Chipmunks are small squirrel-like rodents mostly native to North America although there is at least one Siberian species.
There are several species of chipmunks, I believe the ones on these pictures are all eastern chipmunks.
Around here there is a large population living inside the Toronto Zoo — not as exhibits but as local wildlife living on the zoo grounds.
Normally chipmunks are very timid individuals, but in the summertime there are lots of very young individuals all over the zoo grounds that are somewhat less wary of humans and let one close enough to take pictures.
Chipmunks hoard food, and if they collect cultivated crops chipmunks can become pests. A chipmunk with its cheek pouches stuffed is the picture of greed. Chipmunks usually carry food items away from the site where they have found them, they normally collect more than they can consume. Because of this in nature chipmunks play an important role in dispersing tree seeds and spores of various species of fungi they they eat, including truffles.
Interesting factoid: Chipmunks, particularly the eastern chipmunk, are sometimes called petit suisse in Canadian French because the striped coat of the chipmunk resembles the uniform of the Papal Swiss Guard.