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Size Matters: Protecting All Dogs with the 50 Percent Rule

Adapted from The Business of Dog Walking: How To Make a Living Doing What You Love, written by Veronica Boutelle of dogbiz and published by Dogwise.

Sometimes size does matter. While it’s always charming to see a Great Dane and a Chihuahua make friends, or a Mastiff and Pomeranian find common ground to play, the reality is that large size differences between dogs are inherently dangerous, no matter how well behaved both dogs are.

For one thing, small dogs are too often inadvertently injured by larger dogs. This can happen during well-meaning, consensual play. It can happen when an excited larger dog runs over a smaller companion while chasing a ball or bird or butterfly. It can happen when a larger dog simply steps on a smaller dog while vying for a treat or just not paying enough attention to her surroundings.

The larger danger: Predatory drift
And then there’s the phenomenon known as predatory drift, in which the prey instinct is triggered in a non-prey situation. Dogs are programmed to respond to small, running animals and to high-pitched squeaks—both behaviors elicited by prey animals. Unfortunately, sometimes dogs also exhibit these behaviors. It is more common than is generally realized for dogs to kill other dogs in predatory drift incidents. Most often these tragedies occur between dogs who like and regularly interact with each other, such as in dog daycare and group dog walking settings.

Small dogs can look alarmingly like prey animals when they tuck tail and run, and they are often given to nervous squeaks when startled or overwhelmed. These stimuli can kick off predation behavior in other dogs. And when there is a significant size difference, that can mean serious maiming or death for the smaller dog.

Predatory drift can also be a group phenomenon, as the prey sequence is a group activity among wild dogs. In other words, dogs will sometimes gang up on a running or squealing dog. The most famous incident of this kind was a documented case of a group of Beagles who killed one of the pack when it became tangled in a fence and began to struggle and squeal in distress.

There are two critical things to understand about predatory drift: Dogs who kill other dogs in a predatory drift incident are not aggressive or “bad” dogs. They are not intending to kill one of their own. They may have never shown any signs of aggression to another dog in the past. They may be among the most friendly and accomplished players. It can happen to any dog. However, dogs with high prey drive (dogs who like to chase things, especially small animals) may be at higher risk.

The second thing to understand is that predatory drift can—and usually does—happen between dogs who know and like each other. It happens in daycares, on dog walks, in private homes. Dogs liking each other, even being long-time best friends, is no insurance against predatory drift.

The 50% rule
So how to protect against both accidental injuries and predatory drift? Follow the 50% rule. Dogs who have more than a 50% weight spread should not be grouped together for dog walks or in other settings such as daycare or boarding. It’s not enough just to supervise dogs of mixed sizes, as predatory drift happens so swiftly that human intervention from even a couple of feet away is usually not fast enough to save the smaller dog.

If you are a group dog walker, we recommend grouping dogs by weight. This means not walking dogs with more than a 50% weight difference together. For example, a 30 pound dog should not be walked with any dogs larger than 60 pounds. Though predatory drift can happen among dogs of the same size, the likelihood that one will be killed or maimed before the drifting dog snaps out of it is far less likely, as a similar-sized dog stands a chance of fighting back.

If you currently walk groups with a broader size range, take steps to rework the dogs in your care into more size-appropriate and safe groups. Everyone benefits, as everyone loses in a predatory drift incident. We often feel badly for the dog who is attacked and their owners, but a drift incident has a large impact also on the dog who drifts and the people who love him. And of course on you and your business, too.

Protecting small dogs from others’ dogs
You can control for size difference in your own groups, but you don’t have control over the environment at large. If you walk small dogs, here are a few tips to help keep them safe from predatory drift incidents involving dogs outside your care:

Choose wisely where you walk. Where you walk makes a huge difference in your risk level. Choose areas trafficked by fewer dogs whenever possible, and ideally areas where you can easily see what’s coming your way.

Exercise, don’t socialize. Always avoid letting small dogs meet larger dogs, even on leash. Remember that any interaction, even social ones, can turn into predatory drift. If you see your professional mandate as exercising rather than socializing, you greatly decrease the likelihood of tragedy.

Leash up, leave, or pick up. If you see larger dogs approaching, try for avoidance first by changing direction and leaving the scene. If you don’t have that option or you can see the larger dog is intent on coming over to join you, leash your small dog if she isn’t already. Once a dog becomes overwhelmed and bolts away you have no way to protect her. If you know you have a dog who is likely to panic and engage in “victim behavior” such as squeaking or squealing, consider picking her up before the larger dog reaches you. While this can sometimes increase the larger dog’s interest, it can also help avoid triggering drift. (If you can avoid picking a smaller dog up, it’s better to, as there is some risk you may be bitten in cases where the larger dog chooses to attack the dog you’re holding.) Keep any interaction as brief as possible and exit the scene as quickly as you can.


This article is adapted from The Business of Dog Walking: How To Make a Living Doing What You Love, written by Veronica Boutelle of dogbiz and published by Dogwise.