Icon of the Arctic, the polar bear thrives in the remote Arctic landscape of ice and snow. World-renowned polar bear scientist Ian Stirling offers his thoughts on the state of polar bears in the wild, the threats they face today, and insights from his recent book, Polar Bears: A Natural History of a Threatened Species (Fitzhenry & Whiteside, 2011).
National Geographic: You began studying polar bears in 1970. What drew you to them?
Ian Stirling: At the time I wanted to do a PhD, there were few opportunities in the Canadian Arctic so, when I got a chance to go to New Zealand and do my PhD on Weddell seals in 1965, and later study fur seals and sea lions in Australia, I jumped at it.
That turned out to be exceptionally good fortune because when the Canadian Wildlife Service was looking for someone to study polar bears and their relationships to seals and sea ice conditions, I was already way ahead in knowledge of ice-breeding seals.
Because of the presence of polar bears and other terrestrial predators in the Arctic, seals are much more nervous about the presence of a person on the ice and thus are difficult to approach and observe. So the seal experience was invaluable to helping to learn about polar bears and seals.
Where was most of your research done?
Western Hudson Bay [in Canada] was one of the areas where I did long-term (35+ years) work on polar bears. I also worked in the Beaufort Sea from 1970 to 2006. Besides that, I worked in the Canadian High Arctic for about 25 years and Southeastern Baffin Island/Northern Labrador for a total of about 10 years.
My studies in western Hudson Bay were the first to clearly (statistically) demonstrate the negative effect of climate warming on polar bears. I did not originally set out to study climate warming; in fact it was not on the radar of biologists at the time.
I was interested in studying long-term natural environmental variation in the Arctic marine system, for which I needed long-term information on numbers, reproductive rates, survival, body condition, and so on of the bears.
This is exactly what you also need for studying the effects of climate warming, so when that appeared to be a possibility, we already had a long-term database, which we then just continued. By the early 1990s, I began to think climate warming was affecting the bears and, with a colleague, published the first paper to that effect in 1993.
Your most recent book, Polar Bears: A Natural History of a Threatened Species, highlights how polar bears survive and thrive in the sea ice environment. What does it mean to be a wild polar bear in the Arctic today?
Life for polar bears in the Arctic today varies greatly with the area. In some areas, like western Hudson Bay and the southern Beaufort Sea, climate warming is having a negative effect on the duration of sea ice for hunting seals in the critical spring period because breakup is getting earlier.
The late spring and early summer are of critical importance to the bears because the ringed seals are born about early April, [and] are weaned at the age of six weeks, at which time they are up to 50 percent fat and not very experienced with predators.
This means seal is a huge food resource, and feeding on ringed seals in many populations probably accounts for up to about 70 percent or so of the energy the bears will require for the whole year.
When breakup gets earlier, it shortens the feeding period at the most important time of the year. In Western Hudson Bay, breakup is now an average of three full weeks earlier than it was only 30 years ago—that is an incredible change, and bears are lighter and reproduction is reduced because of that.
In other areas further north, and in the Canadian Arctic Islands, the effects of climate warming appear to be less, though there is not good long-term data for most areas. For northern Russia, the loss of ice is huge but we have little information on populations.
However, eventually, if the climate continues to warm, all areas will be affected.
You write about the efficiency of polar bears. How do they save energy?
Energy efficiency is important for all animals in the Arctic ecosystem. Most animals in the Arctic take on food when they can and live on it to some degree during periods of food shortage, but most, such as caribou, continue to actively feed through the winter while relying on fat for the shortfall. Most birds simply cannot survive the winter, so they migrate south for the winter.
Polar bears only make a kill every four to six days at the best time of the year (late spring and early summer) and less frequently at other times. In areas where the ice disappears completely for several months (like Hudson Bay) they don’t feed for four to five months and pregnant females for up to eight months.
When there are going to be long intervals of time when there will be nothing at all to eat, then the ability to eat a huge amount, digest it efficiently, and then live off it as needed is critical. This feast or famine life is more extreme for a polar bear than other Arctic animals.
In your book you ask: “Why a marine bear at all”? Why do you think polar bears evolved in this way?
No one really knows this exactly, since obviously there were no humans around to document it. However, it appears that when we got large frozen expanses of ice with seals on them, the land bears were able to go out and scavenge on dead ones or stalk live ones.
