(DRAFT) - Taxonomy
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
TAXONOMY
NAME - SQUIRREL, RED, MOUNT GRAHAM
OTHER COMMON NAMES - SQUIRREL, RED, MOUNT GRAHAM;SQUIRREL, RED, MT. GRAHAM; SQUIRREL, RED; SQUIRREL, SPRUCE; SQUIRREL, SPRUCE, GRAHAM MOUNTAIN; SQUIRREL, SPRUCE, MOUNT GRAHAM; SQUIRREL, SPRUCE, MT. GRAHAM; CHICKAREE, MOUNT GRAHAM;CHICKAREE and MT. GRAHAM
ELEMENT CODE -
CATEGORY - Mammals
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - MAMMALIA,
ORDER AND SUBORDER - RODENTIA,
FAMILY AND SUBFAMILY - SCIURIDAE,
GENUS AND SUBGENUS - TAMIASCIURUS,
SPECIES AND SSP - HUDSONICUS, GRAHAMENSIS
SCIENTIFIC NAME - TAMIASCIURUS HUDSONICUS GRAHAMENSIS
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Mount Graham Red Squirrel
Tamiasciurus hudsonicus grahamensis (Kelson, 1951)
KINGDOM: Animal GROUP: Mammal
PHYLUM: Chordata CLASS: Mammalia
ORDER: Rodentia FAMILY: Sciuridae
Tamiasciurus hudsonicus grahamensis is a small, grayish-brown
tree squirrel tinged with rusty or yellowish along the back. In
summer the white underparts are separated from the darker colored
sides by a dark lateral line that disappears in winter. The ears may
be slightly tufted in winter. The fluffy tail, is both shorter and
darker than the body (01,02). The skull, in comparison to that of
other tree squirrels, is small and rounded with the postorbital
processes present. Cheek teeth (P1/1, M3/3) total 16 and are low
crowned with the crowns tuberculate and capped with enamel. Although
the third upper premolar is absent, one root of the deciduous fourth
upper premolar may remain and give the appearance of a small, peglike
third premolar (02). Whether or not males and females of
T.h. grahamensis differ morphologically is unknown, however,
Hoffmeister (02) studying T.h. mogollonensis from the Kaibab Plateau
and the White Mountains of Arizona, did not consider two barely
Taxonomy - 1 (DRAFT) - Taxonomy
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
significant statistical differences he found to be sufficient to
justify separating the sexes in tabulations of measurements.
Named and described as a subspecies in 1894 (03), the red
squirrel of the Pinaleno Mountains has consistently been considered by
all workers a distinct, if not strongly differentiated subspecies.
Likewise, the subspecific name, grahamensis has been applied by all
workers to the red squirrels of the Pinalenos even while both the
generic and specific designations were changing with improved
understanding of tree squirrel relationships in western North America.
Initially described on the basis of three specimens in comparison with
specimens from the San Francisco and White Mountains of central and
eastern Arizona, T.h. grahamensis was described as yellower on the
upper body parts, conspicuously grayer along the lower surface of the
tail, and showing a more prominent median band of yellowish ochraceous
along the tail (03). These animals were assigned the name
Sciurus hudsonicus grahamensis by J.A. Allen in 1894 (03).
Subsequently, as more specimens of this group became available for
study species and genera were revised, nomenclature changed, and the
following synonyms were applied: Tamiasciurus fremonti grahamensis,
Hatfield, 1942 (05); and Tamiasciurus hudsonicus grahamensis, Kelson,
1951 (05).
Findley (06), studying geographic variation in T. hudsonicus in
Arizona and New Mexico concluded that southwestern red squirrels "show
little geographic variation other than in color and size." In
general, he found red squirrels were smallest in northern New Mexico
and largest among the southernmost populations in Arizona and New
Mexico and that revision of nomenclatorial arrangements was not called
for (06). The Pinaleno population was not included in this analysis
as it was represented by only one specimen; however, he did note that
its color pattern fit that of the subspecific description by Allen in
1894 (06). Hoffmeister (02) examined red squirrels in Arizona and
concluded that there were slight differences in size and that those
red squirrels from the Pinaleno Mountains were the smallest. He
disagreed with Allen and Findley that color was geographically
variable, but rather, stated that color variation occurred randomly
and was great locally (02). Hoffmeister (02) noted that although his
sample of 10 specimens from the Pinalenos was small, recognition of a
distinct subspecies was not well substantiated by his data.
Other common names used for this subspecies and the species in
general include: red squirrel, spruce squirrel, Mount Graham spruce
squirrel, Graham Mountain spruce squirrel and Mount Graham chickaree
(including the abbreviation of Mt. for Mount).
The type specimen, collected in 1894 on the summit of the
Pinaleno Mountains was deposited in the American Museum of Natural
History, New York, New York. At least 24 additional specimens were
deposited in five institutions including the American Museum; U.S.
National Museum of Natural History (including U.S. Biological Survey
Collection), Washington, D.C.; University of California Museum of
Vertebrate Zoology, Berkeley, California; University of Illinois
Museum of Natural History, Urbana, Illinois; University of Arizona
Mammal Collection, Tucson, Arizona (01).
Taxonomy - 2 (DRAFT) - Status
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
STATUS
Coded Status
E: Federal Endangered
Commercial/consumption
Game (Consumptive Recreational)
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Mount Graham red squirrel (Tamiasciurus hudsonicus
grahamensis) has been designated as Endangered pursuant to the
Endangered Species Act of 1973 (50 CFR 17.11; P.L. 93-205,
87 Stat. 884; 16 U.S.C. 1531-1540), as amended. The subspecies has
this status wherever found including the State of Arizona. Critical
Habitat was proposed in Graham County, Arizona concurrent with the
proposed listing of the subspecies. The U.S. Fish and Wildlife
Service has until May 21, 1988 to make a final decision in designating
Critical Habitat.
