Tooth and Claw: Killer Whales

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1:06Adam Hart:You're listening to Discovery from the BBC World Service. I'm Adam Hart and this is Tooth and Claw, the series where I explore our complex and challenging relationships with Earth's greatest predators through the people who have spent their lives studying, protecting, and at times narrowly escaping them.

1:28Adam Hart:Today's predator is the undisputed apex predator of the sea. With its distinctive black and white colouration, this marine mammal is the largest member of the dolphin family. Able to predate even great white sharks, as we heard in a previous series, these skilled hunters are found in waters all over the world. It's time to learn about the killer whale, also known as the orca. Let's dive in with Dr. Lee Hickmott, whale biologist and conservationist, who's an expert on pack ice killer whales and whose research uses them as indicators to assess human disturbance of marine habitats. And Dr Deborah Giles, who goes by Giles.

2:05Adam Hart:She's an expert on southern resident killer whales based with the SeaDoc Society, a programme of the Karen C. Dreyer Wildlife Health Centre at the UC Davis School of Veterinary Medicine. Now Lee, let's start with you. Can you tell us about the pack ice killer whales in the Antarctic? What do they eat and how do they hunt? So pack ice killer whales are a form or eco type of killer whale that lives around Antarctica and they specialise in predominantly eating seals and they do that with probably the most coordinated hunting technique that we see amongst killer whales and that is to create waves to wash seals off of ice flows into the water where they then dispatch and share them between pod mates.

2:48Tell me a bit more about this wave washing technique. They really specialize in living in amongst what we call pack ice. So in Antarctica, through the winter, the sea freezes. And then as spring moves into summer, that frozen sea breaks up into pieces, which we call pack. And these killer whales specialize in traveling through that pack ice, searching for seals to eat. And they do that by swimming through it and spy hopping. So they raise their head up to two and a half meters out of the water to scan the ice visually so looking for their prey and when they see a seal on the ice then what they want to do is find out what type of seal it is because depending on the pod they do have preferences for the type of seal that they like to consume what they'll often do is if the seal is on a large piece of ice is they'll create a wave what we call a subsurface wave.

3:43So they do this by forming up into a line, swim towards the ice, and as they get towards the ice, they come close to the surface, turn on their sides, and as they swim and pump their flukes, that creates a wave, if you imagine a wave coming from the sea up onto the shore. And so as the swell approaches the shore, in this case, as the water that the whales are pushing that's being forced by their flukes, as they raise their bodies closer to the surface, then that makes the wave crest. And so then that wave will crest and crash onto the ice. So their first one is to make a subsurface wave. So they swim and they pump all the way under the ice.

4:25So that creates a shock wave through the piece of ice so that the ice will shatter and break apart. Because what they're looking to do is get close to what that seal is so they can have a look at it.

4:37Adam Hart:Right, so once they've been able to have a look at it, how do they then get to the seal which is still on the ice? Once the ice is broken, then they move under the ice and blow bubbles and the bubbles will then push the pieces of ice apart so that then they can fit their head up through the ice, spy hop again and have a good look at said seal and if it's a type of seal that they'd like to eat. And typically for a lot of pods, their preference is to eat a type of seal called a Weddell seal. So then what they'll often do is coordinate themselves and push that piece of ice out into slightly more open water and then form up again into a line, pump towards the piece of ice, bring their bodies onto their sides and closer to the surface.

5:19And in so doing, they create this wave, the wave crests up and will literally crash down onto the seal itself to push the seal off the ice and into the water. And they might repeat that many times. And once they have, and they have the seal in the water, then it's this sort of delicate game of teaching the youngsters as well as being careful to not be injured by the seal. So they'll often allow the seal to climb back out again to tire itself out. Or as and when it is in the water, then they play this very delicate game of they want to get hold of the hind flippers. So essentially like the tail of the seal.

