Scared Puppy

Question
My husband and I recently purchased a puppy who is 13 weeks old. Its a male Chihuahua/Terrier mix. When I picked him up from the breeder he did seem very timed, when I reached down to pick him up he lowered his head to the floor keeping his back end up. He has never once barked and only whimpered/cried twice in the last three days. Both times he did this he was left a lone and it last for maybe 10 seconds.

The problem we are having is after 3 days he still will "hide" in the back of his cage. Shake when I go in to his cage in the morning to greet him and put out his food dish. We will usually just put him in the middle of the floor on a rug and then slowly let him get use to us. We will  move our hand towards him so he can smell us and become familiar with us etc. Even at this by the end of the day it doesn't seem to have helped at all. He will still shake if we pick him up or pet him. He does not play at all and will mostly just sit where we put him. I have left him alone for 30mins at a time and when I come back he is still sitting in the same spot I left him.

We do not want to be forceful but at the same time really want him to feel free to walk out of his kennel if he wants to, or follow us out of the room. I am also concerned that he is so afraid of everything. Its seems when he sees me walk into the room he starts shaking.

Any suggestions on  how to get this little guy to bond with us? Thanks in advance!

Answer
This puppy is TOTALLY unsocialized to humans.  THAT BREEDER IS AN ABOMINATION.  The puppy is fortunate to have you.

It's been only three days.  DO NOTHING to force this dog to interact with you (as you have been) and give him EVERY opportunity to (slowly) come out of his fear state.  He is at the end, or close to the end, of a natural fear state in the development of the domestic dog (8 to 10 weeks of age, give or take) and has had a horrible beginning in that "breeder's" home.  It will take him time to learn to trust you.  You have approximately TWO MONTHS to socialize this dog to other humans (very slowly) and other places (outdoors).  This puppy is apparently (by nature) very submissive and possibly by breeding, and is unnaturally fearful; he must slowly but surely come to see other people and places as POSITIVE and rewarding, and this will involve DAILY outings (not now, wait about two weeks) in places that slowly expose him to people, other dogs (only on leash and NO large adult dogs at first).  While doing this, you must CLOSELY observe his body language.  DO NOT attempt to "comfort" him if he appears fearful; instead, walk in a circle, get his attention, and then reward his non-fear state.  It would be best to find a VERY EXPERIENCED positive reinforcement trainer (do your HOMEWORK, be certain the person uses ONLY positive reinforcement and get REFERENCES and CHECK THEM before hiring him/her.)  You're going to need some help so this puppy will gain confidence and lose his fear (as much as possible).  Don't pick up this puppy or pet him on the head or back, those are both extremely dominant behaviors; wait until he is coming toward you.  Offer him tiny treats (something special) when he does approach you (and be sure you reward his confidence, NOT his fear; observe his body posture.)  Of course it's important for the puppy to become accustomed to "restraint" (being picked up, hugged, etc.) and overt affection from humans (being petted.)  But you must do this slowly because right now he is scared stiff (literally.)  Call veterinarians in your area and ask for referral to an EXPERIENCED positive reinforcement trainer.  CALL REFERENCES before bringing this person into your home.  If you don't like something the trainer says, find another one.  Trust your instincts.  A puppy kindergarten would be terrific but only after this puppy begins to come out of his shell, and even then you must be vigilant regarding how many puppies there are, what their ages are (puppies of a more or less similar age only) and how large they are (don't subject this dog to hysterical 50 pound puppies.)

Read about fearful dogs.  Patricia McConnell Ph.D. has a book on this topic.