The Bullmastiff – Ultimate Breed Information Guide

There are few dogs more intimidating than mastiffs. And the bullmastiff, especially, possesses a self-confidence and athleticism to make anyone think twice about approaching them.

But these dogs are more than just stoic guardians. In the right home, they can be devoted and gentle family pets. Keep reading to find out if you have what it takes to turn the “gamekeeper’s night dog” into the perfect canine companion.


General Characteristics of the Bullmastiff

  • Other names: Gamekeeper’s Night Dog
  • Height: 24 to 27 inches
  • Weight: 100 to 130 pounds
  • Lifespan: 7 to 9 years
  • Origin: United Kingdom
  • Colors: Fawn, red, brindle
  • Activity level: Moderate
  • Grooming needs: Minimal
  • Best suited for: Experienced guard dog owners

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The bully is a powerful breed with the athleticism and drive of the original bulldogs and the size and strength of the mastiff. “
Side by Side” by Michelle Mitchell / CC BY-NC-ND 2.0

The History of the Bullmastiff

As the name suggests, the bullmastiff owes its existence to two dog breeds: the mastiff and the bulldog.

In the United Kingdom in the 1800s, many wealthy families held large estates complete with herds of game that were hunted to feed the family and distinguished guests throughout the year. While poaching was a high crime, punishable by hanging, many of these estate keepers still experienced frequent game loss at the hands of trespassers.

Gamekeepers were often employed to protect the herds from poachers. But, even when armed with weapons and horses, this job often proved dangerous and difficult. Trespassers facing the hangman’s noose and the real possibility of starvation weren’t afraid to act violently against those that tried to stop them.

Many gamekeepers turned to the help of dogs to guard the grounds and help chase down poachers. The mastiff was a natural choice. The old English mastiff was a large, powerful dog who could easily subdue even the most violent of men. Unfortunately, they would have to catch them first, a skill that these slower, heavier dogs did not excel at.

The old English bulldog had been bred for centuries to restain bulls both for sport and on the farm. They were highly athletic, strong, and capable of running down poachers with ease. Unfortunately, they were more aggressive than desired and it was not uncommon for these dogs to maul trespassers to death before they could be identified.

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The bullmastiff is no stranger to working in dense vegetation. These powerful dogs would accompany gamekeepers as they patrolled large estates looking for poachers. If one was found, they would track, chase, and pin the perpetrator to the ground until the handler arrived. “Heff Out on His Walk Today” by Dan Ciminera / CC BY-ND 2.0

In an attempt to get a highly athletic dog with the power of a mastiff but less aggression than a bulldog, gamekeepers started crossing these two breeds. After much trial and error, they eventually found that crosses resulting in 60% mastiff and 40% bulldog made for the perfect guard dog.

By 1924, the English Kennel Club recognized the bullmastiff as a purebred breed. The AKC followed shortly thereafter in 1934.

Today, these bullies are still powerful and effective guard dogs, but more often than not, their night job now involves cuddling with children or snoring at the foot of the bed.

The Temperament of the Bullmastiff

This bully is confident, stoic, and bold. They are fearless in the face of danger to themselves, their family, or their property. And loyal to those they know well.

In the home, these dogs are typically docile, preferring to lounge around or snuggle in for a good cuddle with their owner. Outside, they are observant and ever-aware. They do not accept strangers on their property without their owner’s okay first. Because of their history, they are more likely to tackle and hold a presumed trespasser than to bite or chase them.

The bullmastiff can be a loving and protective family dog, but they aren’t for everyone. Learn more about them above.

Bullmastiffs will not hesitate to spring into action if they feel anyone in their family is in danger. This is worth keeping in mind before inviting your overly rowdy friends over, especially in your dog doesn’t know them that well.

These dogs can be possessive and territorial, yet, they live to please their owner. They are easy to train assuming a strong relationship with the handler.

While their ancestors may have prowled hundreds of acres of land searching for trespassers, today’s mastiff is just as happy to guard the suburban backyard as the sprawling junkyard. They require only moderate exercise but aren’t great choices for city life, as they can get possessive of any area they frequent.

