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One day is not nearly enough time to decide. I also have a dog that takes a bit longer to integrate with other dogs, but given time at his pace is very doable. I recommend keeping them separate for a while longer and see if his body language softens as the days pass. I would not let them interact too close right now seeing as Kota has already nipped twice at the pup and you wouldn't want your pup to be come fearful of other dogs so soon.

How does he react when the pup is put in a crate or behind a gate?

 

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Don't force Kota into anything, just do a rotation until he settles with the new changes and see if he will eventually approach her through a barrier. I do recommend taking them for their daily walks together with your boyfriend, just have them on opposite sides with no contact. Take a different elevator if needed too. Baby steps.

 

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Shot, I forgot about the puppy shots. Kota could still come along for her putty breaks. or is she going on puppy pads indoors?

I personally would leave Kota with you guys. The more he's around, the faster he will get used to her being there. Just my opinion though.