ARCTIC TUNDRA BIOCIATION 



Origin 



The tundra fauna probably began to evolve late 

 in the Tertiary, along with the tundra flora, as the 

 continent cooled and the Arcto-tertiary flora re- 

 treated southward. The true arctic fauna is appar- 

 ently derived from previously wide-ranging forms 

 able to tolerate cold climates (Johansen 1956-58) 

 and from coniferous forest and grassland, fresh-water 

 marshes, the seacoast (Stegmann 1938), and moun- 

 tainous or upland regions (Larson 1957). Adapta- 

 tions in the avifauna proceeded along lines either of 

 toleration of the many hours of darkness and severe 

 cold of the winter climate, or to the development of 

 extensive migrations, sometimes far into the southern 

 hemisphere as in some shorebirds and terns. 



During glacial periods of the Pleistocene, the 

 tundra of the Alaska refugium was isolated from the 

 tundra south of the glacier but in direct contact over 

 the Bering land bridge with the unglaciated tundra 

 of Asia. During this time there was doubtless an 

 exchange of fauna with emphasis on invasion of 

 Eurasian forms into North America. With recession 

 of the glacier and disappearance of the land bridge, 

 the Alaska tundra again became isolated from Asia 

 and connected to the North American tundra. This 

 has allowed Asiatic species to disperse over North 

 America to varying degrees (fresh- water triclads : 

 Kenk 1953, birds: Cade 1955). Some species, such 

 as the grizzly bear, doubtless invaded the tundra from 

 the western coniferous forests, perhaps since Pleisto- 

 cene time. Other species now on the tundra are prob- 

 ably derived from refugia in the Arctic islands and 

 from south of the glacier (Rand 1954, Johansen 

 195^58). 



Composition 



There is enough uniformity in the animal life 

 of the arctic tundra in North America and Eurasia 

 so that only one biociation is presently recognized. 

 Circumpolar distribution is characteristic of both 

 vertebrates (Udvardy 1958) and invertebrates 

 (Netolitzky 1932). Common animals of the tundra 

 are those listed below, which are conspecific or repre- 

 sented by equivalent species on the two continents. 

 Marine or strictly coastal species and those of more 

 limited distribution are omitted (Bailey 1948, Ban- 

 field 1951, Bee 1958, Harper 1953, 1956, Manniche 

 1910, Manning 1946, 1948, Porsild 1943, Preble 

 1908, Rausch 1953, Salomonsen 1950-51, Soper 1944, 

 1946, Stegmann 1938, Taverner 1934, Taverner and 

 Sutton 1932) : 



Mammals 



[Masked shrew 



Arctic shrew 



Arctic hare 



Arctic ground squirrel 

 (suslik) 



Tundra vole 



Brown, European, Siber- 

 ian lemmings 



Collared lemming 



Gray wolf 



Arctic fox 



Grizzly bear 



Polar bear (limited to 



coast ) 

 Ermine 



Wolverine (glutton) 

 Barren ground caribou 



(reindeer) 

 Peary's caribou (limited 



to North) 

 Muskox 



The muskox, formerly of wide distribution, is 

 now restricted to North America and Greenland. 

 The tundra in North America is richer in species, 

 both of mammals and birds, west of Hudson Bay 

 than it is eastward, and richest in Alaska. 



The most abundant mammals on the tundra are 

 lemmings, and in peak years their numbers are enor- 

 mous. Among the larger animals the caribou form 

 large herds and are important in the food and eco- 

 nomics of Eskimos and Indians. Seton (1912) esti- 

 mates their original number at 30 million, but they 

 are much reduced at the present time. There are 

 also fewer muskox now (C.H.D. Clarke 1940). 



Birds 



Yellow-billed loon 

 Arctic loon 

 Red-throated loon 

 White-fronted goose 

 Oldsquaw 

 Common scoter 

 Rough-legged hawk 

 Gyrfalcon 

 Peregrine falcon 

 Willow ptarmigan 

 Rock ptarmigan 

 Sandhill crane 

 Semipalmated plover 

 Black-bellied plover 

 American golden plover 

 Long-billed dowitcher 

 Whimbrel 

 Ruddy turnstone 

 Knot 



Sanderling 

 Baird's sandpiper 

 Pectoral sandpiper 

 Purple sandpiper 

 Dunlin 



Red phalarope 

 Northern phalarope 

 Pomarine jaeger 

 Parasitic jaeger 

 Long-tailed jaeger 

 Herring gull 

 Glaucous gull 

 Arctic tern 

 Snowy owl 

 Horned lark 

 Common raven 

 Water pipit 

 Lapland longspur 

 Snow bunting 



In addition to these species, the North American 

 faciation contains the whistling swan and snow goose 

 in the north : Canada goose and semipalmated, least, 

 and white-rumped sandpipers rather generally dis- 

 tributed ; and in the west, the Eskimo curlew (now 

 probably extinct), Hudsonian god wit, stilt and buiT- 

 breasted sandpipers, and Smith's longspur. The 

 Eurasian faciation also contains some species limited 

 to it : two species each of swans and geese, several 



318 Geographic distribution of communities 



