As developed as Yosemite Valley may seem with its hotels, stores, restaurants, and museums, you are in the wild here and are likely to see wildlife. Bear warnings abound, especially in the campgrounds, where bears are known to frequent the dumpsters. I heard loud noises in the campground in the middle of the night when I had to use the bathroom. However, I saw no sign of bear anywhere. You probably would have more luck spotting one in the backcountry, which is probably the only place in the park you might encounter a mountain lion, the park's other large mammal predator. Check with a ranger for safety information about encounters with these animals.
You will very probably spy mule deer--so-called for their large ears--especially in the meadows of the valley. I've also had them tramp through my campsite and cross in front of my car on Tioga Road. Coyotes are also somewhat common. Though I didn't see one, some other visitors I spoke with spotted a coyote in the meadows along the Merced River. I did have an elusive fox scamper in front of me on the John Muir Trail. Squirrels and chipmunks abound in the park. Don't confuse the two: a ground squirrel's body may be striped like a chipmunk's, but it lacks the facial markings. Despite their cute appearance, the Park Service highly discourages feeding these critters; their bites and scratches can be quite painful. Still, you'll see many tourists luring them with food to get a close-up video. At night, you can spot bats fluttering around lighted areas as they swoop down on insects.
Bird life is rich and varied here. A visitor favorite is the Stellar's jay, commonly seen around the Visitor Center and campgrounds. You'll recognize it by it's blue body, black crest and distinctive cry. Ravens seem to show up at the campgrounds just in time for breakfast every morning. On the top of the valley rim near Yosemite point, I saw a number of hawks, circling, soaring and swooping. Scores of other avian species inhabit the park from wading blue herons to woodpeckers to owls. A stop at the Visitor Center or a ranger talk will better acquaint you with Yosemite's wildlife.