I cannot recommend specific works cause most I've read were in not english. Ethology is the field that studies animal behaviour and cognition. I'll brush up on a few thoughts, you can verify them if in doubt/interested. Another comment replied to you with exemples of painful events that can make one suffer badly: having your bodily autonomy violated especially is pretty traumatic whether you have language to rationalize it or not, for humans as for animals. That's because animals do have a sense of self - a lot more than a newborn human. Besides, animals worry for their future and try to prevent bad things from happening to them. There are also universal things that go beyond language, abstract thinking and society - think motherly love - and it can lead to huge amounts of suffering even without complex thoughts around it. Animals grieve, and allegedly may have committed suicide on occasion.

I understand the difference between pain and suffering you're meaning to convey, but animals are not a good exemple here.

> Suffering is mostly constructed by human brain with the help of language and thoughts around pain. Think of animals! They have pains, sometimes, but they don’t suffer because they don’t have to think of past or future and just stay mindful, mostly always. They don’t have words like “suffering” and “pain” and “what would others think” or even a sense of self.

Please go read some science before saying shit like this based on intuition. Litteraly none of this is true. You can look up ethology books, for exemple. Or actually any article about animal behavior and intelligence will teach you more than you seem to currently know.

> The existance of the "happy ones" and the existance of those that are so un happy that would want to cease to exist. The first doesnt affect the second.

It does, if the existence of the happy ones relies on the suffering of the others - like it does in our world.

> Those who dont want to exist can cease to exist if they want to.

Which in turn will make other people suffer (family, closed ones etc).