There have been numerous studies and observations that suggest that an animal grieving on the death of their family or pack member is genuine. The initial research had claimed that monkeys and elephants are the only animals that are sad and upset about their partners' death.
But detailed research has shown that the mourning death has been seen in various species throughout the animal kingdom. The unique thing that was discovered during these studies is that most of the creatures not only mourn, but they also perform animal death rituals that will help them to cope with the loss of a companion or offspring.
Check out how different animals mourn the death of their family or pack members.