82 
ORDERS OF MAMMALS— GNAWING ANIMALS 
It is seldom that anyone sees a live Beaver in its 
haunts during the middle of the day, but it is 
possible to do so during the hour before sunset. 
In public zoological gardens and parks, the per- 
sistence and success of this animal in avoiding 
observation is very disappointing to visitors, 
and exasperating to directors and keepers. 
This is the largest gnawing animal in North 
America. A huge specimen caught in Maine, 
in 1900, weighed a trifle over 50 pounds. A 
large one in the New York Zoological Park is 31 
inches long, has a tail 12 inches long and weighs 
44 pounds. 
The American Beaver is still found in a few 
localities, — but in very small numbers, — from 
the Rio Grande in Texas throughout the Rocky 
Mountains, Sierra Nevada and Cascade Moun- 
tain regions northward to the limit of trees, and 
southeastward through Canada to northern New 
England. The number now remaining in Col- 
orado has been estimated at one thousand. 
The Beaver’s efforts are directed toward its 
own preservation and comfort. It builds ex- 
tensive dams of mud, grass and sticks, in order 
to create ponds in which it can hide from its 
enemies, maintain a safe refuge close by the wood 
on which it feeds, and have an under-water door- 
way to its house or burrow. More than this, 
the pond serves as a refrigerator, in the bottom 
of which the animal stores its supplies of food- 
wood for winter use, when the surface is frozen 
for a long period. 
Sometimes when food-wood on a beaver pond 
becomes scarce, the animals dig canals into 
places where fresh supplies can be cut, and 
floated down to the pond. These canals are 
usually about two feet wide. 
A Beaver is readily recognized by its very flat, 
hairless and scaly tail, which beyond the hair 
of the body is about 9 inches long by 4 inches 
wide. The tail is never used as a trowel in building 
dams, but only as a propeller in swimming. 
Dam-building is done in two ways. With 
his front feet the animal digs up soft mud, holds 
the mass with his fore legs against his breast, 
and swims with it to the dam. There he deposits 
it where it is most needed, and pats it down with 
his front feet. To strengthen the structure, he 
brings sticks four or five feet long, and one or 
two inches in diameter, from which he has eaten 
the bark. These he usually lays upon the dam, 
crosswise or nearly so, and fills between them 
with mud. 
When Beavers have to build a dam exceed- 
ing fifty feet in length, to flood low ground, they 
usually lay it out with a curve up-stream. The 
dam built by the Beavers in the New York Zoo- 
logical Park is about forty feet long, and three 
feet high, and quite sharply curved up-stream. 
In most localities inhabited by Beavers, the 
banks of the streams are so low that the animals 
cannot burrow into them, and consequently 
they build houses for themselves. The ordinary 
Beaver house is a huge pile of neatly trimmed 
six-foot poles, with all spaces between the sticks 
plastered full of mud. The one in the Zoological 
Park is about fifteen feet in diameter, and five 
feet high, with a central chamber above high- 
water-mark, and its only entrance is well under 
water. If a beaver house is attacked, the occu- 
pants immediately seek refuge in deep water. 
SKULL OF BEAVER, A TYPICAL RODENT. 
The trees which furnish bark most prized by 
the Beaver as food are the poplar, cottonwood, 
willow, birch, elm, box-elder and aspen. The 
bark of the oak, hickory, or ash is not eaten. 
The Beaver’s front teeth (incisors) are very 
strong and sharp, and the muscles of the jaw are 
massive and powerful. It is no uncommon thing 
for a Beaver to fell a tree a foot in diameter in 
order to get at its branches. It is said by some 
observers that large trees are made to fall as 
the Beavers prefer to have them, — -toward their 
pond. In felling a tree, they first remove the 
bark from a circle a foot in width, just above 
