It's cold. It's difficult. It's dangerous. And you won't find the job on craigslist—but what a thrill to work with wild polar bears. PBI Chief Scientist Steven C. Amstrup says the first bear of the season still takes his breath away, even after decades in the field.
Every spring, scientists take a census of the polar bears in the Southern Beaufort Sea using a capture-recapture technique. The study helps scientists determine what's happening with this population—and to share this information with the world.
The Southern Beaufort Sea population is one of the best-studied in the world. Such long-term studies are important because they:
- Document change
- Play a key role in government decisions
Data from this population, for example, helped lead to the U.S. decision to list the polar bear as a threatened species.
How Fat is That Bear? The scientists collect data on:
- Size and health of the population
- Number of bears in each age and sex class
- Movement patterns of the bears and how they're responding to declining sea ice
Alarm Bells. In 2006, scientists reported clear signs of stress in the Southern Beaufort Sea polar bears compared with 20 years ago, including:
- A drop in the survival rate of cubs
- Lower body weight and smaller skull sizes in adult male polar bears
The Western Hudson Bay population showed the same signs of stress before its numbers crashed, dropping from about 1200 bears in 1987 to about 950 bears in 2004.
Dramatic sea ice changes are taking place in the Chukchi Sea. But because these polar bears freely roam from the U.S. to Russia and back, scientists weren't able to obtain a complete picture of how the population was faring—until recently.
A new U.S.-Russia management treaty now allows scientists on both sides to cross borders. Research on the U.S. side resumed in 2008 after 15 years with no data.
The Chukchi Sea effort is led by the U.S. Fish & Wildlife Service (FWS) in collaboration with the U.S. Geological Survey (USGS). Right now we know little about the status and health of the Chukchi Sea bears, but the capture study will:
- Provide a window into reproductive success, survival rates, and population size
- Determine if these bears are showing the same signs of stress as the Southern Beaufort Sea population
- Answer basic questions such as what bears are eating and how much time they're spending in the water
The knowledge gained will help policy-makers with environmental planning, including managing oil and gas activity.
Scientists in the field place satellite collars on a select number of bears every spring. The technology lets research teams follow polar bears across the Arctic from the comfort of a warm office hundreds of miles away. Especially in winter, we have no other practical means of learning about polar bears during 24 hours of darkness, when arctic blizzards howl and temperatures plunge.
The collars allow scientists to:
- Track movements and habitat use
- Determine hunting patterns
- Measure the total distance traveled
- Map home range areas
- Collect data on cub survival rates
The collars are designed to fall off on their own in 14 months. Only female bears can wear collars. A male polar bear's neck is as wide as its head, so the collar just slips off!
Tracking technology continues to improve, so scientists are developing a new collar design as well as alternative tracking methods. These include smaller ear- and glue-on satellite tags. The non-collar tags don't deliver as much data—but they will allow scientists to track adult males and subadult bears, which will add to our understanding of polar bear ecology.
Many parts of the Arctic are so remote that scientists don't have a clue about how many polar bears are there. In fact, of the 19 polar bear populations, scientists don't have enough data on seven of them to even make a census estimate!
PBI helped fund studies to refine techniques for taking accurate population counts by air. Aerial surveys would be far less expensive and time-consuming than traditional capture-recapture methods. Although capture efforts give us more detailed information on a population's health and movement patterns, aerial surveys will allow us to take a quick snapshot of how many bears there are in populations that we know little about.
PBI thanks the National Fish & Wildlife Foundation and Conoco for major funding. Thanks, also, to Dr. Steven C. Amstrup, PBI Senior Scientist, past chair of the IUCN Polar Bear Specialist Group and former project leader for Polar Bear Research with the U.S. Geological Survey's (USGS) Alaska Science Center; to George Durner, current project leader for the USGS, and his team; to Dr. Eric V. Regehr and Karyn Rode of the U.S. Fish and Wildlife Service (FWS), principal investigators on the Chukchi Sea study; and to PBI Biologist Mike Lockhart, who assisted with field work in both the southern Beaufort and Chukchi seas.