Two dolphins have been recorded having a conversation for the first time after scientists developed an underwater microphone which could distinguish the animals' different voices". Researchers have known for decades that the mammals had an advanced form of communication. But scientists have now shown that dolphins alter the volume and frequency of pulsed clicks to form individual "words" which they string together into sentences in much the same way that humans speak. Researchers at the Karadag Nature Reserve, in Feodosia, Ukraine, recorded two Black Sea bottlenose dolphins, called Yasha and Yana, talking to each other in a pool. Each dolphin would listen to a sentence of pulses without interruption, before replying. Lead researcher Dr Vyacheslav Ryabov, said: "Essentially, this exchange resembles a conversation between two people. "Each pulse represents a phoneme or a word of the dolphin's spoken language. "The analysis of numerous pulses registered in our experiments showed that the dolphins took turns in producing [sentences] and did not interrupt each other, which gives reason to believe that each of the dolphins listened to the other's pulses before producing its own. "This language exhibits all the design features present in the human spoken language. This indicates a high level of intelligence and consciousness in dolphins. Their language can be ostensibly considered a highly developed spoken language, akin to the human language."