plovers and saiulpipers, and another pipit antl bunt- 

 ing. 



Less than one-third of tlie above species of birds 

 are entirely terrestrial in their life requirements. 

 .Many species get their food from the fresh-water 

 l>onds and lakes or on the margins of these bodies of 

 water, so characteristic of at least the low arctic tun- 

 dra. On Banks Island in the high arctic, one study 

 (Manning ct al. 1956) gave the following population 

 per S(iuare mile (260 hectares): 08 Lapland long- 

 spurs, 15 sandpipers and plovers of several species, 

 4 horned larks, 1.5 ptarmigans (2 species), and less 

 than one snow bunting. 



Reptiles and amphibians are poorly represented 

 where not absent, and the invertebrate fauna is com- 

 paratively restricted in variety. In the ponds on the 

 west side of Hudson Bay occur a stickleback fish, 

 a flatworm, a leech, an annelid, a few snails, a couple 

 of phyllopods, a few species each of Cladocera, 

 Copepoda, Ostracoda, and Amphipoda ; a good repre- 

 sentation of dytiscid and hydrophilid beetles, and an 

 abundance of midge fly larvae. Since the lakes and 

 rivers thaw out for only a few weeks, annual produc- 

 tivity is low (Frey and Stahl 1958). Fish are more 

 numerous in rivers, and are largely migratory sal- 

 monids. Pond life in the Alaskan tundra is essen- 

 tially similar to that near Hudson Bay (Johansen 

 1922). 



On land, the snails Sticcinca and Vertigo are 

 found in wet tundra on the west side of Hudson Bay. 

 Spiders and mites are well represented. Springtails 

 and flies are especially numerous among the insects, 

 and there are a few species of Lepidoptera, Cole- 

 optera, and Hymenoptera, but species of Hemiptera, 

 Homoptera, Orthoptera, Odonata, and Neuroptera 

 are scarce or absent. Ants are scarce on the tundra but 

 bumblebees are conspicuous. Especially noteworthy 

 are the vast devastating hordes of mosquitoes, black 

 flies, and deer flies that reach a peak of numbers in 

 mid-July (Seton 1912, Shelford and Twomey 194L 

 McClure 1943). The invertebrate life of western 

 Greenland is essentially similar (Longstaff 1932). 

 Quantitative studies of the soil fauna in eastern Green- 

 land showed that springtails and mites, especially 

 Oribatidae, reached populations of 780,000 per sq m 

 in bush tundra, but only 3000 per sq m in the lichen- 

 moss barrens (Hammer 1937). Seven different so- 

 cieties of invertebrate fauna have been differentiated 

 here (Macfadyen 1954). 



In comparison to the arctic, the antarctic supports 

 a limited fauna. .Among the invertebrates, one study 

 found several peculiar species of Protozoa, 16 species 

 each of rotifers and tardigrades, two fresh-water 

 crustaceans, mites, and at least 18 species of insects. 

 Vertebrates are primarily marine although several 

 species, especially birds, nest on land (Lindsey 

 1940). 



I'\)()(l is more abundant along tlie slnires of north- 

 ern oceans ; the association of sea and land provides 

 niches for various species not found abundantly in- 

 land (Freuchen and Salomonsen 1958). During the 

 winter the sea is covered with ice, there is little or 

 no light, and phytoplankton is scarce or absent 

 e.\ce])t for reproductive spores and eggs. However, 

 nutritive salts, such as nitrates and phosphates, accu- 

 mulate in large supply, so that in May when the ice 

 disappears and light returns there is an almost explo- 

 sive development of phytoplankton followed by micro- 

 crustaceans and other zooplankton. This is the key 

 to the teeming abundance of fish, sea birds, and ma- 

 rine mammals that occur at this time. Large colonies 

 of fulmars, cormorants, auks, murres, guillemots, 

 gulls, and others nest on ledges of precipitous cliff's or 

 in some cases on islands or shores down close to the 

 water. Eider ducks and other waterfowl are fre- 

 c|uently numerous. Vegetation is best developed in 

 and around these colonies because of the rich nutrient 

 added to the soil from the excreta of the birds. One 

 of the most common seals is the ringed seal which 

 remains over winter, even in the high arctic, by keep- 

 ing blow-holes open through the ice. The harbor 

 seal and harp seal overwinter in the more open 

 waters of the low arctic. Other species of seals, 

 whales, walruses, and polar bears occur during the 

 summer throughout most of the maritime areas of the 

 arctic. 



Animal adjuslments 



White coloration is common, especially over 

 winter, in several mammal species (artic hare, col- 

 lared lemming, gray wolf, arctic fox, polar bear, 

 ermine, Peary's caribou) and in a few birds (willow 

 and rock ptarmigans, snowy owl). When the ground 

 is covered with snow, white coloration, of course, 

 conceals both the prey and predators. Many of these 

 species acquire darker coloration during the months 



FIG. 24-2 Rock ptarmigan 

 males: left, summer plumage; 

 right, winter plumage 

 (courtesy Bert Babero). 



Tundra biome 319 



