Are Dogs' Nose Prints Really Unique and Unchanging?

Source: m01229/CC BY 2.0

I was somewhat surprised when I read a recent article by a team of Korean investigators, headed by Hyeong In Choi of Seoul National University, in the scientific journal Animals. My surprise came from the fact that the authors stated that, "The objective of this paper is to focus on the canine nose pattern (nose print) by studying if it can be used similarly to the human fingerprint as a unique biometric marker for each individual dog."

As a scientist and dog owner residing in Canada, I knew that the Canadian Kennel Club has been accepting dog nose prints as proof of identity since 1938. A few places in the United States have also adopted dog nose printing as a common way of identifying lost dogs as well. The stated belief is that nose printing is a more reliable way of matching identity, since a dog tag on a collar can be lost, and microchips can malfunction or become dislodged, making them useless for determining the dog's identity. The argument is that the nose print serves as a unique biometric marker for individual dogs.

Fingerprints Versus Nose Prints

The most familiar biometric marker of identity for most people is fingerprints. The uniqueness of fingerprints and their usefulness for identifying people was first established by Francis Galton, an eminent 19th-century scientist whose life and career spanned the reign of Queen Victoria. He made significant contributions to the study of psychology and statistics, but also did important work in establishing the forensic usefulness of fingerprints, and establishing the first system for classifying them. Galton claimed that fingerprints were unique and that no two individuals have the same fingerprint patterns. (Recently it has been determined that the actual probability of finding two identical fingerprints is one in 64 billion, even including twins. Given the fact that the population of the entire world amounts to under 8 billion, that makes it highly unlikely that any two people alive today will have the same fingerprint.)

Of course dogs don't have fingerprints. However, the substitute biometric marker for fingerprints in dogs is their nose print. It has been supposed that just as the pattern of every person's fingerprints is unique, each dog's rhinarium (the section of bare skin at the tip of a dog's nose) has a distinguishing design of dimples, dots, and ridges that, when combined with the shape of his nostril openings, is believed to make a mark that is distinctive enough to conclusively identify one dog among all others.

Is There Any Scientific Proof?

So what is the evidence for this assertion that every dog's nose print is unique? This turned out to be one of those puzzling situations. I did a fairly extensive literature search to try to find out what the evidence was for the uniqueness of canine nose prints. I found several veterinary texts which asserted that canine nose prints were unique enough to be able to be used for identification, but none of them provided any references to actual scientific data on dogs. In fact, most of them referred to articles using nose prints to identify cattle. There is a lot of literature on the bovine nose print suggesting uniqueness and invariance, but the only report I could find on dogs was a three-paragraph short note in the journal Veterinary Quarterly in 1994, which stated that in the course of developing a computer program to recognize canine nose prints an unspecified number of Doberman pinschers were tested and their nose prints were found to be unique. On the basis of that literature search, I can only conclude that the assertions about dog nose prints are extrapolations based on the data collected mainly on cattle. Given that fact, it then made sense why the Korean team collected their new data.

The New Data

This contemporary study used a very small number of dogs, namely two litters of beagles for a total of 10 dogs. The researchers were asking two questions: if the canine nose pattern is properly formed by two months of age and if this nose pattern remains unchanged throughout the first year of the dog's life. Obviously, given such a small sample, the assumption of the uniqueness of an individual's nose pattern could not be definitively tested, however by using dogs in the same litter the chance for similar patterns might be increased.

The findings were quite clear. By 2 months of age, the nose print pattern was established, and monthly testing over the first year of their life showed no changes in the pattern. Furthermore, the investigators were able to show that a computer program could be used to identify nose prints. This result suggests that if a database could be established for dogs' nose prints, then the canine equivalent of the Automated Fingerprint Identification System (AFIS) used by police forces to identify potential criminal suspects by their fingerprints, might be useful to locate and identify lost dogs.

A Unique Canine Keepsake

Even in the absence of such a database, it is a fun project to collect your dog's nose print, perhaps to frame it as a unique keepsake of your pet. The process is really quite simple and only requires a roll of paper towels, some food coloring, and a pad of paper. First blot your dog's nose with a paper towel to dry it out a bit. Then dip a piece of paper toweling into some food coloring and dab it onto your dog's nose. Gently press the pad of paper to your dog's nose, curving it around or rolling it in a smooth motion from one side to the other to ensure that you get the impression of the entire nose. You'll probably require a few attempts before you get a clear picture of what you want (especially if you have a squirmy dog). Once you get your clear print, immediately clean your dog's nose. You now have a frameable memento that may well be completely unique to your pet.

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission.