A female Round-tailed ground squirrel (Spermophilus tereticaudus).

We were leaving our hike through Sabino Canyon and had stopped to
look at a Thrasher pair feeding their young in a cholla cactus
nest. We were surprised to see this ground squirrel at our feet,
standing on its hind legs literally two feet from my youngest
daughter. Normally these squirrels keep a healthy distance and
retreat into their burrows whenever humans get too close. This
one was very bold and readily took a pistachio nut meat that was
offered. She seemed most attracted to my youngest daughter and
sat and ate two pistachios while we watched from about 3 feet.