XXXXXXXX,
Congratulations on the new puppy! You'll have a fun holiday season.
His hair loss pattern is pretty classic for flea allergies. Meaning a flea bites them, and they are allergic to their saliva and they start to lose their hair on their back legs and back end.
However, your guy is a little young for that and since you're in Alabama, chances are its pretty cold for fleas. So I am not convinced that is your only option. Young dogs do not have very good immune systems and are more likely to get things that grown up dogs usually don't get. For instance this could be a skin mite or ringworm.
There are mites and type of ringworm that you can get from your dog. So I would suggest heading into your local vet and having them scrape his skin to look for mites and look for ringworm.
Mites tend to be very itchy and dogs often have crusting around the eyes and ears. Ringworm tends to have flaky or dry skin but does not always itch them. If you notice your self itching or having round, lesions on your skin, you need to head to your doctor or dermatologist as well. But first head on in with your little man before you charge up on your insurance.
Good luck and again, please enjoy your holiday with your new little buddy!
Dr Michael
Dog Veterinarian
4+ years additional specialty training after vet school