What shape is the pupil of squirrels?
Here's a good photo of a squirrel eye showing the pupil being round.  



Source: https://www.treklens.com/gallery/photo390926.htm

Also, these acrylic squirrel eyes for taxidermy show a round pupil.   



Source: https://www.mckenziesp.com/Squirrel-Eyes-Acrylic-C3837.aspx