Hibernation concentrates chemicals

Some pollutants build up in grizzly bears even as they doze through the winter, tests of the animals' hair and fat indicate.

Hibernating bears don't drink, eat, or excrete waste, so food- and waterborne contaminants neither enter nor leave their bodies. Nevertheless, chemical concentrations in the animals' fat may change as they use up that energy source.

The body converts some compounds into water-soluble metabolites that get excreted in urine. In a slumbering grizzly, such metabolites might accumulate.