The Kaibab squirrel (''Sciurus aberti kaibabensis'') is a tassel-eared

squirrel Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...

that lives in the

Kaibab Plateau The Kaibab Plateau is a plateau almost entirely in Coconino County, Arizona (but extending slightly north into Kane County, Utah) in the Southwestern United States. The high plain is also known as the Buckskin Mountain, Buckskin Plateau, and K ...

in the

Southwest United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...

, in an area of . The squirrel's habitat is confined entirely to the

ponderosa pine ''Pinus ponderosa'', commonly known as the ponderosa pine, bull pine, blackjack pine, western yellow-pine, or filipinus pine is a very large pine tree species of variable habitat native to mountainous regions of western North America. It is the ...

forests of the North Rim of

Grand Canyon National Park Grand Canyon National Park, located in northwestern Arizona, is the 15th site in the United States to have been named as a national park. The park's central feature is the Grand Canyon, a gorge of the Colorado River, which is often consider ...

and the northern section of

Kaibab National Forest At 1.6 million acres (650,000 ha) the Kaibab National Forest borders both the north and south rims of the Grand Canyon, in north-central Arizona. It is divided into three major sections: the ''North Kaibab Ranger District'' (offices in Fredonia ...

around the town of

Jacob Lake, Arizona Jacob Lake is a small unincorporated community on the Kaibab Plateau in Coconino County, Arizona, United States, at the junction of U.S. Route 89A and State Route 67. Named after the Mormon explorer Jacob Hamblin, the town is known as the "G ...

. This squirrel is not found anywhere else in the world. In 1965, of Kaibab squirrel habitat within Grand Canyon National Park and Kaibab National Forest were declared the Kaibab Squirrel

National Natural Landmark The National Natural Landmarks (NNL) Program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only national natural areas program that identifies and recognizes the best ...

Description

Kaibab squirrels usually have a black belly (which is sometimes gray), white tail, tufted ears and chestnut brown head. The tufts on the ears grow longer with age and may extend above the ears in the winter, and may not be visible in the summer.

Ecology

The Kaibab squirrel lives in ponderosa pine forests, where it builds its nest out of twigs and pine needles. Kaibab squirrels, ponderosa pines, and the fungi which grow in the vicinity of the ponderosas exist in a

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

relationship. The squirrel eats

acorn The acorn, or oaknut, is the nut of the oaks and their close relatives (genera ''Quercus'' and '' Lithocarpus'', in the family Fagaceae). It usually contains one seed (occasionally two seeds), enclosed in a tough, leathery shell, and borne ...

fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...

, and

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

(especially an underground truffle), as well as the seeds, bark, and twigs of the trees where it makes its home. The Kaibab squirrel's most significant source of food is the seeds found within ponderosa pine cones. Young squirrels are born between April and August. In the past the Kaibab squirrel was given species status (''Sciurus kaibabensis'') but today is considered a subspecies of the

Abert's squirrel 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 fo ...

, (''Sciurus aberti''). The Kaibab squirrel is an example of

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

occurring through

geographic isolation Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

, but not because of the canyon. Compared to the Kaibab squirrel, the Abert's squirrel, with its several

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

, has a much broader distribution and is found on the South Rim of the Grand Canyon. The difference between North Rim and South Rim Abert's squirrels has given rise to the commonly held but incorrect assumption that the canyon itself acted as a barrier preventing gene flow between the two populations. However, modern Kaibab squirrels are descended from populations of Abert's squirrels that dispersed into the Grand Canyon area following the last Ice Age. As the climate warmed, ponderosa pine stands and the Abert's squirrels living there were limited to areas of high elevation like the Kaibab Plateau. These isolated populations eventually became modern Kaibab squirrels and, as the climate cooled again and ponderosa pines once again grew at lower elevations, other Abert's squirrel subspecies returned to the Grand Canyon area, filling in their former niches on the South Rim.

References

* "Evolutionary Genetics and Phylogeography of Tassel-Eared Squirrels (Sciurus aberti)" Trip Lamb, Thomas R. Jones and Peter J. Wettstein ''Journal of Mammalogy'' Vol. 78, No. 1 (Feb., 1997), pp. 117–133

External links

Photographs of Kaibab squirrels in the wild

Kaibab squirrel on YouTube
{{Taxonbar, from=Q1721379 Sciurus Squirrel, Kaibab Endemic fauna of Arizona Natural history of the Grand Canyon Taxa named by Clinton Hart Merriam Mammals described in 1904