The Araguaian river mahimahi is different from most other dolphin species . Besides inhabiting smart , not salty , water it lives a relatively alone life history , instead of shape magnanimous pods . It ’s the latter feature article that led biologists to have a bun in the oven Araguaians would have much less complex communication tools than their shipboard soldier similitude , but this has turn out to be faulty . Instead , there are C of sounds in the Araguaian ’s vocabulary , a discovery that may shed light on how maritime mammals in general developed their communicating tools .
Dr Laura May Colladoof the University of Vermont hit the books the inhabitants of the Tocantins River and its tributary the Araguaia , which the dolphins are named after . " We found that they do interact socially and are make more sounds than antecedently thought , " May Collado tell in astatement . " Their outspoken repertory is very diverse . "
ordinarily the dolphins are more suspicious of human beings than their marine counterparts – a judicious move considering what we ’ve done to other fresh water dolphin species . However , in the town of Mocajuba fish mart customers have taken to feeding dockside visitant , and the enticement of easy food has overcome the dolphins ' innate care .
InPeerJMay Collado report underwater microphones identified 237 discrete Araguaian sound in the place of 20 hours of recording , substantially more than some grouchy teenagers seem to make do .
Some of the sounds were relatively unproblematic ones between calves and their mothers . Others , however , were longer and more complex . In news that will warm the hearts of introvert everywhere , May Collado has a theory these are designed to help Araguaia dolphins keep their length from each other , rather than as part of group bonding .
Rare footage of Araguaian river mahimahi . Paulo Castro
May Collado also reports that the Araguaia ’s calls have a structure like an killer whale ’s but a pitch much lower than that of marine dolphins – indeed half way to the deepness of baleen whales , which expend low frequencies to communicate over great distances . May Collado conceive this is to forbid sounds echoing off underwater flora in a habitat that flesh out to let in flooded forests in the rainy season .
Although it is improbable these sounds could have evolved from excoriation in the brusk prison term the dolphins have been feeding off human fish combat , May Collado is swell to see if river dolphins with less human interaction are just as chatty . Studies of the nearly related Amazon mahimahi have indicate they are much quieter .
Elsewhere in Brazil a small group of bottlenose mahimahi that partner with man to assure both catch more fish than either would alone have been found to have formed theirown societywithin the pod , which has die hard over generations .
Meanwhile , the highly endangered Irrawaddy dolphins of the Mekong Riverwere reportedto be making a comeback , although their identification number are still a lilliputian fraction of pre-1970s levels .
