When we lived in Inverness with our first two pygmies we took them out for walks along the Caledonian Canal - Q 'what kind of dogs are these ? ' A 'Viking dogs' . The older of the two was very protective of her young niece and if approaching dogs looked aggressive she would rear up in preparation for a Glasgow handshake ! Not even a Staffie phased her. Anyway, I would say if the introductions are done properly then respectful co-habitation should be possible but each species should have a place of safety available at all times.