1:10 Since the French Bulldog was pregnant, its relationship with the other dog in the household, a Maltese, began to worsen. It is a known fact that hormone changes during a dog's pregnancy can make her become defensive. In the case of this French Bulldog, she likely regarded the Maltese as a competitor for resources and the owner's attention. Too bad that the owner missed the initial signs of changes in her dog's behaviors. Had the owner interfered and made it clear to the dog that, despite its instincts taking over, it still needed to perceive the owner as the leader, the French Bulldog might not have become an aggressive dog. Newborn puppies will trigger a dog's maternal instincts and therefore changes in behaviors as well. Even a calm and well-socialized dog can become possessive (or aggressive) to anyone approaching its litter. The once well-behaved French Bulldog bit and injured a person; it also became aggressive to anyone except the owner. All these sudden behavioral changes could have stemmed from the dog's maternal instincts to protect its pup. Motherhood changed this dog's behaviors. The dog trainer was right. The owner needed to give up her dream of raising celebrity dogs and making money out of them.