13 week old puppies

Question
i have 2 puppies from the same litter they are pitbulls and sometimes they will start crying and biting at their back feet is this normal?

Answer
This doesn't sound right to me a lot of puppies will chew on their hind leg nails or lick their paws, but if they are crying while doing that they should be checked for fleas, ticks, and maybe even an x-ray done on their hips and legs, a doctor would have to watch the way they walk on their hind legs, check the pads of their paws and if nothing apparent they take x-rays and maybe even blood tests to rule things out.  I would take them to a vet if this behavior continues because they are like babies and crying while acting something like biting them selves is the only way they can tell you that something can be wrong. I hope this helped, Sincerely Concerned, Angela