Flying the flag for polar bear research

Polar bear mother and cub
If the bears have to stay on land for longer and longer periods whilst waiting for the sea ice to freeze, there are more hungry bears on land. Obviously in some areas that can increase the risk of confrontation between humans and polar bears, and it does.
Dr Jon Aars
2013 marks the 40th anniversary of the signing of the International Agreement on the Conservation of Polar Bears in 1973. Although the efforts of the polar bear range states – Denmark, Norway, Canada, Russia and the United States – have gone a long way towards protecting this magnificent species, Ursus maritimus, the effects climate change is having on the sea ice upon which the bears livelihood depends presents a whole new challenge for polar bear conservation in the 21st Century.

Due to these efforts an estimated 20-25,000 polar bears continue to occupy much of the animal’s historic range, but they have been listed as ‘vulnerable’ on the International Union for Conservation of Nature (IUCN) red list of threatened species since 2006. The World Wide Fund for Nature (WWF) recently declared 2013 ‘Year of the Polar Bear’ and launched the Arctic Home campaign, which aims to raise awareness and funds for the protection of polar bears and heir habitat, alongside Coca-Cola.

Dr Jon Aars, a research scientist at the Norwegian Polar Institute in Tromso, is a member of the IUCN/SSC Polar Bear Specialist Group who has been involved in surveying and monitoring polar bear populations in Svalbard, the Arctic archipelago which constitutes the northernmost region of Norway, for almost a decade. Dr Aars, who has also acted as a scientific adviser on the recent BBC series The Polar Bear Family and Me, and for the episode of Frozen Planet entitled ‘On Thin Ice’, aired in 2011, spoke to ScienceOmega.com about ongoing research into polar bear biology and behaviour, and how expanding our understanding can help protect this species…

In what ways have you observed the relationship between polar bears and sea ice changing over the last decade?
In some parts of the Arctic there have been large shifts in sea ice availability there are parts of the sea where sea ice is not present as much as it used to be. The effect that has had on polar bears is different in different places. The most significant impact it has had on polar bears has been in the Western Hudson Bay in Canada and the Southern Beaufort Sea in Alaska. The main effects have been on reproduction and survival. In Hudson Bay it has also been shown that the population itself has decreased and researchers can, at least partly, link that to longer and longer parts of the season with less access to sea ice.

In other parts of the Arctic, changes have been less extensive and have probably not had much effect on the polar bears at all yet. What we have seen in Svalbard, where I work, is that there are some areas where polar bears females go specifically to den – to deliver cubs – and they have been having problems getting to those areas in recent years because of a lack of sea ice on the routes they use.  

Is the relationship between polar bears and humans also changing, or has it changed?
Different sorts of space use by polar bears are observed depending on the state of the sea ice. If there is good accessibility to sea ice and thus to hunting fields, polar bears will usually be found on the sea ice. In some areas where there is no sea ice for much of the season, the bears will be on land and we have seen that historically. If the bears have to stay on land for longer and longer periods whilst waiting for the sea ice to freeze, there are more hungry bears on land. Obviously in some areas that can increase the risk of confrontation between humans and polar bears, and it does. 

What are the challenges of tracking, surveying and monitoring polar bears in terms of technology, working conditions, etc.?
We use collars on the bears for satellite tracking and also use some other sorts of technology to find out about their biology. Of course you need to be able to catch the bears, so that’s one challenge. There are sometimes difficult conditions. There’s also the challenge of getting equipment that works. It’s difficult because the equipment gets exposed to saltwater, very cold temperatures and wide variations in temperature. It’s harder to work with polar bears when it’s up to telemetry data because they are rougher with the equipment. Despite having had problems with many different brands of equipment, we have also had some success.

Are the collars designed to fall off after a certain amount of time?
There are number of different ways to do it. Some collars fall off when the battery stops working. Some of them have a timer that releases the collar; you can set it for the date when the battery is estimated to run out and then it falls off at a certain date after that. You can also use attachments made out of a certain type of metal which corrodes when exposed to saltwater. With these, of course, there is no set date but it will usually fall off after a few years. 

What information can be collected using the capture-recapture method?
What we get back from capture-recapture is, particularly, the opportunity to put on collars. This means we can say a lot about the behaviour of the bears, for example, about how dependent they are on sea ice and how they behave when there is less or more of it. We can get information on reproduction because it is possible to see how many cubs each bear has, how many bears have cubs, when they start reproducing, and which bears mate with each other. We also get indications of survival, both by ageing the bears and by observing whether the same bears are captured each year. After a few years, that data can be entered into models to obtain estimates of the survival rates of bears of different ages and sexes and so on.

Does this have any adverse effects on the bears (that we know of)?
Based on many studies from the polar Arctic, we have not been able to show many effects on the bears from handling. There are several publications that have looked at the likelihood that capturing bears has significant effects on their survival, reproduction or behaviour. Of course in the few hours after you have caught and collared a bear it won’t behave normally, but no significant effect on what it does later has been found. They don’t seem to move away from the area where they were captured or use smaller home ranges, for example, and it has not been shown that bears with collars have fewer cubs or lower rates of survival.

There is always the risk when you handle any animal that some will be lost, but for the polar bears this risk is so insignificant that it almost non-existent. Typically, when polar bears are handled one in a thousand is lost, which is a very low rate for mammals. This is because the tranquilliser we use is handled very well by polar bears, so administering the drug will not kill them. If a bear does die it is more likely to be because it was already in poor physical condition.

If bears are drugged close to open water and swim away before they have fully recovered from the after-effects there is the risk that they will drown, but we are very careful these days. Accidents are very rare, especially compared to many other mammals which handle the drug less well. It’s a very lucky position for polar bears that they tolerate the drug so well. It means that the impact handling has on the bear is very, very low.

How much have modern methods and techniques revealed about the movements of polar bears?
We have learned a lot about polar bear movement from using collars. If you only use capture-recapture you usually catch the bears in a specific season, typically in spring but also in summer/autumn in some places. Using only that data you wouldn’t know anything about what they were doing for the rest of the year. Often we find, for example, that the bears are in the same position every spring, but from spring to spring they may venture hundreds of kilometres from that area. Many bears have migration routes.

What we’ve learned particularly from Svalbard is that different bears have different strategies. Some bears stay in the local area all year round, but other bears travel from the islands onto the pack ice and back. The two types face totally different challenges when things happen to the sea ice. Those on the pack ice might have to travel longer distances to get back to the islands if the sea ice retreats. They may at some point have problems getting to the denning areas. Those that stay on the islands, on the other hand, have to survive longer periods in the summer when they can’t hunt at all, but are at least safe in that area and will always be able to get to a place where they can den.

In the 40 years since the International Agreement on the Conservation of Polar Bears was adopted, how do you think has it helped?
When polar bears were first protected, climate wasn’t an issue. Nobody talked about sea ice melting, because that has happened rather rapidly more recently. The main concern back then was that numbers were getting low due to excessive hunting. In many cases Arctic scientists thought that hunting pressure was so high that it would be problematic for polar bears in their near future.

That was what led to the polar bear agreement, and the idea was very important in some parts of the Arctic. There were no quotas and a lot of animals were being killed. In Svalbard, for instance, somewhere in the region of several hundred bears per year were being shot, from a restricted population. Their numbers have recovered quite well as a result of the agreement in a number of areas. It could have been very different if they were not protected, and so from that perspective it has been a success.

Another important effect of the agreement is that a lot of research on polar bears was done because of it in many parts of the Arctic. That means that we know a lot more about polar bear biology today than we did 40 or 50 years ago, and we can use that information to say how able the species will be to cope with climate change in the future.

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