Luke Tipple speaks with marine biologists & stars of the Shark Week show Shark Women, Alison Towner & Leigh de Necker.
Shark Week: The Podcast takes you on a deep dive into the battle between great whites and orcas, also known as killer whales, off South Africa’s coastline. Marine biologists & stars of the Shark Week show Shark Women, Alison Towner & Leigh de Necker join host Luke Tipple to discuss how the notorious predator has become prey and explain the vital role great whites play in sustaining healthy ocean ecosystems.
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Learn More About Shark Week: https://www.discovery.com/shark-week
Find episode transcripts here: https://shark-weeks-daily-bite.simplecast.com/episodes/s3-ep9-why-orcas-are-killing-great-whites-in-south-africa
For more about sharks, head to SharkWeek.com
[00:00:00] Luke: Between the two islands of Geyser Rock and Dyer Island, near the small town of Gansbaai in South Africa, lies one of the deadliest stretches of water in the world. Shark Alley, home to a large population of great white sharks. But in recent years, the great whites seem to have vanished.
[00:00:20] Luke: Welcome to Shark Week: The Podcast! I'm Luke Tipple, marine biologist, and a frequent voice on my favorite things, oceans and sharks. I'm stoked to bring the magic of Shark Week, right to your ears. Sharks have been a big part of my life for over 20 years now, studying them and diving with them all around the world.
[00:00:38] Luke: I guess that's given me some of the street cred to participate in many Shark Week documentaries throughout the years, and, now, to be your host. So whether you've never seen Shark Week before, or you've been a diehard fan over the 30 plus years it's been around, this podcast is for you.
[00:00:58] Luke: Today, I'm thrilled to say we're joined by marine biologist and great white shark expert, Allison Towner, and marine biologist and shark nutritionist, Leigh de Necker, two of the stars of Shark Week documentary, Shark Women: Ghosted by Great Whites.
[00:01:13] Luke: How you doing guys?
[00:01:14] Alison: Hi Luke. We're really well, thanks. How are you?
[00:01:15] Luke: I'm doing really well. Alison it's great to chat to you again. And Leigh, are you there?
[00:01:20] Leigh: Thank you so much for having us looking forward to chatting.
[00:01:22] Luke: Of course. Well, thank you both for the show. I watched it and, I gotta tell you, it came out really well.
[00:01:28] Luke: I really enjoyed it and I loved the whole theme of, you know, shark women putting together a team and you guys going out there and you guys crushed it, obviously, and found a lot of really cool stuff. You guys have fun making it?
[00:01:40] Leigh: Oh, it was so incredible. Getting to work with Ali, who's been a friend of mine and colleague for a very long time was just, I mean, I learned so much from her every day and we had so much fun and then having Zandile as well. It was the first time I had met her.
[00:01:55] Leigh: Just an incredible human and, I must admit, it probably goes down as one of the coolest experiences of my life. It’s safe to say that.
[00:02:04] Luke: And Alison, you were, kind of in charge of putting the team together, is that right?
[00:02:08] Alison: Well I guess we, like Leigh said, we all go back. We're good friends. And we talked about our wishlist of what we wanted to do if Shark Week ever gave us an opportunity to have a show.
[00:02:18] Alison: And yeah, this was, this was perfect for us. We were thrilled to, you know, just have the platform to get out there and go on this adventure. And, as Leigh said as well, it's kind of… it's a bit of a first, right? We all go way back, but we haven't actually been together on a show before. So it was, yeah.
[00:02:36] Alison: I also feel so humble because, you know, it's not often that I get my friends on camera with me, that kind of thing.
[00:02:40] Luke: That is definitely cool. When you just get to call up your friends and say, all right, we’re gonna go have this amazing adventure and even just watching the beginning of the show, I mean, you guys are under the water, on the water, above in the air, kind of all over the place, diving with great whites, watching them jump.
[00:02:54] Luke: I mean, you packed a whole lot in the hour long show, but, Leigh, I actually wanna start with you because your title, at least in the show, and it might be a little tongue in cheek, but your title is shark nutritionist, which I think is one of the coolest job titles I’ve ever heard. Tell me about that.
[00:03:10] Leigh: Yeah, so I did my master's degree, focusing on the diet of the great white shark in False Bay, specifically. And I also looked at the diet of another species that's an apex predator, in False Bay, known as the broad nosed seven gill. So, with some really, really interesting findings from that research, yeah, I suppose it led me to have that title and I absolutely love it and getting more insight into shark diet and obviously having Ali, who focuses on their movement.
[00:03:45] Leigh: It makes us quite a nice team to look at what the sharks are doing in our south African waters.
[00:03:53] Luke: Yeah. And what are the actual practical applications for knowing what a shark eats in, you know, conservation sense or scientific sense? Like what can we learn and know, and, you know, make better or do differently?
[00:04:05] Leigh: So… well firstly, I'll just give you a little bit of background as to how we find out what sharks eat. We used to use stomach content. So that would mean, typically having a dead shark, which is not ideal for research. You don't want to be killing these animals to learn about them unnecessarily.
[00:04:23] Leigh: So we use what is called a stable isotope analysis and all that involves is getting a small piece of tissue from the animal. So we used blood as well as muscle tissue. And you don't need any more than about the size of a small fingernail, just a muscle biopsy from the shark. And then you need muscle from the potential prey items that they could be eating.
