Neurophysiology of Territorial Aggression in Dogs & Common Behavior Modification Approaches

https://youtu.be/MRw_nOS34-A

TRANSCRIPT:

Hi, my name is Eileen Koval and I will be discussing human behavioral interventions for stranger-directed territorial aggression in pet dogs.  Probably everyone listening to this episode knows at least one dog on their street who has this issue, if they don’t have a dog themselves who is a bit territorial.  Dog aggression toward unfamiliar people that occurs on (or near) the home property is a common issue faced by dog owners and dog trainers in the United States.  As many of you may have experienced, dogs sometimes claim territory beyond the actual boundaries of their home property, such as the sidewalk or across the street and may react when people enter those spaces.  These aggressive behaviors can be due to a multitude of factors, including human factors and factors inherent to the dog themselves.  Dogs displaying territorial aggression may have strong genetic factors predisposing them to fearfulness, anxiety, and/or guarding behaviors as a result of purposeful human-selected breeding.  Peréz-Guisado & Muñoz-Serrano described in their (2009) research study how humans sometimes choose dogs specifically for these territorial behaviors when they bring them into their home – they may like the way the dogs look, or they like the idea of the dogs keeping certain people away from their property.  They either ignore or sometimes reward the barking and growling at people who come near the home.  However, they may later become surprised when the aggression is directed toward unintended people.  According to veterinary behaviorist Dr. Lore Haug in her 2008 research article, a lack of appropriate early socialization during the first year of life can result in neuroendocrine changes that correlate with fearfulness and aggressive behavior.  Dr. Haug’s article, as well as Herron et al.’s (2009) article, describe that maternal stress, stress during early life, hormonal issues and illnesses can also result in increased fearfulness of strangers, over-reactions to environmental changes, and aggression. 

Fearfulness is a welfare issue for dogs in and of itself since it decreases the quality of life of the dog.  However, when fearfulness in a dog is manifested as aggression toward strangers then it becomes bigger problem with potentially serious implications for the well-being of both dogs and their owners.  According to the Animal Legal & Historical Center, owners of aggressive dogs may endure issues with local authorities as well as economic damages from lawsuits and victims’ medical bills.  This is something more people are worrying about nowadays with the litigiousness of modern society.  I have had many clients mention that people made claims against their homeowners’ insurance for territorial aggression dog bites.  As for the dogs, the dogs themselves may face owner-relinquishment – owners saying “I simply can’t handle this behavior anymore” and giving them up to a shelter.  They may be seized by local authorities, or euthanized.  This makes it imperative that owners take territorial aggression seriously and seek intervention as soon as it appears before the behavior intensifies and becomes well-practiced.

The types of interventions that owners and trainers attempt are widely varied.  A 2024 study by Johnson & Wynne found that 57% of owners used traditional approaches that cause fear and pain to the dog to suppress aggressive behaviors.  This can include a wide range of techniques from yelling, pinning dogs down, snapping the leash, or hanging dogs from a leash in the air or using shock collars.  These techniques have also been promoted by popular social media trainers, such as Cesar Millan to curb aggression.  Probably most of you have seen his show or have seen him on TV.  Similarly, a 2026 research study by DeLeeuw & Williams’s found that 54% of trainers who worked dog behavioral issues utilized aversive methods.  Conversely, a 2020 research study by Vieira de Castro et al.’s found that dogs subjected to aversive training showed more behavioral signs of stress, higher cortisol levels, and a pessimistic outlook both inside and outside of training scenarios than dogs who engaged in only reward-based training.  Unfortunately, 75% of the owners included in Herron et al.’s (2009) study had tried physical corrections first before seeking the help of a veterinary behaviorist.  The do-it-yourself interventions including leash corrections, kicking the dog, shocking the dog with a remote collar, or jabbing them the neck.  Overall, twenty-five percent of these dogs displayed immediate aggression to the owners in response to the physical corrections.  The American College of Veterinary Behaviorists published an official letter condemning the use of aversive physical and psychological punishment during training.  They warned that these training methods are inhumane and increase the risk of immediate and future aggression.  They recommend exclusively reward based methods to address the dog’s emotional state and teach new behaviors around visitors and pedestrians near the home.   

