The term soft mouth is used by breeder

Breeder

A breeder is a person who practices the vocation of mating carefully selected specimens of the same breed to reproduce specific, consistently replicable qualities and characteristics....

s and users of hunting dog

Hunting dog

A hunting dog refers to any dog who assists humans in hunting. There are several types of hunting dogs developed for various tasks. The major categories of hunting dogs include hounds, terriers, dachshunds, cur type dogs, and gun dogs...

s to refer to a behavioral tendency to pick up, hold, and carry quarry

Hunting

Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...

 gently. It is not a preferred characteristic of terrier

Terrier

A terrier is a dog of any one of many breeds or landraces of terrier type, which are typically small, wiry, very active and fearless dogs. Terrier breeds vary greatly in size from just a couple of pounds to over 70 pounds and are usually categorized by size or function...

s and ratters, who are expected to roughly shake and mangle pests such as rat

Rat

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

s and snake

Snake

Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s in order to kill them quickly and efficiently. It is desirable in gundogs such as retriever

Retriever

A retriever is a type of gun dog that retrieves game for a hunter. Generally gun-dogs are divided into three major classifications: retrievers, flushing spaniels, and pointing breeds. Retrievers were bred primarily to retrieve birds or other prey and return them to the hunter without damage...

s and spaniel

Spaniel

A spaniel is a type of gun dog. It is assumed spaniels originated from Spain as the word spaniel may be derived from Hispania or possibly from the French phrase "Chiens de l’Espagnol" . Spaniels were especially bred to flush game out of dense brush. By the late 17th century spaniels had become...

s which are expected to produce quarry intact and in good condition, and is a notoriously difficult behavior to teach to a dog without an inborn temperament

Temperament

In psychology, temperament refers to those aspects of an individual's personality, such as introversion or extroversion, that are often regarded as innate rather than learned...

 to do so. As a result, breeders and users of gun dogs arrived on this term to describe a characteristic important to this enterprise. Dogs breeds known for producing more soft-mouthed individuals include Golden Retriever

Golden Retriever

The Golden Retriever is a medium-sized breed of dog. They were historically developed as gundogs to retrieve shot waterfowl such as ducks and upland game birds during hunting and shooting parties. As such, they were bred to have a soft mouth to retrieve game undamaged and have an instinctive love...

s, Cocker Spaniels, Poodle

Poodle

The Poodle is a breed of dog. The poodle breed is found officially in toy, miniature, and standard sizes, with many coat colors. Originally bred as a type of water dog, the poodle is highly intelligent and skillful in many dog sports, including agility, obedience, tracking, and even herding...

s, and Gordon Setter

Gordon Setter

A Gordon Setter is a large breed of dog, a member of the setter family that also includes both the better-known Irish Setter and the English Setter. Setter breeds are classified as members of either the Sporting or Gundog Group depending on the national kennel club or council. The original purpose...

s, but in any litter some individuals may be much less soft-mouthed than others, as there may be relatively soft-mouthed individuals in a litter of even classically hard-mouthed breeds such as Jack Russell Terrier

Jack Russell Terrier

The Jack Russell terrier is a small terrier that has its origins in fox hunting. It is principally white-bodied smooth, rough or broken-coated which is commonly confused with the Parson Russell terrier and the Russell terrier with the term "Jack Russell" commonly misapplied to other small white...

s or Mastiff

English Mastiff

The English Mastiff, referred to by virtually all Kennel Clubs simply as the Mastiff, is a breed of large dog perhaps descended from the ancient Alaunt through the Pugnaces Britanniae. Distinguishable by enormous size, massive head, and a limited range of colors, but always displaying a black mask,...

s.