Briefing Chat: Orcas smashed a sunfish to bits — researchers aren't sure why

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0:48Ten years after Troy, Odysseus is still lost. I'm Tristan Hughes. And all of this month on the Ancients, I'm going to be sailing through Homer's treacherous world of monsters, witchcraft, and tempestuous gods. Exploring the real archaeology and history beneath the myths. Join us on the Ancients from History Hit. Listen now and subscribe on your favorite podcast player.

1:19ACAST helps creators launch, grow, and monetize their podcasts everywhere. ACAST.com Hi listeners, Benjamin here. Welcome to the Friday edition of the podcast, where we talk about some of the stories we've read about in the Nature Briefing, which is, of course, Nature's daily email roundup of the latest science news. And joining me this time is Nick Petrichow. Nick, how are you doing? I'm doing well, Ben.

1:50How's it going for you? It's going A-OK, thank you very much. A couple of stories today. Why don't I go first? And there's kind of a through line, Nick, into the story that I covered on the Wednesday show. We're heading back to the Amazon for some newly discovered things, things that are new to science. But in this case, it's not archaeological remains. It's insects. And this is a story I read about in Nature based on a presentation at the Brazilian Society for the Advancement of Sciences annual meeting.

2:20So this is still preliminary data, but some of the numbers involved are quite something. I imagine so. I mean, many people will be aware of the fact that many insects are not known to science, and there's a lot of them, and they're all quite small. So it's hard to get sort of an assessment of them. But I'm guessing that they've tried to do that in the Amazon. Is that what you're hinting at? That's absolutely right. And yes, you're right across the board there. Generally speaking, very, very small, although we'll get to some that are pretty big in a bit. And well, the Amazon, the lush rainforest, has a huge amount of biodiversity, as we know.

2:51And most of it is unknown, it has to be said. But now hundreds of scientists in Brazil are collaborating on this epic project to count every species of insect in one expanse from the ground to the canopy. And I think this is where this maybe differs from other examples of projects, because trees in the Amazon can be, you know, pretty big, right? And they're looking at different layers, as I say, from the ground to the top. Yeah, and the ecosystem can vary quite a lot between the canopy to the ground as well,

3:22especially for insects, for whom the ecosystem can be like just a little bit of a tree. Yeah. And what they've done in this instance, they've deployed three arrays of traps. Now, each array consists of five mesh traps in a vertical stack, if you can imagine that. So one's at the floor, and one is about 30 metres, so about a 10-storey building height above it. And there's three more of these in between. And when an insect flies into one of these traps, it's funnelled into a collecting bottle,

3:54and they then are collected in ethanol, preserving their DNA for analysis. And that's key here. Scientists can't go and sort of count these one by one. They're collecting a large amount of these insects, and then doing what's called DNA barcoding, which allows them to look at short fragments of DNA to work out whether a species is new to science, or whether it's already been established, this sort of thing. You said that the goal is to catalogue every insect species, but that sounds like it would only capture the flying ones.

4:26What are they doing about other insects? Yeah, that's a great point, and one that I wondered about too. And to catch species that would otherwise have been missed by this sort of trap, the team organised a collecting blitz of sorts last November that used around 50 extra collecting methods. And in one example, they used rotting meat to attract insects that feed on carrion, that sort of thing. And they used light traps to sample nocturnal insects that may have been missed otherwise.

4:56So they've done their best to try and run across the gamut. And as I understand, they've been looking in a particular area of the central Amazon in northern Brazil, and they've been collecting insects for over a year. And the results are five and a half million specimens, of which 600,000 will ultimately have their DNA sequence. Then a huge network of taxonomists will combine this genetic data with looking at the insect's physical traits to identify, like, what are these species?

5:29And of course, if it's a new species to science, they get to describe it and name it. I mean, it sounds like a heroic effort and, you know, an important one to know what insects are there. But do they think it could have other impacts? Could it tell us a little bit more about the overall ecosystem and how it works? Yeah, I think that's the central thrust of this. Now, I've covered the naming of species and why this is important in the past. And we know that insects around the world are under threat. You know, climate change, insecticide use, habitat loss, certainly in the Amazon, that's an issue.

