130 PHYSICAL GEOGRAPHY.

 

marked. A particular species, at a given elevation on one
range, is frequently entirely wanting on a neighboring
disconnected range, even when the same conditions of
heat, moisture, and vegetation exist. The temperature
of the intervening lower country, through which the ani-
mals would have to pass in order to reach the adjoining
slopes, forms an impenetrable barrier.

342, Natural Boundaries of Zones of Animal
Life.—Large bodies of water, deserts, or moun-
tain-ranges, mark the boundaries of regions of
animals as well as of plants; but the influence
of temperature is so important, that even when
these natural barriers are wanting, the horizontal
range of animals is sharply marked by the iso-
thermal lines.

In North America, there are well-marked zones of ani-
mals, which extend from east to west across the continent.
Here, although no natural barriers exist to limit the wider
range of the animals, yet they seem unable to permanently
pass the limits of the isotherms, which mark the climatic
conditions necessary to their vigorous growth. This in-
ability doubtless arises from the distribution of the flora,

on which, directly or indirectly, they are dependent for
their food.

343, Acclimation—The power of becoming
acclimated, or being able to live in a climate dif-

fering from that in which they were first created, _

appears to be possessed by animals, as a class, to
an exceedingly limited extent.

‘Man, and his faithful friend, the dog, form an exception
to most other animals in this respect. They are able to
endure both the severe heat of the tropics, and the rigor
of the Arctic regions. The reindeer thrives amid the
snows of Lapland or Greenland, but perishes from the
heat of St. Petersburg. Monkeys are indigenous to the
tropics, but die with consumption, even in the compara-
tively mild climate of the north temperate zones. |

844, Horizontal Distribution of Animal Life.
—The vast number of species of animals, the pe-
culiar laws of their growth, and their power of
adaptation to change of circumstances, render
their accurate distribution into zones or regions
a task far beyond the scope of an elementary
book.- It will be sufficient for our purpose to
divide the fauna of the earth into those found, in
general, in the three mathematical climatic zones:
the Torrid, the Temperate, and the Polar. The

accurate limits of these zones would be found in |
the isotherms, but in a general description, little ©

difference would be noticed. On the map, the
actual limits of some of the more important ani-
mals are given. These limits, it will be noticed,
in most cases follow the general direction of the
isotherms.

345. Characteristic Fauna.—aA careful study

of the map of the distribution of animal life, will
show that each continent possesses a fauna pecu-
liar to itself. This arises, generally, from some
clearly traceable peculiarity in the distribution
of the heat and moisture, or in the nature of the
vegetation. Some of these peculiarities will be
discussed in a brief review of the characteristic
fauna of each of the continents. The following
are the characteristic tropical, temperate, and are-
tie fauna.

346. Tropical Fauna.—The abundance of
heat, moisture, and vegetation of the’ torrid
zone causes its fauna. to excel all the others
in the number and diversity of terrestrial
species, as well as in their size, strength, and
sagacity.

The following animals are found mainly within .
the regions of the earth included between the
Tropics of Cancer and Capricorn.

Mammalia are represented as follows:

Monkeys, by the man-like orang-outang, the
chimpanzee, gorilla, baboon, and other species.

 

Fig, 116, Lion,

Carnivora, or flesh-eating mammals, by the lion,
tiger, panther, and puma. :

Herbivora, or plant-eating mammals, by the ele-
phant, rhinoceros, tapir, and hippopotamus, the
horse-like zebra and quagga, the giraffe or camel-
opard, and the camel.

Cetacea, or whales, by the sperm whale, found
only in tropical or temperate waters.

Cheiroptera, or bats, by a number of species.

Marsupials, by the kangaroo of Australia.

Birds are represented, in tropical regions, by