03/06/2020

New Insight Into Whales On The Go

16:22 minutes

a pod of whales seen from over head. you can see some of them are coated in a yellow film
Killer whales in Antarctica, as shown here, often display a yellow coloration due to diatom accumulation on their skin, evidence that they are not sloughing skin in frigid waters. Credit: SR3/NOAA Fisheries.

Like the seasonal migrations of birds, whales are roamers. Every year, they travel thousands of miles, from the warm waters of the equatorial regions for breeding to the colder polar waters for feeding.

But how do they find their way so consistently and precisely every year? The stakes for getting lost can be high. Hundreds of whales and dolphins strand themselves on beaches every year, and many of them die as a result. 

New research in Current Biology this month adds more weight to one idea of how whales stay on course: Similar to birds, whales may detect the Earth’s magnetic field lines. Duke University graduate student Jesse Granger explains why a strong connection between gray whale strandings and solar activity could boost the magnetoreception theory.

Meanwhile, other research in Marine Mammal Science explores why whales leave the food-rich waters of the Arctic and Antarctic at all. Marine ecologist Robert Pitman of Oregon State University’s Marine Mammal Center explains why this annual movement may not be about breeding—but rather, allowing their skin to molt and remain healthy. 

a close up of a whale swimming where you can clearly see a thin coating of yellow film over its skin
An Antarctic killer whale shows a heavy infestation of diatoms. Credit: Cotton Coulson/courtesy Robert Pitman
a woman holds up a blackish gray transparent membrane that is shedded whale skin
A woman holds molted sperm whale skin. Credit: Michael Nolan

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Segment Guests

Jesse Granger

Jesse Granger is a PhD candidate in Biology at Duke University in Durham, North Carolina.

Robert Pitman

Robert Pitman is a marine ecologist at the Marine Mammal Institute of Oregon State University in Newport, Oregon.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. You know, everything’s big when you’re a whale, from your meals to your heartbeat to your travel plans. Gray whales– the world’s farthest traveling mammal– listen to this day– they voyage more than 10,000 miles around in their journey from the cold feeding grounds of the Arctic waters to the warm waters off the coast of Mexico, where they breed.

But one question still perplexes scientists. And that’s, how do they do it? They don’t get lost along the way. One theory that’s hard to test in a whale– maybe they can sense the Earth’s magnetic fields, a skill we know exists in many other species.

Well, my next guest is the author of new research where she asks if whales do use magnetism to find their way. Then we might see them more likely to get lost during solar storms, right? Magnetic solar storms on the Earth’s magnetic field can get a little out of whack. She’ll explain it better than I can.

Jesse Granger is a bio physicist and PhD candidate in biology at Duke University in Durham, North Carolina. Welcome to Science Friday.

JESSE GRANGER: Hi. It’s a pleasure to be here.

IRA FLATOW: Nice to have you. You were interested in whether gray whales are more likely to get stranded during solar storms. Why is that?

JESSE GRANGER: Well, actually as crazy as it sounds, this is not entirely new research. There is a professor who had done similar studies with sperm whales in the North Sea. And he had shown that sperm whales were more likely to get stranded when there were a lot of sunspots on the sun. And we know that sunspots generally mean that the sun’s more active. There may be a solar storm.

And so we were interested in seeing whether or not that was true for other whales. And we looked into specifically gray whales and showed, yes, it does seem that these gray whales are stranding– live stranding– much more often when there are a lot of sunspots.

IRA FLATOW: What is the physical connection between the whales and the solar sunspot?

JESSE GRANGER: So that’s is a great question. We can’t really say for certain right now. We don’t really have the data to say, oh, this is exactly why this is happening. Our best guess right now is that these whales are magneto receptive, so they can sense magnetic fields.

They’re using the Earth’s magnetic fields to help them migrate, especially since they’re going over such long distances with such good precision. It would make a lot of sense if they were magneto receptive.

And these solar storms coming off of the sun really can do a lot of damage to electromagnetic systems. And they push around the Earth’s magnetic field. And they’re also letting out a lot of radiation along the electromagnetic spectrum. Any parts of that could potentially disrupt a magnetic sensor.

IRA FLATOW: Hm. What would you expect then that other creatures that use magnetic sense– like birds– might also be then thrown off during a solar storm?

JESSE GRANGER: Yes. And actually, we have some preliminary research that seems to indicate that is true. There has been work going on for decades now. Back when passenger pigeons were a thing, they showed that their race times were a lot slower when the sun was more active. There was research that showed that migratory birds’ arrival and departure times seems to match up somewhat with solar activity.

And there’ve been some studies which have tried to– in the lab– replicate a solar storm. Of course, that’s kind of hard to do. But they also seem to show that seems to be affecting the animal’s ability to use the magnetic field in some way.

IRA FLATOW: OK. So then– OK, if whales can sense the magnetic lines, what about a solar storm would be causing them to strand themselves?

JESSE GRANGER: Yeah. And that’s the question that we were really curious about. And we came up with– well, we came up with one hypothesis first. And that was well perhaps the solar storms are pushing around the Earth’s magnetic field.

