Warning Signs of Potentially Dangerous and Aggressive Dogs

Updated on April 10, 2017
alexadry profile image

Adrienne is a former veterinary hospital assistant, certified dog trainer, behavior consultant, and author of "Brain Training for Dogs."


Sometimes, dog owners find behaviors in their canines that are far from what would be expected of ''man's best friend." Such behavioral issues are often ignored or excused with phrases such as ''he will grow out of it," ''it's just a phase,'' or ''he only does it every now and then." Sugar-coating such issues, however, does not help at all and, in many cases, these behaviors are likely to escalate and exacerbate if left untreated.

Signs of Potential Problems That Should Not Be Ignored


Growling is a warning sign that should not be ignored. While some people appreciate growling because it indicates that the dog is warning them before biting, a growl should not be underestimated because it may indicate that the dog has a low-level threshold or is weak-nerved.


Biting is, of course, the most obvious act of aggression that dogs express. The bite does not have to break the skin to be considered a significant threat. Often times, owners start seeking help once the dog has bit somebody, which is too late. In many cases, signs of increased aggression were ignored or they may have been too subtle to be noticed by the inexperienced eye.

Signs of Dog Aggression

Related to Feeding

  • They growl when eating
  • Lift their lips and snarl while eating
  • Get tense and tend to stop eating as you approach
  • Growl when they are chewing a bone
  • Steal food and get aggressive when trying to retrieve it
  • Respond aggressively when they are found scavenging the trash. For more on this, read "Dog Resource Guarding."

Related to Sleeping

  • Growl if forced off a bed or couch
  • Growl if allowed on the bed and the owner moves too much
  • Growl if awakened
  • Growl if touched while sleeping

Related to Being Touched

  • They do not allow children to touch them
  • Growl when groomed or when nails are clipped
  • Dislike being touched on the head/shoulder area
  • Do not like to be touched from above
  • Aggressive when given medicine or shots

Related to Playing

  • Growl if their toys are touched
  • Will not let children near their toys
  • Get too rough when playing

Related to Being Disciplined

  • React aggressively to being reprimanded

Related to Being Exposed to the Outdoors

  • Chase cars, small animals, joggers, or bikers
  • Lunge towards other dogs or people
  • Act aggressively towards strangers
  • Act overly protective of their owners
  • Growl if owner shakes hands or hugs another person
  • Bark aggressively at other people when in the car
  • They are fence-aggressive and very territorial

As seen, the signs are all out there. It is very harmful to ignore them in the hopes that they will disappear. Unfortunately, these behaviors often return and grow in intensity if they are not nipped in the bud. If your dog displays any of these signs, please don't try to solve them on your own, but consult with a veterinary behaviorist or a certified applied animal behaviorist.

Possible Causes of Aggressive Behavior in Dogs

Painful Medical Conditions

It is very important to have a veterinarian rule out any physical conditions that might be affecting such behavior, especially if the unwanted behavior is abnormal and/or sudden. Even the most docile dogs can sometimes become quite aggressive if they are in pain. An example of this that is quite common is when a very well-tempered dog suddenly snaps when its head is touched because of an underlying painful ear condition. For more on this read "Medical Causes for Dog Aggression."


Another issue that may cause behavioral changes is a condition called ''hypothyroidism." It is certainly worth discussing with the vet to see if your dog has this condition. All it takes to rule it out is a thyroid blood panel.


Hormones also play a role in aggressiveness. Well-behaved male dogs suddenly become aggressive when they detect a female in heat nearby. While neutering may help a male dog have a better disposition, it is not really a ''cure-all'' for major behavioral problems that are not hormone-related. For more about this read "Pros and Cons of Neutering Dogs."

