To determine the age of a squirrel, observe its appearance and behavior. Newborn babies are pink and hairless until they are 3 days old. Their eyes are closed, with no slits visible. Their ears are flat to the head. At 1 to 2 weeks old, a baby squirrel begins to exhibit slightly grayish fur. The eyes appear as actual slits, and the ears are positioned slightly away from the head.
A squirrel that is 3 to 4 weeks old has thicker fur from head to tail. The eye slits now show signs of opening. Lower incisor teeth are begin to emerge.
At 5 weeks old, squirrels have a full furry coat and fully opened eyes. Upper incisor teeth appear and the baby begins to nibble at solid foods. It is crawling now, and more active. At 6 to 7 weeks the squirrel’s tail takes on a furrier look and is thicker and fuller. The squirrel is walking and playing at this age and can eat solids but still requires its mother’s milk.
When a squirrel is 8 to 10 weeks old, it is very active and can climb, jump and hang from branches. It looks very much like a smaller version of its adult counterpart. The baby should be able to crack and shell nuts at this age and shows the first signs of weaning.
At 11 to 18 weeks, the baby squirrel looks like fully grown adult. Rehabbed babies are usually released back into the wild at the age of 18 weeks, depending on their overall health.