This subspecies is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild animal
(alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation, or foreign law; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
USFS -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public lands under their control. Also responsible
for management/recovery on Forest Service lands. The
Forest Service is responsible for integrating
management, protection, and conservation of Federally
listed species into the Forest Planning process
(36 CFR 219.19 and 219.20).
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
Status - 1 (DRAFT) - Status
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
STATE: Arizona
DESIGNATED STATUS: Group 4, AZ List of Threatened Wildlife
ADMINISTRATIVE AGENCY: Arizona Game and Fish Department
STATE STATUTE: Ariz. Rev. Stat., Section 17-231(B)7.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
None.
ECONOMIC STATUSES:
This subspecies has been a legal game animal in the past;
relative subspecies are still hunted in Arizona and other western
states. This subspecies also has a value related to society's need to
retain it as a living subspecies in the wild.
82/12/30:47 FR 58454/58460 - Notice of review
85/09/18:50 FR 37958/37967 - Revised notice of review
86/05/21:51 FR 18630/18634 - Proposed rule
86/07/31:51 FR 17429/ - Announcement of public meeting
87/06/03:52 FR 20994/20999 - Final rule, Endangered
Status - 2 HABITAT ASSOCIATIONS
HABITAT - TERRESTRIAL
TERRESTRIAL
SOCIETY OF AMERICAN FORESTRY TYPES
SAF TYPE STAGE CLOSURE
Douglas-fir-western hemlock mature tree
Douglas-fir-western hemlock Old Growth
Western white pine mature tree
Western white pine Old Growth
mature tree
Old Growth
LAND USE -
Evergreen Forest Land
COMMENTS ON HABITAT ASSOCIATIONS -
Tamiasciurus hudsonicus grahamensis is limited to and almost
totally dependent on mature and old-growth coniferous forests at the
highest elevations of the Pinaleno Mountains (01,07). Mature and old-
growth forests with closed canopies and almost no ground vegetation
provide mushrooms and conifer seeds for food, protective cover, travel
routes, and most importantly, cool, moist sites on the forest floor
for placement of middens, and storage and maintenance of cones in an
upopened condition. Engelmanm spruce (Picea engelmannii), corkbark
fir (Abies lasiocarpa var. arizonica), and Douglas fir (Pseudotsuga
menziesii) either in pure or mixed stands appear to be the most
preferred tree species (01,07). Most such stands are found above
about 9500 ft with some, on northerly and easterly facing slopes or in
otherwise protected areas, extending lower down to about 9000 ft, and
occasionally as low as 8000 ft (01,07). The Mount Graham red squirrel
also uses stands which include mixtures of other species such as white
fir (Abies concolor), southwestern white pine (Pinus strobiformis),
and to a lesser extent ponderosa pine (Pinus ponderosa) (01,07). In
the Pinalenos pure ponderosa pine stands seldom contain red squirrels
and are not known to contain middens or cone storage sites; probably
because the range is at a more southern latitude and such stands are
generally more open and at lower elevations where the forest floor is
warmer and drier than in stands of other species at higher elevations
(01,07). Usually, the higher the percentage of mature spruce,
corkbark fir, or Douglas fir in a mixed stand the more it is used by
red squirrels in the Pinalenos (01,07). Most mixed stands (with
various combinations and percentages of the three preferred species)
occupied by red squirrels occur between about 9000 ft and 10,000 ft
(01,07). Although they may forage in coniferous forests growing on
slopes, red squirrels do not appear to maintain middens on the steeper
ones; few are found on 40 percent slopes and none on 60 percent or
greater (07).
Snags, dead trees, and down logs of all species are important to
red squirrels also. A midden usually has a large tree, often a dead
one, or a snag located near its center (01,07). Such standing dead
trees or snags often have cavities that provide sites for nests or
refuges from predators or bad weather. If the cavity is large it is
sometimes used as an extension of the midden and cones may be stored
there (25,35). The importance of these uses is not known. Down logs
appear to be very important in their association with middens (01,07).
Most middens have at least a few down logs imbedded in or lying across
them (01,07,11,12). If they have cavities they are often used as
Habitat Associations - 1 part of the midden with cones being stored in the cavity (19,35). In
addition to being cool, moist places to store cones they may also
provide protected places to strip cones for their seeds.
Additionally, when snow is several feet deep the undersides of logs
provide natural tunnels for movement from one part of the midden to
another and to nearby upright trees (19,35).
Timber harvest in stands used by red squirrels is thought to
degrade those stands for red squirrels by several means including the
opening-up of both the canopy and the forest itself (01,07). This
results in drying and warming of the forest floor following increased
exposure to sunlight and drying winds (11,21). Further, species and
age composition may be altered, thus likely reducing cone crops of
tree species preferred by red squirrels. Finally, spruce-fir stands
cut at lower elevations on south facing slopes may not be able to
regenerate themselves due to difficulty of germination and
establishment in dried out soils (37,38).
Habitat Associations - 2 (DRAFT) - Food Habits
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
HERBIVORE
LIFESTAGE FOOD FOOD PART
General Myxomycophyta
General Deciduous Shrubs-Leaves/Twigs
General Tree-Bark/Cambium
General Coniferae
General Arthropods
General Aves
General Evergreen Trees-Flowers/Fruit/Seed
Food Habits - 1 (DRAFT) - Environment Associations
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Terrestrial Features: Downed logs
G Snags: Unknown
G Tree Cavities: Unknown
Environment Associations - 1 (DRAFT) - Life History
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
Relatively little is known of the food habits of Tamiasciurus
hudsonicus grahamensis, thus they must be inferred from what is known
about the food habits of the red squirrel in general. Throughout the
year the reproductive parts of coniferous tree species provide most of
the food items that sustain the red squirrel. Seeds of conifer cones
are the single most important food item for Tamiasciurus hudsonicus
(01,07,09). Seeds retained in unopened cones stored in middens
provide the primary sources of energy and nutrients during most of the
six or more months of the year when snow several feet deep covers the
ground and few other foods are available. From late spring through
early fall, however, seeds from cones are also important although less
so than when snow covers the ground. During the period before the
cones are ripe enough to open and disperse their seeds the red
squirrel cuts them and allows them to fall to the ground. Some are
stripped and their seeds eaten on the spot while others are taken from
the forest floor and carried to a midden for storage. Conifers
provide still other food items including terminal buds which can be
important in winter and spring, male cones which can be important for
a short time in spring, and the inner bark or cambium (09).
