KENAI
Bullmastiff

The breeds · working

AKC Working · UKC Guardian · FCI standard 157

Bullmastiff.

The gamekeeper's night dog. AKC standard: foundation breeding 60 percent Mastiff and 40 percent Bulldog; developed in England by gamekeepers for protection against poachers. UKC: developed about 1860 to stop poaching on English estates; the landowners wanted poachers thrown and held but not mauled. FCI: primarily a guard dog and, in olden times, helped the gamekeeper apprehend poachers (utilization: watchdog). RKC: a 19th-century guard dog to assist gamekeepers in thwarting poachers. AKC history feature: nicknamed the Gamekeeper's Night Dog; bred to stop and restrain an intruder, not to injure him, on night patrols at the keeper's side; William Burton's Thorneywood Kennels dogs made the reputation (1901 and 1910 newspaper accounts); first American dogs were imported by the Rockefellers in 1934 to patrol the Pocantico estate.

Breed sets the odds. The parents set the dog. Every number here shows its source, its spread and how sure we are. Nothing on this page is a prediction about one dog.

10.2YRMedian lifespan9.9 to 10.5, measured on real dogs.
0INHeightdogs null, bitches null. An ideal from the standard, not a range.
90–130LBWeight, all linesbreed dogs 110 to 130 lb; breed bitches 90.4 to 120 lb.
2.5+ HRSExercise, every dayRKC: more than 2 hours per day. AKC breed page: energy level 4 of 5. The constraint most homes get wrong.

The body

What the breed is built like. Registry standards give an ideal, not a range.

Height at the shoulder

dogs 25 to 27.2 in · bitches 24 to 26 in

Breed clubAKC breed standard, 1992

Range printed by every source; center blank. FCI converted from cm.

Weight

dogs 110 to 130 lb · bitches 90.4 to 120 lb

Breed clubAKC breed standard, 1992

The FCI female band sits about 10 lb under the AKC and UKC band; low and high span both. FCI converted from kg.

Coat

AKC: short and dense, giving good weather protection; red, fawn or brindle, a very small white spot on the chest allowed. UKC: short and dense, lies flat, dark muzzle essential. FCI: short and hard, weather-resistant; long, silky or woolly coats highly undesirable; black muzzle essential. RKC: the gamekeepers of the early days preferred brindle for camouflage when working at night; fawn, often with a black mask, is now more numerous

Breed clubAKC breed standard, 1992

Shedding

RKC: sheds (yes). AKC breed page: shedding level 3 of 5

Breed clubThe Royal Kennel Club

Heat tolerance

4 of 5 · AKC: coat short and dense, giving good weather protection. UKC: short and dense, lies flat to the body. FCI: short and hard, weather-resistant, lying flat to the body

DerivedAKC breed standard, 1992

Derived from the coat description (4 = short dense). Coat-only; the breed's heavy build and short muzzle are not in the rule.

How long they live, and what they cost

Measured on real dogs, with the sample and the spread. Never a guess.

Median lifespan

10.2 years (9.9 to 10.5)

MeasuredMcMillan KM, 2024

Median age at death in a UK sample; a population figure, never a prediction for one dog. Registry page bands (the AKC header's life-expectancy range) are not medians and are not used here.

The dog at home

What the breed asks of a day. The first thing most homes get wrong.

Exercise need

RKC: more than 2 hours per day. AKC breed page: energy level 4 of 5

Breed clubThe Royal Kennel Club

RKC band mapped: more than 2 hours = 150. The AKC breed page scores energy 4 of 5 and the Mastiff and Neapolitan RKC bands are up to 1 hour, so this breed carries the highest RKC band of the four mastiffs; shown as printed.

Exercise need

RKC: more than 2 hours per day (large house, large garden, town or country). AKC breed page: energy level 4 of 5, mental stimulation needs 4 of 5

Breed clubThe Royal Kennel Club

Energy

AKC breed page energy level 4 of 5; playfulness 3; trainability 4; barking level 1; drooling level 3 (AKC bands, 1 to 5). AKC standard: powerfully built but active, showing great strength, endurance and alertness

Breed clubAKC

Grooming load

2 of 5 · RKC: grooming once a week; coat length short; sheds. AKC breed page: coat grooming frequency 1 of 5

Breed clubThe Royal Kennel Club

RKC band mapped: once a week = 2.