We see the same sort of thing today with the brown (grizzly) bears along the northern coast of western Canada and Alaska that are seen out on the ice in early spring scavenging on seals killed by bears and apparently going hunting on their own as well. There is a great deal of variation in coat color of grizzlies, so I expect the lighter-colored ones probably were more successful so that natural selection favored them and, over the longer term, they simply became white.
The same sort of selection for white color appears to have taken place with Arctic wolves.
In your book you write:
“There is something special about the polar bear that takes me beyond science and objective description. That special sense is also at the heart of my concern about the effects of climate warming on the Arctic, and the world in general, as symbolized by the polar bear…After 40 years of studying polar bears, I am still overwhelmed by a feeling of privilege when I watch an undisturbed wild bear.”
“At special moments when I have time to watch an undisturbed polar bear, I am often struck by an overwhelming sense that it is simply where it belongs. A wild polar bear is the Arctic incarnate. The Arctic is not a forsaken wasteland to a polar bear; it is home, and a comfortable home at that.”
National Geographic: What will be lost if the polar bear becomes extinct in the wild?
The above statement is obviously quite personal and might not be shared by everyone in the same way. However, to me, the evolution of large predators into specialized habitats anywhere in the world (like the polar bear, tiger, snow leopard, leopard seal, orca) is both a scientific marvel and a thing of exquisite beauty.
The loss of any such animals from our natural environment makes us poorer in a broad philosophical sense but also in an ecological sense, because it is likely to change the overall balance that has evolved between all the species in the system.
I also think that if we don’t care about the loss of some important animals initially, then we will care less about those that follow, and that lack of caring and insensitivity is likely to increase with time to the detriment of the entire planet.
How is the polar bear a symbol of global changes?
The big picture importance is for the ecosystem as a whole, but the polar bear is the symbol of the system. Without the bear, it is no longer complete and the world as a whole no longer has a complete Arctic system as a part of a complete world ecosystem.
What type of sea ice do polar bears frequent?
The best sea ice is the annual ice over the relatively shallow continental shelf where biological productivity is greatest—thus there are things for the invertebrates, fish, and seals to eat.
Productivity is much less over the deeper areas of the Arctic Ocean so there are far fewer seals there.
Ringed seals winter under the ice and keep breathing holes open by scratching the ice with the claws of their foreflippers. They need to surface to breathe, so they use their breathing holes as well as natural cracks, where they are accessible to the bears.
As sea ice declines, how are polar bears adapting?
Basically, they are not able to adapt to the loss of ice. They need access each year for enough time to capture enough seals to give them the fat they need to survive.
Although they can make good use of scavenging on a dead whale, seal, or walrus, such windfalls are not predictable [enough] to make a living on.
Some bears on land may eat things like grass, berries, or goose eggs, but while such things may help a few bears for a short period of time, it is not enough to survive upon for the year.
Have you ever been harmed during the course of studying the bears?
How do Inuit rely on polar bears?
Inuit likely learned [how to hunt seals] from watching how bears do it…standing still for long periods by a breathing hole with a spear, or using dogs to sniff out seal birth lairs.
How are the Inuit responding to changes in the Arctic?
Winter travel over the ice [has become] less safe because the timing of [the] breakup, locations of weak spots, and so on.
In some areas along the northern Alaskan coast, the greater expanses of open water mean that big storms are washing away some of the land villages are built on, requiring them to be moved at great expense.
You highlight new innovations for studying polar bear behavior in your book. How have remote high-definition cameras contributed to polar bear research?
So far, all these sorts of ideas are at the developmental stage. For the most part, such new technology has not been used quantitatively for scientific applications. The potential is definitely there, though so is a lot of cost.
How do polar bears react to the cameras?
Polar bears are investigative and will break things that they can get hold of, as happened with the ice-cam in the book [Polar Bears: A Natural History of a Threatened Species].
What do you hope readers learn from your book?
I would like people to develop an understanding of how polar bears have adapted to become so successful and comfortably at home in what, to humans at least, seems an incredibly harsh and challenging environment.
In gaining that understanding, they will develop a realization of why sea ice is so critical to the survival of polar bears, and that leads to an understanding of why the loss of sea ice because of climate warming will, in time, have such a negative effect on [the] polar bear as a species.
What steps can people take to help polar bears?
Encourage our politicians to show global leadership in slowing and eventually stopping climate warming and, as individuals, doing what we can to reduce our individual and community carbon footprints.