Fungi including false truffles and various mushrooms may be
available in spring and summer, depending on environmental conditions,
and some may be stored for late use (09). False truffles (Rhizopogon
ssp.) appear to be located by smell (09). Red squirrels also take
more animal material than other tree squirrels; Smith explains this as
fulfilling salt or calcium requirements (09). Such items have
included bird nestlings, insects, and egg shells; however, bone seems
to be taken more often than other animal materials (09).
Only a general outline of the food habits of the Mount Graham red
squirrel is known (01,07). It has been observed using cones of
conifers including Engelmann spruce, corkbark fir, Douglas fir, white
fir, and Southwestern white pine (01,19,35). Dried mushrooms have
been found on middens and are thought to have been cut by red
squirrels and then placed on the midden for later use (19,35). A few
bones have also been found on middens (19).
HOME RANGE/TERRITORY:
Tamiasciurus hudsonicus grahamensis is a solitary, vigorously
territorial tree squirrel (09). A primary midden with nearby,
satellite middens is the focal point of the territory of each
individual red squirrel (09). Whenever another red squirrel, and
sometimes other animals including tassel-eared squirrels and people,
approaches a midden its owner becomes agitated and may voice a typical
red squirrel ratchet-like territorial chatter. This chatter does not
seen to be elicited as easily as with other subspecies of red squirrel
(01,07). Red squirrels in the Pinalenos have been observed to chase
tassel-eared squirrels (Sciurus aberti) away from the red squirrels's
midden (01). During mid-spring, territoriality relaxes and non-owner
red squirrels have been seen several times digging in a midden with
the owner watching from nearby (35). Home range size, seasonal or
other changes in size, boundary definition, or other details relating
Life History - 1 (DRAFT) - Life History
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
to home range and territory for this squirrel are unknown.
PERIODICITY:
Tamiasciurus hudsonicus grahamensis is a diurnal animal and is
not known to be active at night (01). It is active year-around, and
does not hibernate (01).
MIGRATION PATTERNS:
Tamiasciurus hudsonicus grahamensis is not known to be migratory.
Information to date indicates that all habitat in the Pinaleno
Mountains that can support resident red squirrels is occupied and thus
there is nowhere to migrate to or from (01,07). It is possible that
during the fall some dispersing young-of-the-year move into marginal
or unsuitable habitat in an attempt to establish residency (19). Such
attempts are probably unsuccessful over the long run due to inadequate
microclimatic conditions for midden establishment on the forest floor
or other interferences, including possible interactions with tassel-
eared squirrels (19), with the gathering and storing of sufficient
cones to sustain the squirrel through the winter.
COVER/SHELTER REQUIREMENTS:
The conifer forests where Tamiasciurus hudsonicus grahamensis
lives provide it with such necessities as travel routes, protection,
nest sites, food items, and midden sites (01,21). Although only the
general outline of this squirrel's requirements have been worked out,
some specifics have been investigated for a related subspecies,
T.h. mogollonesis in mixed conifer habitats between 8,400 ft and
9,000 ft in the White Mountains of eastern Arizona (11,21). These
habitats consist of various combinations of 7 conifer tree species:
Engelmann spruce (Picea engelmannii), blue spruce (P. pungens),
corkbark fir (Abies lasiocarpa var. arizonica), Douglas fir
(Pseudotsuga menziesii), white fir (A. concolor), southwestern white
pine (Pinus strobiformis), and ponderosa pine (Pinus ponderosa) which
makes up 60 percent or less of the total volume of the stands; and one
deciduous tree species, quaking aspen (Populus tremuloides) (21).
This variable mixed-conifer habitat and these tree species, excepting
blue spruce, are also found on the Pinaleno Mountains (36). A food
source (conifer cones) and a place (the midden) to store the cones for
use during the winter, when snow covers the ground and few other food
items are available, are primary features of red squirrel existence
(09,10,11,14,21). Thus, habitats providing the best conditions for a
sufficient supply of cones and for the establishment and maintenance
of middens are critical to the coninued existence and recovery of red
squirrels in the Pinaleno Mountains. Accordingly, Vahle and Patton
(21), after investigating 141 middens or cache sites in eastern
Arizona concluded: "The best site conditions are provided by
undisturbed groups of trees containing one or more dominant
cone-bearers 18 inches DBH (diameter breast high) or greater.
Douglas fir is the most common species of large diameter in these
sites. Trees in the grouping often are closely spaced in an area of
one tenth arce or less. Their average DBH ranges from 12 to 14
inches, representing a basal area of 150-200 square feet per acre.
Centered within these sites are one or more large structures (live
Life History - 2 (DRAFT) - Life History
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
trees, snags, or downed logs) 20 inches DBH or greater, which are the
nuclei of the food caches. These structures are also used either as
a food source, feeding perch, or nest site." Further, average
density of all tree species on cache sites was 210 trees/ac and nests
were usually 15-30 ft above ground in trees averaging 15 ft from the
center of the cache and 14 inches DBH (11,12). In the Pinalenos
similar results were obtained from an examination of 13 middens
between 9,000 ft and 10,700 ft: trees of 18 inches DBH or greater
grew on 77 percent of the cache sites; species of large diameter were
most often Engelmann spruce (38 percent of the cache sites) and
Douglas fir (38 percent) and each was more than twice as common as
the next most common, corkbark fir (15 percent); average DBH of all
trees was 13 inches; an average basal area was 377 square feet
per acre (possibly over-estimated due to the small size of sample
plots); average density of all tree species at cache sites was 311
trees per acre, and no data was taken on nest trees (01).
