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
Baltica belt of the Timanide orogeny and overlain by Mesoproterozoic sediments. The margin became a passive margin facing an Ural Ocean in the Cambrian-Ordovician. The eastern margin stretches south through the Ural Mountains from the northern end of the Novaya Zemlya archipelago. The margin follows the bent shape of Novaya Zemlya which was caused in the Late Permian by the Siberian Traps. It is clear from Baltic endemic fossils in Novaya Zemlya that the islands have been part of Baltica since Early Palaeozoic, whereas the Taymyr Peninsula farther east was part of the passive margin of Siberia in the Early Palaeozoic.