Today, you’ll learn about how some sharks have social relationships, how shark attacks often happen because swimming humans look like other sea creatures, and how your cat might be snacking on endangered sharks!
Today, you’ll learn about how some sharks have social relationships, how shark attacks often happen because swimming humans look like other sea creatures, and how your cat might be snacking on endangered sharks!
Sharkship.
Sharks could use glasses.
Check your cat’s food ingredients for shark.
Find episode transcripts here: https://curiosity-daily-4e53644e.simplecast.com/episodes/blood-brothers-seeing-eye-shark-bark-vs-bite
For more about sharks, head to SharkWeek.com and don't miss #SharkWeek starting 7/24 on Discovery and streaming on discovery+.
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NATE: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from Discovery. Time flies when you’re learnin’ super cool stuff. I’m Nate.
CALLI: And I’m Calli. If you’re dropping in for the first time, welcome to Curiosity, where we aim to blow your mind by helping you to grow your mind. If you’re a loyal listener, welcome back!
NATE: Today, you’ll learn about how some sharks have social relationships, how shark attacks often happen because swimming humans look like other sea creatures, and how your cat might be snacking on endangered sharks!
CALLI: Without further ado, let’s satisfy some curiosity!
[SFX: Whoosh]
NATE: Calli, we’ve got a great friendship. But did you know some sharks also build close relationships?
CALLI: Really? I always thought they were more solitary creatures?
NATE: Researchers recently found that bull sharks can develop meaningful relationships with each other. These bonds approach what we think of as friendship. They may even have a distaste for some of their peers as well! How cool is that?
CALLI: That's incredible! How does that even work, though?
NATE: Researchers at Fiji’s Shark Reef Marine Reserve collected data from more than 3,000 sharks over the course of 14 years and discovered that some sharks prefer to keep company with certain other sharks. They’ll follow them around as they hunt, swim, and even sleep.
CALLI: Following them around? How could they be sure it was friendship and not just some hunting benefit or something?
NATE: Researchers wondered the same thing, so they used social structure analysis based off of behavioral data of those more than 3,000 sharks. Unfortunately, even with this data, they couldn’t pin down an exact clear reason as to why they’d hang out. But researchers did notice that some of the sharks had similar personality traits, like boldness or curiosity, with the sharks they hung with.
CALLI: Huh, boldness sure, but I guess I wouldn’t have thought of bull sharks as curious.
NATE: Right? This study goes against many of our preconceived notions about sharks. Some researchers also think that even if they don’t have things in common, some sharks might just like each other! Some of the sharks that paired up didn’t share personality traits, it was more of an opposites attract kind of thing! If that's true, it means that bull sharks have a much more complex emotional capability than we previously believed. We might even be able to add them to the small group of “social species” like humans, elephants, or chimps.
CALLI: That's intelligent company to keep. I wonder if there is trust in those friendships like there are in human friendships.
NATE: These marine biologists are actually hesitant to call these kinds of relationships “friendships.” That kind of language would have us seeing too much of ourselves, and human-like behavior like trust, in the sharks. We should let sharks be sharks, and researchers were clear to define friendship as a relationship of mutual affection between people, not animals.
CALLI: I'll go with sharkship then. Either way, I’m glad they have companions they like hanging with. But wait, if there are sharks they like, are there other sharks they….don’t like? Is there a sharks Mean Girls?
NATE: There might be! Research also showed that many of the bull sharks actively avoided certain other bull sharks. Sometimes, there were clear personality differences. A bold shark wouldn’t necessarily get along with a more meek shark. Or a curious shark wouldn’t get along with a more hesitant one. But sometimes, the differences weren’t so clear. Some sharks might just not like each other!
CALLI: Man, they really are more like humans than I thought.
NATE: Right? But true friendship is just for people. People like us, Calli.
[SFX: Whoosh]
CALLI: Nate, do you ever worry about shark attacks?
NATE: I mean sure, and movies like Jaws just made that worse! A shark with a taste for human? No thanks.
CALLI: I get that, but let the movies stay in the world of fiction! New research shows that great white shark attacks on humans often happen because the sharks think we are other ocean prey. They don’t have any malicious taste for human flesh.
NATE: What do they think they’re trying to eat then?
CALLI: When you’re kicking around swimming in the oceans, to the sharks you look a lot like a seal!
NATE: So what is it about how we swim that makes sharks think we are adorable semi-aquatic marine-mammals?
CALLI: That's just what the research team from the UK and Australia wanted to know. So they compared footage of seals swimming and videos of humans swimming. But what they saw was, well, what humans saw. So to get a better understanding of why these attacks might happen, they altered the clips to simulate how they’d look to a great white.
NATE: How do you go about simulating a shark's vision?
CALLI: The researchers attached a GoPro to an underwater scooter and set it to move through the water at the same speed as great white sharks to simulate looking for prey. Then, they took these recordings from the GoPro and used computer models and those videos of humans and seals swimming to see how both look to a shark from below the surface.
NATE: How’d they alter the video? What does a shark's sight look like?
CALLI: Researchers believe that great white sharks are colorblind and can’t make out fine details. Don’t get me wrong, they’re still visual hunters who rely on keen eyesight, but they’re built to notice things like motion and shadows rather than specific shapes or differentiating details of their prey.
NATE: What kind of differentiating details are we talking about?
CALLI: Well, like if that limb paddling through the water is a flipper… or an arm. Sure, if you use human eyes, swimmers and seals look way different, but to a creature focused on motion as it looks up through the water, that bobbing paddling mound of flesh swimming across the surface looks a lot like a seal, even if it is wearing board shorts.