[00:04:46] Leigh: Then, long story short, you compare the muscle of the shark with that of its prey and you can get good insights into what they're eating. So essentially, it's based on the idea that you are what you eat. So the samples go into a big, fancy machine beside a bunch of data. And then I analyze that and I can tell you what the shark is eating, the percentage of that particular species in their diet.
[00:05:09] Leigh: And also the position in the food web that the shark may hold. So you can get incredible insights just by looking at a small piece of muscle from the shark. And that, again, advantage is that you don't need to have dead animals. So to answer your next question in the application of this.
[00:05:30] Leigh: Anything we can learn about sharks, any research… the more we know about them, the more we can contribute to their conservation. So, if we know what they're eating, we can have a good idea of what other species are important, what species we need to protect, beyond just the apex predator. We can highlight important hunting grounds for them and look at setting up potential marine protected areas, around those sites.
[00:05:57] Leigh: Yeah, so everything… the more we learn, the more opportunity we have to contribute to conservation. And that's the application for, not only shark nutrition, but all aspects of shark research.
[00:06:08] Luke: Yeah. Now, with your research, what was one of the more surprising things that you found?
[00:06:14] Luke: I mean, we've all seen sharks jumping outta the water, chasing fur seals, but were there things in their diet that you were kind of like, I didn't really realize that?
[00:06:21] Leigh: Well, like I said, my research focused on two species, so I looked at the two apex predators being the white shark and the broad nosed seven gill shark in False Bay.
[00:06:31] Leigh: And what was really interesting was that the broad nosed seven gill shark… I don't know if you know what it looks like but it's a very prehistoric looking animal. It looks like a big smiley dinosaur. You wouldn't really expect them to be these apex predators. If you look at a white shark and compare it to a seven gill and the way the white shark launches itself out of the water to catch a seal, it's just… you don't really know how the seven gill compares.
[00:06:56] Leigh: But what I found was the seven gill actually has more seal in its diet than the white shark does. So essentially, if you had to look at it from a stable isotope point of view, the seven gill shark is at a higher level in the food chain than the great white, which doesn't really make sense, but it seems that it's because they are eating more seal than the great white. And this is likely because they eat seal more consistently, whereas great whites focus on eating seal seasonally.
[00:07:28] Leigh: And it would be quite interesting to see how much that has changed now. Obviously, we are probably gonna go into a little bit more with Ali as to how everything's changed. I'm talking… this research was done a couple of years ago, so it would be interesting to relook at it and see if it's changed now that white sharks are being pushed away from seal colonies for extended periods of time.
[00:07:55] Leigh: But nothing too out of the ordinary, in the diet… no humans, you'll be pleased to know. But yeah, fascinating nonetheless.
[00:08:04] Luke: I think we definitely need to see now the broad nosed seven gills going after seals.
[00:08:09] Luke: Like, in one way shape or form. We need to figure out how to capture that footage, ‘cause it sounds pretty cool.
[00:08:15] Leigh: So, that is definitely high on the list of things to see. So it is likely that they are predominantly nocturnal hunters and being able to try to witness sharks hunting at night is already a challenge in itself.
[00:08:30] Leigh: But as to… if we, again, like I said, how a great white has to launch itself completely out of the water to catch a seal… how this broad nosed seven gill is doing it, it's difficult to say. The… our theory is that it could be scavenging, but there's too much seal in their diet to suggest that it's only scavenging. So there is likely active hunting taking place.
[00:08:51] Leigh: So yet another mystery in the shark world needing to be solved, maybe Shark Woman, too, can look into that.
[00:08:58] Luke: Oh, love it. We’ll definitely have to do that. Now Alison, why don't you take us through the setup of Shark Women? Like, you have a very special connection to this area and to some particular sharks.
[00:09:09] Alison: Yeah, I mean, I guess one thing that has been highlighted in the press quite a lot, the last couple of years, is how South Africa's white sharks have vanished or how they've disappeared from Cape Town areas. And there's been a lot of theory and speculation thrown out there but actually the science… it's almost like the science has struggled to keep up with the situation.
[00:09:27] Alison: So each year Shark Week comes back and we, you know, we've been covering sort of aspects of it. But this time, you know, we were really allowed to go out as an all-girl team and sort of try and pick up the pieces of the puzzle. And so, yeah, we started off in Gansbaai. So Leigh mentioned her masters work there with the isotopes in False Bay, False Bay being very close … well, being Cape Town.
[00:09:46] Alison: So Gansbaai is just down the coast, I'd say a hundred miles or so east. And, we started off at Dyre Island. So basically, trying to look at the site where I've done most of the white shark research and I guess where most of… yeah, a lot of Shark Week shows have been filmed around Dyre Island, right?
[00:10:02] Alison: With the hunting strategies of great whites, with the breaching behavior. And so we decided that's where we're gonna start. That's our ground zero. And we're gonna see, first of all, can we get any detections on our underwater receivers downloaded, to verify if white sharks have been through? So, yeah, after doing that, I mean, Leigh and I did the receiver dive, and then Zans, actually, she went in the water to see in the kelp forest regions, if there's any other additional prey species, basically trying to piece together the whole story of, if the white sharks aren't around, why?
