Experienced and professional animal trainer provide their insights in answering this question :
A. You should have it checked by your vet just to rule out any pain or medical condition causing the aggressive behaviour. It may just be age related and as it is getting older is becoming less tolerant of situations which you will have to be aware of and work around.

How to Identify Common Pet Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced pet care professionals :

As a dog ages, it`s common to have some health concerns. Something like dental pain, arthritis, or vision and hearing loss can trigger aggression in a senior dog. If a dog is experiencing dementia or confusion, these can also trigger aggression.
If a dog that has never shown any sign of aggression suddenly begins growling, snapping, or biting, it may be caused by a disease or illness. Pain is an especially common cause of aggression in dogs. 1 Your suddenly aggressive dog may have an injury or an illness that`s causing major discomfort and stress.
For a Jack Russell that is very aggressive with other dogs, a technique is to squirt the terrier in the face with water whenever he growled at other dogs. No scolding or other action is required in this instance – just a surprise squirt. A Jack Russell Terrier that bites can be a big problem.
Often it`s a sign of a lack of socialization and is common among some rescue dogs. However, a sudden change in behavior towards aggression in a usually friendly dog can also be a sign of injury or illness. If the aggression has come on suddenly, contact your vet.
Stop it or remove your dog from the situation before it escalates. Do not discipline your dog with physical, violent, or aggressive punishments. Opt for positive reinforcement before resorting to the use of aversives. Remember to reward your dog for good behavior.
Avoid triggers. You cannot expect your dog to behave until they have learned how. For example, if you know your dog has become more aggressive in high-energy play situations, stop going to the dog park until your dog has learned to remain calm. Reinforce calm behavior with rewards.
Aggression in dogs can be due to guarding territory, resources, or a family member; fear; frustration; prey drive; or pain. In all of these situations, a dog may be pushed too far and can transition quickly from reactive, fearful, or guarding behaviors to being aggressive.
Many older dogs show increased aggression, anxiety, or compulsive behaviors. These behaviors are aggravated by body inflammation, sensory changes, and cognitive decline.
A Jack Russell Terrier that bites can be a big problem. You must stop this behavior before it becomes dangerous. Don`t allow your Jack Russell to win any games of aggression. The outcome could certainly send the wrong message to him.
Dogs usually bite your hands to get your attention and as part of play. Puppies can chew on your hands while teething, and sometimes dogs can nip out of excitement. Usually, it`s nothing to worry about, but it one does need to shape appropriate behavior to teach dogs not to be mouthy.
Once a dog has bitten, she is more likely to bite again because she has learned it works for her and stops the unwanted interaction. So, dog guardians need to take preventative measures to reduce the likelihood of a bite. You can start by educating those around you to treat your pet with respect.
In general, dogs do not feel guilty after they bite. They may cower, lower their heads down tails between their legs. All these are learned behaviors in response to an act and not guilt. Bad behavior or fear in dogs can be a learned response.
However, there`s no guarantee that an aggressive dog can be completely cured. In many cases, the only solution is to manage the problem by limiting a dog`s exposure to the situations, people or things that trigger her aggression. There`s always risk when dealing with an aggressive dog.
Treatment. It`s important to keep in mind that there is no such thing as a cure for aggression. Aggressive behaviors are managed and reduced through proper treatment with a veterinary behavioral professional. It`s also essential to understand that aggression is a behavioral problem, not an issue of obedience.
The instant you feel your dog`s teeth touch you, give a high-pitched yelp. Then immediately walk away from him. Ignore him for 30 to 60 seconds. If your dog follows you or continues to bite and nip at you, leave the room for 30 to 60 seconds.
Stay calm, and back away slowly. Instead of screaming, or yelling at the dog, speak to him in a soothing tone as you slowly back away. Don`t make direct eye contact. Staring in the eyes of an aggressive dog may prompt him to attack.
Sometimes, it can even be hard to know why this is happening. Dogs typically bite just one person in the household because they have a bad past experience, aren`t well-socialized, or the person doesn`t know how to interact properly with dogs. It could also be resource-guarding behavior.
Fear or anxiety related aggression is perhaps the most common form of aggression in dogs.” Early manifestations of fear related aggression are typically defensive, displayed to increase the distance between the perceived threat, or communicate `stay away`, yet aggression may become more offensive through learning.
Dog to dog aggression is likely to increase during sexual maturity as dogs become more concerned with establishing territory, social status and access to potential mates. Adulthood. This is the period when adolescence ends – usually sometime between 1-3 years of age depending upon the breed and individual dog.
The most challenging time of raising a puppy is the adolescent period. Dogs become “teenagers” and seem to forget everything they have ever been taught. This period is individual to each dog, but it may begin when he`s about eight months old and continue until he`s two years old.
Fear. Most aggressive behavior from dogs is on some level rooted in fear. A dog might be fearful of something or someone getting close to them, or into their space. When whatever a dog is afraid of gets too close, dogs can become overwhelmed or “over threshold” and may respond by biting.
According to the American Kennel Club (AKC), the average life expectancy for a Jack Russell Terrier is between 12 and 14 years. That`s relatively long for dogs. Small dogs tend to live longer than large dogs, but even small dogs` lifespans tends to max out around 15 years or so.
Just as humans stare into the eyes of someone they adore, dogs will stare at their owners to express affection. In fact, mutual staring between humans and dogs releases oxytocin, known as the love hormone. This chemical plays an important role in bonding and boosts feelings of love and trust.
Jack Russell terriers are no more prone to aggression than any other dog breed. But their hunting dog history can lead these terriers to terrorize small pets and chase all the squirrels, rabbits, and mice in your neighborhood. Keep your JRT on its leash to keep small creatures safe.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. My 13 yo Jack Russell has tried to bite me repeatedly, lately. Took an aggressive stance over my kid and snapped at me. What can I do?
ANSWER : A. You should have it checked by your vet just to rule out any pain or medical condition causing the aggressive behaviour. It may just be age related and as it is getting older is becoming less tolerant of situations which you will have to be aware of and work around.

