No fewer
than four species and eight subspecies of
tree squirrels can be found in Arizona's
forests. Of these, the Abert's or tassel-eared
squirrel is the most widespread and contributes
most to the annual squirrel harvest. This
squirrel, with its easily discernable ear
tufts, along with its close relatives, the
black-bellied and white-tailed Kaibab squirrels,
are exclusively inhabitants of ponderosa
pine forests and the life cycles of the squirrels
and the tree are remarkably intertwined.
Less well known is the also white-bellied
Arizona gray squirrel and its close relative,
the rustcolored Chiricahua fox squirrel,
both of which inhabit riparian deciduous
forests and oak woodlands south of the Mogollon
Rim. Another species is the chicaree or red
squirrel (actually more olive or gray than
red in Arizona), which is restricted to the
higher forests of spruce and fir above 8,500
feet elevation. Both the tassel-eared and
gray squirrels average a little under 1.5
pounds in weight, while the diminutive red
squirrel averages just over 0.5 pounds.
Natural History
Tassel-eared squirrels have but one breeding season a year, which is closely
correlated with the production of the staminate flowers of ponderosa pine
in late April, May, or early June. After a lengthy chase, the female comes
into estrus for only one day. She will later give birth to a single litter
of from two to four young in a nest made of pine boughs. Throughout the
summer, the squirrels feed on the seeds of developing cones as well as
on underground fungi or truffles that grow under mature pine trees. These
foods are the most nutritious for the squirrel, and only when they are
exhausted does the animal resort to feeding on the inner bark of pine twigs-the
discarded terminals of which are often seen littering the forest floor.
These "clippings" of inner bark are only an emergency food, however, and
if deep snow-cover or other factors force the squirrel to rely entirely
on this food source, the animal will eventually go into shock and die.
Only after years of research was it learned that the periods of tassel-eared
squirrel scarcity and abundance were related to the amount of snow-cover
and the availability of underground fungi. Most squirrel mortality is during
the late winter, and when snow covers the ground for 80 or more days, the
mortality rate exceeds the squirrel's rather modest recruitment rate. Hunting
apparently has little effect on the animal's numbers as other research
shows the lowest monthly mortality is during the October and November hunting
season.
Hunting and Trapping History
Tree squirrels have an uneven history as game in Arizona. Having gone from
being totally ignored at the time of statehood, to having a limited season
in conjunction with the deer and turkey seasons in the 1920s, the season
was closed in 1935 due to a perceived lack of squirrels. Too many squirrels
in the 1940s resulted in a re-opening of the season, and squirrel hunt
regulations have since been liberalized gradually until every species and
most subspecies are now subjected to limited hunting. Even the once sacrosanct
Kaibab squirrel is now hunted, and the only totally protected squirrel
is the federally endangered Graham Mountain spruce squirrel.
The tassel-eared or Abert's squirrel is the major game species, however,
and the numbers of tree squirrel hunters and harvest depends largely on
the vagaries of tassel-eared squirrel numbers. Questionnaire data collected
since the early 1960s show that the peak number of hunters was in 1986
when 21,402 squirrel hunters took to the field and bagged nearly 165,000
squirrels for a hunter success of 2.5 squirrels per day. Since 1990 the
number of hunters has generally averaged between 12,000 and 18,000 a year
with the average annual harvest being between 50,000 and 100,000 tree squirrels.
Habitat