Questions & Answers

    © 2009 Adrienne Janet Farricelli


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      • profile image

        Nemon 3 months ago

        My dog has never displayed any of these behaviors, yet she HURT another dog. She fought a dog giving NO PERCEIVABLE WARNING. None. She didn't growl, she didn't bare her teeth, she definitely did not bark. She just snapped. She went from happily sniffing butts to I'm-going-to-rip-your-throat-out in milliseconds. I don't trust her with any dog anymore, even though she's always loved meeting and playing with most dogs. It wasn't territorial, it was not about food, not about protecting me or fear or pain.

        No article I've read addresses this kind of aggression or how to manage it. Now I have a mini-heart attack every time there's another dog near us while we're walking even if nothing is going on and they are twenty feet away. I don't even fully trust her with people anymore (though she's never EVER acted even remotely aggressively towards a human).

        She's a five year old Staffordshire Terrier mix. Is it really a "Pit Bulls-are-evil-silent-killers" behavior? What am I to do? Dare I ask, will she turn on me? She is so subdued and tolerant and happy I never imagined she could be aggressive like she was. But she WAS. I don't trust her anymore and it feels wretched.

      • alexadry profile image

        Adrienne Janet Farricelli 3 months ago from USA

        Heidi, have a dog trainer/behavior consultant see your dog. He/she may help you with a counterconditioning/desensitization program. Good that you haven't reprimanded him as that would just add fuel to the fire.

      • profile image

        Heidi R 3 months ago

        I have a two year old standard poodle who is a little on the protective side--of me and of his home and yard. He never growls, but has grabbed at people's hands and freaks out if a stranger approaches me too suddenly. If someone comes into the house, I usually distract him with a chew treat and he eventually settles down. I sense that he is insecure and nervous, so I haven't reprimanded him for this behavior in the past, fearing it might make him even more anxious. Any suggestions?

      • profile image

        John Watson 6 months ago

        My brothers Labrador has just tried to bit my feet in a very aggressive loud attack. I was wearing shoes so no damage. The dog was sleepy , had just woken and showed no real warning sign. It looked at my feet and just went after them.

      • profile image

        sarah 3 years ago

        Thank you

      • alexadry profile image

        Adrienne Janet Farricelli 3 years ago from USA

        Sounds like a serious case of resource guarding. I would recommend consulting with a behavior professional that can guide you through behavior modification. The below article gives an example of behavior modification for resource guarders but must be implemented with a behavior professional for safety, so please find a professional to help you out.


      • profile image

        sarah 3 years ago

        Hi we are expecting a baby in 8 months time and have some concensa about are dogs behavior such as he steels food and when u try and get it back he will grown come towards u a bite u when I try and eleven my daughter up he will sit next to her and growl at me if I put my hands near he will bite he sleeps in bed with me and my boyfriend he is OK most times but if u get out of the bed and get back in he will do the same he is continually humping if he has something he should not have glands u want *t back HDTV will show bad aggression what do we do: ( other than that he is loving likes lots of cuddles says good morning to us in the morning

      • alexadry profile image

        Adrienne Janet Farricelli 5 years ago from USA

        Monu, I can write a book on the topic, I am sorry to hear you found it bland. However, if you see I have several links throughout the article if you wish to expand on the topic. Notice that this is about the "signs" so if I were to write about dog ownership, it would be off topic for this title and would turn out being too long. Please also note I am not for the assertive strategy when it comes to aggression. I treat several cases of canine aggression and don't use this approach and more than rules and boundaries I am for management. If you wish to expand on the topic note that I have many articles tackling this as I have treated many cases of dog aggression in my career.

      • profile image

        monu 5 years ago

        what a bland article. iT Doesn't seem to explore why dogs seem to have these problems- most problems that occur in dogs are due to owners not being assertive enough or not setting rules and boundaries which aggression can be a typical behaviour of. How about educating people on what they can do to avoid this

      • profile image

        Stacey 5 years ago

        Thank You

      • alexadry profile image

        Adrienne Janet Farricelli 5 years ago from USA

        Sorry, we're not that widespread yet! You can find good force-free trainers though by looking at the Pet Professional Guild website. Best wishes!

      • profile image

        Stacey 5 years ago

        Arizona is quite a ways from South Florida... Any chance you have an affiliate/ associate here in Florida?

      • alexadry profile image

        Adrienne Janet Farricelli 5 years ago from USA

        Yes, I agree, there are quite many options when it comes to training. Maybe you can come see us at Rover's Ranch Home in Arizona, we'll work on any issues your dog has as we offer board and training! Kind regards!

      • profile image

        Stacey 5 years ago

        Our Bear is a 3 year old Chocolate Lab, fixed with a few skin issues but otherwise healthy. He is an amazing watch dog, is gentle with my cats and LOVES my kids. Lately he has developed food aggression - not the kind of food aggression where you can't approach him at his dish... but rather while my kids are eating, walking with food, or carelessly talking with food in their hands. He has tried to steal food from them and inadvertently bitten them, as soon as he scarfs down his stolen food (with or without biting) he runs and hides because he knows he's done something wrong. We have tried to get our kids to be more careful around him (he will not approach the table) but it seems now he's has become a bit more brazen and has bitten my son while he was bringing scraps to the composter. He bites while in the act of stealing or eating the stolen food. This is the same dog that will let you reach into his bowl while he's eating with no issues at all, so I've found most of the food aggression behavior modification techniques to be geared towards a totally different issue. Please help, the kids are afraid I'm going to find him a new home -and if he bites them again - I'm afraid they might be right

      • profile image

        JTJ 5 years ago

        No, I've never heard of a class like that - I'll have to look into it. I'm from Australia and I find besides basic training, classes are quite limited here in variation. Even finding a good behaviorist was almost impossible. We are moving to the US in July (dog and I), and I'm excited for the many classes and possibilities there in the dog world! So I'll definitely start looking out for those kinds of classes when I arrive! And checking out your hub now, thanks!

      • alexadry profile image

        Adrienne Janet Farricelli 5 years ago from USA


        For the barrier frustration, have you ever though about enrolling him to a reactive rover class? These are classes often organized by trainers and specialized in cases such as yours. For protective of the car behavior, see if my hub can help you:


      • profile image

        JTJ 5 years ago

        My dog has most of the problems listed under "exposed to outdoors", I feel this is due to a mixture of a lack of proper socialization (on my part) - and several bad experiences he's had outdoors and on leash (neighbor hit him, dogs have attacked him, etc).

        He's very leash reactive/aggressive. He'll be perfect and playing with another dog one minute, but as soon as that leash is on or I hold his collar, he'll get very aggressive at the other dog. Same goes for behind a door/fence/window, yet have them on the same side together and he plays perfect. I've been told this is 'barrier frustration', that comes across as very aggressive. It's really hard to take him anywhere or on walks, so sadly we don't get to do much out of the yard, as everywhere has to be on leash. I wouldn't want to take him anywhere off-leash either for a fear of just in case he does have a freak-out moment.

        He also barks in the car aggressively at people outside of the car - I don't know if that one also falls under barrier frustration, or just strangers in general. Sometimes in the car he's fine, others not so much. It's odd. He also will not growl, but more of a sigh/sulky groan if I move around too much in bed and he's on the end of the bed - but this started after I accidentally pushed him off the bed in my sleep. I must have moved my leg and he slipped off, so now anytime my leg moves he panics..

        I got a behaviorist to come see him, she said he's an incredibly unsure and anxious/nervous dog, but in no way is he "aggressive". Watching her work with him was incredible. She worked mostly on 'energy' etc, she took him down to a busy carpark on leash and had strangers/men walk up to her and shake her hand while he sat next to her not even looking at the stranger. It was incredible. I'm still lacking that leadership and calm/assertive that she has, but hopefully soon I'll be able to be calm/assertive and have that same control.. I find that he has a bit more confidence when he's around other dogs, so at a dog park he's great with everyone. BUT - we haven't been to a dog park in a very long time as our last trip there a man started kicking all the dogs for fighting, even the ones who were just in the area of the fight. My dog wasn't fighting, but I saw the mans foot come at him and I got down and scooped up my dog, told the man 'where to go', and left the park. Haven't been back since..

