I have two dogs 1 poodle (12 years), sitzhu (4 years) both been together for 4 years.

Son bought a labrador (5 months) - the sitzhu has attacked poodle 4 times for no reason.

First - pierced ear (no vet required), second bit leg (4 stitches), third bit leg again (no vet required), fourth bit back of neck, serious major surgery so far $900 in vet bills over 3 days.

Why all of a sudden is sitzhu attacking poodle?