5:57So the furthest from its teeth and to a lesser extent, the claws on its four flippers. The seal is trying to protect itself. So it will hold itself very close to the piece of ice. And then the killer whales nudge in on each side of it. And as it turns towards one to bear its teeth at them, that inevitably flicks out its hind flippers from the other side. And then the killer whale from the other side will be waiting to try and take those. And it will realise that, spin again, bare its teeth at that killer whale, and then the killer whale on the other side will do the same until eventually it's tired enough that one of them will take it down.

6:33So particularly when it comes to Weddell seals, they are the most successful, you know, large mammalian predator on the planet, certainly a hunt success rate of over 90%. If they find a Weddell seal and they want it, invariably that Weddell seal doesn't live another day.

6:49Adam Hart:Yeah, I mean, we've had some remarkable group hunting strategies across tooth and claw with all kinds of predators, but this is comfortably the most complex. So pack ice killer whales are found in the Antarctic and mostly are hunting seals. How about the southern resident killer whales that you study, Giles? Whereabouts are they found and what do they mostly hunt? The southern resident killer whales range in the listing documents say that the range is southeast Alaska to the north and Monterey, California to the south. Really, their territory is maybe 50 miles or so north of the top of Vancouver Island in BC, Canada, down to Monterey.

7:27They are obligate fish eaters. They preferentially forage on the largest of the Pacific salmon called Chinook salmon. When there's enough fish, when the fish are schooling, they do cooperatively hunt. They definitely share food, which is an interesting aspect of this population in that the average size Chinook salmon in Washington state is just 12 and a half pounds now, what we would consider puny fish.

7:54Adam Hart:So how much salmon do they have to eat today to keep going? Because they're pretty big animals, it feels like they might need quite a lot of fish. So every whale needs to eat several hundreds of pounds of food per day per whale. If it's pregnant or lactating, especially a lactating female, it's three plus hundred pounds, an adult male, same thing. So it's a tremendous amount of foraging that has to happen in order for these guys to meet their basic daily caloric needs. Fish used to be massive. Fish coming out of the Snake River, which is a tributary to the Columbia, would have been over 100 pounds.

8:30So we've got photographs of fish that are 116, 120 pound Chinook salmon. And so when you think about it in those terms, or even as recently as 50 to 80 years ago, it was not uncommon at all to have a 50 to 80 pound Chinook salmon available to these whales throughout their entire range. So when you think about it in those terms, it's not so hard to imagine that these whales would have been well-fed. These whales, you know, were eating an incredibly nutrient-dense food source for a very, very long time. And so nowadays with the stocks of salmon throughout the entire Pacific Northwest and up into Alaska with the stocks of salmon being highly, highly depleted, in many cases the salmon themselves are on the endangered species list.

9:19Their size has diminished significantly. That's a lot of extra foraging that these whales have to engage in in order to make sure that they're getting enough to eat.

9:29Adam Hart:So the salmon now are much smaller and much less abundant. That's exactly right.

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10:36Adam Hart:You're listening to Discovery from the BBC World Service. I'm Adam Hart and this is Tooth and Claw. Joining us are whale biologists Dr Lee Hickmott and Dr Deborah Giles. We've been talking about the pack-eyes killer whales which Lee researches and the southern resident killer whales which Giles researches, But there are a number of different killer whale groups around the world. In fact, on our last series of Tooth and Claw, we spoke about a pair of killer whales in our Great White Shark episode who were attacking great whites off the coast of South Africa and eating their livers. Search BBC Tooth and Claw Great White Shark to listen to that programme.

11:12Adam Hart:So, we've been painting the picture of an extraordinarily adept predator here. In your view, Lee, what is it about the killer whale that makes them so successful as a predator? I guess for killer whales, it's their intellect, their knowledge and their culture. Because by passing down information over many generations and teaching their offspring how to forage and certainly in many forms, individuals staying within their family groups for their lifetime or certainly for long periods of their life. and that groups can stay stable for long periods of time, that by developing specific adaptations and passing those behavioural specialisations of how you acquire prey successfully onto subsequent generations, they become incredibly successful and hence why they've been able to populate every ocean on the planet and are found in incredibly high numbers at high latitudes, so up towards the Arctic and down and around Antarctica.

