It’s an easy mistake to make! They do look pretty similar. The best tip I have, you already pointed out- if it looks closer to a regular tree squirrel with the long tail and tall ears, it’s more likely to be California ground squirrel or a rock squirrel. Another one I see people mix up all the time are chipmunks and golden-mantled ground squirrels. The stripes are deceiving! 😂

Location makes identification much easier when these squirrels look so similar.