Another squirrel question (age).....

[Mr. 16 gauge]

Well, I finally got out Sunday for some squirrel hunting.....put the duck hunting on the back burner and got out the 10/22 and some shells and went to the woods.....I was fortunate enough to take two nice fox squirrel! So I get them home, and never having hunted squirrels before (except as targets of opportunity), I start checking the wild game cook books for recipes.
Now most of the books I have say to "cook an older squirrel longer, as they most likely are tougher".

O.K.....so the question is: how to you tell if you have an 'older' squirrel vs a 'younger' squirrel? I didn't have time to check and see if they had an AARP card before I shot them!