Pet Articles

Dog Biting – Dog Aggression

Some people believe that once a dog bites, it will likely bite again. Is this true? What causes a dog to bite? How does one judge if a dog is aggressive? Where can one receive help for aggression problems?

If a dog bites once, will it likely bite again? Not necessarily. It depends on the situation in which the biting occurred. Once a dog has bitten, it should set off an alarm in the owner’s head. The dog is in need of IMMEDIATE behavioural modification techniques to reduce aggressive tendencies. First of all, one must think about the reasons why dogs bite in the first place.

Biting is a natural behaviour exhibited by the canine species in order to survive. Biting is used for obvious reasons such as hunting and killing prey. It is also used for communication between dogs to exhibit rank or to ‘put a puppy in its place’. The pet dog has undergone years of domestication and has reduced the use of their powerful jaws to live in the human society. However, a significant percentage of domestic dogs have bitten a human, and aggression is the number one cause of surrendered and/or euthanized dogs. In most cases, this drastic solution can be avoided by educating owners and working with them to reduce aggression. A dog bites when it does not want you near them or you are in an area that they are ‘protecting’. Therefore, when placed in a different situation, the dog may not bite again.

Genetic factors may also play a role in whether or not a dog may bite. Some breeds are selected for their protection or guarding capabilities. For example, many breeds instinctively chase moving objects, which can escalate into predation. Socialization is also an important factor, because fearfulness or anxiousness is another common cause of aggression.

The best way to deal with canine aggression is to prevent it from developing in the first place. As a new puppy owner, there are a few points to keep in mind as you are training your puppy to reduce the chance of future aggression. Nipping is commonly seen between littermates at play. It may be a cute behaviour as a puppy, but that puppy will soon grow up to be an adult with much stronger jaws. The adult dog will not understand why the previously accepted play biting is no longer acceptable. Play biting and rough housing should not be allowed from day one. This is accomplished not by physical force, but by teaching a dog to associate non-aggressive behaviour with positive reinforcement. Studies have shown that this method is superior to other methods that use punishment as a means of teaching. For more details on what to do about nipping and biting dogs, visit

It is difficult to get accurate dog bite statistics because many bites go unreported, unless the person seeks medical care. Statistics Canada mortality data showed that an average of one Canadian per year died from dog bites between 1991 and 1994. National morbidity data for 1993 showed that 656 Canadians were hospitalized that year for dog bites. Children younger than 10 were four times as likely to be hospitalized as people aged 10 and older. The vulnerability of children to dog bite injuries, particularly on the face, is often attributed to the fact that their small size makes them less intimidating to dogs. As well, immaturity and lack of judgment sometimes lead children to act in ways that animals perceive as threatening or aggressive. Therefore, it is important to teach children how to approach an unfamiliar dog. If a dog is unknown to you, remember that anything can happen. If the owner of the dog is present and they say it is okay to pet the dog, have the dog approach the child. Children should not approach or touch a dog that does not approach or touch them first.

How does one judge aggression in an unfamiliar dog? Dogs will display similar body language signals to tell you that they are uncomfortable with their current situation. These signs include backing away from strangers, staring at the ‘threat’, growling, or teeth-baring. A fearful, uncomfortable or insecure dog has a higher likelihood of biting.

Dogs bite out of fear or protectiveness. It is important to properly socialize a fearful dog at a young age and expose him/her to as many new environments as possible. With patience, an older fearful dog can also learn to become less fearful in strange environments. Lots of praise (and treats!) can be given to the dog while he/she is in a new environment or meeting a stranger. The dog will then learn to associate new and strange things with something positive. For protective dogs, it is important to reward the dog for doing good behaviours when a stranger approaches. For example, as a stranger comes closer, make sure the dog is sitting and give lots of praise as he/she continues to sit as the person approaches. Eventually, the stranger will be able to come close enough to give the dog a treat. Once again, the dog will learn to associate the stranger with good things and forget about being protective. Consistency and patience are important.