      • alexadry profile image

        Adrienne Janet Farricelli 5 years ago from USA

        Answered to your post on the hub "signs a dog is about to bite"

      • profile image

        Lyn 5 years ago

        I have a one year old lab/catahoula leopard. He's a sweetheart loves people has shown no signs of aggression. We took him on a hike recently with some friends and another dog. The other dog was off the leash as ours was on a leash. They did very well together the whole hike. When walking back to the car our dog ran ahead to the other and latched on to his ear. He had a good grip on the ear wasn't making any noise or moving. He would not let go when told and wouldn't let go when he was approached and told no, drop. Eventually we had to pry is myth open. He did not puncture the other dogs ear, no blood. Should we be worried he was trying to hurt the other dog or he is secretly aggressive?

      • alexadry profile image

        Adrienne Janet Farricelli 5 years ago from USA

        Can you please provide more details, please? Does she go to the door to tell you she has to go out and becomes aggressive then? What kind of aggression do you see? Growling, trying to bark, snarling? Have you tried to ask for a sit and reward her before sending her out?

      • profile image

        Ann 5 years ago

        My lab gets aggressive when she wants to go out to go to the bathroom...she doesn't bark...what would you suggest that I do?

      • alexadry profile image

        Adrienne Janet Farricelli 5 years ago from USA

        You need to take care of this problem as it is getting out of hand. A protective dog should protect only when there is a real threat. Your dog is not supposed to be taking this role which he is not temperamentally able to do withstand. I recommend seeing a professional at this point. I would also not allow this dog to follow her every where and develop this dysfunctionally strong attachment. Here is an article about protective behavior:


      • profile image

        magicaamy 5 years ago

        We have a malamute and for the most part he is great. However he is overly protective of my teenage daughter. He has to be with her 24/7 and if she goes away for a night or even during school time he pouts and walks around looking for her. But what my concern is he growls when we try to wake our daughter up. He lays his body on top of her. We use to think that him being so protective of her was a good thing but, my husband and I mean no hard to our child yet the dog acts like we are trying to harm her. Even if she ismt sleeping and we go toards her he gets between her and us sometimes making a small growl and sometimes just to be inbetwen us.How can I break him of this habit and still keep him protective of her from strangers and such. TY in advance

      • profile image

        Betty Hamnett 6 years ago

        The humane society tells you that the dog doesn't like other dogs, so you take the dog on walks without a lease to be able to attack other dogs, did you not understand what they said about the dog? I hope you paid for the vet bills because of you negligence.

      • RxTech profile image

        Josue Nieves 7 years ago from Florida

        very informative hub,thank you for all the excellent information.

      • profile image

        EA 7 years ago

        I adopted a dog from the local humane society. the humane society told me 'he doesn't like other dogs'. brought him home, when I took him for walks, I noticed he would charge other dogs visciously. I was worried about it so I called the humane society. Beforethey got back to me the dog attacked the neighbors dog, bit him in the back and had him pinned down before the neighbor could get him off the dog. Luckily the neighbor works with dogs. I sent him back to the humane society and told them to put him down. The last I heard, they will not put the dog down. The trouble is, this dog is dangerous.

      • alexadry profile image

        Adrienne Janet Farricelli 7 years ago from USA

        Tammy: your dog evidently dislikes getting its toenails trimmed.. and has learned how to stop you from doing it.. try to make nail trims pleasant again... here are some tips:



      • alexadry profile image

        Adrienne Janet Farricelli 7 years ago from USA


        Many dogs dislike being bothered when they are sleeping.. I would discourage petting when a dog is asleep.. really any dog.. you never know.. they may be having a bad dream or wake up startled and react..

        Leaning over him may be seen by him as something threatening or some way of your husband establishing dominance over him..so he feels the need to correct him with a growl...

