Do animals mourn their dead?

Have you ever wondered if animals have emotions, more specifically, do they mourn? Is it possible for animals to comprehend death?

"Chimps are not silent. They are gregarious, loud, vocal creatures, usually with relatively short attention spans", she said.

"But they could not take their eyes off Dorothy, and their silence, more than anything, spoke volumes."

Read the entire article:
http://www.telegraph.co.uk/earth/wildlife/6444909/Chimpanzees-grief-caught-on-camera-in-Cameroon.html

There is also much to be said about the many death rituals performed by other species. Why do they do this? How would this benefit them from an evolutionary standpoint?