eastern chipmunk
Refers specifically to the species Tamias striatus, a small striped ground squirrel native to eastern North America.
I spotted an eastern chipmunk in the park.
シマリス is the general term for chipmunks (genus Tamias), while とうぶしまりす specifies the eastern chipmunk species.
Compound of 東部 (tōbu, 'eastern') + 縞栗鼠 (shimarisu, 'chipmunk'), literally 'eastern chipmunk'. The reading follows standard on'yomi for 東部 and kun'yomi for 縞栗鼠.