[MARMAM] Humpback Whale acoustics question

Kelvin Aitken kelvin at kaphoto.com.au
Mon Sep 11 20:52:24 PDT 2006


I have spent a lot of time photographing Humpback Whales in the Pacific. 
I have seen some behaviours on which I would like some more information.

Is a vertical stance by a humpback able to provide it with increased 
acoustic reception? (Some recent photos showing examples can be found 
among the web pages here: 
http://www.marinethemes.com/Tonga2006/index.html) I have photographed 
females that hang motionless in a head down position and generally 
(though not always) I have photographed singing males in a vertical or 
near vertical (head down) position. I assume that to some degree a 
vertical downward facing position would enable a male to bounce sound 
off the sea bed which could partially explain the usual singing 
position. Would a vertical position give an advantage when receiving sound?

Spyhopping: Tourists are usually told that when a whale "spyhops" or 
raises it's head above the surface in a vertical or near vertical 
position, it is looking at the boat or other whales or in some way 
satisfying it's curiosity visually. However, I have rarely seen spyhops 
where the eye of a humpback is above the surface, as the eyes are 
situated well back from the snout. Almost all spyhops are done with 1/4 
to 3/4 of the snout above the water (and sometimes less) so an above 
water visual check hardly seems to be an adequate explanation for this 
behaviour. Also, since a large part of the suspended planktonic 
animal/plant life is found in the top meter of sea water, it would be 
logical to think that it would be easier and more visually satisfying 
for a whale to be well below the denser and usually rough surface.

I know that crocodiles have sensory pits around the mouth similar to the 
Ampullae of Lorenzini found in sharks, that are able to pick up surface 
vibrations which is why they may raise their snout to place these 
sensory pits on the water/air interface. Would a spyhopping whale be 
placing their jaw in the water/air interface to better pick up 
vibrations? Would a vertical humpback be using it's jaw or skeletal 
bones to detect or enhance sound waves travelling through the water?

Any informed comments or references to articles would be much appreciated.

With thanks,
Kelvin Aitken.




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