Gorilla mum Gana at Münster Zoo couldn't accept her baby Claudio's death. For days, she carried his dead body around and defended it against the zookeepers. This isn't unusual for great ape mothers who lose offspring, researchers say. Some moms won't even let go their baby's dead - and in the meantime, mummified - body for weeks.

Orcas, dolphins and other sea mammals also carry around their dead offspring for a while - not an easy task underwater. Researchers observed dolphin moms trying to balance their dead baby's body on their beaks, and diving after it when it finally sank to the ground. When adult dolphins die, their companions guard the dead bodies for days as well.

Elephants are famous for their excellent memory - no wonder they mourn especially long and intensively for their dead. A group of elephants congegrate around a dead elephants body in a kind of wake. Even elephants from other groups come to say goodbye to the deceased. Elephants have also been seen visiting the bones of other dead elephants, and touching the skeletons with their trunks.

Baboons show strong signs of stress when a close companion dies. The concentration of stress hormones in their blood rises, researchers have shown. To cope with the loss, baboons tend to seek out their friends. They dedicate themselves to grooming, which helps to lower their stress hormones.

When a crow dies, other crows summon members of their species, and together they gather around the carcass. They'll also typically stop eating for some time after a death. The effects of grief are especially evident in birds that spend their entire life with one partner - like geese or songbirds. Effects sometimes extend to the remaining partner stopping eating, and eventually dying itself.

Fish often remain unusually still after a fellow dies in the same aquarium. Researchers say this behavior is probably due to stress hormones released into the water by the dying fish. Few studies have looked into whether fish actually mourn their dead, but this seems conceivable - at least for fish that live in pairs, like the French angelfish.

There are also cases of animals grieving for members of other species. Take, for example, "Muschi" the cat and "Mäuschen" the Asiatic black bear. The pair became inseparable at Berlin Zoo - and when the bear died, the cat refused to leave her companion's enclosure. She stayed there, meowing mournfully.

People grieve deeply when they lose their beloved dog. The same goes for dogs who lose their masters. The German shepherd "Capitan" for many years stood guard at the grave of his master at the Villa Carlos cemetery in Argentina.