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How to Treat Puppy Leash Aggression

Haley photo


January 22, 2024

Dog Reactivity

How to Treat Puppy Leash Aggression thumbnail

Can Young Dogs Be Reactive?

Aggression is usually rare in puppies — but some dogs can start displaying reactivity at a young age. If you're worried about puppy leash aggression or think your family's new addition might be leash reactive, you've come to the right place.

Here are some key things to know to help your pup grow up into a happy, confident, well-behaved dog!

Are leash aggression and leash reactivity the same thing?

Everyone’s favorite answer here: It depends.

"Leash aggression" and "leash reactivity" are often used interchangeably. They terms can have slightly different nuances in meaning, though, depending on who exactly you’re talking to:

  • Leash aggression refers to aggressive behavior displayed by a dog while on a leash. This aggression can manifest as growling, barking, lunging, or even attempting to bite when the dog is restrained by a leash.
  • Leash reactivity can be a broader term that encompasses a range of behaviors exhibited by a dog while on a leash. Reactivity can include not only traditionally-considered aggressive behaviors but also fearful, anxious, or overly excited emotional responses. Per Sniffspot's proprietary survey research, 66% of dogs are reported by their guardians to be reactive — and 65% of these dogs are leash reactive specifically.

Both refer to undesirable behaviors (like barking, growling, lunging, whining and pulling) your puppy might show when they encounter a specific trigger (like other pets, strangers, bikes, or cars) on leash — so in this article we’ll treat both terms the same way.

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What's at the root of most leash aggression and leash reactivity?

More often than not, leash reactivity is caused by one of two major F-words: Fear and Frustration.

Typically, a dog who is being reactive on their leash has one of two goals in mind. They either want to get away from something they’ve seen in their surrounding environment (fear) or they want to get closer to something (frustration).

Fear-based leash reactivity: Dogs have a negative association with a scary stimulus

In fear-based leash reactivity, your dog’s fight or flight response has been triggered and — no matter which instinct they’re inclined to follow — they feel trapped by their leash.

Even a dog who instinctively wants to run from a perceived threat will often fallback on seemingly aggressive behavior, like barking and growling, if their leash makes fleeing the scene impossible. (Think of this like the classic "fight or flight" response we hear about in almost all animals. If we've removed the flight option by holding our dogs still on a leash, they're left with fight as a go-to fearful response.)

Dogs experiencing fear-based leash reactivity will often seem even more aggressive than their more excitable frustration-based counterparts. Anyone with a tiny dog who becomes a barking machine at the sight of any bigger dog on walks knows this all too well!

Frustration-based leash reactivity: Dogs want to access something in their environment but can't

Frustration-based leash reactivity stems from a dog’s unmet desires. This could be anything from the desire to play with another dog on a walk to a desire to run up and say hi to every human they see to a deeply-ingrained need to chase all squirrels, birds, and other small creatures.

Just because a dog wants to do something, however, doesn’t mean they should — take the all-too-common doggy desire to dart into traffic and chase cars, for example. While using a leash is a fabulous way to manage these situations, it's inevitable that some undesirable replacement behaviors might bubble up when we restrict our dogs from following their natural urges.

A puppy pulls on their leash

What age does leash reactivity usually develop in dogs?

Leash reactivity can develop at various ages in dogs. There isn't a specific turning point that always applies! Certain factors may contribute to the development of leash reactivity at different life stages, though.

Here are some things to consider:

  • Leash reactivity is commonly observed during the adolescent phase (between six months and two years of age). During this period, hormonal changes, increased independence, and a heightened sensitivity to the environment can contribute to reactive behaviors. Sometimes dogs outgrow these struggles on their own, while other times they’re a sign of a long-term struggle. Regardless, it’s important to help your teenage dog through their reactive displays!
  • If a dog has not been adequately socialized during the critical period of puppyhood (up to around 16 weeks of age), they may be more prone to developing reactivity, especially if they have a bad experience later on. Early positive associations and exposure to various stimuli, including people, animals, and environments, is incredibly important.
  • Dogs that have had negative experiences while on a leash, such as being attacked by another dog or facing frightening stimuli, may develop reactivity as a protective response. Traumatic events can contribute to fear-based reactivity at any age, but especially when dogs are young and impressionable. These can unfortunately be even more harmful than a lack of socialization can be, meaning it's important for dog guardians to be on the lookout for fearful behaviors and make thoughtful risk assessments.
  • Changes in a dog's living environment, routine, or exposure to new situations can trigger reactive behaviors. Moving to a new area, changes in the household, or disruptions to the dog's routine may contribute to leash reactivity.