REPRODUCTIVE SITE REQUIREMENTS:
Because so little is known about the requirements of Tamiasciurus
hudsonicus grahamensis we must infer its requirements from information
about red squirrels from elsewhere in North America. Breeding
activities take place in the trees within the territory of the female
(09). Parturition occurs in a nest located either in the upper
branches or in a cavity of a tree near the primary midden (08,10,11).
About 12 inches in diameter, the globe-shaped nest is usually about
15-30 ft above the ground (11). An external nest is constructed of
twigs and leaves and lined with grass (11). A cavity nest is lined
mostly with grass (10). The young are nursed and raised in the nest
where they remain for 6 to 7 weeks before venturing out (14). For the
5 or 6 weeks, between the time the young squirrels begin exploring
outside the nest to the time they are weaned and leave to establish
their own territories, they share the mother's territory (14).
REPRODUCTIVE CHARACTERISTICS:
Although little is known of reproductive characteristics of red
squirrels in the Pinaleno Mountains they are probably similar to red
squirrels elsewhere. Red squirrels reach sexual maturity after their
first winter (12) and few live more than 7 years (13). Spring
breeding begins as early as January (14) or as late as April (09,15).
In Arizona, pregnant red squirrels have been found in April in the
Pinalenos (01) and elsewhere in the State (08). When the female goes
into estrus she relaxes her territorial behavior and allows males to
enter her territory unchallenged for her single day of receptivity
(09). Following that day during which she leads the males in a '
'mating chase' through the trees, mating with one or more dominant
individuals, she is no longer receptive and resumes her territorial
behavior (09). Fewer yearling females breed (24 to 88 percent) than
adult females (15,16). Breeding adult females vary from 32 percent
to 100 percent (09,15,16,17,24). Red squirrels in coniferous forests
in western North America are usually reported to have 1 litter per
year (12,17). Two litters per year have most often been reported for
red squirrels in mixed or deciduous forest especially in eastern
North America. In Quebec, Lair (12) reported 50 percent of breeding
Life History - 3 (DRAFT) - Life History
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
females produced a second litter in one year and 29 percent in the
following year. Hoffmeister (02) has suggested the possibility of 2
litters per year in the Pinalenos and Brown (08) reported females with
embryos in July and lactating up to August 6 in other parts of
Arizona. Red squirrels are not reported to form pairs. Gestation is
35 days (24). Mean litter size of red squirrels varies from 3.3 in
Colorado (17) to 5.4 in Quebec (24). It may be lower in the Pinalenos
where two females each contained three embryos (02) and one female was
observed with three young (19). Rausch and Reeder (15) reported
overall reproductive rates varied annually from 30 to 60 percent in
all places where they have been studied (07).
PARENTAL CARE:
Because so little is known about this subject for Tamiasciurus
hudsonicus grahamensis information for red squirrels from other places
is summarized. Red squirrels are born blind and hairless and remain
in the nest where they are nursed by the mother until they are 6 to 8
weeks old and begin their first explorations outside the nest (09,14).
They are weaned at 7 to 11 weeks and are independent enough to leave
and begin establishing their own territories at 9 to 12 weeks (09,14).
The mother is the only parent that plays any role in caring for the
young (09,14). Other than nursing the young and keeping other
squirrels away the mother provides little care (09). She does not
bring them solid food nor does she do anything more than the most
incidental teaching (09,14). Smith (09), however, reports that all
four families he observed were moved from one nest to another by the
mother who either carried each one or tried to lead the young, and if
failing in that, carried each individually to the new nest (09). Once
the young leave or are excluded from the mother's territory the mother
treats them like any other red squirrel, if not even more aggressively
(09).
POPULATION BIOLOGY:
Little is known about short term fluctuation or long term trends
in numbers of Tamiasciurus hudsonicus grahamensis. It has been
suggested that red squirrels in the Pinalenos were more abundant
during the latter part of the 19th and early part of the 20th century
than since the mid-20th (01,20). Because of the dependence of red
squirrels on closed canopy and old-growth forests (11,21) it is
probably that over the last hundred years cutting and opening up of
such forests at progressively higher elevations in the Pinaleno
Mountains has altered and reduced forest habitat and, thereby, red
squirrel numbers (01). Other factors including fire and windfall have
likely also contributed to a reduction in the quality of red squirrel
habitat (01). It has further been suggested that competition from
tassel-eared squirrels, introduced in the Pinalenos during the 1940s,
have contributed to red squirrel declines in mixed conifer forests
where the ranges of the two species overlap (02,20,22,23). Still
another factor that may have influenced population declines is cone
crop variation (01,07). In other parts of red squirrel range cone
crop failures have resulted in population declines of 60 to 80 percent
(07). Predation and disease are not known to have been limiting
factors on red squirrel populations elsewhere (01). Mortality,
Life History - 4 (DRAFT) - Life History
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
probably related to over-wintering (15), is greatest among juveniles
and is about 67 percent; most of the young that do reach adulthood do
not make it past 2 or 3 years (10,13,24) and very few make it past 7
years (13). High mortality has been reported for both females and
young between parturition and weaning (15). Survival rates vary by
age, season, and sex. Annual survival rates over all age groups range
from 33 to 59 percent (15,24). Juvenile rates were lower (31 to 49
percent) than those for adults (48-74 percent) (15,2). Reported sex
ratios (female:male) vary from 1:1 (or ratios not statistically
different) (15,24) to ratios favoring males (e.g. 23:25 (12) and
100:188 (14) for juveniles, and from 100:102 (14) to 43:57 (15) for
adults). Rausch and Reeder (15), however, report seasonal changes
including a near 1:1 ratio shortly after the breeding season, more
males after the late summer early fall period during which all adult
female mortality occurred, high adult male mortality during the
breeding season, and replacement of lost males by near-equal numbers
of males and females, followed once again by a near 1:1 ratio shortly
after the breeding season. Recovery potential is probably moderate
and probably depends on curtailing piecemeal loss and degradation of
habitat combined with habitat restoration including both artificial
reforestation and natural forest regeneration. Population density
objectives have not yet been established. Reproductive rates were
reported to vary annually from 30 to 60 percent in all places where
they have been studied (07,15).
