Satellite Collars
Scientists who study polar bears gather valuable data from satellite collars. But how do they work? And what information do they gather? This Q & A column features an exchange on this topic between two PBI Advisory Council members, JoAnne Simerson and Dr. Andrew Derocher. Simerson, who posed the questions, is an animal behaviorist with the San Diego Zoo. She organizes and leads PBI's popular In-Field Lecture Series in Churchill each fall. Derocher, who provided the answers, is a polar bear scientist with the University of Alberta in Edmonton, Canada. He is also the chair of the IUCN's Polar Bear Specialist Group.
What are the satellite collars made of?
The collars are made of a plastic belting material that sheds water and ice. It is the same material used in conveyor belts in freezers – 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?
We use a GPS–satellite-linked system. The GPS (geographic positioning system) is the same as what people use in cars or while hiking. Every four hours we get a position on each collared bear that is accurate to within 10 meters or so (30 feet). The position information is transmitted to overhead satellites once per day. The collars last for about 14 months and most collars are fit with an automatic release mechanism that will open the collar and let it drop off. Then, with the help of a VHF beacon, we can find the collar, refit new batteries, and send it out again.
How long does the battery in a collar last?
Most collars will work for 14 months, but we do see premature failure sometimes. If we get 12 months, then we're pretty happy.
How do the collars come off?
The collars are sometimes removed by us, if we recapture the bear, or they drop off with the automatic release mechanism. The release mechanism has a clock, and we can set the day that we want it to drop off. The release mechanisms are reliable, but we also have aluminum nuts that will corrode and allow the collar to drop. Failing these methods, the collar belting will wear out and then drop off, but this takes longer and we try to not have collars on bears that are not providing data.
How many bears are collared each year? How many were collared this year?
This varies. We are hoping to collar 14 adult females this year in Western Hudson Bay, another 25 in the Beaufort Sea, and 16 in Foxe Basin. 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.
What data do you collect?
We only collect location information: six locations per day, 365 days per year.
Have any bears died as a result of collars?
We have no evidence to suggest that the bears cause them any problem. The collars weigh only 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. We don’t see any evidence in the data that females with collars have fewer or smaller cubs. Sometimes if the bear gets very fat there can be some hair loss, but this is unusual and I have not seen this for many years. This was more common with earlier collars that had metal brackets to reduce wear on the collar belting.
What information is learned as a result of the collars?
The location information is the key component, but we can also determine hunting patterns for the bears, total distance moved (moving more is costly for a bear), home range areas, and habitat selection. When we couple this information with other data from the population, we can put together a solid overview of the population's status. For example, the date at which the bears leave shore and when they return to land can be determined very accurately. We know that the duration of hunting time on ice is a sensitive component of the life history of a bear. We can also monitor the survival of offspring with a mother by locating her at intervals.
What is the greatest benefit of the collars?
We can get a good overview of the population’s ecology by following just a few animals intensively. These bears can provide much more information than just catching them once every few years. We can follow the populations over time and try to determine if we are reaching any critical thresholds in the population. We need early warning mechanisms and the collars are one possible means.
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 bears in winter when there is 24 hours of darkness. We are able to gain insights important in understanding what is happening to the bears relative to climate warming. We cannot wait for the symptoms to turn into 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 research, we would not know what climate change is doing to the bears. Without this information, we could easily see the bears slip away without time to intervene or to bring about changes in policies that will reduce negative impacts. It doesn’t matter if we are talking about the number of bears harvested, the effects of
pollution, the effects of disease, or most insidious, the effects of climate warming—the data is needed.
What are the satellite collars made of?
The collars are made of a plastic belting material that sheds water and ice. It is the same material used in conveyor belts in freezers – 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?
We use a GPS–satellite-linked system. The GPS (geographic positioning system) is the same as what people use in cars or while hiking. Every four hours we get a position on each collared bear that is accurate to within 10 meters or so (30 feet). The position information is transmitted to overhead satellites once per day. The collars last for about 14 months and most collars are fit with an automatic release mechanism that will open the collar and let it drop off. Then, with the help of a VHF beacon, we can find the collar, refit new batteries, and send it out again.
How long does the battery in a collar last?
Most collars will work for 14 months, but we do see premature failure sometimes. If we get 12 months, then we're pretty happy.
How do the collars come off?
The collars are sometimes removed by us, if we recapture the bear, or they drop off with the automatic release mechanism. The release mechanism has a clock, and we can set the day that we want it to drop off. The release mechanisms are reliable, but we also have aluminum nuts that will corrode and allow the collar to drop. Failing these methods, the collar belting will wear out and then drop off, but this takes longer and we try to not have collars on bears that are not providing data.
How many bears are collared each year? How many were collared this year?
This varies. We are hoping to collar 14 adult females this year in Western Hudson Bay, another 25 in the Beaufort Sea, and 16 in Foxe Basin. 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.
What data do you collect?
We only collect location information: six locations per day, 365 days per year.
Have any bears died as a result of collars?
We have no evidence to suggest that the bears cause them any problem. The collars weigh only 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. We don’t see any evidence in the data that females with collars have fewer or smaller cubs. Sometimes if the bear gets very fat there can be some hair loss, but this is unusual and I have not seen this for many years. This was more common with earlier collars that had metal brackets to reduce wear on the collar belting.
What information is learned as a result of the collars?
The location information is the key component, but we can also determine hunting patterns for the bears, total distance moved (moving more is costly for a bear), home range areas, and habitat selection. When we couple this information with other data from the population, we can put together a solid overview of the population's status. For example, the date at which the bears leave shore and when they return to land can be determined very accurately. We know that the duration of hunting time on ice is a sensitive component of the life history of a bear. We can also monitor the survival of offspring with a mother by locating her at intervals.
What is the greatest benefit of the collars?
We can get a good overview of the population’s ecology by following just a few animals intensively. These bears can provide much more information than just catching them once every few years. We can follow the populations over time and try to determine if we are reaching any critical thresholds in the population. We need early warning mechanisms and the collars are one possible means.
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 bears in winter when there is 24 hours of darkness. We are able to gain insights important in understanding what is happening to the bears relative to climate warming. We cannot wait for the symptoms to turn into 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 research, we would not know what climate change is doing to the bears. Without this information, we could easily see the bears slip away without time to intervene or to bring about changes in policies that will reduce negative impacts. It doesn’t matter if we are talking about the number of bears harvested, the effects of
pollution, the effects of disease, or most insidious, the effects of climate warming—the data is needed.
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