[00:10:31] Luke: And Zans is your teammate, Zandile Ndhlovu, who is an incredible free diver. And I know she helped you out a lot on this mission.
[00:10:38] Alison: And looking from her prey component, Zans was sort of the eyes underwater in the kelp forest to see, well, is there a healthy flourishing population of other species of sharks that may well be prey for them.
[00:10:48] Alison: And Leigh and I were purely looking for data in the beginning. So, when we got the receiver out of the water, it was literally like, okay, have we got white shark detections? And that's from acoustic tags that we deploy in the great whites… and we could see we did, but the detections were very transient. So it's in and out.
[00:11:02] Alison: The great whites are not hanging around and it supports all of our observations for the last couple of years.
[00:11:06] Luke: Well, take us through that last couple of years, because, you know, if people haven't seen it in the media, what has been going on because, for a lot of people, they'll just associate, you know, South Africa in general, but your particular area with great whites and they have been scarce or disappearing. Is that correct?
[00:11:23] Alison: Well, yeah, exactly. I mean, I've been based in Gansbaai studying great whites… white sharks for the last 15 years. And we always had, let's say, about 5 to 10 white sharks per trip on average, comfortably throughout the year, and, post 2017, that, like, dramatically changed.
[00:11:39] Alison: It wasn't a gradual decline. It wasn't as if the sightings started to get less and less over time. Literally the sharks vanished and then vanished again. And it just kept on going, like this really abrupt disappearance. And that was right in sync with the arrival of killer whales. Not just any killer whales, killer whales with a specific, select hunting strategy for sharks.
[00:12:00] Alison: So, I guess for me, it was really nice because I've now teamed up with cetacean specialists that I never worked with before, because we were studying such different, you know, areas of ocean ecology. Like the killer whales in South Africa were predominantly offshore and not coastal. And now, all of a sudden, here they are!
[00:12:16] Alison: So we've been doing a lot of overlapping our expertise, let's say, but yeah, these killer whales came in and they caused havoc in Gansbaai. Yeah, they hunted the white shark.
[00:12:26] Luke: And what was that particular hunting technique? Like, obviously, they're going after white sharks, but how are they achieving that?
[00:12:33] Alison: So they're ripping them open and they're extracting their liver and, exactly as Leigh said, she studied her seven gills in False Bay. Before they arrived in Gansbaai and started doing that here, they were actually doing it in False Bay in 2015 already. Leigh actually came up from a dive… in fact, I'll let you talk about that later Leigh, but she saw the evidence there, and in its rarity. So, basically from 2017 onwards, the killer whales started coming through.
[00:13:00] Alison: We ended up with white shark carcasses on the beach. Shark Week covered it, but since then, it's not been the same. And so now, fast forward to 2022, you know, we've just gone a year with no great white sharks in Gansbaai. So there's a lot of questions as to where they are. And I guess Shark Women, even though the title has been given as Ghosted by White Sharks, it's quite the contrary.
[00:13:19] Alison: We were seeking and looking and found white sharks. But the answer as to where they've gone to was really what was leading the investigation.
[00:13:26] Luke: And what did the data from the receivers actually tell you?
[00:13:30] Alison: So, yeah, it told us that the sharks aren't really hanging around. Whereas prior to 2017, they would be spending time at the Dyer Island system, hunting the seals using the inshore reefs.
[00:13:38] Alison: And these sharks that we saw on the receivers were just zipping in and out, super skittish. It wasn't like they were sticking around. So yeah, we put all of the evidence together from the last couple of years, knowing that the sightings further down the coast of great white sharks had been much more reliable.
[00:13:54] Alison: And we called a fellow researcher in Mossel Bay and Mossel Bay’s also become really well known on the Shark Week map. So we basically followed the sharks east, if you will. And decided that Mossel Bay would be the next logical place to go and have a look for one of the missing white sharks from Gansbaai.
[00:14:10] Alison: And there was actually six, in particular, that we were looking for, that are fond animals of mine. I mean, we've got a whole population here that's basically vanished. So, six seemed a reasonable number to keep the viewers, I guess, engaged with the story. And, actually it's six of my all-time favorite sharks.
[00:14:25] Alison: So yeah… and we had a report that one was in Mossel Bay, so it just made complete sense to go and try further down the coast.
[00:14:31] Luke: Okay, so you've got orcas that are feeding on great whites and they're hunting them and, you know, scaring them, spooking them out of the area. But you're in an area with, you know, high turbidity, low visibility and sharks that are, correct me if I'm wrong, but hunting solitarily.
[00:14:45] Luke: So, how is that message getting out to the sharks that… oi, we all need to bug out and go somewhere else because there's orcas hunting us.
[00:14:53] Alison: Oh, Luke, it's a great question. It's still the question… It's still the question of the hour. Yeah, I mean, look, there's a very high likelihood that, when the white shark carcasses or dead shark carcasses… they actually, the killer whales in South Africa, they aren't just hunting great whites and seven gills.
[00:15:08] Alison: They're also hunting bronze whaler of sharks and, probably, a plethora of other species that we don't know of. The fact is, we only see the carcasses that wash out. So, we know that there's more of them down there on the sea bed, rotting shark carcass delivers necromones into the water, which is basically the scent of death.