In any case, what is the likelihood of a dog that has bitten to bite again? The answer depends on various factors, such as the age and size of the dog, the extent of the bite, the environment in which the incident occurred, and the degree of commitment the owners have for working with the dog to prevent it from occurring again. The last two factors are the most important. Some dogs are not suitable for environments with small children, especially if they have not been properly socialized with children in the past or if the children do not respect the animal. And of course it is up to the owners to be consistent in training and implementing the appropriate behaviour modification program to reduce aggression.

If all these factors are considered and the training is consistent, the prognosis of a successful program is good. It is important to realize that in some cases, success may require restrictions on the dog, such as avoiding certain situations that have elicited aggressive behaviour in the past. Generally, if there has been only one biting incident, prospects for success are good. However, if there has been a history of numerous incidents, the prognosis becomes less favorable. Therefore, it is important for dog owners to recognize the problem early and intervene immediately.

There are a lot of resources to turn to when faced with an aggressive dog. However, in Canada, the dog training and behaviour business is an unregulated field and people can teach any method of training, regardless of how inappropriate or inhumane it may be. With this in mind, any owner who has a dog with a serious behavior problem such as aggression should contact their veterinarian for a referral to a qualified and experienced trainer or behaviour consultant. It is important to realize that isolated biting incidents or sudden changes in behaviour may be due to medical causes, such as pain or neurological changes. A visit to the veterinarian will help rule out those causes and steer you in the right direction.

By Amy Cheung writer

24 Responses to this Article, So Far

  1. Avatar Melissa G says:

    I don’t know what to do…. I have a labradoodle puppy that’s 15 weeks old and he is normally great. He sits and waits for his food, if I use the off command with toys, treats and my clothing he refrains from touching them until I say so, he sits at the door to go out, he gives a paw for all treats, and rings a bell to go outside. We go for walks outside, we use the treadmill, we play fetch. We also go to obedience school and he’s an angel. But at least once a day whether it’s outside playing or just hanging out he start to bark, then growl, then he jumps ups and bites me… If I ignore him he only runs around more quickly and then lunges to bite me….If I force him to sit or command him to sit, he does so but then a few minutes later he’s back to growling, lunging and bitting me….

    How do I get him to stop this behaviour? Why is he all of sudden so aggressive? Any suggestions would be greatly appreciated.

    • Avatar Marko says:

      It sounds like the dog is challenging your leadership daily. This is bad.
      For an aggression free household , You MUST be the leader but the dog is not seeing you as the leader because no dog that knows its place bites the leader…… This is likely happening because you are not acting like the leader in the dog’s mind. You need hands on help from a pro. It will be a great investment if it comes from a pro trainer.

      This is something that needs to be solved asap but there’s no way it can be done as an answer to a post.
      i HIGHLY recommend that you discuss this with the trainer in your obedience class.

      One thing I would suggest is to stop free feeding this dog immediately. Feed the dog’s daily ration but divide it over multiple feedings making SURE that the dog sees you are the giver of the food. make the dog sit for the food each time. This can help but you will STILL Need additional professional advice.
      Good luck.

  2. Avatar michelle73 says:

    I have a 9 month old miniature yorkie that has been bell trained for a long time know, and I am not sure what is going on with him. I used to go to school full time and he was home along, now that I am home with him all the time he gets aggressive with me when i try to leave and he bites my feet and ankles and sometimes draws blood, he has also started going to the basement to pee or poop (even when he is right by the door) . These are both new unexceptable behaviors. Do you have any advice on why he would just all of the sudden start with these 2 bad behaviors and what I might be able to do to get them stopped??

    • Avatar Marko says:

      This aggressive behaviour is 100% unacceptable and it sounds like a behaviour problem.

      For some reason your little dog is challenging your leadership and you need to fix this. Dogs never bite the leader, never. In the dog’s mind you are not exhibiting leadership qualities.
      You the dog’s owner are (likely) exhibiting submissive behaviours to the dog and that is why he is challenging your leadership.

