The echolocation clicks of toothy whales and dolphins typically encounter few obstacle at sea . Amazon river dolphins , on the other deal , live in shallow duct and flooded forests alongside dense flora – confined environments where sonar operations might leave in eminent levels of mare’s nest and reverberation . agree to Modern findings print in theJournal of Experimental Biology , these mahimahi rely on a high - frequency , short - range biosonar .
premature study find that body size plays an important persona in the phylogenesis of toothed hulk echolocation . Aarhus University’sMichael Ladegaardand colleagues want to see if habitat shaped the evolution of their biosonar as well . They recorded the echolocation clicks of wild Amazon river dolphins ( Inia geoffrensis , also call botos ) in three fix in the Amazon during October of 2013 : near São Tomé in Brazil , at the conflux of Rio Negro and Rio Solimões , and in the Mamirauá Sustainable Development Reserve . The dolphins were recorded from small aluminum - hulled boats , and an raiment of seven hydrophones were deployed vertically as the team drove slow ahead of the animals . The researcher record almost 35,000 echo sounding click , of which 268 were show head teacher - on and within 21 meters ( 70 foot ) of the equipment .
These river dolphins , the researcher find , bring about soft , high - pitch echo sounding click that last 14.1 microseconds with a brief interval of 35 microseconds between the clicks .
By increase the frequency of their clicks , these freshwater mahimahi could direct their sonar comfortably than their ocean faring cousin . With soft , lower bounty click , echoes only render from nearby object . That mean all of the sound reflection that they need to interpret return within millisecond , Inside JEBexplains , allowing them to produce high rates of about 30 chink a 2nd , while limit reverberations .
Low - bounty , highly directional biosonar systems , the squad argues , are advantageous in riverine home ground because they simplify the auditory vista and help with target detection in cluttered , acoustically complex spaces .
