The Polar Bear Necessities

16:08 minutes

Buzz over the Chukchi Sea in a helicopter in early spring, and there’s little to see but sky and ice. That is, until your eye catches the maze of polar bear tracks threading across the ice in some areas. The sea, which stretches between northwestern Alaska and northeastern Russia, is home to one of the Arctic’s 19 distinct polar bear populations.

“When you’re out there and you see all these tracks — it feels like there’s a bear party going on, and you just haven’t been invited to it,” says video producer Luke Groskin. He recently made the trip with Karyn Rode, a wildlife biologist at the US Geological Survey, to film her work with the bears for Science Friday.

But as the Arctic continues to warm twice as fast as the rest of the world, the sea’s ice cover is growing fragile — breaking up earlier in the year and melting more thoroughly. Rode says that for polar bears, which spend the majority of the year hunting seals and other prey on the ice, shrinking habitats like the Chukchi Sea are already having an effect.

Watch the rest of the Breakthrough: Portraits Of Women In Science series.

“There is variability, but some of the general responses across populations are increased land use,” she explains. “So there are more bears coming on shore than have in the past, and staying there longer. And when they’re on shore, they typically are losing weight, because they are eating minimally or not eating at all.”

Each year, Rode and her team head out to study the bears, gathering information about their health in a changing climate. The first challenge? Spotting white bears on the snow-covered ice. Most of the time, the team relies on finding and following the freshest-looking tracks. “It’s very hard to just see a polar bear itself,” Rode says.

When the researchers spot a bear, they tranquilize it from the helicopter, then land and make sure the bear is comfortable. Then, they take samples of everything from the bear’s blood to its hair, even a small fat biopsy — all of which can give clues about the bear’s diet, among other factors.

“One of the primary mechanisms in which we think polar bears are affected by sea ice loss is that they have to have the sea ice to access their primary prey, which are ice-associated seals,” Rode explains. “Polar bears have a very specialized diet — typically, 70 percent of their diet is composed of one or two seal species. And so when there’s less ice, you have less of a platform to hunt for seals.”

Rode’s research shows that for the moment, bears in the Chukchi Sea are doing all right. The sea is shallow, she explains in the video, and a good habitat for top prey like walruses and bearded seals. “The Chukchi Sea bears, so far, comparing condition and cub survival since the 1980s to the current data we’re collecting, suggests that the bears there have stayed in pretty good condition,” she says.

In that way, they’re the lucky ones.

Polar bears in the nearby Beaufort Sea, north of Alaska, have also faced significant ice loss, and are showing signs of stress. “That population has experienced declines in body condition, cub survival, and recently, there’s been a pretty significant population decline,” Rode says.

As Rode points out in the video, sea ice isn’t the sole determinant of polar bears’ health. “They have to have prey,” she says. “But there’s no doubt that if you have substantial reduction in sea ice, that they have lost the area over which they can hunt.”

—Julia Franz (originally published on PRI.org)

Segment Guests

Karyn Rode

Karyn Rode is a wildlife biologist at the United States Geological Survey in Portland, Oregon.

Luke Groskin

Luke Groskin is Science Friday’s video producer. He’s on a mission to make you love spiders and other odd creatures.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. The polar regions of the Earth are warming at a faster rate than any other. In the Arctic, patches of sea ice are getting smaller, and the ice sheet is breaking away in chunks in some places. And while the ultimate consequences of the rapid melt to wildlife is still unknown, one of the animals that is already being affected is the polar bear– the iconic polar bear.

There are 19 distinct populations of polar bears living in the Arctic, and monitoring how these bears are holding up– you can imagine what a challenge that is. How do they survive on the barren ice? And how do you get up close to look at them and find out?

Well, that’s the subject of our latest video that’s part of our breakthrough Portraits of Women in Science series. And here to talk about it are our video producer, Luke Groskin. Hi, Luke.


IRA FLATOW: And Karyn Rode, a wildlife biologist with the US Geological Survey. She’s based out in Portland. Welcome to Science Friday.

KARYN RODE: Thanks for having me.

IRA FLATOW: You’re welcome. Karyn, you and Luke went out to the Chukchi Sea. Did I get that right? Which is a rem–

KARYN RODE: That’s correct.

IRA FLATOW: It’s a remote part of Alaska. Can you describe this area? What does it look like out there?

