A 3-4 ft alligator is NOT going to take your leg off, unless you are a pigmy with leprosy .
However an alligator will grow about a foot a year for the first 5 or 6 years and about 5-6 inches every year after that. Then he may have a shot at a adult human leg.
A 3 footer will still bite the sheeooot out of you, and make short work of any small dog or animal.
Great size to throw in somebodys pool or fenced in back yard as a prank though.