Dogs of this breed have two noses.

Both types of animals present with relative frequency, individuals with forked snout. And while this type of nasal pattern is considered normal and desirable in these dogs, a new scientific finding has shown that it can bring associated behavioral problems, compromising animal welfare.

What Causes Double Nose in Dogs

The double nose in dogs is a malformation that has been equated to a cleft lip in humans. Cleft lip occurs when during embryonic development the tissue that forms the lip and the tissue that forms the palate do not join together correctly. This process occurs during the third week of gestation and gives rise to a series of anomalies in the skull and face. For example, palate malformations areas of the unfused lip and widely spaced eyes (hypertelorism).

Surgery in humans, fashion in dogs

Nowadays, when a person is born with a cleft lip, a aesthetic and functional operation before the first year of life.

However, in dogs, the forked nose was consolidated as a fashion in the 20th century. This was due to the false belief that these dogs with two noses could smell more.

Two nostrils that would act as the eyes of a chameleon, completely independently. With all this, the split nose became a tradition for the ancient Iberian pointing dogs.

Double nose and other malformations in dogs

  • Absence of the vomeronasal organ: a dog of the Pachón Navarro breed called donehas turned out to be the first and only case, at least for the moment, of a dog that was born without a vomeronasal organ.
  • the vomeronasal organ, also known as Jacobson’s organis a common organ in some vertebrate animals such as giraffes, dogs and cats, whose function is to detect the pheromones of other individuals.
  • Absence of vomer bone: The vomeronasal organ is housed in a bone called the vomer that is located between the nose and the mouth. It turns out that Hacho not only lacks a vomeronasal organ, but also no vomer bone.
  • Absence of septum pellucidum: the septum pellucidum is a thin septum located in the central part of the brain. The absence of the septum pellucidum is related to alterations in the development of the nervous system that affect sleep and cognitive disorders.
  • Hypertelorism: The eyes of dogs with double noses are further apart than normal, which can cause certain vision problems.
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Behavior Problems in Dogs Associated with Double Noses

  • Difficulty resting and disturbances in the sleep-wake cycle: the absence of septum pellucidum would explain why Hacho had trouble resting.
  • Lack of sexual behavior: Hacho the dog showed no interest in females during heat. This is explained by the lack of a vomeronasal organ.
  • Intraspecific aggressiveness: The double-nosed dog, Hacho, showed aggression towards other dogs despite having been correctly socialized. This could be related both to the absence of olfactory structures and to the hypertelorism.

All behavior problems in dogs could have an organic origin, but studies are lacking.

The case of the Hacho’s forked nose, its lack of olfactory structures and its behavioral problems, is the first to be described in dogs. Susana Muñiz de Miguel, the veterinarian responsible for the discovery, assures that the three things (forked nose, absence of olfactory structures and behavioral problems) are related and that there is no behavioral problem that does not have an organic cause. What the veterinarian Muñiz proposes is more research.

He comments that if there are studies in rodents who underwent removal of the vomeronasal organ and the septum pellucidum, observing how sexual behavior disappeared and changes in the sleep cycle appeared.


  • Muñiz de Miguel, S., et al. 2023. Behavioral disorder in a dog with congenital agenesis of the vomeronasal organ and the septum pellucidum. Veterinary Record Case Reports, e571.

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