      This problem is normally easily solved with advice from a referred professional dog trainer. Ask your vet to refer you to one.
      For more of a personal back and forth on this issue, i also recommend that you post this on our free pet forum to see what others will advise.

      Good luck!

  3. Avatar John says:

    i have a 2 year old french bulldog, a pug,and a lab mix. prob is with the bulldog,recently since we moved to a bigger house he has snapped at me and my wifes hand once,barked visciously at the lab down the hall well away from him twice and pinned the pug down and bit him(without puncturing).he and the pug always get into lil fights over food and the pug gets agitated when the bulldog barks at random noises, people or excitement leading the pug to try dominating the bulldog thus resulting in a lil fight. normally they are just simply pulled apart as they are moreover mildly fighting, but today i attempted to push them apart and the bulldog bit me causing minor puncture/scrapes. really has me worried cause i have a 17 month old daughter who is normailly down and around the area when this happens. based off of prev web pages read, i feel the bulldog is anxious yet territorial and fearful of missing out on food. i can remove the food from the situation but with the forth of july and cars passing by, water heater turning on, etc, etc. its gonna be hard to remove the noisy stimulus. ive been in formed anti axiety meds may be needed, but what is your overalll personal steps forward?please and thank you

    • Avatar Marko says:

      Seems to me that the dogs don’t know who the leaders are and they should ALWAYS be the HUMANS in the household. Here’s a good article w/links to get u started

      If this were my dog, before I would try meds I would seek the advice of a referred professional dog trainer. They see these problems all the time and curing the problem is usually not that difficult.
      I would definitely do this as soon as possible.
      For a better back and forth with more varied opinions I recommend posting this in our pet forum (after registering) for free in this part of the forum.
      Good luck!

  4. Avatar Amy says:

    I have 7 year old domestic long haired cat and my boyfriend as two 3 year old boxers. They have lived in the same home for 5 months. Prior to this, my cat was not around dogs at all so needless to say, he is uneasy, skitish and sometimes will hiss and growl at them just for being in the same room.

    Yesterday when my boyfriend was letting the dogs into the house they startled my cat who then jumped on the head of one of the dogs and then jumped out the back door and took off running. The dogs gave chase and eventually one of them ran down my cat & grabbed him by the head. My boyfriend got to them before they injured the cat fatally but he did suffer a broken jaw in 2 places and a puncture wound on his face.

    The cat is being treated at our local vet and most likely will have to go live at my parents house following his return home as I can not run the risk of this happening again.

    My question is – do I need to be concerned that this will happen again? Either to the other cat in the home or to our children? Presently, the dogs don’t even seem to pay any attention to the other cat as he was a baby when we got him & doesn’t draw attention to himself from reacting to the dogs the way my other cat does.

    • Avatar Marko says:

      This is a VERY tough question and you did not name the breed of dog….but if this happened to me, YES I would be very concerned.
      I cannot know if a different trigger might set off the predatory instinct in your dog….but now it has happened one time, it can happen again.
      I would not be leaving the dog alone unsupervised with the cat or the kids from now on….UNTIL I was 100% certain that the problem is solved.
      A professional obedience trainer that comes to your house to evaluate your situation is highly recommended.
      Good luck.

  5. Avatar Melanie says:

    We adopted a 4 yr-old Beagle mix from the Human Society on Saturday. We spent an hour playing with him their before deciding on bringing him home. He’s not very playful or excitable, but more passive and loves being cuddled and petted. On Sunday, he ran out into our yard so my 8 yr old son went after him and picked him up right away. The dog turned on him and bit him in the cheek, resulting in a trip to the E.R. and 5 stitches to his face. My question is, should I be concerned and bring him back to the pound, or should we try working with him instead. He is very adorable otherwise. I’m on the fence about it. Some people tell me once a dog bites, he’ll bite again. Others tell me to give him a chance since he was brand new to our household. I read your article above and feel like I should try to work with him, however, I’m afraid he could possibly bite my son again.

    • Avatar Marko says:

      This is a tough one but if it were me, I’d probably give the dog a second chance.