These aversive behavioral interventions compromise the dog-human relationship, create fearfulness, and increase the likelihood of immediate and future aggression toward strangers and the owner.  Dogs will have a hard time feeling safe around someone who feels like Dr. Jekyll and Mr .Hyde where they don’t know which version they are going to get – the loving and safe one, or the one who makes them feel afraid and in fear of their safety.  Education may help trainers and owners to understand the reasons for dog’s aggressive behaviors, and how they can help to positively change this in a way that preserves their dog’s welfare.

Biology of the Behavior

A (2015) research study by Range et al. described that territorial aggression is highly common in wolves, who can display intense aggression toward non-pack members who venture into their territory.  They also described that territorial aggression is actually uncommon in feral and free-roaming dogs who live may live in large groups but do not show physically damaging aggression toward each other.  However, as most of you probably have seen, territorial aggression is common in some modern dog breeds that are bred specifically for territorial guarding or aggression toward strangers.  These aggressive behaviors can create serious challenges with the behaviors being incompatible with living in busy urban and suburban environments.  People frequently pass by or visit the dog’s home property, triggering stress for the dogs and the aggressive behavioral outbursts.  As I mentioned earlier, dogs sometimes claim and defend territory beyond the boundaries of their actual home property.  No one except the dog knows where that invisible boundary lies.  This can be highly problematic if dogs get loose from the home property – like if the pool guy or gardener leaves the backyard gate open.  The territorial behaviors that dogs choose to exhibit can vary widely, but the most problematic ones are behaviors that could cause bodily harm to someone.  Veterinary behaviorist Dr. Kenneth Martin describes that the goal of these behaviors is to deter an intruder from accessing the property.  These behaviors can include tensely charging toward a stranger, lunging, muzzle punching, or biting a person.    

Dogs who are experiencing illness or pain can have chronically high stress levels that inhibit learning.  The stress that impairs learning can come from the individual themselves in cases of illness or pre-existing pain conditions; it can come from the surrounding environment; or it can come from the training experience itself.  Issues in the surrounding environment could include stressors such as training in a busy environment, training in an environment with scary noises such as angry barking dogs or loud motorcycles speeding nearby, or noxious odors that bother the dog.  Stress can come from the arrangement of the training itself, including if the training scenario is too challenging, or if it feels frustrating to the dog and unachievable to get the reward.  The training scenario could also be stressful if there is fear or punishment involved as part of the training.  If the dog is unsure what the human wants them to do because of unclear communication then that could also cause stress. 

Internal stressors that inhibit learning can include health issues such as hormonal issues (for example, thyroid issues or Cushings syndrome), acute pain issues (like horrible itching or discomfort from skin allergies), chronic pain can cause serious stress (such as IVDD that we see in longer backed dogs or arthritis), gastrointestinal issues and food tolerances can cause serious pain or discomfort, amongst other health issues.  It can also include serious anxiety related issues. According to veterinary behaviorist Dr. Lore Haug’s article in Veterinary Clinics Small Animals Practice, under-socialization is the most common reason that healthy dogs display aggression.  Xu et al.’s (2023) research study found increased amygdala connectivity in anxious dogs with strengthened connections to the thalamus, hippocampus, and frontal lobe which are all the anxiety neurocircuitry.  The amygdala identifies danger in the environment and signals other parts of the brain to initiate a fight-flight response.  The immediate threat response – the sympathetic-adrenal-medullar axis -- and possibly the longer-term threat response system -- the hypothalamic-pituitary-adrenal axis -- engage when a fearful dog sees a stranger approaching the home property. 

According to da Silva et al.’s (2021) research study, severely anxious dogs may have impaired learning abilities due to their high stress levels that affect proper cognitive functioning.  These dogs have a high baseline anxiety level throughout the day – even when nothing is happening that should cause stress.  This can make it difficult for them to respond appropriately when a visitor comes to the home, even with training to teach new behaviors.  It is imperative to address the chronic anxiety first, including any underlying health conditions that may be causing it.  Özel’s (2024) research article describes how the HPA axis engages when an individual is faced with a long-term stressor, resulting in high levels of cortisol stress hormones circulating in the blood stream and tissues.  The excess cortisol binds to glucocorticoid receptors which are largely situated in the hippocampus and hypothalamus.  This results in decreased connectivity between information processing areas of the brain -- including the mesencephalon and hippocampus -- that can detect and remember rewarding stimuli, contexts, events, and locations.  These high, prolonged periods of distress change brain connectivity in similar ways to what I mentioned earlier about under-socialized dogs, with fear dominating the way the brain reacts.  These dogs experience increased activity in the fear center of the brain (the amygdala) and strengthened connections between threat signaling pathways.  Given the prolonged stress with strengthened anxiety neural circuitry, things in the environment that the dogs sees, smells, hears, or feels can become predictors of negative emotional events that they remember and react to later on.  For example a dog can become fearful of their leash or going on walks if they experienced the sound of a car loudly backfiring while on their walk.  During distress and high emotional arousal, the brain preferentially memorizes these negative events so only negative emotional learning is occurring during these periods of intense stress, known as “distress”. 

