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Characteristics, History, and Health


The Bullmastiff is a large-sized breed of domestic dog with a solid build and a short muzzle. They are a part of the Working Group as classified by various kennel clubs. The Bullmastiff's history dates back to the mid-19th century in England. During that time, gamekeepers needed a large, quiet, fearless dog that could assist with keeping poachers away from large estates. They desired a dog that could track quietly, cover short distances quickly, and pin and hold poachers without mauling them. The result was the Bullmastiff, a dog that was approximately 60% Mastiff and 40% Bulldog.

Main Info
Alternate Names
The Gamekeeper’s Night Dog
Life Expectancy
7-9 years
Average Male Height
25-27 inches
Average Female Height
24-26 inches
Average Male Weight
110-130 pounds
Average Female Weight
100-120 pounds
Coat Length
Coat Type
Coat Colors
Fawn, Fawn Brindle, Red, Red Brindle, Red Fawn, Red Fawn Brindle
Coat Pattern
Black Markings, Black Mask, White Markings, Fawn Mask

Genetic Predispositions and Health

The Bullmastiff breed can suffer from calvarial hyperostotic syndrome, cardiomyopathy (dilated), cataracts, cerebellar abiotrophy, cerebellar ataxia (familial), cervical vertebral instability, cruciate ligament disease, cystinuria, degenerative myelopathy, distichiasis, ectropion, elbow dysplasia, elbow dysplasia (ununited anconeal process or fragmented coronoid process), entropion, familial nephropathy, gastric dilation/volvulus (bloat), hip dysplasia, hydrocephalus, hypothyroidism, leukodystrophy, leukodystrophy (oligodendroglial dysplasia), malocclusion, multifocal retinopathy (CMR1), neuroaxonal dystrophy, optic nerve hypoplasia and micropapilla, osteochondritis dissecans (hock, shoulder or stifle), panosteitis, patellar luxation, persistent pupillary membranes, polydontia (supernumerary teeth), progressive retinal atrophy (dominant), recurrent flank alopecia, retinal dysplasia, sub-aortic stenosis urolithiasis (cystine), and vaginal prolapse. They are also susceptible to different forms of cancer including hemangiosarcoma, osteosarcoma, mast cell tumors, and lymphosarcoma. Genetic testing is recommended, including for the following additional conditions: hyperuricosoria, degenerative myelopathy, and progressive rod-cone degeneration.

Personality and Behavior

Bullmastiffs are known for their bravery, loyalty, and stable temperaments. They are extremely loyal to their families and are generally good with children. Despite their size, Bullmastiffs are relatively inactive indoors and are suitable for living in apartments as long as they get enough exercise outdoors. However, they do not do well in the heat.

They are a quiet breed and not typically known for barking. Bullmastiffs have a strong natural instinct to guard their family and home. They are generally reserved with strangers but do not act aggressively. Instead, they typically use their strength and size to block intruders or unwanted guests. While Bullmastiffs can be stubborn, they are typically more sensitive than they look. They respond well to positive reinforcement training. They are known to drool a lot and some may snore.

Fun Facts

The Bullmastiff's nickname of "The Gamekeeper’s Night Dog" is attributed to their history in England as muscular guard dogs that pursued and held poachers (who typically poached at night).