Testing for social status is normal in dogs. If there is no clear leadership in a group of dogs, conflict may break out until one is established. This aggression may be overt; or it may be so subtle that you’re unaware of what is happening because the bullying occurs when you are not around.

In any group of dogs, the best promoter of peace is a clear pecking order.

But for this to remain stable, the group has to stay constant. Bringing in or removing one member of a group will disrupt the status and necessitate its reestablishment.

An animal that has not learned his place shows no respect for authority or social order, and shows no mercy to subordinates. This is why fights often occur when new pets are brought into the home, or put in with others that have formed a social circle, such as dogs that normally run together in the park.

Most often, newcomers are eventually assimilated into the group, but some tightly knit groups will not easily open up for a newcomer – especially if he poses a threat to the more dominant dogs.

With some other breeds, the social hierarchy is not obvious; while others have a clear, sharply defined one. Terriers are so competitive they cannot tolerate the close proximity of other dogs that might be a threat of any kind.

Only a very small social grouping is possible with these breeds; they will allow no threatening newcomers and will constantly bicker among themselves.

With this type of yorky, the only time peace reigns is usually when the dogs have been housed together from an early age, or when they are a mated pair.

Because ranking is established early, these pre-acquainted dogs may squabble, but rarely get involved in injurious fighting unless extraordinary circumstances prevail.

Another main cause of fighting is a dog’s sexual drive. This natural (and highly volatile) hormonal force is seen most acutely when there is a female in heat around.  A male yorky may become aggressive toward strangers who he thinks might interfere with his possession of the female.

After the actual mating, a previously normal dog may start exerting dominance. However, it is the violent rivalry among male dogs over who is going to mate with whom that causes the worst problem.

If more than one male is present around a female in heat, there will be undoubtedly be a fight for sexual possession.