Grooming

RKC: once a week. AKC breed page: coat grooming frequency 1 of 5, shedding level 3 of 5

Breed clubThe Royal Kennel Club

The work

What it was built to do in the field, and what a test or trial asks of it.

Role

The gamekeeper's night dog. AKC standard: foundation breeding 60 percent Mastiff and 40 percent Bulldog; developed in England by gamekeepers for protection against poachers. UKC: developed about 1860 to stop poaching on English estates; the landowners wanted poachers thrown and held but not mauled. FCI: primarily a guard dog and, in olden times, helped the gamekeeper apprehend poachers (utilization: watchdog). RKC: a 19th-century guard dog to assist gamekeepers in thwarting poachers. AKC history feature: nicknamed the Gamekeeper's Night Dog; bred to stop and restrain an intruder, not to injure him, on night patrols at the keeper's side; William Burton's Thorneywood Kennels dogs made the reputation (1901 and 1910 newspaper accounts); first American dogs were imported by the Rockefellers in 1934 to patrol the Pocantico estate

Breed clubAKC breed standard, 1992

Night guard work against poachers, not a gun dog. The AKC history feature is editorial and quotes the breeder William Burton.

Range

Short and close: AKC history feature says the compact, athletic dog could cover short distances with impressive speed, knock a man down and hold him until the keeper came up; on patrol the keeper kept the dog beside him, and the wrinkling of the dog's forehead signalled someone ahead

EditorialAKC

Single editorial source (the AKC history feature); no standard states range.

Field trial standard

None: FCI classes the Bullmastiff 'without working trial'

Breed clubFederation Cynologique Internationale

How common the problems are

Evaluated dogs skew toward breeding stock; the numbers are still the best there are.

Hip dysplasia

25.7% · 25.7% dysplastic of 7,587 OFA hip evaluations on record (current all-data, accessed Oct 9 2026); 71.2% normal; mild 16.4%, moderate 8.0%, severe 1.3%; breed rank 32 of the breeds listed

MeasuredOrthopedic Foundation for Animals

Voluntary registry: affected dogs are under-reported and evaluated dogs skew toward breeding stock, so true prevalence is likely higher. Rank 1 = highest dysplasia rate among the breeds listed.

Elbow dysplasia

17.2% · 17.2% abnormal of 4,143 OFA elbow evaluations on record (current all-data, accessed Oct 9 2026); 82.5% normal; grade 1 12.4%, grade 2 3.6%, grade 3 1.2%; breed rank 28 of the breeds listed

MeasuredOrthopedic Foundation for Animals

Voluntary registry: affected dogs are under-reported and evaluated dogs skew toward breeding stock, so true prevalence is likely higher. Rank 1 = highest dysplasia rate among the breeds listed.

More

akc bands

AKC breed page trait scores (1-5): Energy Level 4; Mental Stimulation Needs 4; Trainability Level 4; Barking Level 1; Watchdog/Protective Nature 5; Good With Young Children 3; Openness To Strangers 3; Good With Other Dogs 3; Shedding Level 3; Coat Grooming Frequency 1; Drooling Level 3; Affectionate With Family 4; Playfulness Level 3; Adaptability Level 3.

Breed clubAKC

Fourteen AKC bands in one row; the selector reads each by name. Breed-club ratings: a tendency, never a measurement.

What to ask a breeder for

The health clearances the breed’s own club and registry name. Reference only: what to ask for, never a statement about any dog’s health.

How to read this page

Every value carries a label. Measured means peer-reviewed data on many dogs. Studied means peer-reviewed, smaller or indirect. Breed club means a club or registry states it. Editorial means expert opinion with no measurement behind it. Where two good sources disagree, both are shown and neither is averaged.

Published when the entry rests on the best information available from no fewer than three independent sources, checked by a second pass that did not write it. 8 sources on this page. Found something wrong? Tell us and the correction is logged with its date.

Also called
Gamekeeper's Night Dog

Every breed, read the same way.

The breed index grows as entries clear the standard. Gun dogs first.

All published breeds

Your bullmastiff, on the record.

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