6:01And it's really hard to conserve a species if you don't know it's there. I remember talking to someone who discovered a new lizard in Ecuador a few years back, and they said that by giving it a name, by giving it a hook that you could hang a label on, that can then direct things like funds for conservation or, you know, getting media attention, that sort of thing. So I think in that instance, it's kind of important. But it's going to be a heck of a job, though, because they found loads of stuff already. Preliminary data suggests that the number of species could surpass 40,000, many of which will likely be new.

6:35And this number is apparently less than 1% of the widely accepted estimate of all the insects living worldwide. And people put that number at about 6 million. But this 40,000 is for a single location in the Amazon. So if you, much like our story about the archaeology, expand that out, the numbers, I mean, they boggle their mind a little bit. It has to be said. Yeah, yeah, certainly. And, you know, I imagine that the Amazon is a vast area, has a lot of different ecosystems and different places that insects could live. So, yeah, it could be, as you say, a mind-boggling number.

7:08And I'm sure it'll be a lot of work for them to carry forward to the future. But I am curious about some of the examples that they might have found. Can you tell me about some of the cool things? Oh, yes. As someone who's not the biggest fan of insects, who respects them from a distance? This one, it gave me pause for thought, I have to say. But the article quotes one of the leaders of the project, someone called Dalton Ameren, who is an entomologist. And he and his team are sequencing over 300,000 specimens, which they're expecting to have done at the end of August.

7:38And he says that most of the things they've seen so far are flies and mosquitoes, which you might imagine. Some are little moths and butterflies and tiny wasps and bees, cockroaches. And this is where it kicks in. Some of these vary from a half a millimetre long to giant predatory crickets that measure more than 10 centimetres long. That's a pretty big cricket. That's a big cricket, yeah. And apparently, the most abundant insects collected belong to a family of flies called Cicidomyidae, which are commonly known as gall midges.

8:09Now, these are only maybe a couple of millimetres long. And over the past 250 years, scientists have described nearly 7,000 different species of this worldwide. And in this work, they've already found 10,000 species from a single trap. Wow. Yeah, and there's this wonderful quote from Ameren here, in which he says, people tend to picture the rainforest as a Minecraft cube, green and uniform. But in reality, it's far more complex than that. As we begin to understand insect guilds, how they live, and the heights of the forest they

8:42inhabit, the forest becomes an incredibly interesting and rich environment. When a patch of forest is cut down, thousands of species are affected. I think this really does show, like, you know, how much we don't know about the Amazon. But hopefully, we'll learn a little bit more about it from this gargantuan effort. And speaking of, like, new things or learning new things, I wanted to talk to you about a never-before-seen behaviour of orcas, where they seem to, well, to put it lightly, explode

9:13some fish. Right. I mean, this is a sentence that we need to explore. Orcas, sometimes folks still call them killer whales, I guess, but very intelligent creatures. And this is, as you say, what, a new behaviour unknown to science. Yes, this is something that was quite shocking to the researcher who observed it as well. But we'll get into that in a second. So yeah, as you say, orcas are the largest member of the Delphinidae family, so dolphins and the like. And they are predators, and they hunt together quite often. So there's been a lot of different behaviours that have been noted by orcas, where they'll

9:47sort of, like, ram whale sharks and that sort of thing to try and get valuable meat. But in this case, what this was, was this was a single orca holding a sunfish. So this is a great, big, funny-looking fish that looks a little bit like a sun, that's the name. And they're holding it in their mouth, while another orca, not takes a step back, takes a swim back, I guess, and then rams at it at high speed, exploding the sunfish everywhere. And so this is something that I was watching in a nature video made by Maren Hunsberger,

10:20one of our colleagues who's appeared on the podcast. And I was reading about in The Guardian, and I also read the paper in Frontiers of Ethology, where they sort of detailed their observations and what it might mean. Huh. And I'm not sure the right word to describe what happens to this sunfish, then. You can't say it was vaporised, because, of course, it's underwater. So, I guess, chum, what's that? That's that kind of mashed-up fish that's used as bait. Do they turn it into chum, Nick? I mean, it's funny that you should say that, because one of the things that the researchers

