Fox Squirrel vs California Ground Squirrel
Fox Squirrel on left
California Ground Squirrel on right

These are both 4-5 week old male squirrels. The Fox squirrel is of course larger than the CGS but the CGS is more mature. The Fox in this photo weighs 115 gms and the CGS weighs 55 gms so the Fox is twice as heavy. Adults Fox squirrels weight 1.5-2 lbs. Adults CGS weigh .6 to 1.2 lbs. The Fox squirrel lives in trees and the ground squirrel lives in burrows under ground. They both have black claws. The Fox squirrel has beige to red around the eyes, a rounder nose, lighter colored rounder looking ears, their penis is located higher up on the body, they have darker paw pads, darker skin/fur around the mouth and their bellies are white blonde to dark rust red. The CGS has whitish beige around the eyes, a pointer nose which they can twitch, darker pointier ears, pinkish paw pads, pink skin/fur around the mouth and their bellies are beige and black. 

Fox squirrel is above, CGS is below. The Fox squirrel is hunched up in this photo. The Fox squirrel's tail is almost as long as it's body and it has a grey/beige ticked coat on its back. When the Fox squirrel gets older it's tail will be much bushier than the CGS. The CGS just develops more quickly than the Fox squirrel so his tail is bushier at this stage. The CGS has a patterned coat with a white spotted stole across his shoulders which will become more pronounced as he gets older. Baby squirrels have a lot more brown in their coat, perhaps to better camouflage them against the dirt.

Legally California Ground Squirrels are considered agricultural pests and are controlled by the Department of Agriculture whereas Fox squirrels are game mammals controlled by Fish & Game. Not all rehabbers take care of CGS. Please ask them before taking them to their facility. Also ask them if they just euthanize all CGS, some do. If they won't take care of them, find another rehabber. It is legal to rehab them, you just must release them exactly where they were found because they cannot be relocated without a permit. Squirrel Rescue takes in all squirrels. If you can't find a rehabber in your area who will take them, email me for help