      This change in the dog’s environment is a major major stressor for any dog and when your son ran after him (someone the dog does not know yet) the dog may have felt like it was being hunted. Picking up the dog at this stage was obviously the wrong move. The dog likely gave your son warning signs (growling, showing teeth) but he’s a kid so he didn’t read those signs properly.

      This dog like all dogs 100% needs obedience training (from a referred trainer from someone you trust) and I would 100% tell the trainer about this incident. This advice is GOLD and if you accept it you are likely to have a well behaved dog.
      Once your new dog realizes that one of the “leaders” of the house is your son (and the training should address this) – this should never happen again as dogs don’t bite the leader when the leader knows what he/she is doing.
      Under your direct supervision, I might have your son give the dog its food 2-3 times a day. The dog should SEE this. The food giver is often the leader or one of the leaders. But the obedience training is essential.
      Good luck

  6. Avatar Rachael says:

    I got a 3yr old boxer mix from my sister in law about 6 mos ago. She has been around kids and other animals her whole life. Today I introduced raw hide bones to her and my other 2 dogs. I kept them separated in their kennels while they checked out the new treat. My boxer did not seem interested in the chew at all. I then took them out of the kennels and locked the door so there would not be a territory issue with the bones and the cages. About an hour later we heard a growl then a series of loud yelps. We ran into the kitchen to see our little jack russell run out of the kitchen screaming and the boxer chasing after her with her hair raised. We immediately separated them and checked our smallest. She has a bit through her ear and 2 small punctures on her cheek. We controlled the bleeding and cleaned her up. My concern is will this happen again? I do not know what came over her. She has never ever done this before. I do not know if I can trust her around my other animals now let alone my kid. Any suggestions?

    • Avatar Marko says:

      This is a tough one because we have no idea what happened to CAUSE this. Nobody actually saw the attack or what precipitated the attack.

      I might post this in our forum to see what others say… but if it were me, i’d keep a closer eye on the doogers when treats are around (as this may have been a food jealousy thing)….
      good luck.

  7. Avatar Melissa says:

    We have a four year old australian shepard that has been allowed in our front yard right from the start. Her invisible fence line is about 10 feet from the sidewalk. Many people enter our yard to pet her and she has enjoyed a great reputation until last week. She began to act mildly aggresive toward some people walking down the sidewalk about six months ago. This involved some barking and growling. She would stop immediatley when I said “no”. About three months ago she began to chase some people as they left our yard but never even nipped at them which some Aussies do. Again, this wasn’t everyone, just some people. Then last week a girl who has done this many times ran into our front yard straight at our Aussie who then jumped up and bit her on the side. As the girl ran away the Aussie bit her on the calf. We did not witness this and can’t comment on many of the details. She is normally a very well behaved sweet dog. We are all traumitized by this and don’t know what to do. We have moved her fence line to the back yard but wonder what else we can do.

    • Avatar Marko says:

      I’m not sure what a fence-line is but the people who are MOST traumatized are the people your dog is biting and threatening with its aggressive behaviour.

      Your dog needs to be in a 100% fenced environment so it won’t harm anyone.

      If this is not possible, your dog should be indoors. This is a lawsuit just waiting to happen if you do not resolve this.
      You are fully responsible for any and all expenses related to the people and the property that your dog harms. In some countries, this could bankrupt you and your dog can be seized and euthanized.

      If this were my dog, the dog would be fenced 100% of the time or indoors. Walks would be on-leash 100% of the time….and FOR SURE the dog would get some obedience training. If she already had it, it sounds like she needs a refresher course.
      Good luck!

  8. Avatar Lacey says:

    My boyfriend has a male neutered pit bull that is six years old, he has never been aggressive toward any human and is around his family all day every day. At dinner last night my boyfriends nephew bent down and was petting the pit bull on the head and under the chin and suddenly the pitbull bit his nephew in the face. what would make him do this ? is this a common behavior in pit bulls ? is it because he’s getting old? or could he be loosing it?

