Franz Josef Land and snow bunting. Some ivory gulls, little auks and Brünnich's guillemots opt to spend the winter on the islands. The polar bear population of Franz Josef Land lies within the Barents Sea subpopulation, which also includes polar bears inhabiting Svalbard and the western coast of Novaya Zemlya. In 2004, the Barents Sea subpopulation was estimated at 2,650. There is also a population of Arctic fox, which typically have their territories near seabird habitats. Being declared as a marine mammal sanctuary, the island has rich biodiversity of rare marine mammals. Three species of seals habit the archipelago. Harp seal is the
Severnaya Zemlya to a survey of prior observations by De Korte, Volkov, and Gavrilo, thirty-two bird species have been observed on Severnaya Zemlya, 17 of which are known to breed on the islands. Eight species are widespread across the archipelago: five of which are colonial seabirds: little auk ("Alle alle"), black-legged kittiwake ("Rissa tridactyla"), black guillemot ("Cepphus grylle"), ivory gull ("Pagophila eburnea"), and glaucous gull ("Larus hyperboreus"); and three species of tundra bird: the snow bunting ("Plectrophenax nivalis"), purple sandpiper ("Calidris maritima"), and brent goose ("Branta bernicla"). The most common mammal on Severnaya Zemlya is the collared lemming ("Dicrostonyx torquatus"), also known