If you have a dog, you probably know their normal behavior and personality. You likely know how to recognize changes in their personality, and you know how much aggression is too much for your pet, as well.

Although some dogs are naturally slightly aggressive, most dogs don’t show extreme aggression without a reason. If your dog has suddenly become more aggressive than normal, it’s very important to figure out why. In the article below, you’ll find a quick list of some of the most common causes of aggression in dogs to help you get started.

WHY IS MY DOG SUDDENLY AGGRESSIVE?

Dog aggression is defined by a range of behaviors, from holding a rigid stance or hard stare, to growling, lunging, air snapping and various stages/intensity of biting. Since it can have many causes, understanding the various and more subtle signs of aggression may help you determine its source and provide early intervention.

Aggressive dog? Here are 6 possible reasons:

1. Your dog may be bored

Although aggression may seem like a strange result of boredom, many bored dogs turn to aggressive tendencies to relieve their pent-up energy. If your dog spends most of their day in their crate or at home without anything to do, they may become aggressive when you finally interact with them at the end of the day.

To combat this problem, enroll your dog in training or work with them yourself so they have something to spend their mental energy on. Make sure you take them on walks and play with them to burn off some physical energy, too.

2. Anxiety in dogs can cause aggression

Anxiety can quickly lead to aggression in dogs who are very afraid. If your dog is nervous or easily frightened, they may become aggressive when they feel like they need to defend themselves. Although this response is instinctive, it can often happen even in situations when you know your dog is safe—such as when fireworks are going off outside.

Additionally, if you’ve recently experienced any major changes in your household, your dog may become aggressive due to this type of anxiety instead. New pets, new babies, new partners, and new homes can all lead to temporary anxiety and aggression in dogs.

VEG ER for Pets is open 24 hours a day, every day, to diagnose and treat dogs and all pets. If your dog is showing concerning signs of aggression, bring them in to see a vet right away.

3. Pain can cause a dog's aggression

Dogs who are in pain may become aggressive because they are trying to defend themselves from further injury. If your dog is in a lot of pain due to an acute or chronic problem, they may growl and snap at you when you try to touch them. Even if you’re trying to help your dog, their pain may make them lash out.

It is important to take your dog to the vet if they are being aggressive due to pain. They may have a serious underlying health problem or a life-threatening injury that needs to be treated right away.

4. Pregnant dogs can show aggression

If you have an intact female dog, and especially if she has been around any male dogs recently, there is a chance she could be pregnant. Aggression goes along with pregnancy in many dogs because they feel the need to protect themselves and their unborn puppies from real or perceived threats in the surrounding environment.

After a dog gives birth, she may be aggressive toward anyone who tries to bother her or her puppies, too. It is important to provide your pregnant dog with a comfortable, safe place to give birth and raise her young puppies.

5. Neurological problems can cause canine aggression

Neurological problems can happen as a result of health problems like brain tumors or as a result of injury. Any illness or injury that affects your dog’s nervous system can potentially change their personality, leading to aggression and other issues that were not there before.

If your dog is diagnosed with a neurological problem, understand that aggression and personality changes may be part of their life moving forward. Work with your veterinarian to determine which issues you can manage or treat, and which ones you need to learn how to live with instead.

6. Dog's aggression from rabies

Finally, rabies is always a risk in unvaccinated dogs with sudden aggression. Although rabies is extremely uncommon, especially compared to other items listed here, any dog who hasn’t been vaccinated against rabies may potentially contract this fatal and very dangerous disease.

Among its many other symptoms, rabies often causes dogs to become very aggressive. They may also become confused, exceptionally clingy, or prone to mood swings. Rabies also causes foaming at the mouth, inability to drink water, and seizures, before it eventually leads to paralysis and death. It can be spread from dogs to humans, so keeping your pet vaccinated against rabies is extremely crucial.

Aggression in dogs shows in a variety of ways, including foaming at the mouth due to rabies. Dogs with aggression should be seen as soon as possible by an emergency vet at VEG.

DOG AGGRESSION BY GENDER AND AGE

While most causes for aggression are non-gender-specific, there are factors that can specifically influence aggression in a male or female dog. You may see variations of forms of aggression in puppies versus how aggression shows up in senior dogs.

Aggression in male dogs

Testosterone does not make a male dog aggressive, but it can be responsible for a lower threshold of aggressive behavior when a dog is triggered.

• Intact male dogs may become aggressive if they are competing for the attention of a female in heat.  

• Aggression between two male dogs can occur as they strive to dominate access or ownership of resources, from food, beds and sometimes, family members. This can be exacerbated by increased testosterone levels of intact males.

• While both males and females can exhibit territorial aggression, this tends to be more common in males.

Aggression in female dogs

Aggression specific to female dogs is often centered around pregnancy and hormonal influences.

• Fluctuating hormones during heat cycles in unspayed females can impact aggressive behaviors.

• Pregnant females, and those who have just given birth, may be prone to aggression due to inherent protective instincts to guard their pups, even before they are born.

• Post-partum aggression can occur if the mother dog perceives a threat to her litter or due to hormonal fluctuations.

Aggression in puppies

Puppies nip as a natural part of play. They get excited, boisterous, can play rough, growl and bark. This is not aggression.

While aggression in puppies is rare, it can occur. Early intervention is essential for successful behavior management.

• Puppy aggression can be situational (overstimulation, being overtired) or can be indicative of underlying health issues, fear or anxiety.

• Signs of aggression in puppies are similar to those of adult dogs – body rigidity, hard stares, curled lips, deep growls, snarls, snapping, serious bites.

• Additionally, an aggressive play style can be an early warning sign in puppies. This is where there is no balanced back and forth play, snappy grabs at toys, and angry snarling/growling.

Aggression in senior dogs

Aggression in senior dogs is often linked to underlying medical or cognitive changes rather than sudden personality shifts.

Common causes for aggression in older dogs include:

• Pain from arthritis or dental disease

• Vision or hearing loss that startles them more easily

• Canine cognitive dysfunction (similar to dementia in humans), and may create confusion and anxiety

  
  

Signs of aggression in older dogs include:

• Growling

• Snapping

• Stiffness

• Sudden irritability

• Changes in social behavior, such as withdrawing from family interactions or showing intolerance toward other pets

  
  

Recognizing these changes early can help ensure your dog gets the medical care and support they need.

Interesting facts about aggression in dogs

• Studies show that dogs who are “only dogs” of inexperienced dog owners can be more aggressive than dogs in a multi-dog household with an experienced owner

• Small dogs are more likely to be aggressive than medium or large dogs

• In multi-dog households, conflicts arise more often in female/female dog households than in male/female or male/male homes, although individual temperaments ultimately determine compatibility

Contact VEG Vet Hospital if Your Dog is Aggressive with Behavioral Changes

If your dog is extremely aggressive and has experienced sudden behavioral changes without an explanation, or if your dog's symptoms require urgent attention, bring them to VEG emergency vet right away. There is always a risk your dog could be very sick with an illness or condition causing these behavioral changes, and it’s important to rule out rabies in an unvaccinated dog, too.