A marmot near the Lembert Dome parking lot.
More than 400 species of vertebrates live in Yosemite, as well as thousands species of invertebrates live in Yosemite, according to the National Park Service.  The black bear attracts most notice on account of its size and occasional run-ins with humans.  In 2012 a smaller animal, the deer mouse, came to attention as the vector for the spread of hantavirus to several people who stayed in tent cabins in Curry Village.  Also impacting visitors, mosquitoes can be quite a nuisance depending on the time of the year.  Sometimes one only sees traces of an animal such as footprints in the mud or one only hears the animal as in the examples of bats, owls and frogs in the night.
Link: Animals - Yosemite National Park