Differences Between a Mastiff & a Bullmastiff

By Jane Meggitt

Differences between the mastiff and bullmastiff are more subtle than obvious. They are both massive, powerfully built canines, loyal to their owners and quite protective. They are closely related, with the "bull" in bullmastiff originating from crosses with bulldogs in the 19th century. Like many large breeds, both have relatively short life spans, ranging between 8 and 10 years.

Breed History

View of a bullmastiff dog lying on the grass

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Mastiffs descend from the ancient molosser-type dogs, whose origins go back thousands of years. These huge canines were used in war, and as guard animals and in dogfighting. The modern mastiff, also known as the Old English or English mastiff, was employed as an estate guardian in Great Britain from the 1400s.

The bullmastiff was developed in the mid-19th century by gamekeepers seeking a dog as large as the mastiff but with more speed to capture poachers. Crossing mastiffs and bulldogs did the trick. Crossbreeds were common until the early 1900s, when the breed emerged as a specific type.

Height and Weight

Woman reading a book with a big mastiff next to her.

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The mastiff is somewhat larger than the bullmastiff. A mature male mastiff stands at least 30 inches tall at the shoulder, with females standing at least 27.5 inches high. While the mastiff breed standard does not specify a weight, these dogs can range between 130 and 220 pounds, making them the largest of all breeds.

The male bullmastiff stands between 25 and 27 inches tall, with females standing between 24 to 25 inches high. The breed standard specifies a weight range of 110 to 130 pounds for males, and 100 to 120 pounds for females.

Physical Appearance

Face of a bullmastiff

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Both breeds sport short coats. Acceptable colors in the mastiff include apricot, fawn or brindle, the latter dark striping over an apricot or fawn coat. The dog's ears, muzzle and nose are dark, as is the area around the eyes.

Permitted colors in the bullmastiff are fawn, red or brindle, with a dark muzzle preferred but not mandatory. Although the bullmastiff has bulldog ancestry, the breed standard makes it clear that the nose should not have that breed's pushed-in appearance.

Temperament Differences

A Neapolitan Mastiff on a leash

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Neither breed gets along particularly well with other dogs, although the mastiff is somewhat better in that department. The mastiff often tolerates cats, which isn't true of the bullmastiff. Both make first-rate watchdogs, one of their original purposes. Neither barks much. They don't need to, as their sheer size intimidates strangers. Both breeds require relatively little exercise, although the mastiff needs more than his bullmastiff cousin. Without regular exercise, the mastiff is prone to dangerous weight gain. Either breed needs early socialization and obedience classes, because their size can make a disobedient or scared dog potentially dangerous.

Health Issues

A large bullmastiff resting in a urban park

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Both breeds are prone to hip dysplasia, a genetic hip joint malformation requiring surgical correction. Elbow dysplasia occurs more frequently in the bullmastiff. Heart disease also affects both breeds, especially pulmonic stenosis and cardiomyopathy. The hereditary kidney defect known as cystinuria plagues both breeds. Cystinuria usually results in bladder stone formation, which is life-threatening if a urethral blockage occurs. Several different types of cancer appear in both breeds, including lymphoma, bone cancer and mast cell growths.