Read Full Q/A … : Vetinfo

Q. How do I get my 10 wk old puppy to stop biting? He only bites me and my fiancé but licks everyone else. Tried bitter bite spray but he just barks.
ANSWER : A. When greeting your puppy, you should present an appropriate alternative for him to chew on. This can come in the form of toys. It’s normal for this age for puppies to be bitey. When you greet him, immediately offer a toy for him to chew on and calmly pet him. If he bites you instead, there are a few things you can try. You can yelp loudly startling him just as a sibling would do. You can freeze not jerking your hand away since that can likely become a game to him and you can also keep him secured in a play yard where if he bites, you can simply remove yourself from him so he learns all a attention goes away when he bites. Only give attention when he is calm.

Read Full Q/A … : Leerburg

Q. How can you help stop your dog from ‘play-biting’ and ‘mouthing’ when I’m trying to touch him in any way?
ANSWER : A. Is it still a puppy? It is a lot easier to stop a puppy from doing it than an older dog that has been doing it for sometime.
Try this…..as soon as it play bites or jumps up at you. Stop playing immediately stand up and turn your back on the dog, ignore the dog, even carry on with other tasks, or talk to someone else. Once dog stops then try stroking it again, as soon as it play bites again, stop and keep repeating until he doesn’t do it anymore. For it to be successful EVERYONE needs to do it EVERYTIME. Even with a young puppy it may take a couple of weeks. But it will take longer if you don’t persevere.

Q. When my dog wakes, he bites the first thing or person he sees
ANSWER : A. If your dog is startled easily upon waking and is biting people or objects, it is possible that he may have a vision or hearing problem, which causes people to startle him more easily. Making lots of noise before you approach (such as vibrating the floor or turning on a light) may help him to wake easier without startling, and may make him less prone to biting. It is a good idea to schedule a veterinary appointment to check for any health issues that could be causing this response.

If he is healthy and doing this behavior, or is acting aggressively toward others outside of waking up, then speaking with a local trainer or behaviorist in your area is best. Aggression is a hard behavior to train, and requires an expert in person to tailor training to your dog’s specific needs. Neutering may also decrease aggressive or dominant-type behaviors, however it does take times for the hormones to reduce and does not always solve the behavior.

If you are in the united states, you can find an animal behaviorist in your area by clicking this link: http://www.animalbehaviorsociety.org/web/applied-behavior-caab-directory.php

Q. My Bulldog puppy growls, barks and even tries to bite me when I say “no” to him. What can I do?
ANSWER : A. First, avoid scolding him and acting aggressively towards him if you don’t want him to be acting aggressively towards you. There are other methods you can use to communicate to your dog that you don’t want him to continue doing what he is doing. I recommend you stop telling him “no”, scolding him, or raising your voice at him. Everything coming from you should be 100% positive and 100% calm.

