From: Greg Benage [gbenage@ix.netcom.com] Sent: Wednesday, July 19, 2000 12:38 AM To: blue_planet@lists.imagiconline.com Subject: Re: [BLUE PLANET] - Orca question ----- Original Message ----- From: To: Sent: Tuesday, July 18, 2000 7:48 PM Subject: [BLUE PLANET] - Orca question > I always thought that the orca's markings were simply decorative at > best; I never really thought they had any sort of camouflage function. > But the two most ferocious predators in the seas sharing similar > markings can't be a coincidence. Does anyone know what the significance, > if any, of the orca's markings? Check out the pattern on a camouflaged fighter plane the next time you get a chance. You'll see the same kind of scheme. Basically, the dark coloration blends in with the dark water and masks the orca from anything looking down at it from above (or trying to spot it as it swims at the surface). The light coloration blends with the sunlit water and masks it from anything viewing it from below. In other words, it's an evolutionary adaptation that assists in predation, in both the case of the orca and the greater white. Greg Benage Biohazard/FFG *************************************************************************** To unsubscribe from this list send mail to majordomo@lists.imagiconline.com with the line 'unsubscribe blue_planet' as the body of the message. From: Christopher Gribbon [c.gribbon@dundee.ac.uk] Sent: Wednesday, July 19, 2000 5:53 AM To: blue_planet@lists.imagiconline.com Subject: Re: [BLUE PLANET] - Orca question >I always thought that the orca's markings were simply decorative at best; I >never really thought they had any sort of camouflage function. But the two >most ferocious predators in the seas sharing similar markings can't be a >coincidence. Does anyone know what the significance, if any, of the orca's >markings? The only significance I know of for that type of patterning (dark top, light underside. There's a name for it - but it escapes me currently) is that it makes you harder to spot from above or below. If you look up while underwater, the water above you will be lighter ('cos the sunlight / moonlight is coming from that direction, don'tcha know...); if you look down - it's dark. So, if the shark is below you, it wants to be presenting it's dark side to you, and if it's above you, it wants to be light - in order that it blend in better either way. Any elaborations in the patterning (eye patches, fin saddle) are probably for individual marking and identification purposes. Similar patterning is found in many other fish and in birds too (all the beasties that have a routinely 3-dimensional existance, you see). At least - that's my understanding of it. Someone who actually knows something about it is encouraged to correct me ;-) Christopher Gribbon Vision Research Laboratories Medical Sciences Institute University of Dundee Dundee DD1 5EH UK (01382) 344 229 ____________________________________________________________________ "A scientist is meant to be disinterested, pure; his ambition merely to descry the cement of the universe. He isn't meant to use it to start laying his own patio!" - WILL SELF, The Quantity Theory of Insanity *************************************************************************** To unsubscribe from this list send mail to majordomo@lists.imagiconline.com with the line 'unsubscribe blue_planet' as the body of the message.