This article is from the Mastiffs Breed FAQ, by mmcbee@access.mountain.net (Mike McBee) with numerous contributions by others.
Aggression is unnecessary force or dominance in any
situation. Aggression should not be confused with protection
where a dog uses force or dominance to protect its people or
territory when threatened.
The typical Mastiff's temperament, by nature, is one of
gentle demeanor. However, as with any breed, a Mastiff can
become aggressive for varying reasons.
Typically, aggressive behavior is established due to
environment as a "learned response" and/or results from a
lack of proper socialization during the dog's developmental
stages.
A certain percentage of dogs may be genetically unstable and
inherit aggressive tendencies. For this reason, before you
purchase a puppy, it is best to ask the breeders about the
temperament of the sire and the dam and try to see both if at
all possible.
Some dogs may have a predisposition for certain
characteristics which may be the basis for aggressive
behavior: a dominant dog may exhibit Dominant Aggression, an
unsocialized dog may develop Fear Motivated Aggression, or a
dog unsocialized with other dogs may develop Species
Aggression. Most aggression can be prevented by proper
rearing and socialization, beginning as a puppy.
If you are experiencing a problem, consult your Mastiff's
breeder, your veterinarian, and/or a trained animal
behaviorist BEFORE the problem becomes serious.
 
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