Try to figure out ways to clearly communicate what you want to your dog. If you want your dog to leave something or someone alone, I strongly suggest teaching your dog commands like “leave it”. Here is a link to a video in which I explain how to do it:


Another thing I suggest you use is a no-reward marker. This clearly communicates when your dog has done something wrong. No-reward markers have to be introduced during your training sessions. You should be doing at least three training sessions per day, that are something like 3-10 minutes long (working on different things each training session). If you are teaching your dog something BRAND NEW, do not use the no-reward marker, as you do not want to discourage your dog from performing behaviors for you. Use the no-reward marker for known behaviors only. Here is another helpful video about this:


Lure each new behavior (as shown in the video) using high value treats. Let’s say you’re working on “down” which is a behavior your dog knows fairly well. Present the treat to your dog. Ask your dog to “down” (only ask once). If he does not go “down” immediately, say, “uh-oh” or “eh-eh” in a gentle tone, and then place the treat behind your back. This communicates to your dog that they did something to make the treat go away.

After you place the treat behind your back to show your pup “that was wrong” you need to communicate to your pup “let’s try again” by getting your pup to walk around for a second, and then start the behavior all over again. If your puppy is very young, chances are you haven’t taught him a solid “down” behavior yet. So, as I said, do not use this method until you have lured each new behavior as shown in the video.

This is the order in which you should teach behaviors: Lure using a high value treat as shown in the video. After a few successful food lures, lure with an empty hand. If the pup is successful with the empty hand lure, reward with lots of treats. If the pup is unsuccessful, then go back to food-luring a couple more times. After a few successful empty-hand lures, you can begin to add the cue. Say “sit”, then lure with an empty hand, and then reward. Once your pup understands the cue, begin to work on the no-reward marker.

Q. My dog is german shiered about 60 days oid and and started play biting sincs 2 days. Doent respond to commands. How to correct the behavior. pl advise
ANSWER : A. You need to start regular puppy training classes. Ask your local vet to recommend some. You need to stop playing as soon as play biting occurs. Say NO firmly stand up and turn away from pup. Once stops play a game again, repeat when biting occurs again. It is important to be consistent with your training otherwise they will get confused by your commands. Try to avoid rough and tumble games and play ball games instead.

Q. My 20 month Cavalier doesn’t eat unless I let him eat from my finger, then he eats. Sometimes he will only eat once a day and leave his food.
ANSWER : A. It is possible that your dog is just not satisfied with his current food, or may be a picky eater. There are several things you can try to encourage your dog to eat.

The first step is to remove any additional treats or people food that may be more enticing to your dog than his own meal. If you feel you must give him some form of treat, be sure to place them directly in his food bowl and mixed with his regular diet. This allows him to get some snacks while also “forcing” him to try out his current meal to get the reward.

Enticing your dog to try his food by adding a pet-safe gravy or even a few treats of plain boiled chicken mixed in can help. Be sure to mix the foods thoroughly so he must explore his own food before getting the treat.

Some small breed dogs may also have a hard time with certain bowls and their collars. If there is a metal name tag on the collar and a metal bowl, the clinking sound can sometimes scare off dogs and make them not want to eat from their bowl. Using a bowl of a different material, or removing the collar prior to a meal may help with this issue.

Your dog may also just not be into his current food and may like another variety better. You can try a new variety by gradually switching over a period of 7-9 days, slowly adding in more new food and removing old until it is switched. This change may encourage him to try out meals again, and the slow changeover will allow his body to adjust to the new diet without digestive upset.

Q. I have a 8 month old Lab. He gets excited and likes to get mouthy and puts the persons hands in his mouth. Doesn’t bite hard. How can we stop this?
ANSWER : A. Bite inhibition is a great way to stop mouthiness that occurs often with teenaged dogs. There are several training techniques that can be done to help teach your dog how to play nicely! One is to teach a “Leave-it” command. Begin by holding a treat in your hand and asking your dog to “leave it”. If he attempts to chew or bite, a high-pitched YELP! will help. Once he backs away or ignores the treat, ask him to “take it” and offer it to him. Another useful way to teach bite inhibition is through the use of a tug toy. Again, the “take it” and “leave it” commands are used. During a tug session, ask your dog to “leave it” or “drop” and exchange with a treat. If he lets go of the toy, reward him! One final option is also “airplaning” treats. This method involves having your dog sit and then slowly lowering a treat toward him. If he goes for the treat, back away and start over. Once he can sit calmly and not chew on you, reward with the treat! All of these techniques are great for helping teach dogs bite inhibition. 🙂

Read Full Q/A … : Leerburg