How accepting your bully will be of strangers on the street and other pets depends largely on how much socialization they receive as puppies. But even the most socialized dogs can’t overcome an innate sense to protect and a bullmastiff should never be expected to exist harmoniously in a household where strangers come and go at will.

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Don’t let this cute little face fool you, this mastiff will soon be a mighty, 100+ pound powerhouse.

Health Issues Common to the Bullmastiff Breed

Bullmastiffs have many of the same health issues as other bulldog and mastiff types. They are prone to the same joint and bloat concerns as other large breeds and are especially likely to suffer from mast cell tumors and other cancers.

Here are some of the more common health concerns seen in these bullies:

  • Hip dysplasia
  • Elbow dysplasia
  • Arthritis
  • Hypothyroidism
  • Heart problems
  • Entropion
  • Progressive retinal atrophy
  • Bloat
  • Mast cell tumor
  • Lymphoma

Like all large-boned giant breeds, bullmastiff puppies should only be fed large breed specific puppy food. These diets contain the optimal amount of calories, calcium, and phosphorus for slow, sustained growth. Feeding a general puppy food could cause the dog to grow too quickly, putting excess strain on their joints leading to dysplasia and arthritis in the adult dog.

Keeping growing puppies from overtaxing their joints through rough play and jumping is also important to maintain bone health into adulthood. Agility and other impact sports should be avoided until a bully pup is 18 months of age.

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The large-boned bullmastiff has a number of health issues that can shorten their lifespan. Feeding a quality diet, keeping them a healthy weight, and working closely with your vet can help avoid some of these issues. “Dog, Bullmastiff” by Eran Finkle / CC BY 2.0

There is some growing evidence that postponing neutering in males and spaying in females can also help your pup grow up healthy and even avoid some cancers later in life. Of course, this benefit needs to be weighed against the challenges of owning an older, intact animal.

Intact dogs are more likely to develop aggression issues as they become sexually mature. They are also more likely to try and escape and wander than neutered dogs. Because bullies can breed before they are full-grown, it is important to keep your intact pup contained when outside to avoid any accidental litters.

Most important to the health of your future dog is how well you research breeders before you select one. Responsible bullmastiff breeders will screen their breeding dogs for hip, elbow, and other bone issues, cardiac defects, and thyroid conditions. They should also allow you to meet the parents. The temperament of the mother will give you a picture of the temperament the puppies may have.

If your goal is a confident guard dog that will do well with your children, you should be wary of any breeding dogs that show undue aggression.

Before you look into breeders, consider adopting a mastiff in need of a home. While you are unlikely to find a purebred puppy, there are plenty of young and adult bullies in need of a forever home. Unlike a pup, you will know the temperament of the dog you are bringing home beforehand and will even have a good idea of their overall health.

Do Bullmastiffs Do Well With Children and Other Pets?

Despite their historical use as poacher hunters, these massive dogs can make good family pets.

Like many guard breeds, the aggression these dogs possess is generally reserved for trespassers. With family, they can be tolerant, gentle, and very loving. While a dog this size should never be left unsupervised with babies and young children, they do make good playmates for older kids.

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Puppies who are socialized with other dogs are more likely to enjoy playing with other  dogs as adults, but they may still not enjoy living with other dogs. In the end, it will come down to the individual’s personality. “Dog Toy” by Jose Pena / CC BY-NC-ND 2.0

A wellbred and well-socialized bully should not show any aggression with the family or even strangers the family has invited onto the property.

When it comes to other dogs and pets, there is less certainty to how your bully will react.

Because these dogs can be possessive and territorial, they don’t always do well in multi-dog households. This is especially true of males, though even females may not tolerate other females. Even dogs that generally do well together may get in a tussle over food or toys. And, with a dog this large, even the most casual disagreement can lead to serious issues.

But overall, how tolerant mastiffs are of other canine companions comes down to the individual dynamic.

The same can be said of bullies and other pets like cats and rodents. These are powerful dogs that still retain the same prey drive that made them good at running down poachers. This can easily translate to chasing the cat or harassing the hamster.

Early socialization can make a huge difference in how sociable these dogs are with other animals, but it still might not be enough to overcome their innate drives.

What to Consider Before Bringing Home a Bullmastiff

Think the bullmastiff is the perfect dog to keep you or your family safe? Here are a few more things to consider before committing to this breed.

