CHAPTER XXV 



THE ANIMAL LIFE OF POLAR REGIONS 



The environmental conditions of polar regions exhibit many simi- 

 larities to those of high mountains. As one approaches the poles, the 

 spread of the daily and annual temperature range is reduced. With 

 the lowered temperature, the greater proportion of the precipitation 

 is stored as snow, whose accumulation gives rise to mighty glaciers. 

 Abundant ground moisture is provided in places which are freed from 

 snow by sun and wind. Long winters are followed by short summers. 

 Not until the end of May or the beginning of June do the great quanti- 

 ties of snow disappear from the level ground, and the storms precursing 

 winter begin in August. Eternal snow covers even low elevations, and 

 sometimes vast areas, like the inland plateau of Greenland. Glaciers 

 reach sea level. 



But where the sun is not impeded by fog, and where the snow 

 has been blown thin by winds, the ground is quickly freed of its icy 

 mantle, and is warmed, together with the lowermost layers of air, to 

 three to six times the temperature of the air. Favorable conditions are 

 thus produced for small poikilothermal animals, particularly in regions 

 with southern exposure and with sufficient slope to allow the ice water 

 to drain away as melted. Regions lacking such drainage or with north- 

 ern exposures present much less favorable living conditions. At Bel- 

 Sund, Spitzbergen, on the seventh of July, when the ground was frozen 

 below 30 to 35 cm., and the air temperature at the height of 1 m. was 

 + 4.7°, the temperature just above the low plants was -j-15.5°. The 

 warm air flows upward on slopes and assists in melting the snow; 

 slopes with green turf and flowering plants develop in hills up to 

 heights of more than 300 m., and these enable animal life to gain a 

 foothold. Plants with deeper roots, and especially trees, are necessarily 

 wanting in the circumpolar tundra on account of the ground ice. In 

 the mountains, as in the polar areas, regional peculiarities become more 

 and more intensified as one travels from the tree border toward the 

 eternal ice. While this transition occurs within a few kilometers in the 

 mountains, it extends over a vast area in the polar regions. 



Environmental differences between the high mountains and the 

 tundra consist in the reduced pressure at high altitudes, and in the 



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