[00:15:23] Alison: So, probably on a localized scale, we have got that. And we know that sharks have incredible senses of smell. So, if they buzz on into the area that they know and they smell their deceased, they're not gonna hang around. But that, again, is localized and it's probably, on a temporal scale, not gonna be, you know, the ruling factor as to why they don't come back for so, so long.
[00:15:41] Alison: So then the question is, can it be vocal? You know, we’re not talking about one white shark leaving. We're talking about them all scattering and disappearing at once. So is it audio, do the killer whales vocalize, are the sharks able to hear that? And then, that's the signal to get out of there.
[00:15:56] Alison: Obviously some of them succumbing to the killer whales before they even know what's hit them. Is it visual or just trauma from being physically chased around? I mean, if you think of killer whales being the wolves of the ocean, how they hunt white sharks with no question about it and they chase them all over.
[00:16:12] Alison: Like, they basically go after shark, after shark, after shark until they mine sweep the area out. And it's not just two of them doing it. So that's the situation. And I guess any terrestrial predator would not stick around if that was happening. But, I guess every species has their own response rate… but white sharks are pretty adamant not to come back for a while.
[00:16:30] Luke: Yeah. Leigh, what are you seeing? I know that you do a lot of diving in those waters there. Have you seen any changes in the behavior of the sharks that you encounter?
[00:16:39] Leigh: So, unfortunately in places like False Bay, which is where I'm based in Cape Town, we haven't seen great whites for a very long time. I have recently come across seven gills, but they've completely left the aggregation site where we used to find them.
[00:16:55] Leigh: So, as Ali mentioned earlier, back in 2015, some divers reported a lot of shark carcasses at the bottom of a site called Miller’s Point, which was historically a massive aggregation site for seven gills, where you could go dive there and see almost 70 sharks at a time. It was absolutely incredible. And, bear in mind, these aren’t small sharks, they can reach just over three meters.
[00:17:18] Leigh: So they're big animals. And one day, we just got four carcasses and myself and another guy went and did a dive and we brought up a carcass and, as we got onto the boat, it could… we had hardly got our gear off. We just saw this animal moving towards us and it was Starboard, one of the orcas, that swam right underneath our boat.
[00:17:42] Leigh: So this was… and then, well, we did the necropsies after that and exact same… We first thought that it was fishermen because the cut was so clean down the center of the seven gill. It looked like it was done with a knife, like, with such precision. Liver out… but what really gave it away?
[00:18:03] Leigh: One, kind of caught in the act when the Orca swam underneath our boat. And, secondly, with the necropsies, there was distinct teeth marks on each pectoral fin, which looked to be... we consulted with cetacean specialists and they said that that's orca dentition. So yeah, it's quite… it's not great.
[00:18:30] Leigh: Going to sites where you're used to seeing these animals in massive numbers and now… they’re just no longer there. This was 2015. It's a long time ago. And the seven gills just have not returned to that site. Very big shift in the ecosystem and how it works. So, where white sharks used to aggregate in the winter months around Seal Island, hunting seals, white sharks are no longer there.
[00:18:52] Leigh: They haven't been seen for a long time, but now, seven gills and bronze whalers are taking over that space and people who have worked in that area for 20 plus years say when the white sharks are there, there's no other sharks. So it's interesting to see the change in the dynamic and the fact that, every time Port and Starboard are seen in False Bay, there is also a disappearance of the seven gills.
[00:19:21] Leigh: It extends beyond the white sharks, as Ali has already mentioned, and also for us, we do still see sharks around but it's not consistent. There's no real pattern anymore. Yeah, it's all controlled by the presence of Port & Starboard really.
[00:19:37] Luke: So is there a working theory unto why Port and Starboard are there? Is it like a sea change thing or a temperature thing, or is it just a couple of rogue Orcas who are just causing all this damage?
[00:19:49] Alison: No, it's definitely not. So there's an updated killer whale review paper now coming out in South Africa. The last one, it was in 2010. And since then, the changes in killer whale composition coastal are just really, really, really interesting.
[00:20:01] Alison: So, we never had killer whales this coastal before in such numbers and, specifically, this offshore, rare morphotype, that are known to be shark specialists. The other problem with killer whales is, they learn really quick. So they have something called cultural transmission that happens within their groups.
[00:20:18] Alison: So, especially strategy, like ripping a shark open and taking its liver, can be transferred very quickly throughout a population. And, unfortunately, we've now just realized that's going on in South Africa. So it's not just Port and Starboard, the paper on that's been accepted and is about to come out around about the same time this airs on Shark Week, well the footage anyway.
[00:20:33] Alison: So yeah, we can talk about it and it's… there is no clearcut answer but, possibly, the killer whales have come in from offshore because of lack of prey out there. So, I dunno if you remember Luke, you've done some interviews with me in the past, and there's been this talk about demersal longliners and about that being driving factors behind why the white sharks have disappeared from the Cape.
[00:20:54] Alison: And absolutely we do believe that overfishing is probably connected, in fact, very likely connected to, to this whole story. But it's mostly, likely, connected to the killer whales, as opposed to the direct reason the sharks abandoned the Cape and consequently, all of it plays into the idea that, you know, humans have impacted the oceans to cause this, absolutely.
