Mastiff Breed Types -Which One Is Yours?

Japanese Mastiff / Tosa Inu

Posted by John Paul Trueman on

Japanese Mastiff / Tosa Inu

Japanese Mastiff / Tosa Inu

The Tosa-Inu, also called the Japanese Mastiff, is a breed of fighting dog that was developed in Japan from the mid-nineteenth century. Outside Japan, the Tosa was crossbred with large and giant breeds, including the Great Dane and Mastiff, to produce very large individuals, while those bred in Japan remain truer to the original type, at around half the size. The breed is considered “dangerous” in many jurisdictions, and ownership in the UK and Ireland is strictly controlled and subject to license. In the right environment, with firm discipline and a confident owner, a Tosa can be a placid, easy-going giant. However, aggression toward other animals is a significant problem, and aggression toward strangers can also be an issue without adequate socialisation and training.

The breed is not recommended for families with children or other pets, and ownership comes at a large cost, both financially and in terms of responsibility. Tosas need regular intense exercise to stave off boredom and frustration, and enjoy activities, such as cart-pulling, which provide more vigorous exercise than simply lead walking or running. Being a mastiff breed, the Tosa-Inu is known to be a heavy drooler, and its large bulk means that it is not an ideal indoor-only dog. The breed is generally very healthy, with a life expectancy of 10–12 years.

Dog fighting has long been a popular pursuit in Japan, and it still is today, particularly in rural areas, where tournaments are often organised and supported by the yakuza, the Japanese mafia. Dogs involved in these events must be fearless, aggressive, and powerful, and these traits may be seen in the Tosa-Inu, which is still the dog of choice for these fights. Participants are frequently seriously injured or killed, and animal rights groups are actively campaigning for the banning of this “sport”. The breed was developed from molosser dogs, which were large mastiffs used throughout Asia and Europe for centuries as warriors and guard dogs. The modern Japanese form of the breed was established around the mid-1800s.

Dogs exported from Japan to Europe from this point in time were bred with a succession of larger breeds, from the Bulldog and Mastiff to the Great Dane, to produce a western variety of the breed that is significantly larger and more imposing than its Japanese parent stock. The breed has never attracted a large following outside of its homeland, where thousands of litters were being bred annually in the mid-twentieth century. Part of the reason for this is the potential for behavioural problems and attacks on animals and humans, which has led to the introduction of either bans or strict controls on Tosa ownership in many countries.

In the UK, ownership or import of Tosa-Inus requires a legal exemption issued by a court, while in Ireland, the breed has been banned from public housing projects, and is considered dangerous. The Tosa is not officially recognized by either the UK or American Kennel Clubs, and the breed standard in general use is that issued by the Federation Cynologique Internationale.

The Tosa is a massive dog that carries itself with dignity, in the manner of the Great Dane used in its development. It has a strong, broad skull with heavy temporal muscling, and a pronounced stop leading to a powerful, square muzzle. The jaws and teeth are very well developed, and it is important the breed has a perfect scissor bite with no hint of an overbite. The ears are quite small and thin, and hang close to the side of the face, where they are set high. The eyes are a dark brown in colour, are quite small, and usually convey a serene expression.

Every part of the Tosa is heavily-muscled, and this is particularly pronounced in the neck, which has a broad muscular arch, and a dewlap of redundant skin, which is useful to the dog when fighting, so as to allow it to turn on its attacker even while being held. The high withers lead to a wide, straight back and loins, and even the base of the tail is massively muscled. The chest is moderately well sprung, and is deep, which causes the abdomen to be sharply tucked.

The limbs are well angulated, which allows for athleticism and the maximum return on muscular effort. The breed has strong, heavy boning, and tight paws with well developed pads. The Tosa has a short coat of hard, coarse hair. 


Though happy to spend large amounts of time relaxing, Tosa-Inus do need a good deal of daily exercise. Between one and two hours should be allotted daily for walking or jogging, as well as providing access to a secure outdoor garden or yard. Ideally, Tosas should be given more vigorous exercise, for example, pulling a cart, or can be provided with a weighted doggy backpack while out walking. Such exercise aids will give the dog more satisfaction from its daily activities, and reduce the likelihood of aggressive or other undesirable behaviours.


Because the breed’s coat is short and coarse, it does not generally require any special care. Weekly brushing will help to keep the skin and hair in good condition, and occasional bathing may be necessary to help remove any more tenacious dirt and to deodorise. Tosas shed a small amount year-round, and also drool quite a bit, though not as heavily as some other mastiffs. For these reasons, it requires more effort to maintain a Tosa’s home than to groom the dog himself, and keeping packs of baby wipes around the home is a useful way to manage the inevitable pools of slobber before they dry into furniture and carpets.

Tosa-Inus have very strong nails, which are usually dark. Keeping these trimmed is important to prevent them growing into the pads. This requires a strong set of nail clippers, and the habit of nail trimming should be introduced to pups at a young age so it is not resented later in life. With dark nails, it is not possible to visualise the sensitive quick within, and so small, regular trims are preferable to taking larger chunks less frequently, when the risk of hitting this vascular structure increases.

Diet -Feeding 

Like most giant breeds diet should be formulated for a large to giant breed with moderate to high exercise requirements. You should consult your veterinarian or professional nutritionist for advice on what to feed your Tosa Inu  and the correct portion sizes. Their dietary needs will change as they grow from puppyhood to adulthood and senior age. Stay on top of these nutritional requirements, suggested food diet consists of fruit, vegetables, raw chickens whole raw eggs as the shell's are high in natural calcium (never feed cooked!) and a high end kibble, also a joint aid supplement is recommended, not forgetting 10% bones.