Grief is a very human feeling, so much so that today it is still too common to think that the cat does not go through it, or something similar. When you love an animal, to the point that you consider it part of the family, saying goodbye causes pain, and a lot of sadness. But when it is the cat that loses a loved one, what happens? Nothing?
The truth is that he also experiences emotional pain. On YouTube there are numerous videos in which a feline is seen having a bad time after the death of a relative. One comes to mind, where a person is being buried and the cat doesn't want to leave his grave, while another person tries to keep him away; or another, in which a cat is seen watching his favorite human already deceased on a tablet.
What are the symptoms of grief in the cat?
The cat that lives in the house often does not know what has happened, unless of course he has seen it with his own eyes. But he does notice the absence of that person (or animal), and that his family is sad. For him, associating the absence of the human (or animal) with the sadness of the family is something that does not take him long.
If he also felt great affection for him, it would not be surprising if he went through a process of adaptation to the new normality. A new normal in which your loved one is not.
This process could well be called grief, or simply sadness. The name, in my opinion, does not matter a bit. The symptoms are clear: may have less appetite (or even lose it), apathy and isolation are also common reactions, and it is common to meow trying to call him.
What to do to help him overcome it?
From my own experience, I recommend continue with your life, trying not to change the routine too much, and keep the cat company but letting him decide if he wants to snuggle up next to you or be caressed, it is the best remedy that can be given at those times.
In the event that he stops eating, it will be important to contact a veterinarian, especially if more than two days have passed. The ideal is to avoid reaching this situation, offering wet food if necessary (this, being more fragrant, can stimulate the feline's appetite).
Moreover, if you stop drinking, the consultation with the professional will become urgent, so that at the slightest sign of loss of interest in water, a specialist should be consulted. One thing you can do to keep him from stopping drinking, or to get him to drink more, is to buy a source. The cat does not usually like to drink water from a common drinking fountain; On the other hand, if the precious liquid moves, he feels more attracted.
This is a process that the cat must go through. He must learn to live without that loved one. You, like his family, you must respect their space, and not force him to do things that, for now or perhaps forever, do not interest him.
Give it time. You will see how little by little it will recover. Much encouragement.