[00:21:12] Luke: Yeah, it makes sense. I'm curious, do you know, it may be an unanswerable question, but can one killer whale take out a great white or does it take several of them. I'm trying to imagine how they use their dentition to actually just make clean cuts, to get a liver out. It seems like you'd need a buddy to hang onto him while that's happening, right?
[00:21:31] Alison: Yeah. I mean, Leigh will probably agree with this. I mean, she saw just Starboard, but it definitely takes two to tango. I mean, a white shark's a big animal! To be able to manipulate it onto its back, to asphyxiate it and give it tonic mobility to kill it. You know, it's hard to do it with just one, even though they're big animals themselves, the killer whales. I think that they do rely on that teamwork.
[00:21:49] Alison: So, you know, each animal grabs onto a pectoral fin and then they swim away and they tear the shark open.
[00:21:56] Leigh: What’s quite interesting to see and I don't wanna give too much away, but, from that footage, it almost looks like Starboard is supervising while the others do it. So it's incredible to see how quickly they learn from each other.
[00:22:10] Leigh: But yes, the tonic immobility is an incredibly clever strategy. As soon as that shark is flipped upside down, it goes into, like, a sleep-like state and that's true for most, if not all, shark species. So, as soon as it's essentially immobilized, it makes it a lot easier to handle that animal.
[00:22:33] Leigh: So, as Ali said, each of them grabs a pectoral fin, swims away and it just tears open. And I think that's why that cut is so clean that it almost looks like it's been done with the precision of a knife. It's actually torn open.
[00:22:47] Luke: That, you just painted a really clear picture for me now. So, if we imagine that, you know, this is medieval times and we've got two horsemen tying a rope onto someone's arms, which in this case are the pectoral fins, then they're charging away.
[00:23:00] Luke: And essentially, you're describing just the belly splitting open from the tension that's being applied. Is that right? So they're not using their teeth at all?
[00:23:06] Leigh: No. So the teeth are just used to hold on. And so, when we did the necropsies, you could see the teeth marks in the pectoral fins. Which does further prove that that is likely.
[00:23:18] Leigh: And then, now that we've got footage to show it, it confirms what we thought to be true. You don't really wanna believe it ‘cause you think sure. It's quite gory actually…
[WEIRD NOISE IN BACKGROUND]
[00:23:32] Alison: Was that your dog, Leigh?
[00:23:33] Leigh: Sorry, hope you didn't hear that… Yeah, my cat just smacked my dog.
[00:23:38] Luke: I was gonna say, right on cue. Something's getting torn apart, back out there.
[00:23:44] Leigh: It actually sounds oddly similar to the sounds an orca makes… the cat getting upset with the dog! Sorry.
[00:23:50] Luke: I love it. So, I think we've covered the orcas pretty well. And now I know that… one thing left in life is to see that happen. Well… a predation like that, seeing that split apart, my God, that has to be witnessed.
[00:24:05] Luke: Have you guys ever seen that? Spoilers are ok, you can tell me!
[00:24:08] Leigh: No, it's crazy to see. I mean, we've seen a lot of sharks hunting seals and you look at that and you think that's quite brutal and that it doesn't get too much more hectic than that. And then when you hear what the orcas are doing to the sharks, it makes a predation on a seal, not look so bad anymore.
[00:24:28] Luke: Yeah. I mean, seal predations are brutal and I think you guys actually have one... You've probably seen many, but I know there's at least one on your show and it's brutal, it's bloody, but, you know, it's over after a while and not really too bad. But, Alison, where, if we've got the presence of the orcas, they're driving the sharks out, you guys obviously found some sharks, where are they going?
[00:24:54] Alison: Yeah, so again, you're asking all the good questions, Luke. It's almost, like I say, the science really struggles to keep up but certainly it seems to be that we're getting an uptick east in South Africa. So while we're getting traditionally here; always Cape Town, False Bay, Gansbaai, Dyre Island were class as the epicenter of the white shark’s distribution.
[00:25:10] Alison: That's now shifted. Mossel Bay became very much the main focal area. And now, if you just look at the Eastern Cape of South Africa, at the moment, you know, post the killer whales making a direct predation in Mossel Bay just recently. Plenty of white sharks. So, it's dynamic, it's moving, it's changing all the time, but certainly, east seems to be the way to go if you wanna come across your best chances of seeing a white shark in South Africa.
[00:25:32] Alison: And when I say east, I mean, areas like, for example, J Bay, where they're just holding the world’s Surf League competition right now. Plettenberg Bay and East London, areas like that, where the sardine run is happening and there's an abundance of food.
[00:25:50] Luke: Now as those great whites might be moving east, Leigh, do, like, okay, let's sort of extrapolate this. You know, now they're kind of east but not really that far in the scope of things. But you know, 5, 10 years time, if they are continually being driven and chased… Is there a point at which the food of the great whites, you know, their target food, the seals and stuff, they kind of run out, like, where are those populations of animals?
[00:26:15] Leigh: So white sharks have a very diverse diet. We obviously always look at the hunting of the seals ‘cause it's big. It's exciting, but it's only… it only forms a portion of their diet and only really for sub adult and adult great white sharks. So. Whereas juveniles, uh, sharks will typically eat fish and other shark species.
[00:26:38] Leigh: And as they grow a little bit bigger, are they then only do they start hunting seal? So. white sharks will move and, um, eat anything. They can come across another huge, huge thing for white sharks is whale carcasses. If they can come across a whale, Carcas it can sustain them for, um, a very long time. So having a diverse diet is very good for the sharks and their ability to adapt and hopefully survive this because as they move along the coastline, No real shortage of food.
