12:21 25 January 2013
Everybody's favourite cetacean just got a little more
lovable. For the first time, dolphins have been spotted teaming up to
try to rescue an injured group member. The act does not necessarily mean
dolphins are selfless or can empathise with the pain of their kin,
Kyum Park of the Cetacean Research Institute
in Ulsan, South Korea, and colleagues were surveying cetaceans in the
Sea of Japan in June 2008. They spent a day following a group of about
400 long-beaked common dolphins (Delphinus capensis).
In the late morning they noticed that
about 12 dolphins were swimming very close together. One female was in
difficulties: it was wriggling and tipping from side to side, sometimes
turning upside-down. Its pectoral flippers seemed to be paralysed.
The other dolphins crowded around it,
often diving beneath it and supporting it from below. After about 30
minutes, the dolphins formed into an impromptu raft: they swam side by
side with the injured female on their backs. By keeping the injured
female above water, they may have helped it to breathe, avoiding
drowning (see video, above).
After another few minutes some of the
helper dolphins left. The injured dolphin soon dropped into a vertical
position. The remaining helpers appeared to try and prop it up, possibly
to keep its head above the surface, but it soon stopped breathing, say
the researchers. Five dolphins stayed with it and continued touching its
body, until it sank out of sight.
"It does look like quite a sophisticated way of keeping the companion up in the water," says Karen McComb at the University of Sussex in Brighton, UK. Such helping behaviours are only seen in intelligent, long-lived social animals. In most species, injured animals are quickly left behind.
For the love of pod
While it may seem selfless to help an
injured fellow, McComb says the helper dolphins might get some benefit.
Rescuing the struggling dolphin could help maintain their group, and
thus control of their territory. Furthermore, if the group contains
close relatives, protecting those relatives helps the dolphins preserve
their shared genes.
The simple act of working together
could also bond the group more strongly. "It makes a lot of sense in a
highly intelligent and social animal for there to be support of an
injured animal," McComb says.
The act of helping also seems to suggest that the dolphins understand when others are suffering, and can
even empathise: that is, imagine themselves in the place of the
suffering dolphin. But while this is possible, McComb says the helping
behaviour could evolve without the need for empathy.
There have been reports of single
dolphins helping others, generally mothers helping their calves, but no
cases of groups of dolphins working together to help another. Dolphins
have also been seen interacting with the corpses of dead dolphins, which some researchers interpret as a form of mourning.
Journal reference: Marine Mammal Science, doi.org/kbb
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