96 THE FAUNA OF 
forest there is, as already indicated, no seasonal check 
to vegetation, and therefore no marked variation in 
the amount of vegetable food available. But there is 
much evidence to show that the total amount is less 
than might be expected. The tropical forests of New 
Guinea yield almost no food for man, so that recent 
expeditions have had to import every particle @on- 
sumed, and have at times run almost the same risks 
of starvation as explorers in the tundra, even when 
armed with modern weapons. Elsewhere there are few 
human groups indeed who manage to subsist solely on 
the products of the tropical forest, and those who do, 
e.g. the Congo pygmies and the Philippine negritos, 
seem to be few in number, and yet to suffer from chronic 
starvation. They do not reach a high state of civiliza- 
tion. The fact that all the more intelligent of the 
forest animals soon learn to rob man’s plantations, or 
to prey upon his flocks and herds, suggests that the 
wild mammals are no better off than forest-dwelling 
man. ‘The reasons why the conditions should be 
relatively unfavourable in the tropical forests are 
perhaps a little obscure, but we note among them that 
the physical conditions most favourable to plant life 
are not those best suited to the mammalia at least. 
Further, the enormous number of plant species in the 
tropical forest diminishes the chance that a particular 
useful species will occur in numbers. The fact that 
trees of commercial value only occur in isolated speci- 
mens is a great barrier to the exploitation of the tropical 
forest by man, and it has doubtless also its effect on 
the wild animals. If there is one Cembra pine loaded 
with ripe seeds in the taiga, there will almost certainly 
be many in the vicinity; if the squirrels find one 
hickory tree in the American woods whose nuts are 