So the whale thinks that it’s on 3rd Street, but it’s actually on 6th street. Because those magnetic lines have kind of gotten pushed around. And it ends up taking a turn it didn’t mean to because it wasn’t sure where it was. And all of a sudden, it get stucks somewhere where it can’t turn around very easily and gets stranded.

And we were able to actually look into that using a variable called the AP index, which measures how much the Earth’s magnetic field is wiggling around. And there wasn’t any relationship between standings and this a wiggliness of the Earth’s magnetic field due to solar storms.

And man, we were perplexed. That was our first idea. Once we had to scrub it, we ended up talking with an astrophysicist named Lucianne. And she brought up the fact that the sun produces radio frequency noise during these solar storms as well.

And we know from other magneto reception studies– so other studies where we look into whether or not animals can sense magnetic fields– that radio frequency noise kind of jams their sensor. They can’t– they can’t see those magnetic fields when there’s a lot of radio frequency noise. So it’s like, oh man well, maybe it’s the radio frequency noise coming from the sun that’s disrupting these whales.

And we looked into it. And again, we can’t say for certainty that that is the actual relationship that’s happening. But we see a huge correlation between these live gray whale strandings and the radio frequency noise that’s coming from the sun during solar storms.

IRA FLATOW: Could understanding this help us save more whales from stranding, you know?

JESSE GRANGER: It’s a great question. We can certainly predict about how active the sun is going to be better than we can predict when whales are going to strand. So if we have this correlation between strandings and solar activity, we may be able to, at the very least, say, wow, the sun’s a lot more active right now. We’re in the middle of a solar maxima. Maybe we should be a little bit more ready to try and be prepared to find those live whales and try and save them before they end up dying on the beach.

IRA FLATOW: Mark in Dayton, Ohio on the phone has a question for you. Hi, Mark.

MARK: Hi, how are you?

IRA FLATOW: Hi there. Go ahead.

MARK: Yes. So I’ve heard recently some news stories about shifting magnetic poles, that the North Pole is shifting maybe through Russia. And I wondered if– as part of your study– you looked to see if there were differences in the way on migration patterns that corresponded to the moving poles.

JESSE GRANGER: That’s a great question . And that’s some work that has been done by other researchers not with whales. But Ken Lohmann at UNC did some work doing something similar to that with sea turtles and showed that– because those magnetic field lines on the Earth move around quite a lot actually. And they can get closer together and farther apart.

He was able to show that sea turtles nest closer together when those field lines are closer together and farther apart when those field lines are farther apart. So that is definitely research that people are looking into.

IRA FLATOW: That’s cool. What do the whales have in their heads physically that can sense the magnetic fields?

JESSE GRANGER: Oh. What a great question. And I would love to be able to tell you for certain what it is. But we just don’t know quite yet. It’s been a question that has plagued magneto reception researchers forever. I can give you our best guess.

IRA FLATOW: Go for it.

JESSE GRANGER: Yeah. So there are two receptors that we think are probably what’s going on. And maybe an animal has one. Maybe has the other. Maybe some animals have both.

The first is the magnetite based receptor. So that’s going to be essentially somewhere in an animal’s body, maybe dispersed throughout the whole body, maybe localized in one area. They have these little tiny pieces of magnetite. So you could think of like maybe a little iron compass needle. And those are going to wiggle around with the Earth’s magnetic field and, as they wiggle, give the animal some information about which direction they’re facing.

The other’s called the radical-pair mechanism. And it’s a little bit more complicated. But to boil it down to its essential pieces, it’s just a chemical reaction. There’s a chemical reaction happening. And it’s going to happen at different rates depending on which direction you’re facing with the Earth’s magnetic field.

Some people think that chemical reaction is specific to animals’ eyes. And so they essentially can see the magnetic– sorry– the magnetic field. And what’s really interesting about that radical-pair mechanism is that a chemical reaction can’t happen at the frequency it needs to if you have radio frequency noise happening at the same time.

IRA FLATOW: Wow. Well, we wish you the best in deciphering this stuff. It looks like you have a very rewarding career ahead of you, Jesse.

JESSE GRANGER: Thank you so much. It was a pleasure to be here.

IRA FLATOW: Nice to have you. Will you report back to have the answers please?

JESSE GRANGER: Oh, will do.

[CHUCKLING]

IRA FLATOW: Jesse Granger, PhD student at Duke University. Now we’re going to move on to something else about whales. This is a question that we get about whale migration which, of course– if the Arctic is such a rich source of food, why would you ever want to leave it, right? A lot of food there.

Well, for more than 100 years, whale biologists have been torn about this. And one big theory is that baby whales need warmer water to survive and thrive. It makes sense. But my next guest has been researching a different idea. Maybe whales seek out warm water to molt.

That’s right. Maybe all of that travel is about getting rid of some dead skin and keeping the dermal layer healthy. Here to explain is Dr. Robert Pitman, a marine ecologist at Oregon State University’s Marine Mammal Institute in Newport. Welcome to Science Friday.

ROBERT PITMAN: Oh, glad to be here, Ira.

IRA FLATOW: Do whales molt?

