Dolphins try to save pod members who are injured or dying, researchers have filmed for the first time.
Researchers at the Kyum Park of the Cetacean Research Institute in Ulsan, South Korea, filmed around 400 long-beaked common dolphins and noticed some unusual behaviour.
They noticed 12 dolphins swimming very closely together and that one female has struggling to swim; it was wriggling about and had turned upside down.
Although it was splashing its tail, its flippers appeared to be paralysed. The group of dolphins tried to rescue their companion by forming a raft to keep the dying member alive.
They appeared to by trying to help the dolphin balance by pushing it above the water, allowing it to breath.
The dolphin eventually died but five of its companions stayed with her and continued to touch it, until it fell out of sight into the ocean.
Karen McComb at the University of Sussex in Brighton, "It does look like quite a sophisticated way of keeping the companion up in the water.
"It makes a lot of sense in a highly intelligent and social animal for there to be support of an injured animal."
Dolphins' helping sick or injured companions has been recorded in the past. However, researchers note that this normally involves a mother helping when her calf is in difficulty.
Adult dolphins have also been known to keep a deceased dolphin afloat - however previous examples, just one or two dolphins are involved in the rescue attempt.
New Scientist reported that this could be a sign dolphins understand they are mortal and is a form of mourning.
Joan Gonzalvo, from the Tethys Research Institute in Milan, observed a mother with its dead calf in 2007.
She tried to lift the calf to the surface of the water trying to get it to breath: "This was repeated over and over again, sometimes frantically, during two days of observation," Gonzalvo said.
"The mother never separated from her calf. [She] seemed unable to accept the death," he told New Scientist.