        I would recommend leadership exercises for both of you... he should not be protective of you and follow you everywhere and he should not be growling inappropriately at your hubby...(however, leave him alone when sleeping).

        Stop him from following you at all times.. it may look like a form of love but it really is a form of control, sort of like a jealous wife controlling a husband's whereabouts..

        You must take over and be in charge.. he thinks he rules the house and can do what he likes... with leadership exercises things may improve and he may start to relax...

        here is a good article:


      • profile image

        maria 7 years ago

        my german shepard is very protective of me he loves me to death never leaves my side but the problem is with my husband he growls at him when he if pated when asleep or lend over but it has been this way with a couple of our dogs i dont wana get rid of him because it will only happn again with another dog...thank you.

      • profile image

        tammy 7 years ago

        I have a year old dog, he is dangerously aggressive he won't let you brush him or hell bite, you can NOT touch his toenails he will growl and bite and when I try and rub him even when he is wagging his tail and is happy he will try and bite me. When he has done something bad and I discipline him he bites me and growls and it is extremly frightening. And when he gets this look in his eyes like I see in red zone dogs on tv he has that same look and he just stares at me like its a war. I've had him so long putting him doiwn will be heartbreaking. I'm so confused, I don't think ceaser milan could fix him.

      • Doggie Devotee profile image

        Doggie Devotee 8 years ago from Danville KY

        Great informations, a lot of owners seem to ignore some of the signs their dogs are giving.

      • alexadry profile image

        Adrienne Janet Farricelli 8 years ago from USA

        For the food aggression issue this hub may help you out https://hubpages.com/animals/How-to-stop-dog-food-...

        Food aggression is more of a trust issue. About her turning on you because she is a German Shepherd, I really think that any dog can turn on their owner if there is no discipline and dogs run the household.

      • Mrs.Nita profile image

        Mrs.Nita 8 years ago

        I really appreciate this article. I have a 3 year old German Shepherd. I'll admit, she does have food aggression and we've tried to break this every since she was a puppy. I've gotten to the point where I just won't touch her when she eats and usually she eats alone. I've also noticed that when in the yard she tends to bark and everyone who comes by and if she sees another dog she'll bark and then she'll go and pick up one of her toys;growling and shaking the toy in her mouth. Her hair is standing up when she does this. When I catch her doing this, I make her come and sit down. She doesn't like to be still, so she knows she's being punished. After sitting for awhile, I allow her to get up and she's better, she may run and pace the yard but she won't show aggression. I'm not sure how to break her aggression and what's worse is that I keep hearing people say that German Shepherds will turn on you so

        I think deep down inside I have that fear.

      • alexadry profile image

        Adrienne Janet Farricelli 8 years ago from USA

        My dad was once bit the same way. My dad was visiting a farm and there was this dog that looked pretty quiet. Once, he turned around he got bit pretty well. These are the ''silent biters'' that often decide to bite once the person turns their back. They usually will bite and leave because it is out of fear more than aggression.

      • emievil profile image

        emievil 8 years ago from Philippines

        I agree with a lot of points in your hub. One thing I want to add is that if you are around dogs who are not familiar with you (dogs that you have seen the first time or you seldom see) do not go near them at once. This is true whether they are barking at you or are silently looking at you. One of my dogs does not growl, he does not bark aggressively or sometimes he does not bark at all, but when a local water delivery guy crossed his path, he approached the guy and bit him, sinking two of his fangs! I panicked and got the guy to take his shots at once. That was a wake-up call for us and for the people who go inside our house.

      • Mighty Mom profile image

        Susan Reid 8 years ago from Where Left is Right, CA

        This is a good wakeup call for dog owners. I can't tell you how many times I've encountered dogs and wondered if they were friendly or vicious.

        Another behavior that I find difficult to interpret is dogs barking. When you walk by their yard or their car and they are in the car. I assume they are claiming their territory and thus do not approach.

        Thanks for this useful info! MM


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