SPECIES INTERRELATIONSHIPS:
No direct casual relationships between Tamiasciurus hudsonicus
grahamensis and any species of parasite or predator are known. One
possible relationship may exist with an introduced tree squirrel,
the tassel-eared squirrel (Sciurus aberti). A total of 69
tassel-eared squirrels were live-trapped at Fort Valley U.S. Forest
Service Experimental Station near Flagstaff and were released on
"Mt. Graham" in 1941 (49 squirrels) and 1943 (20 squirrels) (25).
These squirrels have established themselves and can now be found in
all conifer forest throughout the Pinaleno Mountains (02,08). No
competitive relationship has yet been demonstrated.
OTHER LIFE HISTORY DESCRIPTORS:
The regulation of reproductive and other demographic
characteristics of red squirrels has been the subject of studies in
many parts of the red squirrels range. Most studies conclude that
reproductive characteristics of red squirrels are strongly influenced
if not regulated by the quantity and quality of food supply or weather
conditions (15), or some combination of the two (12). Size of cone
crops is highly variable, unpredictable, and specific to the tree
species. Irregularity in cone crop is the norm (28). Engelmann
spruce produce some seed almost every year and generally bear good to
bumper crops every 2-5 years (29). Corkbark fir, the southern variety
of subalpine fir, is not as good a seed producer as Engelmann spruce
and is considered to be a poor producer in general. Cone crop
failures are more common than good crop years (29). Douglas fir
bear good cone crops every 2 to 11 years (30). Jones (31) rated mixed
conifer species by seed productivity as follows: blue spruce >
Life History - 5 (DRAFT) - Life History
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
Douglas fir > Engelmann spruce > corkbark fir or white fir > ponderosa
pine or white pine. His rating was based on investigations mostly in
the White Mountains of Arizona. With the exception of blue spruce,
these species are prominent on Mt. Graham.
Although the many factors that influence cone crops are
incompletely understood (30) some factors are associated with good or
bad crop years. High and low temperature, excessive or deficient
moisture and other weather conditions can have different effects on
cone crops depending on when in the tree's reproductive cycle they
occur. "Bumper crops may occur when endogenous and favorable
environmental conditions are in phase" (32).
Accessibility, a second important aspect of seed availability,
can be extended when cones remain closed beyond the usual time of
shedding and on into winter. Opening of cones and shedding of seed is
irregular and discontinuous and is affected by humidity and tree
location. A cold, wet fall can also inhibit cone shedding.
A third factor influencing the availability of seeds can be
competition. On Mt. Graham, other species utilizing seeds in closed
cones are jays, crossbills, and tassel-eared squirrels. The extent of
this competition is unknown. However, C.C. Smith (07) suggests that
tassel-eared squirrels cannot utilize spruce and fir cones because the
buds and seeds are too small. Further, the tassel-eared squirrels
prefer Douglas fir and ponderosa pine seed. Those animals, primarily
chipmunks and deer mice, that utilize shed seed found on the ground do
not compete with red squirrels who obtain seeds exclusively from
closed cones. Conifer seed availability influences: length of
breeding season; number of adults with 2 litters; number of adults and
number of yearling females that breed; mean litter size at birth and
weaning; longevity of adults born in year under consideration;
eruptive dispersals; diet switches (26,28,33). Miller (34) believes
food availability will also influence pre-implantation losses.
Halvorson (pers. comm. in 28,33) reported that 92 percent of adult
females and 88 percent of yearlings had litters in a good seed year
and 85 percent of adult females and 51 percent of yearlings had
litters in a poor-to-moderate seed year. In his 12 year study (on an
island), there was poor correlation between seasonal densities and
cone crops of the same and previous years. He felt caching,
competition and predation created "noise" in the system.
Conifer seeds have several characteristics that make them
especially good food resources for red squirrels (28). These include
each species being uniformly sized, clumped in a cone that is easily
seen and relatively accessible, periodically abundant, and, not only
easily stored, but durable when stored. One of the more important
features of conifer seeds is their high energy content. The endosperm
and embryo of the seed (the seed coat being discarded) have caloric
values about 1000-2000 cal/gm (dry weight) higher than most angiosperm
seeds (09,28). The source of high caloric values in conifer seeds is
the high lipid (fat) content compared to protein and carbohydrate
content of the seed. Conveniently, lipids are also quite durable
when stored in cool sites such as red squirrel middens (28).
C.C. Smith has presented evidence showing that territories of red
squirrels contain food resources providing sufficient energy to meet
the squirrels minimum annual energy requirements. He found that on
Life History - 6 (DRAFT) - Life History
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
those territories which did not meet an individual squirrels energy
requirements, the squirrel did not remain over the winter. Further,
Halvorson (28) and M.C. Smith (26) have suggested that in years of
heavy cone crops, red squirrels may store more than enough cones to
last them through the winter immediately following the harvest.
Conifers are usually physiologically incapable of producing two years
of heavy cone crops in a row (30), so it would be advantageous to the
squirrel to store more cones than it needs.
