The range includes the territory of five nations: Denmark (Greenland), Norway (Svalbard), Russia, the United States (Alaska) and Canada. These five nations are the signatories of the International Agreement on the Conservation of Polar Bears, which mandates cooperation on research and conservation efforts throughout the polar bear's range. Bears sometimes swim to Iceland from Greenland—about 600 sightings since the country's settlement in the 9th century AD, and five in the 21st century —and are always killed because of their danger, and the cost and difficulty of repatriation.