STEPPES OF ASIA AND AMERICA 67 
(22 pounds), and are sufficiently numerous for it to be 
worth while for the Mongolians to bring their cattle to 
feed upon the pica’s stores, and so dispense with the 
trouble of storing fodder on their own account. Like 
some other of the steppe animals, the picas are remark- 
ably resistant to thirst, and can live in localities far 
from water, where no rain nor dew occurs for months 
at a time. 
As to the carnivores of the steppe, the tiger, though 
usually regarded as a tropical animal, extends far 
to the north, and occurs in steppe regions, perhaps in 
more than one variety. When nobler game fail, it does 
not disdain the rodents, notably the picas. The special 
cat of the steppe is, however, the manul cat (Felis 
manul), a beautiful animal with a bushy tail, about the 
size of the common cat, and apparently allied to the 
wild cat of Europe, but, unlike it, a steppe animal. Its 
main food consists of the steppe rodents, and also of 
the ground-nesting birds. The steppe has also its 
special fox, the corsac fox (Canis corsac), which also 
feeds chiefly upon the steppe rodents. Here as else- 
where the ubiquitous wolf also occurs. 
In regard to the birds of the steppe it is noticeable 
that they tend to acquire swiftness in running, thus 
showing parallelism with the mammals. This is 
carried further in the birds of the warm deserts of the 
world, where we have in ostrich, rhea, emu, &c., 
examples of birds without any power of flight, but of 
great fleetness of foot. The reason for this tendency is 
possibly that the steppe or desert does not, like the 
forest, offer safe places upon which to rest. As the 
birds are exposed to danger so soon as they alight, 
which is necessarily upon the ground, fleetness is a great 
advantage to them. 
E 2 