As summarized by Gurnell (33), for tree squirrels in general,
long-term densities of red squirrels are believed to be importantly
influenced by the density and species composition of mature trees.
They provide the key seedfood and three-dimensional structure within
which red squirrels forage, escape from predators, and use suitable
midden and den sites. Food supply appears further related to
densities of red squirrels, as suggested by Rusch and Reeder (15), in
that they found spring populations to be stable from year to year
regardless of whether cone crops were poor or medium-heavy. This
implied to them that squirrel mean densities were "... determined by
food supply in years of poor cone mast..." and that territoriality
regulated those densities by "...excluding nonterritorial squirrels
from winter cone supplies." Consequently, given the decreases of seed
bearing coniferous trees over the past 100 years, future decreases in
seed bearing or potentially seed bearing conifers can only further
depress the capacity of the Pinaleno Range to support red squirrels
and thereby decrease the likelihood of their continued existence (07).
Life History - 7 (DRAFT) - Management Practices
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Maintaining undisturbed/undeveloped areas
Beneficial Reforestation
Beneficial Restricting Timber Harvest
Beneficial Maintaining Later Stages of Succession
Beneficial Controlling/Restricting Noncommercial Harvest
Adverse Sport Hunting/Fishing
Existing Sport Hunting/Fishing
Adverse Climate Alteration
Existing Climate Alteration
Adverse
Existing
Adverse Food Supply Reduction
Existing Food Supply Reduction
Adverse Inherent Reproductive Characteristics
Existing Inherent Reproductive Characteristics
Adverse Low Gene Pool
Existing Low Gene Pool
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Recreational development
Existing Recreational development
Adverse Highway/Railroads
Existing Highway/Railroads
Adverse Soil compaction by heavy equipment in mine areas
Existing Soil compaction by heavy equipment in mine areas
Adverse Competition
Existing Competition
Adverse Exotic/Feral/Introducted Species
Existing Exotic/Feral/Introducted Species
Adverse Vegetation Composition Changes
Existing Vegetation Composition Changes
Adverse Fire
Existing Fire
Adverse Forest Alteration
Existing Forest Alteration
Adverse Harvesting
Existing Harvesting
COMMENTS ON MANAGEMENT PRACTICES -
Mount Graham red squirrels (Tamiasciurus hudsonicus
grahamensis) are the southernmost red squirrel (T. hudsonicus)
population in North America. They occur only at the highest
elevations of the Pinaleno Mountains where they are dependent on and
are an integral component of the subalpine spruce-fir community; it is
also the southernmost representative of its kind in North America
(01). This community (including the red squirrel) has been isolated
geographically, ecologically, and genetically for thousands of years
since, at least, the Wisconsin glaciation of the Pleistocene (01).
Management Practices - 1 (DRAFT) - Management Practices
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
Long-term geologic and climatic processes, through isolation and
restriction of habitat, and concomitantly reduced population size,
have put the Mount Graham red squirrel in an inherently vulnerable
situation. Such vulnerability is the result of a relatively small
population occupying a restricted habitat area within a single
mountain range, the entirety of which is subject to regional and
localized environmental fluctuations (e.g., drought, late snow melt,
cone crop (failure). Furthermore, because of isolation, there are no
potential sources of recolonizing individuals to contribute to
population recovery when severe reductions in numbers occur (01).
Thus, even what are considered normal population fluctuations
elsewhere may well pose a significant hazard and potential for
weakening of genetic viability for the Mount Graham red squirrel.
Mean litter size of red squirrels varies from 3.3 in Colorado (17) to
5.4 in Quebec (24). It may be lower in the Pinalenos where two
females each contained three embryos (02) and one female was observed
with three young (19). Rausch and Reeder (15) reported overall
reproductive rates varied annually from 30 to 60 percent in all
places where they have been studied (07). In spite of its
vulnerability this endemic red squirrel survived in the Pinalenos
Mountains for several thousand years (01). During the last hundred
years, however, both natural (e.g., fire, windfall) and human-related
(e.g., timber harvest, road and recreational construction, and heavy
equipment (used rural development)) events have further restricted
habitat, thereby increasing the red squirrel's inherent vulnerability
(01).
This subspecies has been a legal game animal in the past;
related subspecies are still hunted in Arizona and other western
states. It has further been suggested that competition from
tassel-eared squirrels, introduced in the Pinalenos during the 1940s,
have contributed to red squirrel declines in mixed conifer forests
where the ranges of the two species overlap (02,20,22,23).
Several examples of red squirrel declines from elsewhere in North
America illustrate the extent to which red squirrel populations can be
affected by natural and human-related events. Winter red squirrel
numbers in a white spruce forest in the interior of Alaska decreased
by 67 percent after the second year of cone crop failures (26). Over
a 10-year period in the same general area, Wolff and Zasada (27)
reported densities up to 82 percent lower following years of cone crop
failure. Also, in the same kind of forest in the same area, Wolff
and Zasada (27) reported average decreases in red squirrel midden
densities of 66 percent in 3 forest units subjected to shelterwood
harvest and of 100 percent in 3 clear cut forest units. Density in
uncut forest around the cut units decreased by 17 percent. This
decline was "at least partially related to vacated middens in or close
to road rights-of-ways or log decks" (27). Density in an uncut forest
of the same kind 3 km from the cut units increased by 14 percent. In
a Douglas-fir dominated mixed-conifer forest in eastern Arizona,
Vahle (11) reported midden densities on level sites to be 35 percent
lower on cutover than on uncut areas (07).