12:23Adam Hart:And they've got this very specialised way of approaching their prey in these different ecotypes, but does that limit them a bit? Are they adaptable? If suddenly pack-eye seals become much less abundant, would your killer whales be able to switch, say, to hunting fish, for example? So that's a really interesting question and point about an animal that we have proven and are very aware are incredibly intelligent and have shown fantastic adaptations. But part of those specializations mean that they have passed that knowledge on over many generations. And so by being specialized, they are very efficient and adept at what they do.

13:10But because of that cultural knowledge and cultural learning, the likelihood of or the scenario of switching prey and adapting their behaviour, given that these animals are very long lived with lifespans not dissimilar to our own, that they may be at a disadvantage. So generalist predators may be more successful than animals that have become specialised if prey in their particular habitats start to become limited, as Giles has alluded to, to do with southern residents and availability of salmon there or particular species of salmon. And for animals or ecotypes in Antarctica, for example, then climate change being a large concern for them and the amount of ice and what their seal prey are doing.

14:02So back to your question of can they adapt? The evidence suggests that despite their intellect, these are creatures of habit and their specialised nature means it's unlikely that they would be able to adapt in the timeframes that we're looking and experiencing now to do with impacts of how we as humans are affecting our planet and the ecosystems within it.

14:24Adam Hart:Now I said at the top of the programme that killer whales are basically big black and white dolphins. We associate dolphins with lots of vocalizations. Are killer whales very vocal? So killer whales are very vocal, as you mentioned, being a dolphin. So they produce echolocation clicks, which is how they're using sound to see their world. They produce tonal sounds like whistles and also what we call burst pulse calls as well, which are rapid, rapid series of clicks that are so close together that we don't really discern them as separate clicks. And some of those calls can be transmitted over 10, 15 kilometers.

15:04So they're able to use a lot of sound sometimes in their foraging. Some types of killer whales will produce certain herding calls in Iceland, for example, to herd their fish prey. So pack ice killer whales are fascinating in that a lot of their seal prey is out on the ice. And it does seem that on occasions they are aware that those seals can't hear them and so make calls to one another to bring other pod mates in in order to start foraging. That's really fascinating because in most mammal eating killer whales will be silent when they're foraging because they don't want to alert their prey to their presence and with the reduction of sea ice the Antarctic Peninsula is easier for ships to travel through parts of the killer whale habitat that previously were either very inaccessible or were only accessible on the odd occasion.

15:58And that has implications to do with the acoustic environment of these killer whales. They need to be communicating acoustically. They also need to be listening for prey. And when there are a lot more ships, there's a lot more noise in the water. And so as well as nutritional stress that can happen by there being a lack of prey, they can also be stress caused by noise within their environment.

16:21Adam Hart:Now killer whales are one of only very few mammal species that go through the menopause and groups often seem to be led by a post-menopausal matriarch. Why are they so important for the group's survival? Could you unpack that a little bit for us? These females can have a post-reproductive lifespan that is longer than the entirety of their pre-reproductive and reproductive lifespan. So they can live 40 plus years after giving birth to their last calf. And these are females that play an integral role in the cohesion of the family. They forage for preferentially forage for the males in the family, which is kind of fascinating.

16:58But when you think about it from an evolutionary perspective, it's actually a way for her to ensure that her genes are being passed on. She can protect and feed, you know, go to places to make sure that her daughters and grand calves are well fed. but one of the ways that she can ensure that her genes are being passed on through the son is to make sure that her sons get big and old because it's the biggest and oldest males that are chosen as mates and it's definitely the females that are choosing who to mate with so the biggest oldest males are the ones that are chosen so mom and grandmother feeding those males make sure that they get big and old and then when he sires a calf the responsibility of raising that offspring is the responsibility of a different matriline.

17:44So in a way, it's this brilliant way of mom passing on her genes without having to have the extra burden of another mouth to feed. We also see these post-reproductive females intervening on behalf of their males. So our colleagues at the Center for Well Research documented that males whose mothers are alive and post-reproductive have less rake marks. So whales engage in play that can be rough. You know, it's not an agonistic sort of behavior, but just roughhousing. And these grandmothers will step in and put a stop to the roughhousing so that her sons are not going to become injured, which I think is very fascinating.

