Murder Comes Naturally to Chimpanzees - A major study suggests that killing among chimpanzees results from normal competition, not human interference. Apart from humans, chimpanzees are the only primates known to gang up on their neighbours with lethal results - but primatologists have long disagreed about the underlying reasons. One proposal was that human activity, including destroying habitats and providing food, increased aggression. But the new findings, published in Nature, suggest this is not the case. http://www.bbc.com/news/science-environment-29237276
In a related story, Chimps beat up, murder and then cannibalise their former tyrant. This is one of just nine known cases where a group of chimpanzees has killed one of their own adult males, as opposed to killing a member of a neighbouring tribe. https://www.newscientist.com/article/2119677-chimps-beat-up-murder-and-then-cannibalise-their-former-tyrant/
Monkey seen caring for dying mate then grieving after she dies - The alpha male of a group of snub-nosed monkeys and his dying partner spent a final, tender hour together beneath the tree from which she had fallen minutes earlier, cracking her head on a rock.