ROBERT PITMAN: Whales are like human beings. They molt constantly if they’re in warm enough water. If you follow around a whale in tropical waters quite often, you’ll see a trail of skin bits behind them. So given the opportunity, they molt all the time.

IRA FLATOW: It’s like us. We have skin. And we stay in the water too long, and it just flakes off. That’s what’s happening? Because whales have the same kind of skin, right?

ROBERT PITMAN: Yeah. Our skin is the first line defense against bacteria and microbes. And the best way to deal with it is just to constantly slough it. Let them go, and we don’t have to worry about it.

IRA FLATOW: Mhm. OK. So let’s talk about this idea that they go to the poles, they go to Antarctica, they go to the Arctic, there’s a lot of krill, they eat stuff, and then they come back to the warmer waters. And you’re saying that it’s not just enough to have their babies. But it’s to get rid of the skin.

ROBERT PITMAN: Yeah, we’ve been working on killer whales in Antarctica for 15 or 20 years now. And we’ve put satellite tags on quite a few of them. And we’ve got some really surprising results with their migrations.

They take six to eight weeks. They go straight north into the edge of the tropics. They turn around and go straight back where they came from. We were very surprised by this because they wouldn’t do it for food if they came back to the same place they left. And they can’t be having calves because they’re traveling at full speed. So something else had to be driving that.

And we noticed that the killer whales in Antarctica quite often are very yellowish. And it’s because they have a diatom coating on them. This is an algae. And it can accumulate because they’re not sloughing their skin, as they would normally.

So we know that they’re going to have to do something about that. They can’t allow this build up. It’s like having fouling on the hull of a boat.

And we have pictures of the same killer whales that we photographed at one time covered with this yellow algae. And then the next time we see them, they may be completely clean. And those are whales that have gone to the tropics, sloughed their skin, the diatoms have dropped off, and then they come back down to eat again.

IRA FLATOW: Wow. I’m Ira Flatow. This is Science Friday from WNYC Studios talking about whale skin with Robert Pitman. You know, when my skin itches, I can scratch it right. I can get my arm around it. Could that be the reason why whales surface and jump around? Maybe they’re scratching or trying to get rid of their skin?

ROBERT PITMAN: It’s interesting. But you do see whales scratching on logs at sea. They rub up against each other quite a bit. I’ve been off of Western Australia. You’ll see a humpback whale breach. And you go over there, and there’s just skin all over the surface of the water.

And it might be like if you get a sunburn, and the skin starts to come off. And it gets itchy. Maybe they have to deal with the same thing.

IRA FLATOW: Do whales get sunburn?

ROBERT PITMAN: They haven’t been. We don’t really know. I mean, with the thinning of the ozone layer, there’s a possibility that whales have gotten sunburned. But we haven’t really looked into it all that much.

IRA FLATOW: Do you see any changes in whale migration due to the warming of the oceans at all?

ROBERT PITMAN: We haven’t yet. But there’s a lot of whales that we don’t know where they go to breed. A lot of the blue whale, fin whale, sei whale– they just kind of go out into the middle ocean, find some quiet place, and have their calves, and then go back to the Arctic or the Antarctic– wherever they came from.

So we don’t know anything about breeding grounds on a lot of these things. But a lot of the coastal breeding species– the humpback, right whale, and gray whale– they seem to be going to the same places they always have.

IRA FLATOW: So why do you care so much about the skin of a whale?

ROBERT PITMAN: Two reasons, I think. One is that this has been an interesting question around for a long time. For over a century, we’ve known that whales go to low latitudes to have their calves. But nobody’s been able to adequately explain why they do that.

And this idea of thermal regulation for the calf has been popular. But physiologists have mostly told us that large whales don’t need to go to the tropics to have their calves. Those calves are big enough that they’re not going to be thermally constrained in icy water. So it’s been a question that has needed answering for a long time.

And the other thing is this is the biggest migration on Earth. We’re talking about millions of tons of animal flesh traveling thousands of miles every year. And so ecologically, it’s kind of a big deal, and it’s good to understand why they do that.

IRA FLATOW: Have whales evolved to do this over the time?

ROBERT PITMAN: I think the whales have kind of an issue here. They have to go back to warm water to change their skin. It’s like a deep diving whale or a sperm whale or something has to go back to the surface to breathe.

So we think that they’re going back to ancestral habitat, that when, for instance, they go to Antarctica they are essentially holding their breath. They’re getting to feed in a place with a tremendous amount of food. But then they have to run back to the tropics and change out their skin.

IRA FLATOW: Well, with all those whales and all that sloughing off of skin, does it have effect ecologically on the oceans?

ROBERT PITMAN: You know, it’s probably part of this conveyor belt, whales taking themselves to the tropics. They poop when they’re in the tropics. They die sometimes. They’re prey for killer whales and sharks. And sometimes, they feed. So it’s very important ecologically for what’s going on here.

IRA FLATOW: That’s very interesting. Thank you, Dr. Pittman, for sharing that new knowledge with us. Dr. Robert Pittman, a marine ecologist at Oregon State University’s Marine Mammal Institute in Newport.

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