You only need to step inside a pet shop to see the vast array of collars, harnesses and leads available to dog owners. Owners can choose a particular look, colour scheme and material type. But amongst all of this, there is a more serious question of the role of the collar and the impact it may have on the dog. Historically, collars were used as a means of identifying a dog as being owned. Today, in the UK, as in many countries, it is a legal requirement for a dog to wear a collar and tag to provide key information about the dog, in order to identify the owner and to return it should it become lost. However, collars are now commonly used as a means of restraint and control for dogs to make sure they don’t wander off when out for a walk.

The problem is that the neck is a pretty sensitive area of the body, and many dogs pull on the lead. Ultimately, the neck connects the head to the rest of the body, carrying some pretty vital anatomical features such as the spinal cord, major blood vessels, the windpipe and the food pipe. Serious damage to the spinal cord in the neck can result in paralysis, or even death. Similarly, damage to the windpipe can impact a dog’s ability to breath or even result in choking, another potentially fatal injury. Linking to our normal research area, heat-related illness, compression of the windpipe can impact a dog’s ability to breathe effectively, impairing their ability to cool. When it’s hot outside, allowing a dog to pull on a collar and lead could potentially result in them over heating more quickly.

In fact, when questioned, almost 50% of owners suggested that their dogs pulled on the lead. This might range from a consistent light pull, to an owner being ’towed’ up the street by an overzealous dog. And of course, there is the sudden jerk on the lead from a normally calm dog, as a cat goes running across the road. On the other end of the lead is the owner, perhaps getting a little impatient at the 17^th lamppost being sniffed, and offering a quick tug on the lead, or the frustrated individual jerking the lead to remind their dog to listen and behave. In all these instances, the resulting impact is a pressure applied to the dogs’ neck.

Two aspects are worth exploring; the impact of the type of collar – are some better than others? And the impact of the force applied – is a light pull on the lead less likely to cause harm?

Anne has been exploring just this topic, using pressure sensors attached to various styles of collar to test how much force then could be applying to our dog’s necks. Because of the risk to the dogs’ neck, and to retain consistency, a model neck (plastic pipe) was used instead of actual dogs. Working with Dr Mandy Roshier and Prof Donal McNally from the University of Nottingham, eight different collar types were tested. These were chosen to represent the range of commercially available types rather than focusing on specific brands: a rope slip lead, leather and thread, plain webbing, webbing padded with neoprene, thicker neoprene padded sports, wide lurcher, rolled collar and check chain.

The forces tested aimed to replicate a light pull on the lead (40N), a strong pull on the lead (70N) and a lead jerk (~141N).

The collars reacted differently in both the way the pressure was distributed and the amount of pressure applied to the model neck, the pressure increased as the force applied to the collar increased. Arguably the most interesting and valuable finding was that the pressure exerted on the neck model ranged from the lowest, 83kPa at 40N to the highest, 832kPa at 70N across the range of collars. To put this into context, in humans, pressure over 33.3 kPa has been shown to increase intraocular pressure (pressure within the eyeball which can lead to pain and ultimately blindness) and compress blood vessels, limiting blood supply to tissues. Tourniquets used in emergency situations to stop serious blood loss following trauma are used at a pressure of 33.3kPa on the arm and 40.0kPa on the thigh. In horses, pressures above 30kPa under the saddle are associated with back pain.

30kPa is enough pressure to strangle a human, and 230kPa is enough pressure to crush a human’s windpipe.

In short, no single collar tested provided a pressure anywhere near low enough to remove the potential risk of injury when pulling on the lead. Where dogs pull on the lead or the lead is jerked, there is a risk of injury to the neck for all collar types and styles tested, even where collars are padded or wide fitting. Collars are a great way to display tags and add a little personal flare to your dog. But for restraint and control, a non-restrictive harness is a much better option, and in hot weather a harness is definitely the safest option.

The full article is available here as a pre-print copy: FINAL Canine collars – an investigation of collar type and the forces applied to a simulated neck model