"Introduce dog in neutral, fenced outdoor space. Avoid crowded area or objects that could cause conflict. If outdoors isn't option, use a spacious indoor area, removing items of potential contention."
"Introduce dogs with a knowledgeable partner. Watch for positive body language and signs of discomfort. If unsure about their interactions, consider involving a professional trainer for guidance."
"Use parallel walking for new dogs with comfortable distance buffer. Switch side to allow scent investigation. Handler should remain calm and loose-leashed. Gradually decrease distance as dogs relax."
"Return to an enclosed area and drop leashes, praising calm interactions. Look for signs of mutual interest, like play bows. Watch for respectful interactions: a balance of action and pauses."
"Reintroduce toys slowly, always supervising. Watch for playful interactions and avoid signs of guarding, such as standing over the toy or snapping."
It can take months before your new dog and resident dog mellow into true comfort with one another, so have patience with them as they get used to siblinghood. Enjoy watching lifelong friendship bloom.