Dogs often have more than one name within their household. Hyde.
Most people understand dogs instinctively are protective of their territory and loved ones. It is their nature to warn you of danger, or protect you from what they perceive as harm. Most people also understand a dog will snap out of fear or pain. However, when aggressive behavior is sudden, or turned toward members of the household over food or bedding, it’s important to understand why and take control. This unaddressed behavior is what places many dogs into shelters and on the unadoptable list.
As pack animals, dogs instinctively follow a natural order. In the wild, a pack leader protects and directs his pack. He often postures his dominance to those lower in the ranks as a reminder. Generally, dogs are taught submissive behavior by their mothers. For example, if the puppies are playing too rough, she may roll them onto their backs. However, as adults, certain breeds are more domineering by nature, and if aggressive behaviors toward you are allowed, they instinctively see themselves as higher in the pack order. A domineering breed with a meek owner can be an unhealthy combination.
It is not uncommon for shelter or rescue dogs to have a bad start to life. If you don’t know the details of your dog's history, learning what triggers his sudden behavior often is through trial and error. If his past abuser was a child or a particular gender, or even wore a certain color of shoes, these memories are imprinted and associated with pain.
What Can Be Done
Ruling out any contributing medical condition is the first step. Talk to your veterinarian. Spaying or neutering also is beneficial, especially in males, and don’t forget about proper exercise. Exercise not only releases pent up energy, but bonds them to you. If you know your dog isn’t good around men or children, avoid these situations, or put them in a separate room when you have guests. Also, talk to your vet about recommending a professional behaviorist or trainer.