What is the puppy doing when Merlin snaps at her? Our older dog couldn't cope with Meadow wanting her to be a loving mum, and as puppies don't understand doggy signals until they are about 20 weeks old, she didn't pick up Jenna's message to stay away. Puppies usually squeal before they are hurt, did Merlin back off at all when she did? You might find it helpful to keep them separated for periods of time, in the early days and only put them together under very close supervision for short periods. Lots of treats and goodies in this together time might help Merlin to see the puppy in a positive light! If they can be separated by a baby gate or puppy pen that is good because they can still see one another. Merlin also needs to get used to the puppy's smell as it will be strange to him, grooming them with the same brush can help with this. It took 2 or 3 months before we could leave Jenna and Meadow together for short periods in the same room without supervision. Meadow is now 7 months, can understand all of Jenna's signals, and ignores them at her peril! Jenna has never hurt her despite the growls and snaps, and will play happily for much of the time, when Meadow really pushes it J will put her in her place. Things will get easier as the puppy grows. One of the advantages for Merlin not becoming a mum/ dad substitute is that the puppy will make her primary bond with you rather than the other dog.