ECOLOGICAL 99 



Maral Stag and the reindeer, the roe-deer and the broad-antlered 

 elk or moose. The carnivores are represented by wolf, fox, lynx, and 

 bear, and by smaller types, so fine of fur, like sable and ermine, 

 mink and marten. Both tree-squirrels and ground-squirrels are 

 much in evidence, and another typical rodent in the clearer stretches 

 is the Variable Hare, which, like the Arctic fox and the ermine, puts 

 on a white dress when winter comes. This may help in part as a 

 cloak of invisibilit}', but its chief value is probably that it conserves 

 the precious animal heat better than any other colour. 



Very characteristic of the forest mammals is the relative frequency 

 of hibernation, as illustrated by marmots, sousliks, chipmunks, and 



Fig. 27. 



Greenland Falcon [Hierofalco candicans), a very successful bird of prey in 

 Arctic regions. Like many other inhabitants of the far north, it is pre- 

 dominantly white in colour. From a specimen. 



some squirrels. Thrse winter sleepers are imperfect in their warm- 

 bloodedness ; when the cold sets in they cannot produce enough of 

 heat to make good what is lost ; they relapse into a strange state of 

 suspended animation, but before this grips them they obey an 

 instinct to creep into a sheltered corner, where the temperature 

 rises above that of the surrounding world. There they lie low, with 

 the heart beating feebly and the breathing movements scarce 

 perceptible. They have no income except a little oxygen, and no ex- 

 penditure except a little carbonic acid gas. The process of excretion 

 stops and the blood undergoes a marked change. The usual reactions 

 to stimuli, or answers-back to provocations, are in abeyance. It is 

 a strange relapse towards reptiledom, but if it is a weakness, it 

 becomes a strength. For most of the "winter sleepers" — not that 

 it is really sleep that they illustrate — reawaken in spring much 

 refreshed and ready for their meals. 

 While three or four of the forest mammals turn white in winter 