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How do I know if my puppy has leash aggression or is just being excitable because they’re young?

Distinguishing between leash aggression and excitable behavior in a puppy can be challenging. Both may involve barking, pulling on the leash, or other energetic reactions out on your walks. You don’t want to panic about your dog’s long-term behavior if it’s just a normal phase — but you also want to take any signs of reactivity you see seriously so that you can start helping your pup right away.

Here are some components to think about when trying to determine whether your puppy might be on their way to becoming a leash-aggressive dog or is simply being excitable:

  • Body language: An excitable puppy may exhibit loose, wagging body language. They probably have a bouncy or playful demeanor — without the intense tight posture seen in many forms of leash reactivity or aggression in adult dogs. Nervous dogs are more likely to show the whites of their eyes (this is called whale eye) as well as dilated pupils, often while lip licking. They might struggle to break eye contact with their triggers as they display these early warning signs of discomfort.
  • Triggers: Leash aggression occurs in response to specific triggers, such as the presence of other dogs, unfamiliar people, or certain environmental stimuli. Excitability, on the other hand, may be triggered by a variety of things (or nothing at all) including the anticipation of play, novel experiences, or simply the wind blowing in the breeze.
  • Ease of redirection: An excitable puppy is more likely to respond positively to redirection, training cues, or a change in focus than a dog who is deeply afraid of a particular trigger. They may quickly shift from excitement to a calmer state or at least be able to pay attention back to you more easily. They also probably show more confidence on leash in general, which makes it easier for them to offer you eye contact and keep a loose leash instead of fixating on the world around them.
  • Consistency of behavior: Leash aggression tends to be consistent in specific situations or with certain triggers. It is not solely linked to moments of high energy or excitement.

If my dog is leash reactive as a puppy, does that mean their behavior will be even worse in adulthood?

Leash reactivity in a puppy doesn't necessarily predict that the behavior will be worse in adulthood. A puppy's behavior is still highly malleable! Training interventions can be particularly effective at a young age.

That said, a very young dog displaying leash aggression might suggest that the behavior is at least in part genetic, meaning it could be more difficult to completely address. Regardless of your individual dog’s history and predispositions, though, the most important thing is to address the reactivity as early as you can, starting with a comprehensive exam by a veterinary professiona.

The right, humane training methods and proper socialization experiences can go a long way!

Sniffspot Dog running on field

Get safe exercise for your dog by renting a private dog park near you

Further reading and learning

There are countless great resources for how to live with and train a reactive dog! Here are a few that we like.

Sniffspot blogs on canine reactivity

We have an entire blog category devoted to dog reactivity and related problem or unwanted behaviors. One of our primary goals is to be a welcoming community for reactive dogs — that’s why we have intentional rules (like gaps between arrivals and transparency about other animals within view) to keep all Sniffpots safe.

Here are a few specific articles:

  • How to Train a Reactive Dog: A Beginner’s Guide for everything you need to know to get started implementing a training program for your reactive dog, including how to set up some initial training sessions and supplies you need to have on hand (like high-value treats, a treat pouch, sometimes a basket muzzle, and more)
  • How to Socialize Your Reactive Dog for help on how to give your fearful, frustrated, or otherwise reactive dog positive experiences with other dogs and people
  • Dog Reactivity Chart for help understanding the current level of reactivity your dog shows in different moments

Other training resources on dog reactivity

Good luck, and remember: you’re not alone. When in doubt, get in touch with a professional force free trainer or veterinary behaviorist you trust. (They should be able to help you rule out medical conditions, choose the right training tools, implement counter - conditioning, and teach you about other behavioral therapy).

And know you can always bring your dog to a Sniffspot for some playtime!

Trainer Review of this Article

There is so much misinformation out there, and we want to make sure we only provide the highest quality content to our community. We have our articles reviewed by qualified force free trainers.  

This is the trainer that reviewed this article:

Shannon Finch
AnimalKind Training
M.Ed. Humane Education
Karen Pryor Academy Certified Training Partner
Certified Tellington TTouch and TTEAM Practitioner

Sniffspot's Proprietary Survey Statistics

Sniffspot Research 2023, n = 4,092

Get your dog the safe enrichment they need by renting a Sniffspot

Sniffspot Dog swimming in pool
This infographic about dog reactivity is set in a green and white color scheme. Graphics and illustrations show stats like the dog breeds with the highest levels of reported reactivity, the most common reactivity triggers, and how dog reactivity is concentrated in different areas of the United States.
Haley photo


January 22, 2024

Dog Reactivity

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