All pets are considered real property. I do not know if there is any formal method to get the dog. You could call the local SPCA and see if they know anything. Othrewise, write to your son, tell him that unless he can flind a home within 60 days for the dog you will consilder it abandoned proprety [if he lived with the dog where he had to pay rent to you, then you could follow the normal procedures for abandoned tenant property]. Since the dog is over 15 months old, it is really too old to place with a pet store or be able to sell it to anyone, so if you tell your son that you are treatling it as propety that was abandoned by its owner and it has no value so does not need to be auctioned off and that you are doing him a favor to keep the dog [you might want to lie and say you are sending the dog to a relative so when he gets out he does not come to your house to try to get the dog back]. If when he gets out of jail he tries to sue you, a judge wlill probably declide in your favor and certainly could find that the dog has little or no value and award only that amount to him. Since it is considered personal and not real property, specific performance is not required so all he can get is money and not the return of the dog.

not spell checked.

My initial opinion is that dogs are not real property they are chattels and a bailement was created for which you may request a fee. If the fee is not paid then you may obtain title. However for an opinion that may be relied upon, then some legal research needs to be done. I could do so for a nominal fee. Contact me directly.