水中音に関する研究-5-インダス河イルカPlatanista gangeticaの水中鳴音について〔英文〕

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Recording of the underwater call and observation of the relative behaviour of the river dolphin (Platanista gangetica) living in the Indus River were carried out. All of the underwater calls emitted by this dolphin were clicks which were continuously emitted. This call was mainly used for echolocation and, when small fishes were thrown into the pond, it was observed that the repetition rate of clicks emitted by the dolphin searching for bait rapidly became higher. The repetition rate was 30-200/sec. (usually 40-100/sec.) The analyzed patterns were monotonous and the particularly strong frequency band was not constant.The clicks emitted by the Indus River Dolphin were very similar to the call of the dolphin living in the Ganges River, but the stratiformed sound, burst, twitter and whistle which the Ganges River Dolphin emitted were not observed with the Indus River Dolphin.!?1. The underwater calls of the Indus River Dolphin were recorded in Pakistan were compared with that of the Ganges River Dolphin of the same species. 2. This dolphin lives at deep places and sinuous places of the Indus River and is always emitting the calls. 3. The emitting interval of underwater calls almost constant all day. 4. All of the calls of the Indus River Dolphin are of the type of so-called "Clicks" and play an important role in echolocation. 5. The analyzed pattern of these calls are monotonous and no special strong frequency band is recognized. 6. The repetition rate is 30-200/sec. (usually 40-100/sec.). 7. Regarding that the Ganges River Dolphin was under the breeding condition, the clicks of the Indus River Dolphin and the Ganges River Dolphin may have no difference at all. 8. Other calls observed in the Ganges River Dolphin were not recognized in the Indus River Dolphin.
長崎大学水産学部の論文

水中音に関する研究-5-インダス河イルカPlatanista gangeticaの水中鳴音について〔英文〕

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