I will always hate with all my being the view and take of Watership Down as a depressing or dark story in the sense of "uhhhh life is suffering".
I don't care if it's in jest. The story isn't even remotely similar to that.
Where in this story of rabbits surviving together as a group facing adversity is that part understood? The story DOES have elements about death and the naturalness of it. They are rabbits after all. But death is far from being the most "in focus" element of the whole work, at least in that sense. Almost no important character dies or suffers an extremely tragic fate.
Yes, there is an entire warren being destroyed and yes, there are also rabbits that accept to die in order to have the security of being protected by a man, but those cases in particular are never treated as "normal" or left alone.
Do you even forget this little sentence right after the part about the rabbits being destroyed by the man?
"Would that the dead were not dead! But there is grass that must be eaten, pellets that must be chewed, hraka that must be passed, holes that must be dug, sleep that must be slept. Odysseus brings not one man to shore with him. Yet he sleeps sound beside Calypso and when he wakes thinks only of Penelope."
Or precisely the phrase with which begins that same chapter:
Rabbits (says Mr Lockley) are like human beings in many ways. One of these is certainly their staunch ability to withstand disaster and to let the stream of their life carry them along, past reaches of terror and loss. They have a certain quality which it would not be accurate to describe as callousness or indifference. It is, rather, a blessedly circumscribed imagination and an intuitive feeling that Life is Now. A foraging wild creature, intent above all upon survival, is as strong as the grass. Collectively, rabbits rest secure upon Frith's promise to El-ahrairah.
Come on, even the ending is a HAPPY ending. Hazel dies of old age, in peace being greeted by the legendary figure they admire as a hero, under the promise that all the rabbits will be well.
Certainly the depiction of Watership Down in nature is not just about how "realistic" it is just to show a dark morality of animals killing each other. Rather, it actually depicts these creatures' drive to survive and how circumstances lead them to break down barriers and accomplish things together that seemed impossible. How they all have a concept of life and struggle to reach it.
Nature in its essence and complexity is how it is actually created and affected by its own inhabitants, who through their actions are the origin of all good and bad.
And, call me crazy, but all this is FAR from representing misery and tragedy. It is pure light and hope.
Foolish anyone who believes that Watership Down is purely dark and depressing.