The Kaibab squirrel (''Sciurus aberti kaibabensis'') is a tassel-eared squirrel that lives in the Kaibab Plateau in the Southwest United States, 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 t ...

forests of the North Rim of

Grand Canyon National Park Grand Canyon National Park is a List of national parks of the United States, national park of the United States located in northwestern Arizona, the 15th site to have been named as a national park. The park's central feature is the Grand Canyo ...

and the northern section of

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

around the town of Jacob Lake, Arizona. 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 e ...

Description

Kaibab squirrels usually have a black belly (which is sometimes gray), white tail, tufted ears and chestnut brown back. 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 (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

relationship. The squirrel eats

acorn The acorn is the nut (fruit), nut of the oaks and their close relatives (genera ''Quercus'', ''Notholithocarpus'' and ''Lithocarpus'', in the family Fagaceae). It usually contains a seedling surrounded by two cotyledons (seedling leaves), en ...

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

, and

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

(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 it is now considered a subspecies of the Abert's squirrel (''Sciurus aberti''). The Kaibab squirrel is an example of

evolution Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

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

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

, 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
{{Authority control Sciurus Endemic rodents of the United States Endemic fauna of Arizona Natural history of the Grand Canyon Taxa named by Clinton Hart Merriam Mammals described in 1904