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The bully loves his space and getting outdoors. They are not great choices for people living in apartments or large cities. (

Activity Level

These bullies are quiet in the house, especially once they have matured, but they do require at least daily walks to get out excess energy. Many of these mastiffs have found success in the agility ring as well as in dog sports like tracking and cart pulling.

A yard is a must for these dogs. They enjoy walking the fence line and observing everything going on in the neighborhood. They are quieter than most guard dog types so they might be a better choice for busy streets or neighborhoods.


Bullmastiffs are intelligent dogs, but they can be independent. Consistency is key to getting a well-trained bully. Even though these animals are known for their ferocity when running down a trespasser, they can be very sensitive in their relationship with people they trust. Don’t assume you need to “dominate” or use a hard hand to train these dogs. They’ll respond better to consistent, high-energy training that appeals to their desire to please.

Enrolling your pup in training classes is a must to establish good manners early on as well as get them plenty of socialization. Take your puppy everywhere with you and introduce them to animals of all kinds. Try to make sure all experiences with new situations and people are positive.

Bullies have a deep instinct for guarding property and people and no special training is needed. But it is a good idea to work with your mastiff on greeting behavior, wait, and recall commands so you can remain in control when new people come to your house.

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The bully has a short coat that is relatively easy to care for. Depending on the depth of their facial wrinkles, they may need a little extra attention in the form of daily wipe downs with cleanser to keep those areas clean and dry. “2010-07-15_0110” by Richard Wood / CC BY 2.0


These bullies have a short coat that does not require a lot of upkeep. Weekly brushing and the occasional bath should be plenty. Like all dogs, they need their nails trimmed frequently.

Despite their short coat, these dogs have enough weight on them to keep them comfortable in cooler weather. They do need shelter in very cold and inclement weather as well as protection from the heat.


These large breed dogs require large breed puppy food while they are growing. Once they reach adult size, they should be transitioned to a quality adult food for either all breeds or large breeds. Make sure the food has plenty of quality animal protein and fat to support a healthy coat and joints.

This is a heavy set breed that should carry a lot of muscle, but it is still important to keep your bully from gaining too much excess weight. You shouldn’t be able to see any ribs, but you should notice a slight indent behind the rib cage. Work with your vet to make sure your bully maintains optimal weight for their build.


Most purebred bullmastiffs will cost between $1,000 and $2,000. This is a fairly short-lived breed and they do age fast. Be prepared to pay for increased medical bills sooner than with a medium-sized dog. These dogs can put away a lot of food, so make sure to factor that into your yearly budget as well before deciding on this breed.

>>>Find out what it really costs to own a dog.

10 Fun Facts About the Bullmastiff

Now that you know a little more about what it takes to own a bully, here are some fun facts about the breed.

  1. These bullies were used to guard many of the diamond mines in South African in the early 1900s.
  2. Bullmastiffs worked independently to track and subdue poachers and don’t always get along well with other dogs in the house.

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These mastiffs only come in three colors: fawn, red, and brindle. All variations should have a black mask and no white markings except for possibly a small white spot on the chest. “My Boy Heff” by Dam Ciminera / CC BY-ND 2.0

  1. These mastiffs are a direct result of straight crosses between Old English Bulldogs and Old English Mastiffs.
  2. The Cleveland Browns NFL team uses a live bullmastiff named Swagger as one of their mascots.
  3. These mastiffs were bred to track and chase down intruders silently and rarely bark.
  4. John D. Rockefeller is said to have brought the first bullmastiffs to the US in the 1920s to guard his estate.
  5. These bullies are much less likely to bite than other guardians even when going after trespassers because their original purpose was to pin poachers down without mauling them.
  6. The bully featured in the movie “Rocky” actually belonged to Sylvester Stalone as they couldn’t afford to use a professionally trained dog for the role.
  7. The black mask is a required feature of the breed, but a recessive genetic trait can cause masks without pigment or to have a liver coloration.
  8. These dogs have been used for police and military dogs.

Before You Go

Not sure this thick boned guard dog is right for you? Here are some other breeds to consider.

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Dog, Mastiff” by Erin Finkle / CC BY 2.0