NATE: That’s really interesting. So what you’re saying is that a movie like Jaws… is a lie? Sharks don’t actively hunt humans like that?
CALLI: I hate to break it to you, Nate, but Hollywood has lied to you. One of the researchers, neurobiologist Laura Ryan, put it best, “Great white sharks are often portrayed as ‘mindless killers’ and ‘fond of human flesh.’ However, this does not seem to be the case, we just look like their food.” And to think they’ve had such a bad reputation for so long.
NATE: All those shark attacks are just a simple friendly misunderstanding.
CALLI: I’m not sure I’d go quite so far as to say friendly, but here is something interesting Nate: How many shark attacks do you think happen every year?
NATE: Oh boy. With how big the news is every time there's an attack, I’d have to say… a few thousand at least, right?
CALLI: Nope. Despite what you hear, in 2020, there were only 57 shark attacks all over the world. From 2015 to 2019, the annual average was around 80. And there are almost 8 billion people on Earth. Wanna know what the odds are of you being attacked by a shark with those numbers, Nate?
NATE: I think I get the point.
CALLI: Point zero zero zero zero zero zero zero zero seven percent! That’s eight zeros!
NATE: So why are people so afraid of sharks if an attack is so unlikely.
CALLI: Well, I think people get afraid of what COULD happen, even if it is tremendously unlikely. And when you have movies like Jaws or Deep Blue Sea showing sharks actively hunting humans, it creates a fear inside of people, no matter how irrational that fear may be.
[SFX: Whoosh]
NATE: Calli, this story is about sharks, of course, but also…cats.
CALLI: Two apex predators.
NATE: You bet. But one might actually be eating the other, even if you live far from the ocean. Researchers recently examined 45 different kinds of cat food from Singapore that had vague ingredients like “real fish” or ”white fish” or “ocean fish.” Shockingly, they found shark in one third of those cat foods!
CALLI: One-third?! But how did they identify sharks? It all looks, and smells, pretty much like fish to me.
NATE: They used a system called “DNA barcoding” where you look at short sections of DNA in specific genes to identify species. They looked at 144 cans of cat food, and 48 of them contained shark meat. The most common species found in the cans was blue shark.
CALLI: Oh no! That feels a bit misleading, that's not white fish at all!
NATE: It gets even worse. One of the other most commonly found was the silky shark, a breed listed as “vulnerable” by the International Union for Conservation of Nature. That means it’s nearing extinction.
CALLI: That’s so terrible, Nate! But you said this was in Singapore, right? My kitties aren’t eating cat food from Singapore, are they?
NATE: Well, this study was actually inspired by a 2019 in the US study that found that 63% of the tested cat foods in the United States contained shark meat. Not only was the shark contents not promoted, a whopping 70% of the shark-containing cat foods had meat from the shortfin mako shark… an endangered species.
CALLI: That’s terrible! This has to be some kind of accident, right?
NATE: I’m afraid it might not be! Since the 1960s, the population of sharks around the globe has dropped almost 70%. Some sources think that as many as 70 million sharks are killed each year for their fins. It’s terrible, but on the global market, shark fins can fetch as much as $700 a pound. The shark fin industry might then be sending the rest of the shark, which is basically worthless on the global meat market, to the pet-food industry to try to make a bit more money.
CALLI: That can’t be legal.
NATE: That’s the worst part: it is all legal. And, it gets even worse. Many of these finless caracasses are just wasted. An even more common practice for shark fishermen is something called finning.
CALLI: I know I’m gonna regret this but… what’s finning?
NATE: Some fishermen just collect those valuable fins to sell to industry for things like shark fin soup. They’ll catch the shark, cut off its fin, and throw the still living shark back into the ocean. Without their fins, they can’t swim properly and often become prey or simply die of blood loss. What’s wild is that in many places this too is 100% legal. And while it remains so, it's really unlikely that anything changes.
CALLI: That’s really sad, Nate. I’m actually speechless right now. Is there anything I can do?
NATE: Unfortunately not too much, but pay attention to the labels on the cat food you buy. Look to see if there are any specific fish breeds listed on the can, or if the labels simply mention “white fish” or “ocean fish.” By avoiding those ambiguous labels, we can try to send a message to the pet food industry that we want clearer nutritional labels, and shark-free pet food!
CALLI: Would that stop the shark meat trade?
NATE: Not entirely. But it would help consumers to make more informed decisions. It’s not much, but it's something we can do to keep our pets shark-free, and keep meat of endangered species out of our cupboards.
CALLI: In the meantime, I’m going to tell my fellow cat owner friends, and see if I can support the International Union for Conservation of Nature in any future efforts to get some of these laws changed.
NATE: I hope we can! Because that could make a real difference.
[SFX: Whoosh]
NATE: Let’s recap what we learned today to wrap up.
CALLI: Recent research found that bull sharks develop relationships with other bull sharks that seem to approximate human friendship. The way these sharks travel, sleep, and hunt together, and avoid sharks they don’t like, is making researchers reconsider sharks as more complex social creatures.
NATE: Sharks don’t have a taste for man, we just look a lot like prey! Researchers recently confirmed that great white sharks attack swimming humans because from beneath the water, we look a lot like sharks’ natural prey, seals. Even still, you have far less than a 1% chance of being attacked.
CALLI: Recent studies have found that many kinds of cat food contain shark meat, including meat from endangered sharks. While it might not shut down the shark meat industry, avoiding noncommittal labels that say things like “contains real fish” or “contains ocean fish” can help keep shark out of your pet’s diet.