Warmer temperatures and earlier melting of sea ice are causing polar bears to go hungry. The number of undernourished bears has tripled in a 20-year period.
Seth Cherry of the University of Alberta, Canada, and colleagues monitored the health of polar bears in the ice-covered Beaufort Sea region of the Arctic during April and May in 1985, 1986, 2005 and 2006.
They immobilised the bears using tranquilliser darts and measured the ratio of urea to creatinine in their blood. A low ratio means that nitrogenous waste material is being recycled within the body and indicates the animal is fasting – a state which usually only occurs temporarily in males during the spring breeding season.
In 1985 and 1986 the proportion of bears fasting was 9.6 and 10.5 per cent respectively. By 2005 and 2006 this had risen to 21.4 and 29.3 per cent.