Originally only one squirrel species inhabited the Ponderosa pine forest around the rim of the Grand Canyon, the Abert squirrels. About 10,000 years ago when Arizona’s Grand Canyonwas formed, the squirrels were separated into two species - the Abert squirrels, who inhabit the south rim; and the Kaibab squirrels, who inhabit the north rim. One population of squirrels had become two separate populations that could no longer reproduce. These squirrels are an excellent example of
allopatric speciation, where geographical isolation leads to the formation of two distinct species from a common ancestor. The Abert and Kaibab squirrels have evolved different physical and behavioral traits in order to adapt to their respective environments and are considered to be distinct species today.