KARYN RODE: Well, so the Chukchi Sea is an area between northwest coast of Alaska and the eastern coast of Russia. And the time of year that Luke and I went out is March and April, and at that time of year, it’s mostly covered with sea ice.

And sea ice isn’t really a flat pancake. There’s currents and winds that create openings in the ice. So there are some areas of open water, and there’s also areas that the ice comes together that form pressure ridges, so kind of rumbly ice. So it’s actually a pretty dynamic landscape.

IRA FLATOW: Mm-hmm. And Luke, you had to do some pretty intense training before you made that trip, right?

LUKE GROSKIN: That’s true. In order to actually go out over the Chukchi Sea, you have to take a helicopter– or an airplane, but in this case we took a helicopter– and as part of the training to go out there, I had to take a dunker course– basically, an underwater egress course where they flip you upside down and simulate a helicopter crash. It was pretty intense. Not something I want to go through again, but definitely confidence-boosting when you’re in a helicopter flying over the ocean.

IRA FLATOW: But I’ll bet your first sight of the ice out there made it all worthwhile. What was that like?

LUKE GROSKIN: Absolutely. I mean, when you’re out there and you’re filming, and you’re just staring out at just endless ice as far as you can see, it’s beautiful in it’s darkness. It’s just sky and ice. And it just sticks with you in your head.

And of course, the entire time, you’re looking down for polar bears, and, technically, you shouldn’t be looking for polar bears. You should be looking for polar bear tracks, which are, in the location where we were, numerous. It was pretty incredible to be looking down and just seeing all these tracks that would suddenly meet up with other tracks.

So I was expecting, like, they would find one set of tracks and eventually you’d find a bear. But instead, it was you would see one set of tracks and they would zigzag back and forth, and meanwhile, you’re getting completely nauseated, because the helicopter swirling. And then they zig back the other way. And then you run into another set of tracks. And then, are those the first set of tracks? Or is that a new set of tra– oh wait, now there’s a third set of tracks.

And the entire time you’re trying to figure out which way you’re going, and you’re just hoping one of these tracks will lead on to a bear.

IRA FLATOW: Dr. Rode, as Luke said, the ice is white, the polar bears are white. How do you scout a polar bear from the air?

KARYN RODE: It’s very hard to just see a polar bear itself. I mean, as Luke described, we’re mostly tracking, and that’s how we find the majority of the bears. But tracking conditions vary, so you can go out there, and if the ice has been stable– meaning that there hasn’t been any wind recently and no new snowfall– then it’s like Luke described, which is there’s tracks everywhere, and you’re trying to determine, is that a week old? Is that a day old? Should we follow them? Will it lead us to a bear?

IRA FLATOW: Hm. Do you have to just use your judgment from past experience to know what to do in these cases?

KARYN RODE: Yeah. I mean, we often use the strategy of landing. You can actually look at the track closer and get a sense for how hard it is, because of that spin from the day before. It will harden, and the snow inside the track won’t be soft, and you’ll have, at least, a better idea of whether it’s been in the past 24 hours or not. So there’s some strategies you can use to try to figure out if it’s– how new it is.

LUKE GROSKIN: But it feels like– when you’re out there and you see all these tracks– it feels like there’s a bear party going on, and you just haven’t been invited to it. Like, you just see so many of them and you’re like, where are they? They’ve got to be here. We know they’re out there.

IRA FLATOW: Karyn, you’ve been going out for years. Does this ever get old? I mean, are you getting too jaded, now?

KARYN RODE: I don’t think so. I mean, because it’s always a challenge, and it seems like it’s somehow different every time. You know, just when you think you’re really good at finding bears and making it all happen, then you have an unusual set of circumstances. We often come across, really, something interesting and unique every year, as well.

IRA FLATOW: Luke, what was it like your first time?

LUKE GROSKIN: Seeing the bear?


LUKE GROSKIN: Well, the first bear that we– when they first spotted the bear, I couldn’t see it at all. It took me at least a minute to be like, OK. Oh, there’s the bear. And then, of course, it had a big number on its back, and I’m like, what? Why is there a big number on this bear’s back?

And I asked, and they were like, well, we caught that bear two weeks ago. And I was like, oh, no. We’re not going to be able to capture this bear, and we’re not going to be able to film that. And I mean, that’s a really critical component of the research, is that they don’t want to catch a bear again. And they don’t want to harass a bear again, and they don’t want to be near the bear that they’ve already caught.

