Help a new Surprise Hamster Mom!

[Ehales]

So recently a tenant of ours moved out. And much to our surprise, upon cleaning the apartment we found a very angry, very lonely Russian Dwarf Hamster. Now we are animal fanatics with twenty years between in the veterinary industry but we are hamster virgins! We immediately knew he was a new family member but man, he does not feel the same affection for us! He “growls” or “barks” when we open his cage. He seems healthy and we are happy to simply keep him alive with food and water but my heart breaks that he will never know cuddling or affection. Does anyone have tips on “taming” him? We don’t need a show hamster or a “toy” but I don’t would love to help him relax at least. Thank you!