I don't what's more incredible--the fact that they truly help people catch another sea creature or that they've managed to have a unique accent to set their "helping group" apart.
The ever-friendly dolphins, who don't love them?
In Laguna, Brazil, some bottlenose dolphins actually chose to be literally humans' sea allies to catch fish. There, the water's too murky for the fishermen to see. So, when there are shoals of mullet, the social sea creature gives our men a signal instead (i.e. abrupt dive or tail slap) to cast the nets.
And with having these dolphins as their eyes underneath, fishers tend to catch larger and more fish. But this occurrence could actually be a mutual thing. “Dolphins likely reap similar benefits,” says Mauricio Cantor of the Federal University of Santa Catarina in Brazil. That is, the disorientation from our nets could've been of help for them to easily gobble up fish.
But, of course, not everybody from these Cetaceas are cooperative. So, researchers wanted to know if there's something that sets the helpful dolphins apart. Specifically, they've looked into the sounds they make when foraging both on their own and when with people.
Surprisingly, results showed that the helpful and unhelpful dolphins indeed have distinctive whistles. And while it has been established how dolphins whistle differently per region, "it is much less common to find such acoustic differences among dolphins of the same population that inhabit such a small area," Cantor says.
What's more is that such difference also goes even when the cooperative ones are foraging alone! This means that such change in whistles may not have been specifically for the messages they carry to people but a way to help them recognise each other. In short, this could be way of exclusivity in the social group.
This may even be a certain dialect or slang, “as if they speak the same language but use some ‘expressions’ that are exclusive to their social community," Cantor explained.
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