Over the years, there has been growing pile of evidence that animals can also feel grief. In the book "How Animals Grieve" by Barbara King, she describes how elephants, baboons and cats attend to the corpse of their companion as if they are holding a funeral.

While this has been quite evident in terrestrial animals, the extent of this emotion has not been studied in whales. Until recently, a new study in the Journal of Mammalogy said grief is also found in several mammalian species in the ocean.

Melissa Reggente of University of Milano-Bicocca in Italy collected data from unpublished reports of whale behavior and identified seven pieces that showed mourning, including Indo-Pacific bottlenose dolphins (Tursiops aduncus), spinner dolphins (Stenella longirostris), killer whales (Orcinus orca), Australian humpback dolphins (Sousa sahulensis), sperm whales (Physeter macrocephalus), Risso's dolphins (Grampus griseus) and short-finned pilot whales (Globicephala macrorhynchus).

The observation was based on 14 events from 3 oceans. All species showed the same gesture toward a deceased companion. Reggente told National Geographic that the only possible explanation for such behavior is "grief."

"They are mourning," Reggente told National Geographic. "They are in pain and stressed. They know something is wrong."

The study also identified several ways whales mourn for their dead ones. For example, some touch their dead companions using their fins, while some circle around their dead as if guarding them so other species would not feed on their dead body.

Whales are highly sociable species. Studies showed that they form actual friendships, even lifelong bonds with their companions. Some researchers have observed that whales, even after years of migrating and breeding, return to meet their companions each year.

Not all whales are endangered, but the preservation of these ancient species is a priority. For the past centuries, their population decline has been attributed to commercial whaling and the degradation of the quality of the waters where they live.