Human beings are not the only ones who can suffer from insomnia, pets sometimes get it too. Unless your pet is keeping you up at night, you may never even have a clue that he is not sleeping and since they can not speak, this can make it especially difficult. Temporary bouts of insomnia can appear with your animal for the same reasons that insomnia appears in humans. It is likely that something is bothering your animal resulting in his sleep loss.
Dogs and cats are much attuned to what is going on with their owners and around the house in general. If there is construction going on very nearby that is causing a lot of chaos, this can affect your pets sleep pattern, if there is someone new sleeping in your home, you will likely notice a difference in your pet, and if there is a lot of fighting and arguing going on, that too can affect your pet and his sleeping. This is something that pet owners usually never give too much thought to but it does affect your animal.
There are other causes of why your pet might not be getting his proper rest at night, perhaps he is not well. Pets usually get insomnia when they are uncomfortable. Consider everything when it comes to evaluating your pet's insomnia because they can not tell you what is bothering them but if you watch for signs, they are surely to appear.
Is your pet scratching himself more than usual, if so maybe he has fleas or allergies that are keeping him up, maybe he is not getting much sleep because he is getting up to go to the bathroom more than usual which too can indicate a problem. Your pet could also have arthritis setting in; this is quite common in dogs and tends to often affect their hip which makes sleeping very uncomfortable.
In any case, if you notice any unusual patterns with your pet, including the inability to sleep at night then you should take your pet to his veterinarian and have an exam done to rule out any possible causes. If your pet's insomnia is stress related then the vet can likely prescribe something that will offer him great relief so he can start sleeping normally again. In many ways pets are like people and some of the same things that upset people, upset pets too. If pets do not get enough exercise, they will not sleep like they should, if they have a stomach ache, they might not sleep either. Older dogs also are the ones who require less sleep than younger ones do.
If you discover that your dog is not sleeping like he normally does then do not wait too long before taking your pet to the vet because it is a sign that something could be medically wrong. You can attempt some self help measures such as making a comfortable spot for him to lie on and maybe making sure that he gets more exercise but there is only so much that you can do on your own.