Sometimes it seems that an aggressive action occurs suddenly for no apparent cause. Intensive, crowded living conditions may make an animal more suspicious and defensive.

These pent-up frustrations may seemingly discharge out of the blue. But there always has to be a trigger of some sort to set off the aggressive reaction, even though it may not be apparent.

An obvious instance is the dog that is possessive of his belongings, territory, or companion. This type of yorky is may be docile until there will come an actual threat to his ownership. The presence of this challenging person or animal initiates an aggressive guarding of whatever the yorky considers to be his.

In some dogs, human intervention has adjusted the normal, ritualistic expected triggers of aggressive behavior so that a dog reacts to things that normally would not bother him.

In this way, the creation of various breeds has produced certain dogs with more feisty or aggressive natures. In certain dogs, in fact – the natural controlling inhibitions have somehow been eliminated.

In a fight, therefore, a weaker dog may continue to resist until he is nearly dead or the stronger may continue to attack even after his adversary has surrendered. In this case, the trigger initiating the aggressiveness is no longer the threat that would once have been necessary.

It is simply the presence of other animal that keeps each one going.

Sometimes there’s absolutely no way of predicting what will set a dog off. Changes in routine and set circumstances can cause an aggressive reaction – either fearful or antagonistic. Some dogs may react badly to somebody who doesn’t show the signs he normally associates with people.

Animals build up special expectations of the world, and any changes that differ from these expectations are upsetting. The unusual motions or odors connected with mental retardation, nervousness, schizophrenia, or a physical impairment (such as a limp) can all act as triggers.

Some dogs even react badly to minor unfamiliarities in their own owners. Because of this, if you wear unusual clothing or appear drastically different, a dog may suddenly attack or at least be warily antagonistic.

Dogs have even been known to attack their owners fall accidentally – possibly because the dog no longer recognizes the owner rolling on the ground. Or it could be that a dog’s dominance and leadership drives make him seize this chance to be superior.