Polar biol. doi:10.1007/s00300-008-0530-0 (2008)

Credit: ISTOCKPHOTO.COM / JAMES RICHEY

Polar bears in the Beaufort Sea region of the Arctic are finding it increasingly difficult to find food during springtime, suggests a new study.

Seth Cherry of the University of Alberta, Canada, and colleagues located polar bears by helicopter and anesthetized them using a dart gun before taking blood samples to determine their serum urea to serum creatinine (U/C) ratios. U/C values, which are low when bears are in a physiological fasting state, were obtained for 436 individuals during April and May of 1985–1986 and 2005–2006. Of the bears sampled by Cherry's team, the numbers fasting were 9.6 per cent in 1985 and 10.5 per cent in 1986, increasing to 21.4 per cent in 2005 and 29.3 per cent in 2006. Polar bears from all sex, age and reproductive classes were more likely to be found fasting in 2005-2006 than in 1985–1986. During all years of the study, adult males involved in breeding comprised a high proportion of the bears with low U/C levels.

Satellite data over this period shows significant declines in the extent of Arctic sea ice, a change that may affect the bears' ability to hunt and catch seals during the spring feeding period.