the bay, but did these researchers

think it's common? Like, are all the squirrels out there that we see when we're going to work or going to the park or out on a run? Are they just eating meat all the time and like we just haven't noticed? So Jennifer says that squirrels are actually like raccoons, bears, coyotes. They're just really flexible animals. And this vol population had a huge increase this year, you know, five to six times higher than normal. So the squirrels just took advantage of that. Yeah. And Jennifer said the next big thing is to find out like how these squirrels learn this

behavior. Are they teaching each other? Does this abundance of vol meat like lead to more squirrel babies? There's like so much to explore. All right. Speaking of animals undergoing change, let's talk about this new study of species on early earth. What's going on there? Okay. So first, just for context, if you look back at all the fossil evidence we have of life on Earth, we have an abundance of fossils starting around 540 million years ago. It's called the Cambrian explosion, which is when suddenly there are fossils of ancient mollusks and stuff. But before that, things are really more of a mystery. Why is that? So there's a few reasons. One researcher said that the time period is just less studied. And also, it's generally harder for organisms from this time to become fossils because their bodies were so

soft and like they had no shells, no skeletons. They're not only soft, but also they're small. They're microscopic. So making it very difficult to, you know, accumulate enough data to have a manifold analysis. Okay, that is Shu Hai Shao, a geologist from Virginia Tech. He's tried to find and study new fossils from this period, and now he's trying to make sense of it all and draw out lessons about how biodiversity has changed throughout Earth's history, including in that early period. Interesting. How's he doing that? So Shuhai and his team use the existing fossil record, even though it's small, as a sample of all the species at different times in history. Kind of like in an election, right? So the postal, you know, take a small sample of the voters

and they get an idea, you know, what the voting result will look like. So from the small number of fossil samples, they can make some big picture. inferences about the history of life on Earth. Okay, that makes sense. Tell us what they found. So their data published this month in the journal Science has finally provided quantitative confirmation of some hunches scientists have already had. For example, there's this period called the boring billion. This is a time span of a billion years, starting around 1.8 billion years ago, in which paleontologists have guessed that there was probably very little diversity of life and pretty low turnover of species. And according to the paper's data, that's true. And they also found

that right after the boring billion, there are ice ages that were followed by super rapid species turnover and like a boom of diversity, which has made shoehigh wonder if ice ages reset evolution. And that's definitely one thing he wants to look into. And other researchers I talked to also told me that they just want more research and fossil data about the boring billion era in general. Because honestly, like this kind of work on early life is just really important to understand not only how life started, but how life adapts to environmental changes. Like thinking about climate change now and in the future. All right, let's go from one ancient era to another. Now we're going to talk about our ancient relationship with dogs. I have a very present-day relationship with my dog Bromo, who's kind of like my best friend.

Totally. I mean, I think our relationship with dogs as humans is just very longstanding. Researchers think canids, which include wolves and dogs, were probably first domesticated in Eurasia between 19,000 to 12,000 years ago. And new archaeological evidence published in science advances gets a closer look at that relationship in Alaska. in a window of time 12,000 years ago. Okay, so just paint me a picture of what Earth was like in that time and how this relationship played out. Well, with the end of the last Ice Age, people had begun to cross the land bridge between Asia and North America. Researchers believe those people likely came with Kainid companions.

And new evidence of Kaded Bones from Alaska supports that theory. Their paper analyzes more than 100 specimens, but the most interesting bone was excavated in 2018 outside of Fairbanks. Their researchers found a single tibia or lower leg bone, and DNA evidence suggests the bone belonged to some kind of ancient wolf or like proto dog and dated the bone to 12,000 years ago. Interesting. What made that leg bone such a fascinating find? The clues inside the bone. The team sought permission to analyze the bones from the Healy Lake Village Council, which represents the indigenous people of the area. And when the scientists did a chemical analysis of the bones, they found substantial traces of salmon proteins, meaning these kinds of these kinds of

canids regularly ate fish. That's very Alaskan of them. But I mean, how do we know that these canids weren't just out there hunting salmon themselves? So salmon is not naturally available in big quantities in Fairbanks, which is why researchers think they were probably getting salmon from humans, like proof of domestication, at least for this one ancient wolf. An archaeologist Angela Perry, who was not a part of the study, agrees with this conclusion, that this 12,000-year-old wolf with a salmon diet was either intentionally fed by humans or was heavily reliant on scraps, which suggests that this wolf lived in close, constant contact with human communities. Sounds just like my dog when he sits under my kitchen table and begs for scraps.

Juana, thank you so much for letting us just babble about science. Yeah, you're one of our favorites. Wow. What an honor. Please let me come back. I love this. You can hear more of Wana on Consider This, NPR's afternoon podcast about what the news means for you. This episode was produced by Rachel Carlson in Jordan Marie Smith.

It was edited by Rebecca Ramirez, Christopher and Taliatta, and Ashley Brown. Tyler Jones, check the facts. Beth Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber. And I'm Jessica Young. Thanks for listening to Shortwave, the science podcast from NPR.