In response to my article on "What a Dog's Tail Wags Really Mean" I received a note about a Labrador Retriever named Molly. It read in part:

After her accident [involving a collision with a motorcycle] the vet had to amputate her tail leaving a stump of only around two inches. She recovered okay and still has a personality that is good with people and kids (just like before the accident) but something has changed in her dealings with dogs. We always took her to an off-leash dog park here in Vancouver and she always had good relations with the other dogs. Since her tail was cut off though, other dogs seem to be suspicious of her and they don't come up to her the same way they used to. A few have actually snapped or growled at her, which never happened before. Could this be because her tail is gone so that the other dogs can't understand her tail communications anymore?

Given the importance of a dog's tail for signaling this is a likely conclusion. This idea that tail length might influence canine communication worried me particularly in the context of tail docking, which is where a dog's tail is deliberately cut short in certain breeds of dogs, such as Rottweilers, Doberman Pinchers, Cocker Spaniels, Boxers and so forth. My concern has always been that docking significantly limits the use of tail signals and thus reduces the effectiveness of a major channel of communication in dogs. Although this is an important issue I could find no data in the scientific literature which addressed the question of whether dogs with short or missing tails had signaling problems. To shed some light on the matter I carried out an observational experiment and published the data in my book "How to Speak Dog." In our study we observed dogs interacting in a confined city park area where dogs were allowed to be off leash. We tallied 431 encounters between dogs. Most of these (382 or 88 percent) were typical canine greeting behaviors, often followed by play behaviors including the usual chase games. The remaining 49 encounters contained an aggressive element on the part of one or more of the dogs involved. These could be as mild as a snarl and a snap with no physical contact or as severe as an actual physical assault drawing blood. The dogs involved were coded simply on the basis of whether they were tailless (most likely docked) or with a tail (undocked or only partially docked). To be classified as being tailless the dog had to have a tail approximately six inches or less in length (we eliminated small toy dogs from the sample confining our observations to dogs that stood approximately 18 inches at the shoulder or more). The proportion of dogs with tails was considerably higher in this population, and amounted to 76 percent, as opposed to 24 percent of dogs without tails. However, when we looked at the dogs involved in aggressive incidents 26 (or 53 percent) of these confrontations included dogs without tails. On the basis of the number of dogs with and without tails, we would have expected only 12 aggressive incidents (24 percent) to involve tailless dogs. The surplus number of confrontational incidents involving tailless dogs is highly statistically significant when we do the appropriate calculations. Thus our results show that dogs with short or absent tails are twice as likely to have aggressive encounters as dogs with longer, and hence more visible, tails. One cannot help but wonder if the increase in aggressive encounters in short tailed dogs might not have to do with the ambiguity or absence of appropriate visible tail signals that could have indicated a social versus a hostile attitude on the part of the docked tail dogs and thus avoided a potential conflict.

Of course one might argue that this study might be flawed because many of the dogs which have docked tails are working dogs designed for guarding and protection functions, such as the Rottweiler, Boxer or Doberman. Thus they might be expected to have a somewhat more forceful and insistent personality which might lead them into confrontations with other dogs. This led the biological researchers Steven Leaver and Tom Reimchen of the University of Victoria in British Columbia to try another approach, which was published in the scientific journal Behaviour. They constructed a robot dog which stood around 20 inches at the shoulder and was stuffed with cotton and covered with black synthetic fur so that it looked much like a Labrador Retriever. It could be fitted with a 12 inch long tail or a 3.5 inch short stubby tail (see the figure below) and this tail's movements could be remotely controlled.

dog dogs canine canines pet pets robot tail wag wagging long short docking

Starting with the long tailed version of the robot they placed the robot dog in an off-leash exercise area. They found that when the robot's tail was wagging (non threatening) other dogs would approach it in what looked like a playful manner, however when its tail was held upright and was motionless (a dominant threat signal) the other dogs avoided it. This is exactly what we would expect if the dogs were reading the robot's tail signals as if it were a real dog. Next the researchers replaced the long tail with the short "docked" version and again the robot dog out in exercise area. Now the other dogs approached it cautiously and in a guarded manner, regardless of whether the tail was wagging or not. The impression the researchers got was that the other dogs were acting as if they could not make up their minds as to whether the robot would receive their approach in a friendly or a hostile manner.

Obviously a real dog with a docked tail could use some strategies involving other aspects of their body language to offset the problems associated with a missing tail. However this study shows that at the very least dogs with short docked tails are at a disadvantage when interacting with other canines and that can place them in jeopardy of misunderstandings by other dogs. Such cases of disrupted communication might in turn lead to aggressive encounters. Tail movements and tail positioning are vital channels of communication among dogs, and perhaps we humans should think twice before we dock their tails and deprive them of its benefits-especially if the tail docking is being done solely as a matter of fashion or style.

Stanley Coren is the author of many books including: Born to Bark, The Modern Dog, Why Do Dogs Have Wet Noses? The Pawprints of History, How Dogs Think, How To Speak Dog, Why We Love the Dogs We Do, What Do Dogs Know? The Intelligence of Dogs, Why Does My Dog Act That Way? Understanding Dogs for Dummies, Sleep Thieves, The Left-hander Syndrome

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

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