[00:27:11] Leigh: So that's the upside for them. I don't think food shortage will be an issue. However, Cape ver is a very, very nutritionally rich food for sub adult and adult grade white sharks. So, um, they won't be getting one of their favorites, but, um, I am pretty confident that they'll still be able to sustain themselves with what is available in our very abundant waters.
[00:27:35] Leigh: I think the fear is more the ecological impact of losing an apex predator in places where you have seal colony, cuz cuz they. Control the structure and function of that ecosystem. So without your white sharks, your seal populations expand, and we are already seeing that this isn't even, you know, something you would think would happen over a long period of time.
[00:28:01] Leigh: It's already happening. There are plenty cap fors, Cape vers, eat PED Soine other fish. Fish that the penguins rely on fish that bigger fish rely on fish that we rely on. So now all of a sudden you've got ex extra pressure on the fish populations. Ultimately, the fish populations will take strain collapse in your seals are without food.
[00:28:25] Leigh: Your big fish are without food. Sharks without food and we are gonna struggle for food. And I think the African penguin is gonna take the biggest knock in the long run. So because the penguins
[00:28:34] Luke: rely on the, the fish, right?
[00:28:37] Leigh: Yes. For sure. Yeah. And what, what. I think it's not so much that we are too concerned about the great whites surviving or, or not.
[00:28:47] Leigh: Let me put it this way. Not finding food as they move. It's more about losing them in really important ecosystems. What are the long term implications for those ecosystems?
[00:29:09] Luke: Uh, let's give, put some numbers to this and perhaps, I don't know, Alison, this might be a question for you, but when you talk about the, the seal populations expanding, like, what are they. Currently, what are they increasing to? Uh, cause I think those, the, the sheer numbers might surprise some people.
[00:29:26] Alison: Yeah. I think what's really important to consider.
[00:29:28] Alison: I mean, the Cape first seal population is in South Africa are extremely healthy di island. I mean, it's quoted between 45 to 50,000 seal island, false bay, I think also around the 60,000 mark hay. Yeah. It's quite high. There's no shortage of deal. Yeah.
[00:29:42] Luke: I mean, that's 60,000 seals on, on an island. That's not that big, right?
[00:29:48] Alison: That that's resident populations on the colonies. And now if you look at, I mean, I guess maybe some chart we, viewers might not even know this, but South Africa has its own species of penguin at the African penguin. It's critically endangered. So experts give it maybe 10 years at most before it could possibly be extinct because the numbers.
[00:30:04] Alison: So so low and they just keep declining due to prey removal due to climate pressures. Um, we, they can't afford any more predation pressure from, you know, over abundance seal populations or competition for food. So yeah, it's, it is a really sinister situation. And I guess it shows us an adversely just how important it is to have white sharks around.
[00:30:24] Alison: So
[00:30:25] Luke: are the, are the seals also predating on the penguins then? They
[00:30:28] Alison: are. Yeah, they, um, they're performing more bold and risky behavior because they've got no, no fear or risk curbing their, their distribution in their, their movement. So they're just hanging out off of like areas like dire island. And after one day we, I think we picked a bike seven dead African penguins that just had this.
[00:30:43] Alison: Stomachs ripped out by the Cape first seals. So even if it's, you know, not really sustaining the first seal population to do that, they're doing it anyway. And it's because they're, you know, there's too many of them and they're too bold. It's, it's all about balance.
[00:30:56] Luke: Yeah. And when you say, uh, so the numbers, uh, you know, 60,000 in a seal colony, has that increased maybe by 10% or 20% since, you know, 2017, when the sharks started to deplete?
[00:31:09] Luke: Um, I
[00:31:09] Alison: don't think there's any percentage increase that I can quote directly, but I'm. I'm just sure. For, if, if I'm talking about the effects directly on the penguins, the seals are definitely more abundant. So what, again, we need to,
[00:31:22] Luke: I mean, anecdotally they're growing and also the behavior is changing in a detrimental way to everything else around
[00:31:28] Alison: it.
[00:31:28] Alison: Exactly. And I mean the, the different seal colonies along the coast of South Africa, I mean, Every single one of them's really healthy. Right. But remember as well, we did have the die off of Cape first seals now last year, which took a lot of seals out of the Western colonies. So maybe the ocean does have its way sort of balancing things out, but certainly that, that prolonged hanging around colonies when they're not supposed to be doing that's, that's really a very impactful factor in a ecosystem that wouldn't usually have it for.
[00:31:54] Alison: Um, particularly the di E.
[00:31:56] Luke: Okay. So we're, we're moving up east. We're looking for the great white going up east and, and looking at the Sadine run. And this is something that I've always dreamed about. I, I will be over there shortly to go and see this, but I'd never thought about great whites being in that mix.
[00:32:10] Luke: That seems really unusual.
[00:32:11] Alison: Yeah. I mean, it's something that we've tried to get for years at the footage of, of, of white sharks on the society room, because technically everything's there Luke to entice a white shark to be around from a predatory perspective, but it is, it's really just underwater a chaos.
[00:32:26] Alison: It's the biggest migration of, you know, Marine, um, Biomass, uh, that rivals the, the African V beast on the, you know, on the plane of Africa. So it's a huge movement of fish. It's huge amounts of food, huge amounts of predators, but really hard to find white sharks and amongst it all, because there's just so much going on underwater and often quite challenging conditions.
[00:32:46] Alison: So yeah, we were stoked to, to the locate, a white shark up there on, on, and we genuinely did like the micro length footage that you see of me in the air. I promise you. I know sometimes we. We might dramatize things a bit for viewership a little bit for some of the shows, this was 100% genuinely a white shark on the Sadine run.
[00:33:03] Luke: Yeah. It wasn't clear from the footage, how close in context it was to the Sadine run. Do you think it was kind of a, just biting its time and hanging out on the outside? Or was it just belly full, just
[00:33:13] Alison: chilling. It was right there. Very close to Saudian action and li Zs were on the action. So it was actually quite harrowing.
[00:33:22] Alison: I guess, I suppose when we came back down, we, we landed near the Harbor and that afternoon people on the Harbor had reported seeing a white shark, uh, coming on in, on the inside of the, the jetty wall. So we, it possibly could have been the same animal, but yeah, it was close to the action and pretty close to alien Zs were getting in the water.
[00:33:38] Alison: Um,
[00:33:39] Luke: so now that you've, you know, established that there's sort of white sharks moving over east Allison, what is the next step for you and your research? Do you continue to focus on the white
[00:33:48] Alison: shark? Yeah. I mean, it would be really silly now to abandon ship with them because there's now with all research, when you answer questions, a whole bunch more questions, uh, presented.
[00:33:57] Alison: And now for me, it's imperative to really understand where of these sort of localized aggregation hotspot shifted to not only from an ecological perspective, but obviously for bay, the safety, um, in, in Cape town back in 2006, there was a specialized workshop that got held by various stakeholders in government because there.
[00:34:15] Alison: Rate of bite incidents in the Cape from white sharks, some fatal, and they really needed to handle the situation. And the shark spot as program was developed and all these different be the safety mechanisms. So we don't have all that much of that up in Eastern Cape of South Africa. And, and that now really needs to be watched very carefully because there are human repercussions.
[00:34:34] Alison: If we've all of a sudden got white shark shifting into areas that there's. Bathers and, and little warning. So understanding the, the movements of the white sharks, how, you know, how this is gonna play out. Obviously the ecological side of things range president, you know, the, the ecosystem impacts need to be, need to be balanced before this, this becomes.
[00:34:53] Alison: Yeah, really, really, really profound. Um, and of course there's economic impacts as well. So certainly follow what the white sharks are doing. If we had more access to funding. I think I see I said this on the last podcast with you, you know, shark weeker, one of the only funding mechanisms we have, you know, these film crews coming down and giving us the resources to put satellite tags on individuals.
[00:35:13] Alison: It's almost unaffordable in South Africa and the government don't sponsor shark research. It's privately raised funds. So yeah, absolutely keep tabs on what the white sharks are doing more now than ever. But also collaborative, um, research with other species and, and, and, and the fact that government now have science, that they can use predictively model, the seasonality of the killer Wells, and try and try and work out some kind of strategy to mitigate impacts on the sharks and the ecosystems.
[00:35:38] Alison: There's a lot Luke to say, where's this going? I think it's only just started to be honest.
[00:35:42] Luke: well, as it going, it just keeps going. Doesn't it. But. Yeah, you actually bring up a, an interesting point that Lee, perhaps you can speak to, cuz now you do have these two very large, you know, apex species, but also very publicly visible, you know, beloved species, you know, facing off against each other.
[00:35:59] Luke: But now the opportunity for researchers from both camps to kind of work together, do you think that having the citations and the shark researchers working together will, you know, help stimulate some of that, uh, government interests that will lead to more finding.
[00:36:14] Leigh: Sure. We, we can only hope so, like, um, but as Ali said, , yeah, it is very difficult in South Africa trying to get funding for these kinds of things.
[00:36:24] Leigh: Um, but, but hopefully if, if they start to recognize particularly the ecological impact that extends. Again, like Ali said beyond just the ecological, there's an economic aspect to it too. So you often have to play that card as well to get the funding. So as long as we can try and get these people to understand that not only long term, we are already seeing these effects, we need to find solutions.
[00:36:51] Leigh: And one of the only ways to get to that point is to have the funding, to do the research so we can understand what we are dealing with and find potential solutions. But Ali said earlier, the difficulty is the science just can't keep up with what's happening out there. EV everything is going on and happening so quickly that.
[00:37:11] Alison: We science just take so long to get through peer review. Like our study took five years. Reviewers are like, no, hang on. That can't be, and we're like, but it is happening, but you don't have enough evidence. It's like, well, how much you need? We've had, eight dead white sharks that we know of. And yeah, it's, it's been tough.
[00:37:28] Alison: So international intervention may also be a part of this. I think a lot of the people in the world now are looking at South Africa and I've had a lot of outreach from the states actually saying we are watching down there. We can't believe what's going on. You know? Obviously off the us, you've got really healthy white shark populations that are rebounding.
