When I model characters for animation I look at reference material. Here is a video that shows exactly how a squirrel moves around through an obstacle course.

Squirrel:
https://www.youtube.com/watch?v=nWU0bfo-bSY

I you are going to animate him and have him move like a real squirrel. You have to model him standing on all fours. Here is a video demostrating how to animate a quadruped. It's a horse but the same movement of the back leg applies to the squirrel, it just extends the legs further than the horse. Hope this helps!

https://www.youtube.com/watch?v=glknkt0fDsI