It's always sad to see an animal mourning over another animal. It shows that they also have feelings. We aren't the only ones that care.
Irene, here's a quote from evolutionary biologist Marc Bekoff that makes your point: "Evolutionary continuity...stresses that there are differences in degrees rather than in kind between humans and other animals. That applies to emotions. We share many bodily systems, including the limbic system, where emotions are rooted. So if we have joy or sorrow, they have it, too. It isn't the same joy or the same sorrow. But the differences are shades of gray, not black versus white."