Kya apne kabhi socha hai ki Dolphins paani ke andar echolocation ka use krke rasta kese dhundti hai?
Dolphins ke forehead mein melon hota hai, ye melon fatty tissue aur fluid se milkar bana hota hai. Aur echolocation ke dauran ye ek lens ki tarah focus krne mein kaam krta hai. Echolocation yani sounds ke through objects ko dekhna. Ye bilkul ek submarine mein lage sonar ki tarah hi hoti hai.
Dolphins apne nasal passages se sounds ya clicks ko emit karti hai. Phir ye sound waves pani ke through travel karke kisi bhi object se takrake wapis dolphin ki taraf echo ban kr aati hai. Dolphin ke lower jaw, jo fatty fluid se bhara hota hai, uss echo ko receive karta hai.
Phir ye sound lower jaw se inner ear tak jaati hai, jaha ye nerves ke through directly brain tak pohochti hai. Phir brain iss sound ko ek image mein translate kr deta hai. Dolphins iss process mein normally 30 se 140hz ki echo ka use krti hai.
Iss process se yeh apne environment ko 3 dimensionally explore kar sakti hai, aur low light ya low visibility mein navigate ya hunt kar sakti hai, inki echolocation itni accurate aur efficient hoti hai ki ye football feild jitni duri se bhi ek choti ping pong ball ko identiy kr sakti hai.
Iss echolocation ka use sirf pani ke andar hi kr sakti hai, paani se bahar ye kaam nhi krti.
History
1947 mein, Arthur McBride, Marine Studios (jo baad mein Marineland, Florida bana) ke pehle curator, ne dekha ki bottlenose dolphins (Tursiops truncatus) raat ke samay aur ghaas-pattay waale paani mein bhi nets se bach jaati hain aur enclosing nets mein openings dhoondh leti hain. Isse unhe lagta tha ki bottlenose dolphins mein biosonar ka capability ho sakti hai (McBride, 1956).
Baad mein, kuch dusre researchers jaise Winston Kellogg, Forrest Wood, aur William Schevill aur Barbara Lawrence ka husband-wife team ne dolphin biosonar ke preliminary investigations kiye (Schevill and Lawrence, 1953).
Kenneth Norris aur unki team ne pehli baar bottlenose dolphin echolocation ko conclusively demonstrate kiya. Unhone dolphin ke aankhon par rubber suction cups laga diye aur dekha ki dolphin maze mein vertically hanging pipes aur obstacles ke beech normal swim karti rahi aur clicks emit karti rahi (Norris et al., 1961). Unhone yeh bhi speculate kiya ki sonar sounds directional hain aur dolphin ke forehead ke upar se project hoti hain (melon). Norris ne yeh bhi dikhaya ki Pacific white-sided dolphin (Lagenorhynchus obliquidens) bhi biosonar capability rakhti hai. 1967 mein, do French scientists ne ek blindfolded harbor porpoise (Phocoena phocoena) ko maze mein swim karna sikhaya jo vertically hanging wires se bana tha (Busnel and Dziedzic, 1967).
Zyada tar early biosonar experiments US Navy Marine Mammal Program ke scientists ne kiye. C. Scott Johnson ne pehli baar Tursiops ki hearing ko study karne ke liye ek rigorous psychophysical procedure apply kiya (Johnson, 1966). Unhone paaya ki Tursiops 100 Hz se 150 kHz tak ki sounds sun sakti hai (Figure 1), jo kisi bhi mammal ke liye sabse widest frequency range hai. Unhone ek masked hearing study bhi ki jisme critical ratio ko different frequencies par determine kiya aur yeh dikhaya ki bottlenose acoustic energy ko waisa hi integrate karti hai jaise ki zyada tar mammals.
Forrest Wood aur William Evans ne suction-cup blindfolds ka use karke Pacific pilot aur killer whales mein echolocation dikhayi (Wood and Evans, 1980). Jaldi hi yeh maan liya gaya ki odontocetes (toothed whales) jo clicks emit karte hain, woh echolocating karte hain. Navy program ke early history ko Sam H. Ridgway ki kitab “The Dolphin Doctor” mein summarize kiya gaya, jo Navy Marine Mammal Program ke primary veterinarian the (Ridgeway, 1987).
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