rationalskepticism.org

I don't know for certain whether any other species understands that they will cease to exist at some point. I can't see why most highly intelligent mammals would know death is a thing, having experienced it around them. Whether they know an individual who has died is no longer exists, I don't know.

I don't think the vast majority of animals sit around fearing impending death. Most don't posess the intelligence to understand it.