But it was a big male, and I remember looking down and it, being like, oh, no. But so, it was a mixture of, like, that’s exciting, and also, oh, drat.

IRA FLATOW: The feeling of the bear must be mutual. Our number is 844-724-8255, 844-SCI-TALK, if you’d like to talk about tracking the bear. And also, I noticed in the video– and it’s a great video, it’s up there on our website– is you hover over the bear, Karyn, and then you go for a shot to send a dart into it?

KARYN RODE: Yeah so– yeah. You’re hovering over the bear. The bear is moving, and so you’re moving forward with the bear, and trying to get directly above it so that you shoot the tranquilizer straight down into the muscle.

IRA FLATOW: How close, Luke? You must have been a little weirded out by how close you are to a bear?

LUKE GROSKIN: I mean, if you were riding the bear, you could probably grab onto the helicopter. We were really low.

IRA FLATOW: It was that close?

LUKE GROSKIN: Yeah, it was. They’re right above the bear. They have to do that, in order to get the dart right on it and put it in the right position. It’s pretty dramatic.

IRA FLATOW: And then, once the bear– then you must land, right, Dr. Rodes? You land, and then what do you do?

KARYN RODE: Yeah. So usually, it takes about five minutes for the bear to go to sleep. And then you land, and the very first thing we do is check the bear and make sure it’s in a good position and comfortable. And then we start collecting data, so taking measurements and samples.

IRA FLATOW: Like what? What kind of samples?

KARYN RODE: Blood. Blood can tell you a lot about an animal, about its health. So from blood, we can identify what type of diet it has, whether it’s eaten recently, what pathogens it’s exposed to and what contaminants it’s exposed to.

We collect hair, which gives a lot of the same information, but over a longer or different time period. And we collect a small fat biopsy, which also can tell us information about what the bear’s eaten, a bit more specifically than we can get with tissues like blood and hair.

IRA FLATOW: Mm-hmm. i guess the hair can tell you a lot of stuff about the bear.

KARYN RODE: Yeah. Like I said, it gives a longer time frame, and a different time frame, because what’s in that hair is primarily when it’s grown, and it’s grown at a different time of year than when we capture. And so if we want to know what an animal has been exposed to, other than during the really recent time frame before when we caught it, hair is a good tissue to use.

IRA FLATOW: Now, I learned from watching the video that polar bears switch between living on the sea ice and on the land. What are some of the stresses that come with this dual lifestyle?

KARYN RODE: Well, I should clarify a little bit about that. So you mentioned in the introduction that there’s 19 populations, and there are populations that have always made that switch. But those are actually a minority. So those are mostly populations in eastern Canada, where the environment becomes completely ice-free in the summertime, and those bears have always come on land.

But all the rest of the polar bear population, so the majority of them, have typically not used land, except for denning. And denning, in polar bears, only occurs by pregnant females, so not all sex and age classes like you see in other bears. So it’s really in more recent years that bears have started to summer more on land in a lot of these other populations, than they have in the past.

IRA FLATOW: Mm-hmm. And what are some of the stresses? What is global warming and the melting sea ice doing to the bear population?

KARYN RODE: Well, again, you’ve got a lot of diversity across the polar bears’ range. So it can be challenging at times to generalize what the response is, because some populations have seen dramatic sea ice loss, such as the polar bear population in the Chukchi and the Beaufort seas, but other places have seen very little sea ice loss.

And then you have differences in the ecology of these systems. So there is variability, but some of the general responses across populations are the increased land use. So there are more bears coming onshore than have in the past, and staying there longer. And when they’re on shore, they typically are losing weight, because they are eating minimally or not eating at all.

So for example, in the Chukchi Sea, we know from activity sensors and also observations, that 90% of the time, a bear on shore is just resting. So they’re not trying to feed on the foods that are on land. There tend to be relatively poor resources on land in Arctic terrestrial environments.

IRA FLATOW: Mm-hmm. You’re comparing this Chukchi population of polar bears to a neighboring group in the Beaufort Sea. What differences are you seeing between them?

KARYN RODE: Yeah, it’s interesting. So the Beaufort Sea ranges between the north coast of Alaska and western Canada. And that population has experienced declines in body condition, cub survival, and, recently, there’s been a pretty significant population decline in abundance.

