Kaibab Squirrel
Encyclopedia
The Kaibab Squirrel is a tassel-eared squirrel
that lives in the Kaibab Plateau
in the Southwest United States, in an area of 20 by 40 miles (30 by 60 km). The squirrel's habitat is confined entirely to the ponderosa pine
forests of the North Rim of Grand Canyon National Park
and the northern section of Kaibab National Forest
around the town of Jacob Lake, Arizona
. In 1965, 200,000 acres (800 km²) of Kaibab squirrel habitat within Grand Canyon National Park and Kaibab National Forest were declared the Kaibab Squirrel National Natural Landmark
. It is not found anywhere else in the world.
It has a black belly, white tail, and tufted ears. The tufts on the ears grow longer with age and may extend 1 to 2 inches (25 to 50 mm) above the ears in the winter, but may not be visible in the summer.
The Kaibab squirrel lives in the ponderosa pine forests, where it builds its nest out of twigs and pine needles. It eats acorn
s, fruit
, and fungi
, 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.
Kaibab squirrels, ponderosa pines, and the fungi which grow in the vicinity of the ponderosas exist in a symbiotic relationship.
In the past the Kaibab squirrel was given species status (Sciurus kaibabensis) but today is considered a subspecies of the Abert's squirrel
, (Sciurus aberti).
The Kaibab squirrel is an example of evolution
occurring through geographic isolation. The Abert's squirrel, with its several subspecies
, 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, but 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.
Squirrel
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...
that lives in the Kaibab Plateau
Kaibab Plateau
The Kaibab Plateau is located in northern Arizona in the United States. The plateau, part of the larger Colorado Plateau, is bordered on the south by the Grand Canyon and reaches an elevation of 9241 feet above sea level. The plateau is divided between Kaibab National Forest and the "North Rim"...
in the Southwest United States, in an area of 20 by 40 miles (30 by 60 km). The squirrel's habitat is confined entirely to the ponderosa pine
Ponderosa Pine
Pinus ponderosa, commonly known as the Ponderosa Pine, Bull Pine, Blackjack Pine, or Western Yellow Pine, is a widespread and variable pine native to western North America. It was first described by David Douglas in 1826, from eastern Washington near present-day Spokane...
forests of the North Rim of Grand Canyon National Park
Grand Canyon National Park
Grand Canyon National Park is the United States' 15th oldest national park and is located in Arizona. Within the park lies the Grand Canyon, a gorge of the Colorado River, considered to be one of the Wonders of the World. The park covers of unincorporated area in Coconino and Mohave counties.Most...
and the northern section of Kaibab National Forest
Kaibab National Forest
At 1.6 million acres 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 and the South Kaibab and are managed by USDA Forest Service...
around the town of Jacob Lake, Arizona
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...
. In 1965, 200,000 acres (800 km²) of Kaibab squirrel habitat within Grand Canyon National Park and Kaibab National Forest were declared the Kaibab Squirrel National Natural Landmark
National Natural Landmark
The National Natural Landmark program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only natural areas program of national scope that identifies and recognizes the best examples of biological and geological features in...
. It is not found anywhere else in the world.
It has a black belly, white tail, and tufted ears. The tufts on the ears grow longer with age and may extend 1 to 2 inches (25 to 50 mm) above the ears in the winter, but may not be visible in the summer.
The Kaibab squirrel lives in the ponderosa pine forests, where it builds its nest out of twigs and pine needles. It eats acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...
s, fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
, and fungi
Fungus
A fungus is a member of a large 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, Fungi, which is separate from plants, animals, and bacteria...
, 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
Abert's squirrel is a tree squirrel in the genus Sciurus endemic to the Rocky Mountains from United States to Mexico, with concentrations found in Arizona, The Grand Canyon, New Mexico, and southwestern Colorado.-Etymology:The Abert's squirrel is named after Colonel John James Abert, an American...
, (Sciurus aberti).
The Kaibab squirrel is an example of evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
occurring through geographic isolation. The Abert's squirrel, with its several subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, 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, but 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.