The Mednyi Arctic Fox (Vulpes lagopus semenovi (Ognev, 1931)): A Disappearing Island Endemic

Abstract The biology and history of the decline of the Arctic fox population on the Mednyi Island, Commander Islands, North Pacific, are considered. Currently, this is the smallest and possibly the most ancient island population of canids on Earth. Among the endemics of island faunas, carnivores are generally very rare, and among the canids only the California island fox (Urocyon littoralis) is listed in taxonomic and conservation databases. Questions regarding the species status and phylogenetic history of Commander Arctic foxes, Vulpes lagopus beringensis (Merriam, 1902) and V. l. semenovi (Ognev, 1931), remain open until genomic studies are conducted. Over thousands of years, Commander Arctic fox populations have evolved in an environment radically different from that of the continental Arctic foxes: under conditions of complete isolation, ecological stability, and a mild climate, with neither predators nor competitors from other species. The behavioral ecology of the island Arctic fox has been adapted to life in a super-dense population, where severe intraspecific competition and the risk of inbreeding are prevalent. This adaptation has led to a complete restructuring of the social, reproductive, territorial, and spatial behavior of the island Arctic fox. Historically, the viability of the Mednyi population has been supported by its stable and relatively high population size (over 1000 individuals). Since the discovery of the Commander Islands in 1741, intensive fox trapping on Mednyi Island continued for over two centuries. In the last 40 years, trapping has been accompanied by supplementary feeding. After the cessation of fox trapping and supplementary feeding in 1965, the population size began to be determined solely by the island ecosystem’s natural capacity, which decreased significantly during the second half of the 20th century. The long-term decline in effective population size and artificial selection have led to a significant loss of genetic polymorphism. Genetic degradation and a decrease in the carrying capacity of the island ecosystem have placed the population in a critical state. A sudden outbreak of ear mange in the late 1970s, which killed 90% of cubs, demonstrated the enormous risk associated with the emergence of new pathogens. In recent years, the abundance of food sources (such as deposits of storm-cast macrophytes, the seabird colonies, and the sea otter population) has noticeably diminished, and the Mednyi Arctic fox population has declined to fewer than 60 individuals. The National Park protection regime and the inclusion of the Mednyi Arctic fox in the Red Data Book of the Russian Federation are not sufficient to prevent the population from going extinct. The situation requires targeted conservation measures to protect this disappearing island endemic.