10:53believe may be happening here, and there's a few ideas, because they're not entirely sure what they're doing, is that they could be processing the meat. So, rather than having a great big sunfish that might be difficult for, say, the juveniles to eat that have smaller jaws, what they might be doing is exploding it, or, you know, chumming it, in order to make the parts smaller for the other juveniles to eat. But I will say that one of the most fun parts of this story is that one of the researchers

11:23behind this work was actually in the water with the orcas when this happened, and was recording with a GoPro. And there is a video, and I'll link to it. In the video, you can hear them going, oh, my God, oh, my God, and something else that I wouldn't repeat on the podcast as this happened. So, it was quite a shocking event for them. Goodness me, right. And was the sunfish kind of flapping about? Was it still aware of what was going on before it was ended? That's a very good point. The sunfish was already dead, which is one of the ideas of why the orcas are doing this,

11:54as we said, maybe to process the food. And they did observe that the juveniles did then eat the little bits of the sunfish. So, it was already dead. So, this isn't a hunting behaviour. This is not how they're actually killing the sunfish in the first place. But they have some other ideas of why they might be doing this as well. So, for example, the sunfish have this layer underneath their skin. It's like a fatty layer called the capsule, which is very rich in a very unique microbiome and all the rest of it. And so, one of the other ideas could be that the orcas are trying to get access to that.

12:29They're trying to access this unique microbiome. And that microbiome could be useful for the orcas. It could help them be healthy, or it could intermingle with their own microbiome and, you know, change things in a way that's advantageous to them. The other idea, though, is that maybe the orcas are just doing it for fun. Yeah, that was my question is, could they just be dirtbags who just like exploding fish? Well, yes, orcas are known to play with their food. So, for example, in the 1980s, it was observed that orcas would wear dead salmon as hats, essentially.

13:01Like a group of orcas would just do this for fun, and they are like playful creatures. So, it could be that they're just doing it for fun. But ultimately, the researchers think this shows a great deal of cooperation and coordination as well. Like it's not easy to hold the sunfish in such a way and then ram it with another orca in order to do this. And this, combined with other behaviours that have been observed, as I mentioned, they are known to work together to like ram whale sharks and things to get access to food.

13:31And they do a bunch of other like cooperative behaviours as well. So, this is just showing the degree to which they have this sort of intelligent and collaborative and cooperative behaviour. Right. And you say this is the first time this has been seen and fortuitously captured on film. So, I guess a question is, was this just a one-off? One orca had hold of it and another one rammed it? Or is this a pattern of behaviour? I guess you need more than one example for it to be a pattern. Well, it's a fair point. And this may be a two-off because the researchers did video it again.

14:03So, after seeing this first behaviour, so they have seen it at least twice in the same sort of area. Whether other orcas in different parts of the world do it, they don't know. But at least in this area, which was just off the coast of California, orcas have been seen to do it at least twice. In order to get other footage to maybe see if they do it or just to understand what orcas are doing a little bit more, one of the things they discuss in their paper is the growth of tourism and how many more people have access to underwater drones that could potentially capture footage.

14:37So, that is something that they could potentially look to and maybe do some sort of citizen science sort of thing. However, they do caution that that would have to be approached carefully because tourism can also be very disruptive for marine ecosystems and for the orcas and that sort of thing. So, maybe there's some way that scientists and, you know, regular citizens who happen to have fancy cameras could work together in order to see this a bit more. But, yeah, whether this is a behaviour, I'm not sure, but they've seen it at least twice.

15:07Well, I'm not sure we can top that, so let's call it time for the podcast this week. Listeners, we'll put links to both of those stories so you can read more about them and watch the orcas in their horrific games over in the show notes. And we'll also put a link where you can sign up to the Nature Briefing to get even more stories like them delivered directly to your inbox. And, as always, if you want to get in touch with us, if you want to tell us how you feel about the orcas smashing a sunfish, then you can. You can reach out to us on social media. We're at Nature Podcast or you can send us a good old-fashioned email.

15:42We're on podcast at nature.com. I'm Nick Petra-Ciao. And I'm Benjamin Thompson. See you next time. A-Cast powers the world's best podcasts. Here's a show that we recommend.

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