[00:37:44] Alison: Same with Australia down in South Africa, we can't afford to lose any more great whites. Our stocks aren't healthy. 30 of them at least a year are killed in the bay, the protection nets off Naar then, um, off Durban. So fisheries human impacts already on the white sharks. Then we've got kilo whales it's it needs, it needs some international intervention and, and there are some nice collaborative, uh, work workshops ongoing about the, uh, the ecological role of sharks and how to, how to try and strategize this whole situation.
[00:38:14] Luke: Well, that is a good thing about shark week. Isn't it? Cuz we can come down for a couple of weeks, make a great film, get it exposed to millions and millions and millions of people and come up with conclusions that don't necessarily have to wait for the publish or parish cycle to happen and, and maybe stimulate a bit of, uh, external influence and uh, and funding for you guys.
[00:38:32] Luke: So absolutely. But, I mean, I do wanna talk about that show very briefly in the sense of what you managed to put together. Um, you know, I, I'm very passionate about women getting involved in science and you've done kind of a, I don't know if it's the first, but it was certainly an inspirational all women show.
[00:38:51] Luke: What does it mean to you'd be able to put that together and what was the kind of most memorable thing about it?
[00:38:56] Alison: It was first in that it was the first time that south African women were hosts on short week, like lead host. So that's, that's a big first, we get a lot of internationals come down and film for short week that aren't doing research in South Africa or around south African.
[00:39:08] Alison: So to me it was always a dream, but I'm gonna, I'm gonna pass this on to Lee because, you know, just quickly about Lee. , she's deserved this for so long and the work that she does, I guess it just hasn't had that kind of exposure. And I'm so glad now that that she's had that opportunity. And, and of course, we got to, we got to experience Zs.
[00:39:26] Alison: I'm really sad that Zs wasn't able to be on the podcast, but she is on the SAR team run right now, filming her
[00:39:31] Luke: own show. Zen is of course, Sandy LA under Lovo, of course, sand and Delo. Uh, she's an incredible freight.
[00:39:36] Alison: So, but Lee Lee, you feel exactly the same, right?
[00:39:39] Luke: Yes. Uh, Lee do tell us about zens as well.
[00:39:41] Luke: oh,
[00:39:42] Leigh: Zans is amazing. She's just incredible in the water. So comfortable. So at home and for somebody that hasn't. She, she never saw a white shark before the show. So that was one of the highlights is showing Zans or white shark. And her reaction to it is, is absolutely priceless. Um, she really is a magnificent human being and she she's doing some really good things in the world.
[00:40:05] Leigh: Not only what's, what's the word she's trying to create diversity in ocean spaces. So to allow people from all backgrounds, women, Children men from all color, all colors, all races to be introduced to the ocean space because particularly in South Africa, there's this fear associated with the ocean and lack of resources for education to understanding what the ocean is about.
[00:40:30] Leigh: And she makes it more accessible to everyone, really. So really amazing and inspiring getting to work with her
[00:40:37] Luke: a and Lee. What does being on this show mean to you? I mean, obviously you have a very distinguished, uh, history so far with research, but being front and center of a show like this has gotta be life changing.
[00:40:45] Luke: Wow.
[00:40:46] Leigh: for me, it was, it was really incredible when Allison told me about it and this, this was a while ago when she brought it up, I was like, Ooh, me, am I worthy of this? And she seemed to think that I was, and it it's just incredible being able to share what we have in our south African waters. Um, The diversity we have here is amazing.
[00:41:08] Leigh: It's very dynamic. It's always changing, getting to share it, but also getting to share it with, with women, with, um, ladies who I connect with on a deeper level who have the same goals and aspirations and passion around the ocean. And for conservation, it's, it's really quite meaningful. And when you're filming a show like this, especially your first one, as it, as it was for me.
[00:41:33] Leigh: Naturally you're nervous cuz cuz we are not actresses we're scientists, but from day one I was so comfortable because I just had to do what I do, what I do share what I know to the best of my ability. It, everything was so easy and authentic. And I think that was largely thanks to Allison and Z and just the connection we have to each other, but also.
[00:41:57] Leigh: To the ocean, but yeah, south African woman sharing information on south African sharks, what an adventure, what a privilege. And, um, I really hope that we'll be able to do more of it. Um, yeah. Uh, yeah, I can go on forever on what it means to me, but I might have a
[00:42:12] Luke: cry and to be fair, you guys are jumping in the water with great white sharks and low visibility, collecting data, tagging, spearing, swimming.
[00:42:21] Luke: Freediving. You guys are bad asses. Yeah.
[00:42:24] Leigh: Women can be hardcore too, you know,
[00:42:27] Luke: absolutely. Okay. Well, the show is shark women ghosted by great whites. Uh, I immensely enjoyed it. It's definitely one of my favorite shark weeks this year. So everyone you have to check it out. And that wraps up another episode of shark week.
[00:42:41] Luke: The podcast, I wanna thank Allison and Lee for joining us. We are definitely gonna get Zs on in a future episode cause I really wanna chat with her. Thank you both for your time.
[00:42:53] Luke: All right, wraps up another episode of shark week. The podcast stay tuned to this feed for more interviews with shark experts, that'll give us the behind the scenes scoop on what really happens out at sea. We'll see you again soon.
[00:43:06] Luke: Thanks for listening to shark week the podcast. Be sure to rate us five stars and subscribe for more shark, fun facts. I'm Luke tipple. I'll see you next time.