aggressive dog

A dog displaying signs of reactivity isn’t necessarily aggressive. However, it’s important to understand the difference between these two states, and to prevent a reactive dog from crossing the threshold into anger and hostility.

What does it mean when someone says a dog is “reactive”? This word often causes feelings of uncertainty, trepidation, possibly even fear, because many people believe it means the dog is aggressive or hostile. It’s not surprising, because our perception of reactivity often correlates with a range of unpleasant, problematic personality traits, such as barking at everyone, lunging or charging at people, and growling or snapping. But do such traits automatically mean the dog is hostile and aggressive? Should a dog labelled as reactive always be considered a threat?

These questions have important implications, particularly for thousands of shelter and rescue dogs waiting for adoption. Many come from unknown backgrounds. Some have been neglected, poorly socialized, even physically abused. Occasionally, personality overviews of these dogs may describe their behaviors with phrases like “demonstrates reactivity”. This means potential adopters need to clearly understand what this description may – and may not – imply.

Similarly, existing dog owners often notice reactive predispositions in their own canines – barking or growling at every noise, high strung behavior around other people, etc. Are these behaviors merely exasperating – or cause for deeper concern? Understanding what you’re seeing can make a big difference when it comes to obtaining appropriate behavioral intervention.

Defining reactivity

Steve Frost, Animal Enrichment and Behavior Manager at Chicagoland-based Anderson Animal Shelter, maintains that a dog displaying reactive behaviors “isn’t giving us a hard time; he’s letting us know he’s having a hard time.” Steve explains that shelter workers watch closely for signs of overt anxiety or aggravation in the dogs in their care, and often brief potential adopters. He emphasizes that the goal is not to stigmatize, label or oversimplify. In the average animal shelter, in fact, reactive signs are on display almost daily – and it’s important to help everyone understand the precise patterns being observed.

“Many dogs are under quite a bit of stress in a shelter environment, which can cause them to cross that threshold of ‘acceptable’ behavior,” agrees Michelle Lenz, Animal Care Manager at Naperville Area Humane Society.

Many animal behaviorists concur that the idea of “thresholds” plays a key role in defining and understanding reactive behaviors in dogs. Think of a continuum with multiple points; essentially, a spectrum of progressive behaviors. Upon encountering a particular trigger – for example, a ringing doorbell, human visitor, or another pet – some dogs will remain consistently relaxed, unruffled and calm. Others, however, will cross a threshold and begin to demonstrate one or a series of overzealous responses. Of this subset of dogs, a certain percentage may escalate even further into unsafe, aggressive behaviors.

Different triggers can affect each dog in very different ways. However, if you were to list general examples of behavior corresponding to categories that progress from calmness to aggression, observable behaviors might include one or more of those noted in the table below.

Spectrum of progressive behaviors in dogs

Low end of spectrum – calm, undisturbed dog Approaching trigger threshold – tense, alert dog Crossing trigger threshold Level 1 – reactive dog Crossing trigger threshold Level 2 – aggressive dog
Loose body posture

Soft mouth

Relaxed ears

Responsive to owner/handler

Focused intense staring

Ears forward

Mouth closed

Alert/stiffened body posture

Hackles/tail raised

May be only marginally responsive to owner/handler

“Explosive” barking/yipping

Repetitive, jumping, whining or crying





May no longer be responsive to owner/handler




Unresponsive to owner/hander


Reactivity isn’t aggression – but can turn into aggression

Potential adopters should keep in mind that dogs change and evolve throughout their lives. “The fact that a dog might exhibit reactivity in a shelter should not automatically discount him from becoming a wonderful family pet,” Steve says. “Some of the best learning partners and friends I’ve ever had were dogs labeled ‘reactive’.”

In actuality, Steve continues, “reactivity often starts out as some form of frustration. For instance, dogs might react because they can’t get close to a particular stimulus – perhaps a cat, person, another dog, or a wild animal.” These troublesome behaviors “may begin innocently, with a social desire to play or interact.”

“Reactivity often starts out as some form of frustration.”

Michelle agrees that reactive behaviors, in and of themselves, are generally more irksome and counterproductive than outright dangerous. Those who experience life with a reactive dog know that a daily walk may quickly intensify into a series of leash-pulling adrenaline surges. They understand that enjoying a favorite television program may become virtually impossible when the dog hears a noise outside.

Basic frustration aside, however, Michelle cautions that it’s unrealistic to presume such behaviors will never cross the line into outright aggression. This is because chronic frustration that remains unaddressed can conceivably worsen over time.

“It can lead to anger,” says Steve, “and this anger could eventually lead to negative associations that potentially cause a reactive dog to act aggressively.” Think of a pot of bubbling water on the stove. If ignored for too long, it will gradually boil higher and higher until it spills over, potentially harming objects and/or people in the near vicinity.

This is why Michelle stresses that it’s vital for people to honestly recognize and acknowledge reactive tendencies in their dogs. She stresses that reactive displays should be noted, tracked and taken seriously.

“We don’t consider reactive and aggressive behaviors to be synonymous,” she explains. But no one should ever assume a dog will simply ‘grow out of’ reactivity.” She emphasizes that people with reactive dogs need to invest some time in learning – and applying — positive, appropriate behavior modification techniques to help avoid the possibility of escalation. With the help of a dog behaviorist and/or a positive reward-based trainer, you can get to the root of your dog’s reactivity, and prevent it from becoming aggression.

5 ways to prevent reactivity from turning into aggression

If you have noticed reactive behaviors in your dog, there are some specific action steps you can take to address the issue and prevent him from crossing the threshold into anger and aggression.

1. Don’t be intimidated by labels.
When it comes to reactivity, Steve notes that “labels tend to stick with a dog as a simple fix for describing a very complex interaction.” Realize that your dog learns, evolves and responds uniquely – just like any other living creature. As well, you and your dog should never feel embarrassed or stigmatized for dealing honestly and proactively with a behavioral issue.

2. Recognize outright aggression.

If your dog is routinely snarling and/or trying to bite others, these are aggressive tendencies. Canine aggression is much more than a simple re-training issue. The root cause can sometimes be exceedingly complex, and may even include physical or neurological components. So if you’re noticing such behaviors, always schedule a veterinary evaluation as an initial step.

3. Enlist the help of an appropriate trainer.

“Every dog is different, and it’s well worth getting an experienced, accredited, positive-reinforcement trainer on board to help you accurately assess what’s happening,” says Steve. Michelle adds that accreditation is key. “Look for a CPDT-KA trainer or animal behaviorist,” she advises. The acronym stands for Certified Professional Dog Trainer Knowledge-Assessed, and lets you know an individual has been tested and certified to possess an extensive range of skilled awareness in animal psychology, learning theory, and dog training methodology.

4. Honestly alert others to your dog’s reactivity.

Older programs like The Yellow Dog Project advocated using a simple yellow bandana to let others know your dog needs some additional space, patience and understanding. However, you can also print “I’m in training” on a colorful neck scarf, or simply ask neighbors to give your canine some supportive leeway.

5. Believe in your dog.

Finally, Steve reassures both dog owners and prospective adopters that many reactive canines simply have individual needs. “These dogs may require some investment in terms of time and targeted training,” he says. “But often, with great investment comes great reward.”


Marybeth Bittel is a freelance writer and marketing consultant who lives in the Great Lakes region with her husband and rescue dogs. She has spent more than 20 years working to nurture, re-socialize and rehabilitate abused rescues of all breeds, shapes and sizes.