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.