Белка Аберта: описание и распространение

Species of rodent

Abert's squirrel or the tassel eared squirrel (Sciurus aberti) is a tree squirrel in the genus Sciurus native to the southern Rocky Mountains from the United States to the northern Sierra Madre Occidental of Mexico, with concentrations found in Arizona, New Mexico, and southwestern Colorado. It is closely associated with, and largely confined to, mature ponderosa pine forests. It is named in honor of the American naturalist John James Abert; nine subspecies are recognised. It is recognizable by its tufted ears, gray color, pale underparts and rufous patch on the lower back. The squirrel feeds on the seeds and cones of the Mexican pinyon and the ponderosa pine when they are available, but will also take fungi, buds, bark, and carrion. Breeding normally occurs in summer, with a spherical nest being built high in the canopy.

Abert's squirrel is named after Colonel John James Abert, an American naturalist and military officer who headed the Corps of Topographical Engineers and organized the effort to map the American West in the 19th century.

The currently accepted scientific name for Abert's squirrel is Sciurus aberti Woodhouse, 1853. Woodhouse had initially described the species as Sciurus dorsalis in 1852, but this name turned out to be preoccupied by Sciurus dorsalis Gray, 1849 (now a subspecies of variegated squirrel S. variegatoides), and thus the present species was renamed. There are nine recognized subspecies, including the Kaibab squirrel (S. a. kaibabensis), formerly recognized as a separate species (S. kaibabensis). The nine subspecies are listed in the Distribution section.

Abert's squirrels are 46–58 cm long with a tail of 19–25 cm. They are easily recognized by their long ear tufts, which extend up from each ear 2–3 cm. This gives this species a striking similarity to the Eurasian red squirrel, aside from its differing dark coloration. Abert's squirrels vary in color across their range. Most populations have a gray coat with a reddish stripe down the back, a dark stripe along the side, and a white underbelly. Some populations lack the reddish back stripe, instead having fully gray upperparts. A fully black color morph is present in the foothills of the Rocky Mountains in Colorado. Abert's squirrels on Arizona's Kaibab Plateau, commonly known as Kaibab squirrels, have black underparts and a striking white tail.

Abert's squirrel is confined to the Colorado Plateau and the southern Rocky Mountains of Colorado, Utah, Arizona, and New Mexico; its range extends south in the Sierra Madre Occidental to Chihuahua and Durango in Mexico. Abert's squirrels transplanted to the Graham and Santa Catalina Mountains of Arizona have established stable populations. Mellott and Choate reported Abert's squirrels present in the Spanish Peaks State Wildlife Area, 43 mile (69 km) southeast of the previously known Abert's squirrel range. The distribution of Abert's squirrel subspecies in the Southwest is coincident with the disjunct ponderosa pine forests. S. a. aberti Woodhouse, 1853 – northern Arizona
S. a. barberi Allen, 1904 – northwestern Chihuahua
S. a. chuscensis Goldman, 1931 – New Mexico Arizona border area
S. a. durangi Thomas, 1893 – Durango
S. a. ferreus True, 1900 – Rocky Mountains, central Colorado
S. a. kaibabensis Merriam, 1904 – Kaibab Plateau, northern Arizona
S. a. mimus Merriam, 1904 – New Mexico Colorado border area
S. a. navajo Durrant and Kelson, 1947 – southeastern Utah
S. a. phaeurus Allen, 1904 – northwestern and southwestern Durango and southwesternmost Chihuahua

Abert's squirrels in the U. S. make almost exclusive use of ponderosa pine for cover, nesting, and food. Optimum Abert's squirrel habitat is composed of all aged ponderosa pine stands with trees in even aged groups, densities of 168 to 250 trees per acre (496–618/ha), and 150 to 200 square feet per acre (34.4–45.3 sq m/ha) basal area. In optimum habitat average diameter of ponderosa pines is , with Gambel oaks in the 11.8 to 14 inch (30–36 cm) diameter at breast height (d. b. h.) range. Optimum habitat has some ponderosa pine over d. b. h., which are the best cone producers. Larson and Schubert report that ponderosa pine d. b. h. produced an average of 446 cones per tree per crop. Trees less than d. b. h. produced fewer than 100 cones per crop. In central Arizona, Abert's squirrel summer home ranges averaged and ranged from Ranges were somewhat smaller in winter. Patton reported the ranges of three squirrels as 10, 30, and 60 acres (4.0, 12.2, and 24.4 ha) in Arizona. Hall reported the home range of an adult female as
In Colorado, Ramey found a density of 83 squirrels per square mile (30/km2) in spring 1970 but only 33 squirrels per square mile (12/km2) in spring 1971.

Abert's squirrel is closely associated with, and nearly confined to cool, dry interior ponderosa pine forests. Abert's squirrels occur in pure ponderosa pine stands or stands with associated Gambel oak (Quercus gambelii), Colorado pinyon (Pinus edulis), junipers (Juniperus spp. ), quaking aspen (Populus tremuloides), and Douglas fir (Pseudotsuga menziesii). In Durango and Chihuahua the squirrels are said to inhabit high altitude ponderosa pine stands.

Abert's squirrels are diurnal. They are often active for a short time before sunrise and active for periods throughout the day, and they usually return to shelter before sunset. The most apparent causes of Abert's squirrel mortality are food shortage and injuries (such as broken teeth) that lead to mortality. Eight litters were composed of two to five young each. Young Abert's squirrels are born naked, with ears and eyes closed. At 2 weeks thin short hair is noticeable and the ears are slightly open. By 6 weeks the pelage has developed and the eyes are open. By 7 weeks the tail has broadened and is held over the back, ears are held erect. Mushrooms and bark have been added to the diet at this time. Captive young first venture from the nest at about 7 weeks, but do not venture to the ground until about 9 weeks. By 10 weeks Abert's squirrels are weaned. Mature size is reached by 15 to 16 weeks. Nests are built in trees occurring as part of a grouping of trees with interlocking crowns. Nests are roughly spherical and a small platform often extends beyond the bowl edge on one side. The nests are used year round by most Abert's squirrels for nightly shelter, although females often move the litter to a larger nest when the young are 3 to 6 weeks old. Ponderosa pines produce large cone crops every 3 to 4 years; cones are virtually absent about 1 year out of 4. Abert's squirrels begin eating immature seed shortly after cone development begins in late May. Seeds are eaten through the summer as the cones mature. Seeds from up to 75 cones may be eaten per day per squirrel during the months when seeds form the squirrels' major food. Seeds are disseminated from cones in October and November. Abert's squirrels continue to consume seed from late maturing cones and collect single seeds from the ground. The succulent inner bark of twigs is eaten all year, but most heavily in winter. Needle clusters are clipped from the twigs, the outer bark is removed, the inner bark is consumed, and then the twig is discarded. In winter a single squirrel consumes about 45 twigs per day. Fleshy fungi consumed include members of the following genera: Agaricus, Amanita, Boletus, Hypholoma, Lepiota, Lycopedon, Russula and Tuber. Mushrooms poisonous to humans are consumed by Abert's squirrels without difficulty, including destroying angels (A. bisporigera and A. ocreata) and a species of Russula. suggested that northern goshawks (Accipiter gentilis) may take enough Abert's squirrels to regulate Abert's squirrel populations. Hawks (Accipitridae and Falconidae) prey on Abert's squirrels in central Arizona, but even though other potential predators are present, i. e., gray fox (Urocyon cinereoargenteus), bobcat (Lynx rufus), coyote (Canis latrans), there is no evidence that they prey on Abert's squirrels.