Editing Kaibab squirrel (section)

==Ecology==
[[Image:kaibab-squirrel.jpg|thumb|200px|right|A Kaibab squirrel.]]
The Kaibab squirrel lives in ponderosa pine forests,<ref>{{cite web|url=http://www.jacoblake.com/kaibab_squirrel.html|title=Famous Kaibab White-Tailed Squirrel|access-date=October 26, 2013|archive-url=https://web.archive.org/web/20130615055509/http://www.jacoblake.com/kaibab_squirrel.html|archive-date=June 15, 2013|url-status=dead}}</ref> 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]] relationship. The squirrel eats [[acorn]]s, [[fruit]], and [[fungus|fungi]] (especially an underground truffle),<ref name=sierraclub/> 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.<ref>{{cite journal|author=Woodhouse, S.W.|year=1853|title=Description of a new species of Sciurus|publisher=[[Proceedings of the Academy of Natural Sciences of Philadelphia]]|volume=6|issue=110}}</ref> 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'').<ref>[http://www.wild-facts.com/2012/wild-fact-212-the-grand-relationship-kaibab-squirrel/ Kaibab squirrel]</ref>

The Kaibab squirrel is an example of [[evolution]] occurring through [[Geographical isolation|geographic isolation]], but not because of the canyon.<ref name=sierraclub/> Compared to the Kaibab squirrel, 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. However, modern Kaibab squirrels are descended from populations of Abert's squirrels that dispersed into the Grand Canyon area following the last Ice Age.<ref>{{cite web|url=http://www.sbs.utexas.edu/levin/bio213/evolution/speciation.html|title=Macroevolution: Species Formation|access-date=October 26, 2013}}</ref>

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.