Hypothyroidism
This is another common disease that makes dogs go quiet all of a sudden. This disease occurs when there is a decrease in the production and secretion of the thyroid hormone. Some other symptoms a dog shows apart from going quiet when they have this disease are anemia, excessive shedding, cold intolerance, slower heartbeat, and weight gain.
Heart disease
A weak heart is a major health problem for any dog. Heart muscles not functioning and firing sequentially as they should lead to our dogs getting tired quickly and easily. There is less tolerance to stress, meaning your dog cannot even exercise properly even if he or she wanted to leading to other health conditions.
Other symptoms of heart disease in dogs are coughing, pot belly, elevated respiratory rate, tiredness, and fainting.
Emotional issues
The loss of someone in the family, bad life experiences, sudden change in the environment, etc. These things can lead to your dog developing emotional issues and most dogs with emotional issues deal with it by looking for a quiet place where they can grieve on their own. If you have a strong bond with your dog, he or she would probably communicate with you that they are having emotional issues.
Apart from going quiet all of a sudden, other signs of emotional issues in dogs are loss of appetite, no interest in playing, whining and howling, etc.
Injury
A broken bone, a wound, a sprained ankle, etc, any type of injury can make your dog really quiet, sad, and sleepy. Injured dogs are likely to cry, limp around, or continue nursing the particular spot of the injury. The challenge with realizing or finding out whether your dog is injured is that dogs generally are very good at hiding physical pain and that includes when they are injured.
You see, in ancient times, an injured dog would be vulnerable to attacks not just from other predators, they would also be vulnerable to intimidation and bullying from their kind. Centuries of conditioning and today, you have dogs that still go to great lengths to hide their physical pain.
Detecting that your dog is quiet and not himself from an injury would require careful observation of your dog. When did he start being quiet? What kind of activities did he used to engage in before but can’t do now? Is there a change in his movement pattern? etc.
Excess Exercise
The type of exercise you do with your dog can leave your dog so exhausted that your dog becomes quiet all of a sudden. There are exercise strategies geared toward expending a dog’s energy such that he or she would have no other option than to fall asleep immediately after such a session.
If this is your situation, there is nothing to worry about. Your dog would be back to its normal self after a good rest. This strategy is usually advised for those who have dogs that don’t rest or sleep at night, exercising them properly in the evening just before bedtime ensures they sleep well.
If this is not your case, then your dog being quiet all of a sudden would be due to other reasons.
Obedience Training
“My dog is really quiet and sleepy” you may be saying to yourself. Why is this? Well, your method of training may have made your dog this way. Check yourself, what exactly do you reward in your dog? What does he do that makes him or her receive praises and body rubs from you. If he sits down quietly and you reward him for that, chances are they would stay quiet more to receive your praise and attention.
Boredom
Your dog may be quiet and not himself simply because he is bored out of his wits. Mental stimulation is very important for dogs at every stage of their life, even when they are old or senior citizens, they need mental stimulation to keep their mental faculties in check.
When left on their own, they may develop abnormal behavior which would be another problem on its own. Basically, make sure you engage your dog from time to time, best practice is to have a schedule of activities so that your dog can look forward to doing something with you daily in a structured manner.
Your dog is in heat
The reason why your dog is sitting quietly all of a sudden can be that she has come into season or she is in heat.
To be clear, not all dogs express themselves when they are in heat the same way. Some can get very aggressive, others become more attached to their dog parents during this period, and finally, there are the ones we are interested in, the ones that prefer to be left alone and stay in silence for that period.
They tend to go back to their normal selves after the heat period.
It’s worth noting that mature female dogs can go into heat twice a year and this can last for two to three weeks for each heat session.
Hot Weather
The hot weather condition can cause a dog to be quiet all of a sudden especially if this is a dog that is used to cold weather. Some examples are the Siberian Husky, Shiba Inu, and the Saint. Bernard. Brachycephalic breeds or dogs with short snouts like Pugs and Bulldogs are also known to hibernate and be quiet when the weather is hot.
Naturally, these dogs are unable to dissipate heat, and so when you have hot weather, it means the condition around is extreme for them and their system has to work harder to manage the heat hence they’re being quiet in hot weather.