https://www.wellbeingintlstudiesrepository.org/cgi/viewcontent.cgi?article=1201&context=animsent

Nothing concrete of course, because it’s very difficult to study at a stage where we cannot communicate or directly observe the emotional states of animals, nor ethically design a study where one attempts to cause animals enough distress to engage in self harm or bring about their deaths (and simultaneously prove that was their intent).

It’s in no way a concluded topic, but it doesn’t make sense to reject outright either - and I definitely think there is enough evidence around for animals understanding of their peers mortality, why start with the assumption that they have an inability to recognize their own mortality in the first place? It’s good to be skeptical, but unproven anthropomorphism is just as illogical as the opposite assumption.