Timber harvest in stands used by red squirrels is thought to
degrade those stands for red squirrels by several means including the
opening-up of both the canopy and the forest itself (01,07). This
Management Practices - 2 (DRAFT) - Management Practices
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
results in drying and warming the forest floor following increased
exposure to sunlight and drying winds (11,21). Further, tree species
and timber age-class composition may be altered, thus likely reducing
cone crops of tree species preferred by red squirrels. Finally,
spruce-fir stands cut at lower elevations on south facing slopes may
not be able to regenerate themselves due to difficulty of germination
and establishment in dried out soils (37,38).
UNAPPROVED PLAN:
There is no recovery plan for the Mount Graham red squirrel. A draft
plan is scheduled for fiscal year 1988.
This is a recently listed species. Recommendations made in a
1985 status report (01) will likely form the basis of a recovery
effort. That report recommends maintaining and enhancing present
populations and habitats (mature and old growth coniferous forests)
by:
1) restricting timber harvesting on northwest to east facing
slopes in spruce-alpine fir (SF) or Douglas fir-white fir
(DW) forests,
2) prohibiting habitat altering activities (i.e., development,
road construction, etc.) above about 2980 m and in all SF
forests below 2980 m,
3) decreasing timber harvest in DW below 2980 m to a minimum
and requiring that basal areas be retained at 45 square
meters per ha (200 square ft/acre) or greater,
4) using group selection harvest system to maintain multi-
storied character of forests other than ponderosa pine, and
5) allowing lightning fires to burn themselves out whenever
possible to reduce undergrowth and enhance foraging
opportunities.
Biological investigations should continue and include:
1) refining and increasing the accuracy of population survey
estimates in all habitats, including cut-over areas, to
determine population trends,
2) initiating base-line population surveys in DW to determine
if red squirrels re-occupy that habitat as it grows up
following past timber harvesting,
3) set up of permanent population transects,
4) mapping vegetation by association, density, elevation,
slope, etc., using Landsat imagery,
5) continuing studies of red squirrel habitat characteristics,
6) initiating studies of behavioral interactions and resource
partitioning between tassel-eared squirrels and red
squirrels in the Pinalenos Moutains,
7) monitoring cone crops and preceding weather conditions to
learn relationship to red squirrel populations, and
8) initiating life history, food habits, ecology, and
population dynamics studies of the Mount Graham red
Management Practices - 3 (DRAFT) - Management Practices
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
squirrel to gain understanding of adaptive, reproductive,
dispersal and resource utilization strategies.
This subspecies has been a legal game animal in the past;
related subspecies are still hunted in Arizona and other western
states. Recovery potential is probably moderate and probably depends
on curtailing piecemeal loss and degradation of habitat combined with
habitat restoration including both artificial reforestation and
natural forest regeneration.
Public awareness, appreciation, and support for preservation of
the Mount Graham red squirrel must be encouraged.
Management Practices - 4 (DRAFT) - References
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Spicer, R.B., J.C. deVos, Jr., and R.L. Glinski. 1985. Status of
the Mount Graham red squirrel, Tamiasciurus hudsonicus grahamensis
(Allen), of southeastern Arizona. Unpubl. Rept. by Ariz. Game and
Fish Dept. to U.S. Fish and Wildl. Serv., Albuquerque, NM.
02 Hoffmeister, D.F. 1986. Mammals of Arizona. Univ. Ariz. Press,
Tucson.
03 Allen, J.A. 1894. Descriptions of ten new North American mammals,
and remarks on others. Bull. Amer. Mus. Nat. Hist. 6:320-321.
04 Allen, J.A. 1898. Revision of the chickarees or North American
squirrels (Tamiasciurus). Bull. Amer. Mus. Nat. Hist. 10:249-298.
05 Cockrum, E.L. 1960. The recent mammals of Arizona: Their
taxonomy and distribution. Univ. of Ariz. Press, Tucson.
06 Findley, J.S. 1961. Geographic variation in New Mexican
chickarees. Jour. Mammal. 42(3):313l-322.
07 Allen, L.S., R. Wadleigh, P. Warshall, and R.B. Spicer. 1987.
Mount Graham red squirrel: A biological assessment of impacts,
proposed Mt. Graham Astrophysical Project, Coronado National
Forest. U.S. Dept. of Agri. Forest Service, Arixona.
08 Brown, D.E. 1984. Arizona's tree squirrels. Ariz. Game and Fish
Dept., Phoenix.
09 Smith, C.C. 1968. The adaptive nature of social organization in
the genus of tree squirrels, Tamiasciurus. Ecol. Monog.
38(1):31-63.
10 Hatt, R.T. 1929. The red squirrel: Its life history and habits
with special reference to the Adirondacks of New York and the
Harvard Forest. Roosevelt Wildl. Ann. 2(1):7-146.
11 Vahle, J.R. 1978. Red squirrel use of southwestern mixed
coniferous habitat. Unpubl. M.S. thesis. Ariz. State Univ.,
Tempe.
12 Lair, H. 1985. Mating seasons and fertility of red squirrels in
southern Quebec. Can. J. Zool. 63:2323-2327.
13 Halvorson, C.H., and R.M. Engeman. 1983. Survival analysis for a
red squirrel population. J. Mammal. 64(2):332-336.
14 Layne, J.N. 1954. The biology of the red squirrel Tamiasciurus
hudsonicus loquax (Bangs), in central New York. Ecol. Monog.
24(3):227-267.
15 Rusch, D.A., and W.G. Reeder. 1978. Population ecology of Aberta
red squirrels. Ecol. 59(2):400-420.
16 Wood, T.J. 1967. Ecology and population dynamics of the red
squirrel (Tamiasciurus hudsonicus) in Wood Buffalo National Park.
Unpubl. thesis. Univ. Saskatchewan, Saskatoon.
17 Dollbeer, R.A. 1973. Reproduction in the red squirrel
(Tamiasciurus hudsonicus) in Colorado. J. Mammal. 54(2):536-540.
