A group of dolphins have been witnessed trying to help a badly injured companion by forming a "living raft" to keep it alive.
The "unusual case of care-giving behaviour" is documented in the Marine Mammal Science journal, published by the Society for Marine Mammalogy.
It details an incident at the Cetacean Research Institute in Ulsan, South Korea, where researchers noticed the rescue attempt among a pod of 400 long-beaked common dolphins.
Out of the group, 12 dolphins were seen swimming closely together, apparently attempting to support a female who was struggling to swim.
While the injured dolphin was able to move its tail, her flippers appeared paralysed. The surrounding dolphins looked to have formed a "raft" to lift their companion above the water, in an apparent attempt to help her to breathe.
Although the dolphin eventually died, five of the mammals remained with her corpse, continuing to nudge it until it drifted out of sight.
The research paper points out all previously reported examples of such behaviour have involved only one or two adult animals "which exhibited rescue activities for calves by pushing the animal to the surface or stimulating it by biting".
Karen McComb at the University of Sussex in Brighton, UK, told New Scientist: "It does look like quite a sophisticated way of keeping the companion up in the water."
She added the "rescue" attempt was indicative of strong group bonds and control of territory.
"It makes a lot of sense in a highly intelligent and social animal for there to be support of an injured animal."
An earlier report also by New Scientist suggests dolphins interacting with dead members of their pod could be showing signs of mourning.
Joan Gonzalvo of the Tethys Research Institute based in Milan, Italy, told of her observations of a female dolphin interacting with her dead newborn calf.
The bottlenose dolphin apparently repeatedly lifted the corpse above the surface in an attempt to make it breathe.
"This was repeated over and over again, sometimes frantically, during two days of observation," says Gonzalvo. "The mother never separated from her calf."