Because this breed was developed to hold or "keep" poachers until master arrived, they are unlike other breeds that attack or maul intruders. The bullmastiff would literally sit on or stand over the intruder. It is important to understand this, because often times buyers are seeking a "tough guy," macho dog. Although bullmastiffs look very intimidating, they are (should be) calm and gentle, yet ready to react when called upon. A good description is "strength under control." Yes, they can be trained to bite, however, that is not their true disposition. They have what I like to call a "sixth sense." Bullmastiffs seem to know after a few short moments good intentions from bad ones. They seem to be able to discern a person's character; good or bad. These are not dogs that were bred/created to fight - NOT like a pit bull.
It should also be noted that in this breed the females tend to be (although not always) more protective, having more of the guardian mentality, than the males. Generally speaking, the males are more laid back, and the females more alert and active.
UPKEEP: This is a medium shedder. Brush daily to keep shedding under control. They do not have a double coat, so they cannot maintain their body temperature as well as some other breeds. Due to their short noses, sometimes even recessed, this breed cannot be overexerted in warm weather, and should be kept as an indoor dog year-round.