ZOOLOGICAL GEOGRAPHY.

ShCrliON Ee

ANIMAL LIFE.

—n$9300——_.

CHAPTER I.
Zoological Geography.

339. Zoological Geography treats of the dis-
tribution of animal life. The animals found in
any region of country are called its fauna. Like
plants, animals appear to have been originally
created in certain localities, from which they have
spread, more or less, over adjoining areas.

Though able to move about freely from place
to place, animals are, nevertheless, restricted, by
conditions of food and climate, to well-defined
areas. Animals derive their sustenance, either
directly or indirectly, from plants.

340. Distribution of Animal Life—The distri-
bution of heat, moisture, and vegetation forms the
true basis for the distribution of animal life.

We distinguish a horizontal and a vertical dis-
tribution of animal life.

25,000 feet.
20,000
15,000

10,000

5,000

passing from the base to the summit of a tropical
mountain, the same change is noticed in the spe-
cies of animals, as in passing along the surface of
the earth from the equator to the poles.

In the above chart, the names of the animals
are placed at the greatest elevation at which they
are found. The power of locomotion possessed by
animals renders it extremely difficult to arrange
the fauna in zones according to the altitude. In

As a rule, the luxuriance and diversity of ter-
restrial animal life decrease as we pass from the
equator to the poles. A similar decrease is no-
ticed in passing from the coasts of the continents
toward the interior. Within the tropics, where
the abundant heat and moisture produce a vigor-
ous vegetation, all forms of terrestrial animal life,
save man, attain the greatest development in size,
intelligence, and activity. As we proceed toward
the poles, the species are less developed, although,
in the temperate regions, large and vigorous ani-
mals are still numerous. In the polar zones, the
reindeer and white bear are the only representa-
tives of the larger land animals.

In marine animal life, the law of distribution
is reversed, both the number and size of the
species increasing from the equator toward the
poles. This is probably due to the more equable
temperature of the ocean in high latitudes.

341, The Vertical Distribution of Life—In

general, however, the animals found on the slopes
of tropical mountains, at elevations included be-
tween the sea-level and from 5000 to 7000 feet,
correspond to those inhabiting the tropical zone ;
between 5000 or 7000 feet and 15,000 feet, to
those of the temperate zones. The condor is
found in the high Andes, far above the snow
line.

The fauna of high mountain-ranges are often sharply