18 Ferron, J., and J. Prescott. 1977. Gestation, litter size, and
number of litters of the red squirrel (Tamiasciurus hudsonicus) in
Quebec. Can. Field Nat. 91:83-84.
19 Warshall, P. 1986. Pers. comm. Office of Arid Lands Studies.
Tucson, AZ.
20 Hoffmeister, D.F. 1956. Mammals of the Graham (Pinaleno)
References - 1 (DRAFT) - References
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Species Id ESIS052002
Date 14 MAR 96
Mountains, Arizona. Amer. Midl. Nat. 55(2):257-288.
21 Vahle, J.R., and D.R. Patton. 1983. Red squirrel cover
requirements in Arizona mixed conifer forests. J. Forestry
81(1):14-15, 22.
22 Gehlbach, F.R. 1981. Mountain islands and desert seas: A natural
history of the U.S.-Mexican borderlands. Texas A&M Univ. Press,
College Station.
23 Minckley, W.L. 1968. Possible extirpation of the spruce squirrel
from the Pinaleno (Graham) Mountains, southcentral Arizona. J.
Ariz. Acad. Sci. 5:110.
24 Kemp, G.A., and L.B. Keith. 1970. Dynamics and regulation of red
squirrel (Tamiasciurus hudsonicus) populations. Ecol.
51(5):763-779.
25 Swank, W. No date. Brief summary of Arizona Federal Aid in
Wildlife Restoration projects to December 31, 1953. Unpubl. Rept.
in Ariz. Game and Fish Dept. files., Phoenix.
26 Smith, M.C. 1968. Red squirrel responses to spruce cone failure
in interior Alaska. J. Wildl. Mgmt. 32(2):305-317.
27 Wolff, J.O., and J.C. Zasada. 1975. Red squirrels response to
clear cut and shelterwood systems in interior Alaska. U.S. Dept.
of Agric. For. Serv. Pac. Northwest Forest and Range Exper. Sta.
Res.
28 Halvorson, C.H. 1986. Influence of vertebrates on conifer seed
production. IN: Proceedings - conifer tree seed in the Inland
Mountain West symposium; 1985 August 5-6, Missoula, MT. USDA. For.
Serv., Gen. Tech. Rept. INT 203. Intermtn. Res. Sta. Ogden, UT.
29 Alexander, R.R., R.C. Shearer, and W.D. Sheppard. 1984. Silvical
characteristics of subalpine fir. USDA. For. Serv. Gen. Tech.
Rept. RM-115. Rky. Mtn. For. and Range Exper. Sta., Fort Collins,
CO.
30 Edwards, D.G.W. 1986. Cone prediction, collection, and
processing. IN: Proceeding - conifer tree seed in the Inland
Mountain West symposium; 1985 August 5a-6; Missoula, MT. USDA.
For. Serv. Gen. Tech. Rept. INT 203. Intermtn. Res. Sta. Ogden,
UT.
31 Jones, J.R. 1974. Silviculture of southwestern mixed conifers and
aspen: The status of our knowledge. USDA. For. Serv. Res. Paper
RM-122. Rky. Mtn. For. and Range Exper. Sta., Fort Collins, CO.
32 Owens, J.N. 1986. Cone and seed biology. IN: Proceedings -
conifer tree seed in the Inland Mountain West symposium; 1985
August 5-6; Missoula, MT. USDA. For. Serv. Gen. Tech. Rept. INT
203. Intermtn. Res. Sta. Ogden, UT.
33 Gurnell, J. 1983. Squirrel numbers and the abundance of tree
seeds. Mammal. Rev. 13:133-148.
34 Millar, J.S. 1970. The breeding season and reproductive cycle of
the western red squirrel. Can. J. Zool. 48:471-473.
35 Spicer, R.B. 1987. Pers. obs. Ariz. Game and Fish Dept.,
Phoenix.
36 Kearney, T.H., R.H. Peebles, et al. 1960. Arizona Flora. 2nd Ed.
with supplement. Univ. Calif. Press. Berkeley, CA.
37 Alexander, R.R., and W.D. Shepperd. 1984. Silvical
characteristics of Engelmann spruce. USDA Forest Serv. Gen. Tech.
Rept. RM-114. Rky. Mtn. For. and Range Exper. Sta., Fort Collins,
References - 2 (DRAFT) - References
Species SQUIRREL, RED, MOUNT GRAHAM
Species Id ESIS052002
Date 14 MAR 96
CO. 38 pp.
38 Alexander, R.R., R.C. Shearer, and W.D. Shepperd. 1984. Silvical
characteristics of subalpine fir. USDA For. Serv. Gen. Tech. Rept.
RM-115. Rky. Mtn. For. and Range Exper. Sta. Fort Collins, CO.
29 pp.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Hall, E.R. 1981. The mammals of North America. Vol. I. John
Wiley and Sons, New York. 600 pp.
02 Allen, L.S., R. Waliegh, P. Warshall, and R.B. Spicer. 1987.
Mount Graham red squirrel: A biological assessment of impacts,
proposed Mt. Graham Astrophysical Project Coronado National Forest.
U.S. Dept. of Agri., Forest Service.
03 Yahle, J.R. 1986. Pers. comm. Apache-Sitgreaves National Forest
Springerville Ranger Dist., Springerville, AZ.
04 Spicer, R.B., R.C. deVos, Jr., and R.L. Glinski. 1985. Status of
the Mount Graham red squirrel, Tamiaciurus hudsonicus grahamensis
(Allen), of southeastern Arizona. Upubl. Rept. by Ariz. Game and
Fish Dept. to U.S. Fish and Wildl. Serv., Albuquerque, NM.
05 Warshall, P. 1986. Pers. comm. Office of Arid Land Studies.
Tucson, AZ.
06 Spicer, R.B. 1987. Pers. knowl. Ariz. Game and Fish Dept.,
Phoenix.
References - 3