Mollosso Presa Mayo
"mo-LOSS-oh PRAY-sa MAY-oh"
United States· United States
The Mollosso Presa Mayo is an in-development guardian breed pioneered by dog developer Chad Mayo. It is not a recognised breed and should not be read as one: it is an active breeding project, still working through its foundation generations, and type is deliberately not yet fixed.
At a glance
Quick facts
Size
Giant
Exercise needs
1-2 hours daily, structured
Home size suited to
Large home with secure land
Grooming frequency
Weekly brush; check skin folds if present
Coat length
Short
Sheds
Moderate, year-round
Lifespan
Not yet established (est. 9-11 years)
Town or country
Country or rural estate
Garden size needed
Large and securely fenced
Where it comes from
Origins of the Mollosso Presa Mayo
An active development project begun by dog developer Chad Mayo in the United States, combining English Bull Terrier, Neapolitan Mastiff and Boerboel to build a healthy, agile estate guardian. It is not a settled breed — foundation generations are still being worked through.
- Region
- United States
- Climate it was bred for
- Varied; developed in temperate United States
- Original job
- Estate and property guardian
The long read
About the breed
The programme blends three molosser and bull-type foundations — the English Bull Terrier, the Neapolitan Mastiff and the Boerboel. The Bull Terrier contribution is most visible in the head, producing the distinctive 'big cat' or cougar-like facial structure the project is known for, while the Neapolitan Mastiff and Boerboel supply bone, mass and guarding instinct.
The stated goal is a powerful, healthy, agile estate guardian: heavy bone density and thick muscle, but a dog that stays fit, active and sound rather than ponderous. Temperament is selected for alertness and protectiveness paired with a social, playful side at home.
Because stabilising a new breed generally takes six to eight generations of consistent selective breeding, buyers today are taking on a project dog. Litters can vary in size, head type, coat and temperament, health testing history is short, and no kennel club standard, register or breed-club infrastructure exists yet. Anyone considering one should treat it as an experimental type and expect to work closely with the developer's programme.
Living with one
Temperament & needs
Our own ratings, based on the breed standard and how these dogs behave in ordinary homes.
Friendliness
2/5
Reserved with strangers by design; warm with its own household.
Trainability
3/5
Willing and biddable but needs an experienced, consistent handler.
Energy
3/5
Bred to stay fit and active — needs real daily work, not just a garden.
Barking
2/5
Alerts purposefully rather than barking for the sake of it.
Grooming
1/5
Short coat needs little more than a weekly brush.
Suits a first-time owner
4/5
Not suitable: a guardian breed and an unfinished one, so type and temperament still vary.
Sociability
2/5
Territorial instinct means early, extensive socialisation is essential.
Independence
4/5
Bred to make guarding decisions without direction.
Illustrated breed standard
The points of the breed
Hover or tap a numbered point to read what the standard asks for.
Point 1
Skull
The broad, deep skull carries the Bull Terrier influence that gives the Mollosso Presa Mayo its distinctive 'big cat' or cougar-like face. Because the breed is unfinished, head type still varies noticeably between litters.
Outside the standard
Other colours
Dilute coats you will see advertised. They are the same breed, but no kennel club accepts them.
Fawn
Not in the standard
Commonly seen; no standard yet defines accepted colours.
Brindle
Not in the standard
Frequent in early generations from the Boerboel and Bull Terrier lines.
Black
Not in the standard
Solid black appears via the Neapolitan Mastiff influence.
Blue fawn
Not in the standard
Dilute blue-grey shading, again from the Neapolitan side.
Timeline
History & development
2010s
Project founded
Dog developer Chad Mayo begins a programme to create a healthy, agile estate guardian rather than a heavier, slower mastiff type.
Foundation
Three-breed cross
English Bull Terrier, Neapolitan Mastiff and Boerboel are combined — the Bull Terrier for the distinctive 'big cat' head, the other two for bone, mass and guarding drive.
Early generations
Selecting for soundness
Breeding focuses on health, structure and working temperament, with variable results between litters as expected at this stage.
Ongoing
Six to eight generations to stabilise
The breed remains an active development project; consistent type is typically only reached after six to eight generations of selective breeding, so it is years from being a settled breed.
Today
No kennel club recognition
No major kennel club recognises the Mollosso Presa Mayo. It is listed here as an unofficial, emerging type in progress.
Reference
Breed standard summary
- body
- Deep-chested, short-coupled, heavy bone with thick muscle over a level topline.
- coat
- Short, close-lying and glossy.
- ears
- Medium, naturally dropped, carried close to the head.
- eyes
- Wide-set, medium, dark; alert and steady expression.
- gait
- Free and driving, showing real agility for the mass carried.
- head
- Broad and deep with the Bull Terrier influence giving a distinctive feline, cougar-like profile.
- size
- Giant
- tail
- Thick at the base, tapering, carried level on the move.
- colour
- Fawn, brindle, black and blue-fawn are all seen; colour is not yet fixed.
- temperament
- Alert and protective on duty, social and playful with its own people. Nervousness and indiscriminate aggression are both selected against.
- general appearance
- Powerful, heavily muscled molosser of moderate giant size, agile rather than ponderous. Type is still being consolidated and varies between litters.
Health
What to screen for
Green means little to worry about, amber means ask the breeder for test results, red means manage it actively.
Hip dysplasia
Watch closely
Giant, heavy-boned dog from three at-risk foundations — insist on hip scores for both parents.
Elbow dysplasia
Watch closely
Ask for elbow scoring certificates on every dog in the cross.
Heart conditions
Screen for it
Cardiac problems occur in both mastiff and bull-type ancestry; ask for cardiac clearance.
Eyelid & skin folds
Watch closely
Neapolitan influence can bring entropion, ectropion and fold dermatitis; look for clean eyes and skin.
Bloat
Watch closely
Deep-chested: feed smaller meals and avoid exercise straight after eating.
Unproven genetics
Screen for it
With only a few generations behind it, long-term health outcomes are genuinely unknown.
General information only — always speak to your vet about your own dog.
From real owners
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Made for the Mollosso Presa Mayo
The book, plus prints, hoodies and mugs using our own Mollosso Presa Mayo illustration — and one everyday accessory that suits any dog.
The book
Pawpoint: The Complete Dog Breed Book
Every officially recognised breed plus the unofficial ones nobody else documents. 400+ pages, hardback, printed and shipped from the UK.
Own stock — shipped by us
Framed poster
Mollosso Presa Mayo Framed Poster
Museum-weight print of our Mollosso Presa Mayo illustration, framed or unframed.
Printed to order
Hoodie
Mollosso Presa Mayo Hoodie
Heavyweight hoodie carrying the Mollosso Presa Mayo illustration on the chest.
Printed to order
Mug
Mollosso Presa Mayo Mug
Ceramic mug with the Mollosso Presa Mayo illustration wrapped around it.
Printed to order
Accessory
LED Reflective Lead Light
Rechargeable clip-on light for dark walks.
Fits any dog
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