High winds, broken ice, and
rain. These are not the normal conditions one expects to find during
an expedition to the Arctic to study the ecology of polar bears
but indeed this is what was found during the WWF sponsored field
season in 2002. Dr. Andrew Derocher and Magnus Andersen of the Norwegian
Polar Institute, were based at Hopen Island and in Longyearbyen
in the Svalbard Archipelago during April.
Hopen is normally an ideal location for studying bears as the weather
station provides a convenient place to work and the bears often come
right by the station so they are easy to find. Unfortunately, this year,
the spring was very warm and strong winds broke the ice into small
pieces making it very poor habitat for polar bears. Only one bear passed
the station this year while more than fifty are normal.
Despite these difficulties, they managed to fly out from Hopen using a
small helicopter and sampled several bears. A drug-filled dart was shot
into the rump of each bear from the helicopter. Once the bear was
asleep, a series of body measurements to monitor growth patterns and
condition were collected and a sample blood, fat and milk taken to
monitor pollution levels.
Overall, the poor ice conditions caused a shift northward in the
distribution of the bears. No seal kills were observed in the drift ice
and this suggests the bears were having a tough time finding food. The
generally poor condition of the captured bears further supports this.
Only one maternity den was found on Hopen Island. In a good year, over
thirty dens can be found there. It seems that the late arrival of sea
ice the previous winter makes it less attractive to pregnant females
seeking a safe place for giving birth to their young.
Leaving Hopen Island ahead of schedule, the research team moved into
Longyearbyen -- the main settlement in Svalbard -- and continued to
study the bears in this area. Again, poor weather hampered the efforts
but some valuable insights were obtained on the distribution and habitat
of the bears close into land.
Recent research findings have revealed interesting results. Polar bears
in the Barents Sea drift ice may be more dependent upon bearded seals
than bears living near land. Bears living closer to land rely more on
ringed seals and this difference is due to the preferred habitat of the
different seal species. Understanding the current diet of polar bears is
critical for understanding how climate change may affect the bears in
the future.
Other recent results suggest that the bears in the Svalbard area may be
somewhat smaller than populations in North America. The reasons are
unclear but it may be that life in the drifting pack ice is more
difficult than the more stable ice of North American.
Finally, another interesting part of the puzzle was revealed by research
conducted by Mette Mauritzen who recently completed her doctorate on
polar bear ecology at the University of Oslo in cooperation with the
Norwegian Polar Institute. Dr. Mauritzen found that polar bears living
in the Barents Sea are living on the sea ice equivalent of a treadmill.
Sea ice is pushed around by winds and currents. Polar bears spend most
of the year walking against the drift to ensure they do not lose contact
with ice by drifting out into the open waters further south. This
finding has important ramifications for understanding climate change
impacts because the stronger winds predicted for the Barents Sea under
climate change scenarios would result in polar bears using more energy
to stay with the main ice pack. Using more energy for walking means less
energy for growth and reproduction.
All-in-all, the field season of 2002 was difficult. Polar bears do not
easily reveal the secrets of their life on the sea ice and it takes many
years and great patience to gain the insights needed to conserve these
magnificent animals.
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Andy Derocher, a Norwegian Polar Institute
scientist, with tranquillized polar bear.
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