But the Chukchi Sea bears, so far, comparing condition and cub survival since the 1980s to the current data we’re collecting, suggests that the bears there have stayed in pretty good condition. They’re still recruiting cubs into the population. So pretty different responses to significant sea ice loss that’s occurred in both of those areas.

IRA FLATOW: Mm-hmm. 844-724-8255 is our number. So why don’t these Beaufort bears sort of just migrate over to the more productive Chukchi area?

KARYN RODE: Well, that’s the question that we’re going to look at a bit. And anecdotally, there’s definitely bears that are in western Canada that have been shown to go over to Wrangel Island, which is in the Chukchi Sea. But we haven’t– there hasn’t been a study done, yet, to look at migratory patterns. But certainly some bears may be coming into the Chukchi Sea more than they have in the past.

IRA FLATOW: Mm-hmm. Let me just remind everybody that this is Science Friday from PRI, Public Radio International. We’re talking about polar bears and the new polar bear video up there. It’s our breakthrough video, Portraits of Women in Science series, and it’s done by our video producer, Luke Groskin. Also with us is Karyn Rode, wildlife biologist for the US Geological Survey.

We have a bunch of tweets and phone calls asking all the same thing. It doesn’t happen a lot, but people are– they’re very creative on here. And they ask, can thermal imaging cameras be used to find the polar bears?

KARYN RODE: There are some efforts to do that, now, and including in the Chukchi Sea. There’s been some recent work to look at thermal imagery and try to validate how well it can identify polar bears on the sea ice. So there is some work along those lines to try to use that technique.

One of the challenges with that, though, to keep in mind, is in places like the Chukchi Sea, the bears are really spread out over a really large area. So even with that technology, you might be able to identify bears, but you’re going to have to fly a big area to try to find one. So it may help a little bit in identifying them, but I think tracking, actually, still works pretty well.

IRA FLATOW: Mm-hmm. With the sea ice in particular– and you’re saying that the loss of the polar bears is not consistent over all areas, and I understand you’ve said that, but where it is a problem– what is the problem with the polar bears’ survival in areas– and I’ve gotten a few calls and tweets about that– in areas where they cannot survive? What is the problem there?

KARYN RODE: You mean how– what is–


KARYN RODE: –causing the decline in survival?

IRA FLATOW: Exactly.

KARYN RODE: Yeah. So one of the primary mechanisms in which we think polar bears are affected by sea ice loss is that they have to have the sea ice to access their primary prey, which are ice-associated seals. So polar bears have a very specialized diet. Typically 70% of their diet is composed of one or two seal species. And so when there’s less ice, you have less of a platform to hunt for seals.

And in the populations that have declined, we’ve seen declines in the condition of animals, and we know, in particular, that the condition of females is directly related to the size of the cub she produces, and that the size of a cub is directly related to their survival. So, often, the pattern goes that as female condition declines, you start to see a decline in recruitment of new individuals into the population, and that seems to be the pattern in these areas, where sea ice loss has resulted in population decline.

IRA FLATOW: Mm-hmm. So, Luke, tell us a little bit more about the video, what we will see when we go to your website.

LUKE GROSKIN: Sure. So our video will take you out on the helicopter. You’ll get to see us catch one of the bears and all the testing that will go on. You’ll also get to see that Karyn actually works a little bit with zoo bears and looking at their nutritional requirements and things like that, and how their metabolic rates can inform these wild studies, which I thought was actually kind of fascinating.

Another thing that I actually– we touched on it just briefly– was that it’s not just the bears that are struggling during the sea ice. It’s the bear researchers. While we were out there, the sea ice was starting to break up. And I think, if my memory is correct, the field season, actually, for this team, that was actually cut short, because the sea ice had broken up so much that they actually couldn’t find the bears.

And I experienced that a lot on that first day out that we were flying around. You could see the sea ice was way more patchy than the second day. We got very lucky, because it was a lot more solid.

IRA FLATOW: And there’s only one season, one shot at it.

LUKE GROSKIN: That’s right.

IRA FLATOW: Yeah. Well it’s our video. It’s up there at sciencefriday.com/polarbear. It’s our breakthrough Portrait of Women in Science, and the woman in science we’re talking about is Karyn Rode. She’s a wildlife biologist with the US Geological Survey, and the video was made by our video producer, Luke Groskin. Thank you both for taking time to be with us today.

LUKE GROSKIN: Thank you. And have a happy holiday weekend.

KARYN RODE: Yeah, same.

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