18:23Another just, you know, kind of heartwarming and also heartbreaking aspect to these whales is that, you know, males whose mothers have died are eight to 12 times more likely to die in the year following her death compared to males whose mothers haven't died. And the difference between the eight and the 12 % is that females who are post-reproductive, their sons are 12 times more likely to perish within the year following her death. Males definitely forage can feed themselves, but they're getting that extra nutrients. We don't believe that it's that that's causing their death, but more just that social bond.

18:58The males stay with their mother and are very, very tightly bonded. There was a paper that came out again from the Centre for Wild Research titled Mama's Boys. They definitely are incredibly socially bonded with their mothers.

19:11Adam Hart:We've touched on some of the threats to killer whale populations, such as declining food sources and climate change. Turning back to you, Lee, is there a threat that you're particularly concerned about for your pack ice killer whales? Avian flu is now something that's present in Antarctica and that despite its name can impact seals and cause mass die off of seals and so you know one of my great concerns and another study topic for us in the coming Antarctic field seasons is to understand the implications for seal eating species like pack ice killer whales and what the implications for mass die off of seals be it through climate change or avian flu is and how impacts them and what we need to do from a conservation perspective.

19:57Adam Hart:And to the southern resident killer whales, Giles, they were listed as endangered in the US in 2005. What threats do you see to the populations that you're studying? When they were listed, the three main identified threats were lack of prey, specifically Chinook salmon, vessel presence and associated noise, and then environmental toxicants, so man-made chemicals making their way up the food chain. And by far the biggest threat is the lack of prey because when they're not getting enough to eat, the other two threats are exacerbated. When they're not getting enough to eat, we see amplification of toxicants in their feces, meaning that they're metabolizing their fat stores.

20:35Those fat stores usually lock up the toxicants. The man-made chemicals are almost entirely lipophilic or fat-loving chemicals. and as long as the whales are getting enough to eat those chemicals stay locked up in their blubber the problem though is is that when they're not getting enough to eat they're metabolizing those fat stores and then we're seeing that increase in toxicants which leads to a compromised immune system disease and early death now giles when i think of killer whale research and i'm not

21:05Adam Hart:necessarily immediately thinking of dogs but you actually have a scent detection dog that you involve in your research, don't you? Yes, we sure do. Her name is Eba, E-B-A, Eba the whale dog. Yeah, she's a specially trained scent detection dog. She's the fifth whale dog I've gotten the honour to work with. By utilising a scent detection dog, it allows us to stay really far away from the whales. So for a population that is threatened by vessel presence and associated noise, we don't want to add to that issue. So we stay as far away from them as possible. And with the use of the superpowers of Eba, she can help us detect it from up to a nautical mile away.

21:45We're not usually that far. We're usually about 400 to 500 meters away behind them and to the side and downwind. When the whales leave a scat sample for us, then she has a change of behavior and we're able to hone in on that region really quickly.

22:01Adam Hart:So she's sniffing out whale feces as they appear and guiding your boat in. Yep, that's exactly right. And how valuable is that for your research? Oh my gosh. Lee can attest to how hard it is to get a fecal sample and how important they are. You know, a scat sample, I always liken it to a gold mine because the information that you can glean from just one scat sample, it's unlimited. So we can get things like the DNA of the individual. So if it's a group of whales that we've been behind, which we try and get behind a group, especially a group with females who may get pregnant or be pregnant, if you're following a group of whales and you don't have a drone in the air, you don't know who defecated.

22:44So we can tell the DNA of the host. So who left us the sample? We're now looking at prey DNA. So we can get relative abundance of different prey items that went into making up that fecal sample. We can look at all kinds of hormones, which is what the basis of our research started out as being is hormone work. So we can look at stress hormones, nutrition hormones, hormones, pregnancy hormones. We can see if a female is pregnant, but not only that, we can tell how pregnant. We can look at all kinds of toxicants. So man-made chemicals like PCBs, DDT, those are chemicals that were banned in the early seventies.