As both Özel and da Silva described in their research studies -- dogs simply cannot learn new behaviors effectively when their stress levels are intensely high, either chronically stressed or situationally distressed.  They simply, neuro-physiologically, cannot memorize the new information and they will not be able to recall it effectively in future events, so it is imperative to reduce stress levels through counter-conditioning procedures first.  By counter-conditioning, I am talking about pairing something pleasant – like the dog’s favorite food – with the presence of something the dog is fearful of.  Eventually the scary thing becomes less scary since it predicts the appearance of something rewarding.  This is essential with highly stressed dogs.  We want to change how they feel first and then they can effectively learn both these new emotions and the behaviors we will teach.  Some people may be familiar with highly stressed dogs – where every training session seems like the dog has never learned the behavior before and you keep having to teach and reinforce the same thing continuously.  I tell my clients this can feel like Adam Sandler’s 50 First Dates movie.  Finding ways to lower every day stress levels and arousal levels during training can go a long way.  Stress levels need to be low or moderate – not distress – so that dogs can be guided to good choices.  These low to moderate stress levels will allow their brain to save this learning for future use.  Entering a training session at a low to moderate stress level will also allow them to recall their previous learning.  If stress or arousal levels are too high, they may seem to “forget” their previous learning.  Mild to moderate stress is called “eustress”.  Basically, it is good stress that enhances learning, like what we experience when solving a puzzle.  High levels of fear or stress will cause negative emotional learning to occur.  It will block proper memory consolidation and retrieval of previous learning, which keeps the dog from continuing to learn and progress.

Proposed Solutions

There are various methods used to address territorial aggression in dogs spanning from reward based to aversive methodologies.  Let’s take a look at some of the common methods and break down the basis for the behavior, how it affects the dog biologically, and the long-term effectiveness and welfare outcomes for the dog and humans involved.

An aversive method commonly used with territorial aggression is owner-activated remote shock collars, likely because the dog is further away from the owner so they may be unable to physically correct them through other means.  When a dog notices a person passing by the home or entering the property, the trainer or owner wait for the dog to perform the undesirable behaviors of barking, lunging or growling.  Then, the human presses the remote button on the collar to send a shock stimulation through the tissue and muscle in the dog’s neck, eliciting a painful sensation.  Schilder & van der Borg described in their (2004) study of German Shepherds trained for police work that the dogs frequently elicit a high-pitched yelp, a screaming bark, and sometimes jump against the handler if they are nearby when stimulated with a shock to the neck.  The pain of the shock stimulation is felt by the nociceptors – or pain sensors on the skin surface.  This pain response is sent through the peripheral nervous system to the central nervous system and then noradrenaline is released by the SAM axis, thus activating the dog’s reflexive response of yelping, jumping up against the owner, and stopping their movement toward the stranger.  This is not a thoughtful behavioral response but a reflex to avoid potential tissue injury.  The objective of these trainers is to force a stop to the behavior they do not like through the positive punishment quandrant of operant conditioning – but it is actually more of a classical conditioning they are doing in reality.  The behavior will only continue if the dog associates seeing a stranger entering the property and worries they will experience that painful sensation again, and then try to avoid the person to avoid the pain.

Aboushaar & Serrano described in their (2024) research study how pain activates the HPA axis, so the pain of the shock will result in a neuroendocrine stress response.  Rather than their emotional state being eased, the dog has high levels of cortisol circulating in the bloodstream during this shock collar training – which was also found in Vieira de Castro’s (2020) research study on aversive training methods; the fear center of the brain – the amygdala -- and threat neural circuitry experience hyperactivity; and negative encoding occurs of environmental stimuli and contexts as possible predictors of future threat.  

