It is thought to be caused by exposure to chemicals which affect the endocrine system. The phenomenon was unknown on the Arctic islands, which lie between Norway and the North Pole, a decade ago. PCBs were manufactured for use in electrical equipment, and although many countries have now banned them there is a reservoir of the chemicals that has escaped into the environment. There is a very short and simple food chain here - plankton, fish, seals, and finally the bears themselves. So it is fairly easy to track PCBs and other pollutants.
Seals are the bears' preferred prey.
In spring, after emerging from hibernation, they usually eat the whole seal, though later in the year they will often slit the animal open and simply eat the fat. Although little pollution originates on Svalbard, the prevailing southerly winds dump contamination from industrial Europe on to the islands. With other species affected by endocrine disrupters, it's more often the males that have genital abnormalities. And what's happening to the bears is happening to gulls in the Arctic, too, because of PCBs, DDT and dioxins. Always armed From 1950 until 1972 there were organised bear hunts for tourists who visited Svalbard.