Can you tell me all about satellite collars and why scientists use them?

Answered by Dr. Andrew Derocher, a polar bear scientist with the University of Alberta in Edmonton, Canada, and a member of our Advisory Council. "We can get a good overview of the population's ecology by following just a few animals intensively."

What are collars made of?
Plastic belting material that sheds water and ice. It is the same material used in conveyor belts during the processing of frozen foods—it stays flexible in cold temperatures but is strong enough that the bears can't easily tear them off.

What tracking system do you use?
Early collars were followed by aircraft via the VHF radio pulses they emitted. Later collars communicated with satellites. The most recent collars include a GPS–satellite-linked system. The GPS (geographic positioning system) is the same system your smart phone uses to tell you where you are when you are hiking or driving

At specified intervals we get a position on each collared bear that is accurate to within 10 meters or so (30 feet). The position information is collected by the collar and transmitted to overhead satellites in batches—usually once a day.

How long does the battery in a collar last?
This depends on how much work we are asking the collar to do. Early VHF collars and even some of the first satellite collars could last for two years or more depending on how often they transmitted. More recent GPS collars do a lot more work and usually have a theoretical life of about 14 months. This means a collar could last long enough that a collar deployed in one spring capture season could still be operating in the capture season of the following year (most polar bear work is done in the late winter and spring when the ice is solid and the days are long). But collars often fail and sometimes the bears remove them. So, if we get 12 months, we're pretty happy.

How do the collars come off?
We always put collars on bears loosely enough that if a bear really wants to remove it, it can do so by pushing the collar over its head. But, the hope is that we will remove the collar when we recapture the bear.

Most collars are now fitted with an automatic release mechanism that will open the collar and let it drop off. The release mechanism has a clock, and we can set the day that we want it to drop off.  We usually set the timer so that the collar will fall off shortly after the batteries are drained and the collar is no longer transmitting. That way, if we have not recaptured the bear and removed the collar, the bear is not forced to wear a collar that is no longer working. In addition to the timed release mechanism, the collars are attached with steel nuts and brass bolts. In a salt water environment, this system eventually corrodes and the collar will fall off even if the release mechanism fails. Failing that, the collar belting eventually will wear out and then drop off, but this takes longer and we try to not have collars on bears aftter they have stopped providing data.

Once they fall off, a VHF beacon allows us to find the collar, refit it with new batteries, and send it out again.

How many bears are collared each year?
This varies according to how well financed a project is and how successful we are in catching adult females in any given year. During my colleague Steve Amstrup's 30 years in the Beaufort Sea, the most collars deployed in a single year was around 20, and the fewest was probably less than 10. In 2009 we hoped to collar 14 adult females in Western Hudson Bay, another 25 in the Beaufort Sea, and 16 in Foxe Basin.

What data do you collect?
We collect location information, activity rates, and temperature data. Some collars record how much time a bear is spending in the water. Telemetry is one of the few means through which we can follow polar bears for long periods of time and determine their movements, habitat use, fidelity to areas, and the survival of offspring.

Have any bears died as a result of collars?
We have no evidence that life-threatening injuries have occurred because of collaring. On some bears we have observed hair loss and small abrasions or cuts behind the ears.  This has been most problematic in situations where bears become unnaturally obese from feeding on unnatural food sources, like the remains of subsistence-harvested whales.  We are constantly vigilant for such problems and working to develop methods to avoid even minor injuries. 

We have never seen any evidence that collars interfere with natural movements or activities. Nor do data show any effects on reproduction or the survival of cubs. The collars only weigh two kilograms or so and the bears weigh over 200 kilograms, so at one percent of their weight or less, we are well below where the collars would have a significant mass.

What information is learned as a result of the collars?
Before we can estimate the size and trend of a population, we need to define the population. Only movement data, like those obtained from telemetry, can provide that definition for us. We can also determine hunting patterns, total distance moved, home range areas, habitat selection, how long bears may remain on land when the sea ice is absent, and when females enter and leave the dens where they have their cubs. We can also monitor the survival of offspring with a mother by locating her at intervals, with the aid of the VHF beacon on the collar.

What is the greatest benefit of the collars?
We deploy collars randomly, and therefore can assume collared animals are representative of the population as a whole. Therefore, they provide a window into the movements and activities of of the whole population. Following just a few animals intensively tells us a lot about all of the animals out there. These bears can provide much more information than just catching them once every few years during our annual capture seasons. Importantly, as the sea ice declines due to global warming, collared bears show us how their movements and activities may be forced to change with the changing conditions. This may give us important advance information on the population crashes that are going to come if we do not reduce our greenhouse gas emissions

What do you want people to know about the collars?
The collars provide us with a rare glimpse into the life of the bears that is much less invasive than trying to follow them out on the sea ice. There is no other practical means of learning about polar bears in winter when there is 24 hours of darkness.

We are able to gain insights important to understanding what is happening to the bears relative to climate warming, and to warn managers when climate change effects are going to result in a serious population decline. By following a small number of bears, these animals can help us monitor how the whole population is faring. This data is critical to understanding the future for polar bears throughout the Arctic. By comparing many different areas, we are able to contrast changing ice conditions across the Arctic.

Without collaring and other population level research, we would not know what climate change is doing to the bears. Without this information, we could easily see the bears slip away and only realize the extent of the problem after they are gone.

Despite the advances in telemetry and other research tools, it is important to remember that research will not protect polar bears unless the information we collect is used to guide managers and policy makers into leading the social changes we all need to make. Without dramatic reductions in our greenhouse gas emissions, telemetry and the detailed population understandings it provides only will allow us to become better polar bear historians. 

 

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