Unfortunately, dogs will likely remember not only the presence of a stranger approaching paired with the pain of the shock, but they will possibly remember the presence of the owner as predictive of the shock experience.  This is unintended classical conditioning occurring in which the dog is attaching negative emotional associations to various stimuli, and possibly contexts and environments.  This could increase the likelihood of future fearful and aggressive responses in animals who undergo this training, as well as increasing their anxiety levels outside of training as they may associate the electronic shock with their owner, their home environment and other stimuli or contexts.  This reduces the dog’s overall well-being and quality of life while also increasing the risk of future aggression.  This is not an appropriate method for behavior modification under any circumstances.

An alternative method to addressing territorial aggression is through reward-based training utilizing classical conditioning and operant conditioning procedures.  Veterinary behaviorist Dr. Kenneth Martin described at the 2017 Small Animal Veterinary Congress how it is important to address the emotional state of the animal so the dog will not act defensively based on fear, and then teaching new behaviors around the presence of a stranger once the dog is less stressed and less fearful.  This would include counter-conditioning the presence of passers-by by verbally exclaiming “Good!” and then presenting a tasty treat when the dog – who is kept on leash far away from the sidewalk – happens to notice passers-by who are not directly approaching the property.  I would do this repeatedly over several short 5-10 minute sessions until the passer-by no longer evokes a stress response, as evidenced by a loose, wiggly body seen on the dog.  The stranger becomes a predictor of a valuable food reward and triggers the release of dopamine and oxytocin due to this repeated pairing with food and social interaction with the owner.  Wirth’s (2015) research article showed that oxytocin is important to dampen fear and adrenaline so that positive learning can be committed to memory.  Then, we can begin working on positive reinforcement operant conditioning by teaching the dog to make a desirable behavioral choice and rewarding it.  One way to do this would be to have the owner verbally call the dog to “come” when they noticed a stranger enter the property – the dog would need to start far away from the stranger initially when starting this training -- and then the owner would reward the dog with a jackpot of high value food rewards after coming to them.  Gong et al.’s newly published study recently showed how food jackpots increase dopamine responses and accelerate the rate of learning.  With repetition, the sight of the person will become a predictor of a jackpot reward and an environmental cue for the dog to find the owner.   

Conclusion

This behavior modification supports the animal’s learning because the hippocampus will store positive memories of these training sessions with the reduced stress levels and rewarding experiences.  The hippocampus will communicate with the striatum and should begin to slowly re-assign the presence of a stranger as no longer being threatening, but instead a positive stimulus associated with reward.  Behaviors will change when the dog no longer feels threatened by the strangers’ presence.  Additionally, the animal will cease aggression once they learn behaviors that works to ensure their safety through avoidance that also provide significant value and reward.  The aggression primarily occurs due to fear and an attempt to gain control of a perceived threat

It is the goal to not have animals living under constant command but instead to have autonomy.  This is far preferable, in my opinion, compared to managing the situation with covered fences and having the animal locked away every time guests come over.  Many animals experience significant distress hearing visitors on the property but being unable to interact with them – essentially, barrier frustration, which people are most familiar with through seeing dogs fence fight.  Frustration can lead to future increases in arousal and aggressive behavior when approached by the owner or a guest, or if the animal is released from the space but still in a high arousal state from frustration.  The objective should be to help the animal feel calm and empowered instead of trapped without regard to their emotional state.  The best choices for long term solutions are those solutions that improve animal welfare by increasing the dog’s autonomy while providing training and feelings of comfort around social stimuli.  Thank you for listening!

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Eileen Koval, CDBC, CBCC-KA, CPDT-KA, MSc (in Operations Management) is a fully certified dog behavior consultant with the International Association of Animal Behavior Consultants (IAABC). She is currently pursuing an M.S. in Applied Animal Behavior and Welfare at Husson University. Eileen believes that understanding each dog as an individual is the foundation of a good cross-species relationship. She enjoys helping humans and dogs communicate more effectively to create brilliant relationships filled with joy, purpose, and fulfillment for all involved. Eileen offers private consulting for serious dog behavior issues, obedience/manners, and agility training. She developed a unique online course to help pet parents and trainers teach reliable snake avoidance behavior off-leash through positive reinforcement techniques. These techniques have been applied by trainers worldwide to teach dogs to avoid dangerous environmental hazards and respect off-leash property boundaries. Eileen lives on a small ranch in Las Vegas, Nevada, with her husband and their Nederlandse Kooikerhondjes.