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Polar bear births could
plummet
with climate change
The researchers say projected reductions in the number of newborn
cubs is a significant threat to the western Hudson Bay polar-bear
population, and if climate change continues unabated the viability of
the species across much of the Arctic will be in question.
Using data collected since the 1990s researchers looked at the
changing length of time Hudson Bay is frozen over (the polar bear's
hunting season) and the amount of energy pregnant females can store up
before hibernation and birthing.
An early spring-ice breakup reduces the hunting season making it
difficult for pregnant females to even support themselves, let alone
give birth to and raise cubs. Pregnant polar bears take to a maternity
den for up to eight months and during this time no food is available.
In the early 1990s, researchers estimate, 28 per cent of
energy-deprived pregnant polar bears in the Hudson Bay region failed to
have even a single cub. Researchers say energy deprived pregnant females
will either not enter a maternity den or they will naturally abort the
birth.
Using mathematical modelling to estimate the energetic impacts of a
shortened hunting season, the research team calculated the following
scenarios:If spring break up in Hudson Bay comes one month earli-
er than in the 1990s, 40 to 73 per cent of pregnant female polar
bears will not reproduce.If the ice breaks up two months earlier than in
the 1990s, 55 to a full 100 per cent of all pregnant female polar bears
in western Hudson Bay will not have a cub.
The polar-bear population of western Hudson Bay is currently
estimated to be around 900 which is down from 1,200 bears in the past
decade.
The number of polar bears across the Arctic is estimated to be
between 20,000 and 25,000.The research team says because the polar bears
of Hudson Bay are the most southerly population they are the first to be
affected by the global-warming trend. However, they say that if
temperatures across the Arctic continue to rise, much of the global
population of polar bears will be at risk.
Courtesy:Science Daily |
