PetMD Editorial
Written by:
PetMD Editorial
Published: May 13, 2009

The Bullmastiff is a strong, powerfully-built dog with great intelligence and a willingness to please. Large, agile, and active, it makes for an ideal family companion and protector.

Physical Characteristics

Due to its ancestry, the Bullmastiff resembles both the Mastiff and Bulldog. This powerful and active dog has moderate angulation and a strong and smooth gait. Its body shape, meanwhile, is square, and its expression is keen. Many of these properties enable the Bullmastiff to overtake and overpower intruders. The Bullmastiff's thick, short coat is red, fawn, or brindle in color.

Personality and Temperament

The quiet and gentle Bullmastiff dog requires a loving but firm home and is not meant for timid or delicate owners. It also behaves nicely around children and can be raised with them. Be aware, however, the Bullmastiff does have a stubborn streak. And while some Bullmastiffs can become violent toward strange dogs (especially males), they are regarded as a devoted companion and an excellent guardian. In fact, the breed is not easily agitated and when threatened, it is fearless.


The Bullmastiff dog breed does not do well in humid and hot weather. It functions best as an indoor dog. In addition, the Bullmastiff, being a large animal, requires regular exercise to remain in good shape, which can be satisfied with short romps and walks on a leash. Most Bullmastiffs drool, and some snore. A soft bed and lots of space for stretching are important for the dog. Minimal coat care is required.


The Bullmastiff breed, which has an average lifespan of 8 to 10 years, is prone to major health issues like hemangiosarcoma, osteosarcoma, mast cell tumors, lymphosarcoma, cardiomyopathy, hypothyroidism, and sub-aortic stenosis (SAS). It is also prone to canine hip dysplasia (CHD), gastric torsion, elbow dysplasia, and entropion, which is a minor problem. To identify some of the issues, a veterinarian may run hip, elbow, and eye exams on the dog.

History and Background

The development of the Bullmastiff is recent compared to its ancestor, the Mastiff, which is one of the oldest breeds in Britain. As early as 1791, there were some references to the Bullmastiff and to crosses between the Bulldog and Mastiff. There is little evidence to support the crossing of the breeds at that time, though.

The history of the Bullmastiff is most often associated with the late 1800s, a time when the violent surge of poachers threatened the lives of gamekeepers. The gamekeepers, in turn, required a strong and daring companion that would quietly wait until a poacher arrived with his dog, overcome the dog, and attack when commanded. The Bulldog was not large enough and the Mastiff was not swift enough, so gamekeepers crossed the two breeds to create a perfect dog, naming it the "Gamekeeper's Night Dog." The dark brindle color of the mix was preferred, as it blended with the night.

With the dog’s rising popularity, several estate owners selected it to work as a sentry. Many preferred the lighter fawn ones, which had black masks. This coloration was reminiscent of the dog’s Mastiff ancestry. Breeders started aiming for pure-breeding strains instead of crossing the Bulldog and Mastiff. They aimed to produce an animal with about 40 percent Bulldog traits and 60 percent Mastiff traits, thus creating the modern Bullmastiff.

The Bullmastiff breed was considered pure by 1924, when the English Kennel Club recognized it, followed by the American Kennel Club in 1933.

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