44 Sciurus arizonensisthe remaining months. Arizona gray squirrels nest in dreys
composed of sticks and leaves within the forest canopy, as
well as in cavities within large-diameter trees. Nests are
used to rear the young and as nocturnal rest sites. Nest trees
tend to be in the largest and most interconnected trees at a
site. Communal nesting is known. Male home ranges are
extensive, 113 ha as compared with those of females, which
are 14 ha. Males appear to maximize overlap with females,
particularly during the breeding season. S. arizonensis does
not hibernate. Large raptors, foxes, and bobcats (Lynx rufus)
are probably their major predators. Arizona gray squirrels
are generally silent unless alarmed, when they will bark and
“chuck” from elevated locations. This species is hunted for
food and sport throughout its restricted range. Due to low
human population densities within the range of this spe-
cies, S. arizonensis is of little economic value or detriment.
Habitat loss and degradation due to human development,
timber harvests, and catastrophic wildfi res pose signifi cant
risks to populations. Introductions of Sciurus aberti to por-
tions of the Arizona gray squirrels’ and other species’ ranges
are believed to negatively impact populations of the native
species. S. arizonensis forages extensively on the ground and
in the forest canopy for tree seeds and fl owers, in addition
to fungi. Seeds from the cones of pines (Pinus), Douglas fi r
(Pseudotsuga menziesii), and true fi rs (Abies) are consumed by
removing individual cone scales. Acorns and walnuts are
also eaten when available, along with a variety of other tree
seeds. Arizona gray squirrels will rarely cache seeds by scat-
ter-hoarding in leaf litter and topsoil.
general references: Best and Riedel 1995; D. E. Brown
1984; Cudworth and Koprowski 2010; Hoff meister 1986;
Yensen and Valdés-Alarcón 1999.
Sciurus aureogaster (Cuvier, 1829)
Red-Bellied Squirrel
description: Red-bellied squirrels have a frosted pale to
dark grizzled gray dorsum. Patches of varying sizes and
colors may occur on the nape, shoulders, rump, and sides.
The venter ranges from white through orange to chestnut.
The tail can be a variegated grayish buff when the under-
parts are pale to orange red, or chestnut when the venter
is deep orange. Partial melanism and complete melanism
are common.
size: Both sexes—HB 232–310 mm; T 215–284 mm; Mass
375–680 g.
distribution: This species is found from Nayarit, Guana-
juato, and Nuevo León (México) to central and southwestern
Guatemala. It was introduced to Elliott Key, Florida (USA).geographic variation: Two subspecies are recognized.S. a. aureogaster—eastern México, at elevations below 1525
m, with the exception of a population at Pinal de Amoles
in the mountains of northeastern Querétaro, at an eleva-
tion of about 2440 m. This subspecies has an orange red
to chestnut venter, small inconspicuous postauricular
patches, a less patchy dorsum, and a white tail suff used
with black and sometimes chestnut.
S. a. nigrescens—Pacifi c coastal plain and into the mountains
of central and southeastern México. This form has a
white to chestnut venter, often conspicuous postauricu-
lar patches, a sharp patchy dorsum, and a gray to chest-
nut tail.conservation: IUCN status—least concern. Population
trend—stable.habitat: Red-bellied squirrels inhabit a variety of forests,
especially dry open woodlands, including pine-oak (Pinus,
Quercus) and thorn scrub. It can be found in secondary for-
ests, plantations, and urban areas.natural history: This species is diurnal. Red-bellied
squirrels are adept at moving through closed canopies; how-