(_For illustration, see page 550_)
Among the many kinds of squirrels which lend animation and charm to
the forests of North and South America, none equal in beauty the
subjects of this sketch--the Abert and the Kaibab squirrels. These are
the only American squirrels endowed with conspicuous ear tufts, which
character they share with the squirrels occupying the forests in the
northern parts of the Old World from England to Japan. In weight they
about equal a large gray squirrel, but are shorter and distinctly more
heavily proportioned, with broader and more feathery tails.
Their range covers the pine-forested region of the southern Rocky
Mountains in the United States and the Sierra Madre of western Mexico.
The Abert squirrel and its several subspecies is the more widely
distributed, being found from northern Colorado, south through New
Mexico, Arizona, Chihuahua, and Durango. The Kaibab squirrel, which
is even more beautiful than its relative, shows marked differences in
appearance and yet is evidently derived from the same species.
The typical Abert squirrel lives in the pine forests along the southern
rim of the Grand Canyon in northern Arizona, and the Kaibab squirrel
lives in the pines visible on the northern rim of the canyon less than
15 miles away. It is confined to an islandlike area of pine forest
above 70 miles long by 35 miles wide, on the north side of the canyon,
on the Kaibab and Powell plateaus, directly across from the end of
the railroad at the Grand Canyon Hotel. The two species live under
practically identical conditions as to vegetation and climate.
In these sketches of our mammal life I have repeatedly noted the effect
of changing environment in modifying the animals subject to it. In
the present case the change in the squirrels on the north side of the
Grand Canyon has evidently been brought about by that powerful factor
in evolution known as isolation. Cut off from their fellows by the
deepening canyon of the Colorado, Kaibab squirrels have occupied a
forest island ever since, with the resulting change in characters we
now have in evidence.
The home of both the Abert and the Kaibab squirrels is almost entirely
between 6,000 and 9,500 feet altitude, on the mountain slopes and high
plateaus overgrown with a splendid open forest of yellow pine mixed in
many places with firs and aspens. Occasionally, as food becomes scarce
in their ordinary haunts, they range up into the firs or down into the
oaks and piñon pines. In winter their haunts are buried in snow, but
in summer on every hand present lovely vistas among the massive tree
trunks, varied here and there by gemlike parks. Everywhere the ground
is covered with grasses and multitudes of flowering plants. In the
wilder parts of this fascinating wilderness roam bears, mountain lions,
wolves, deer, and wild turkeys, and only a few decades ago still wilder
men, belonging to some of our most dreaded Indian tribes.
Although these squirrels commonly make use of large knot-holes or other
hollows in trees, they regularly build high up in the branches bulky
nests of leaves, pine needles, and twigs and line them with soft grass
and shredded bark. Sometimes several full-grown squirrels may be found
occupying one of these outside nests, probably members of one family.
They are active throughout the year, but remain in their nests during
storms and severe winter weather. In northern Arizona I have known them
to stay under cover for a week or two at a time in midwinter.
The young appear to be born at varying times between April and
September. Although not definitely known, it seems probable that they
have two litters of from three to four young each season.
The seeds and the tender bark from the terminal twigs of the yellow
pine (_Pinus ponderosa_) furnish their principal food supply. During
periods when pine seeds are not available the squirrels cut the ends
of pine twigs, letting the terminal part bearing the leaves fall to
the ground, while the stem, several inches in length, is stripped of
bark. Often at times of food scarcity the bark will be eaten for a
considerable distance along the outer branches, almost like the work of
porcupines. The ground under the pines where the squirrels are at work
is sometimes almost covered with the freshly dropped tips of branches.
The Abert squirrels also eat the seeds of Douglas spruce, of the piñon
pine, acorns, many seeds, roots, green vegetation, mushrooms, birds’
eggs, and young birds. Now and then they rob cornfields planted in
clearings, but they do little damage to crops. Some years they are
extremely numerous and are in evidence everywhere; again they become
scarce and so wary that it is difficult to see one, even where its
fresh workings are in evidence.
Both these squirrels have a deep churring or chucking call, sometimes
becoming a barking note resembling that of the fox squirrel. They also
have a variety of chattering and scolding notes when excited or angry.
At times they become almost as aggressive as the red squirrel and come
down the tree trunk or to a lower branch, whence they scold and berate
the object of their disapproval.
When much alarmed they are expert at hiding among tufts of leaves near
the ends of branches, on tops of large limbs, or behind trunks. They
will remain hidden in this way for an hour or more, patiently waiting
for the danger to disappear, but one is often betrayed by the wind
blowing the feathery tip of its tail into view.
On the ground the tail is usually carried upraised in graceful curves.
Here these squirrels spend much time among fallen cones and in digging
for roots and other food. When they walk they have an awkward waddling
gait, but when they are alarmed, or desire to move more rapidly for any
cause, they progress in a series of extremely graceful bounds, which
show the plumelike tail to good advantage. When the Kaibab squirrel
is moving about on the ground its great white tail is extraordinarily
conspicuous in the sunshine. This repeatedly drew my attention to these
squirrels, even at such long distances that they would otherwise have
been overlooked.
[Illustration: SHORT-TAILED SHREW
_Blarina brevicauda_