The question implies that domestic cats groom themselves after eating wet canned food but not after eating dry food. I’m not sure that that is entirely correct. This is because it is instinctive for them to groom themselves after eating. And it seems obvious as to the reason why. They start by licking their lips to get rid of particles and morsels of food that remain around their mouth. They move on to other areas of their body. They’ll settle down to a thorough wash in one of their favourite spots.
But I think this feline behaviour has a deeper origin. If you go back to the wildcat ancestors of the domestic cat, they do the same thing. They are surviving on hunting and killing prey. They will have a bloody mouth after eating their prey animal. That needs to be cleaned off both for the purpose of personal hygiene (we know how fastidious cats are about their hygiene) and for the purpose of reducing the odour of blood and food on their person which may attract predators.
So, this innocuous form of feline behaviour is, I would argue, rooted in history. It is said that if you carefully inspect the area around a food bowl containing wet cat food after a cat has fed you will find a multitude of almost invisible particles of wet cat food deposited there. This is indicative of the fallout from eating wet cat food 😉. I suspect that some of these particles fall on other areas of a domestic cat’s body as well.
As to dry cat food, as this is an instinctive behaviour, cats will also groom themselves after eating dry cat food despite the fact that there is little practical purpose. Or, perhaps it is more accurate to say that there is a much-reduced reason for doing so. This is on top of the fact that the reason for grooming after eating has already been substantially reduced because the domestic cat is not preyed upon by predators and their mouths are not bloodied from the blood of prey animals.
As I said, it’s entirely instinctive. It is irrelevant whether it’s needed or not. Domestic cats are programmed to do it. It is in their DNA as inherited over eons of evolution and the starting point is the behaviour of the North African wildcat.
SOME MORE ON CAT FEEDING BEHAVIOR:
