The most common wildlife you'll encounter during your Yosemite trip are members of the rodent family, which includes squirrels, chipmunks, gophers, and mice. Of Yosemite's four species of squirrels, the Western gray squirrel is the easiest to recognize, with its big, bushy tail. Another tree dweller is the pine cone eating Douglas squirrel. The park's golden-mantled ground squirrel has a distinct stripe on its back, similar to a chipmunk's. The California ground squirrel, which has speckled brown fur, lives in underground burrows.
And then there are those endearing yellow-bellied marmots. Inquisitive and usually unafraid of humans, the park's biggest rodents inhabit Yosemite's high country, usually at elevations above 6500 feet. There marmots take refuge from predators such as eagles and mountain lions in the safety of granite talus slopes by burrowing under piles of rock. Marmots often live in small colonies, so if you see one, you should stop hiking, remain quiet, and wait to see some more! When a marmot senses a predator nearby, it will warn others by emitting a shrill whistle.
As with all of Yosemite's wildlife, never feed a marmot or a squirrel, no matter how cute they may look or how much they beg. Handouts just teach wild animals to behave more aggressively and also affects their diet (most human food isn't good for them).