  9. Avatar chad says:

    my 2 year old american bulldog dalmatian mix has JUST stared biting when i go to pet her. she was fine the previous night but none of my family can touch her without getting bit.

  10. Avatar Helen says:

    Our 3 year old shepherd/cattle dog mix recently bit someone. We were out for the day so my uncle, who the dog doesn’t know well, came over to let the dog out of his crate and outside to go potty. The dog growled at him from inside the crate, but my father in law let him out anyway. When he reached down to put his leash on his collar, the dog bit his hand. We realize that this was self defense on the dog’s part. We are so sad and concerned that he will do this again. My husband is not good about disciplining the dog – i am the main “leader” and am very concerned that our dog will bite again due to the inconsistent discipline that he receives. Advice? Should we try to find a new home for the dog (who I love, by the way.)

    • Avatar Marko says:

      No, finding a new home does not solve this problem in any way, shape, or form.

      Sounds to me like this dog might not be the friendliest to strangers….
      The easiest solution would be to rely on people the dog knows and likes when you need their help, not strangers (in the dog’s mind).

      Therefore….If this were my dog I’d have the people that help me become friends with the dog… they can play with the dog, feed the dog a bit….that should make them friends if you go about the process gradually. For even better advice from a greater variety of pet lovers, i encourage you to post this on our forum.
      Good luck!

  11. Avatar Helen says:

    Oops – it was my father in law – not uncle! Sorry about the confusion!

  12. Avatar brittany says:

    hello, i have a question and not sure who to ask. i have a 13 week puppy black lab/ german shepherd mix. and a pit bull 7 years old.i had a meet and greet for them and everything went well. pit bull really got along with my puppy. for 2 weeks they played out back with my supervision. and while my mother was dog sitting for me i guess my pit “attacked” the pup. no injuries happened but she’s now vomiting and refuses to eat. i will be taking her to the vet tonight but my question is should i be worried about my pit being “aggressive” this has never happened before but i have a 2 year old son and now I’m afraid she may attack him.

    • Avatar Marko says:

      Since you have no idea what happened when the dog was in someone else’s care…it’s hard to draw general conclusions.
      Most humans cannot read dog behaviour but dogs almost never do anything without warning. There are plenty of signs…and when they are ignored, it may seem like the dog just attacked.

      Most pit bulls love families. Most pitbulls that are trained get along well with other dogs.

      Since a 2 year old has jaggeddy movements and this freaks out MANY breeds of dog, don’t ever leave the dog (any dog) and child alone without your direct supervision.
      Good luck

  13. Avatar Joshua says:

    So have a delimma I have a delimma, I have a mini American Eskimo she is about 7 years old had her since a pup. She has always been a nervouse dog, she barks a lot at strangers & other dogs she snapped onces at my niece about 1-2 years ago and also our aunt omost as if the dog was startled. so I’ve always tried to keep her away from children and strangers when she was a pup we put her in obedience class for training and would lash out at other larger dogs . Me and my gf have since had a child the dog is now 7 I knew there maybe problems and hoped as time went on she would warm up we’ve been very diligent with small interaction with baby and dog the dog fist last out with aggression when the baby was about 5-6 months when he was crawling on the floor I was right there and intervined. There were a few other lashes out and I’ve kept saying to my self she just needs time to warm up. This past dec /014 she lashed out at a ups driver when I had her out side I didn’t see the guy coming up the driveway and she darted towards him I pulled her back and she got his pant leg not the leg but the loose pants I pulled her in and apologize and ssked if he was ok. Well today my gf called me and said the dog lashed out again the baby is now 16 months and I feel the dog has had omost 2 years to warm up and hasn’t I live in fear she will get ahold of the baby and hurt him it’s omost like a switch she is fine then goes all snaky out of no where’s unpredicable. I know I can’t give her way when we got her fixed as a pup the vet did something and we have to give her medication for incontenence Everyday I love her to death but I fear for my son and honestly don’t know what to do in going to call the vet tomorrow and see my options any advice?

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