Monday, 30 November 2009

Hammerhead sharks and stereo vision

This BiologyNews.Net report summarizes work just published about whether or not hammerhead sharks have any stereoscopic vision. The researchers actually started out convinced the sharks did not have stereo vision, but then....

The scalloped hammerhead had a massive binocular overlap of 32 deg. in front of their heads (three times the overlap in the pointy nosed species) while the bonnet head had a respectable 13 deg. overlap. And when the team measured the binocular overlap of the shark with the widest hammerhead, the winghead shark, it was a colossal 48 deg. The hammerheads' wide heads certainly improved their binocular vision and depth perception.
And then another surprise...
Even more surprisingly, the team realised that the bonnethead and scalloped hammerheads have an excellent stereo rear-view: they have a full 360 deg. view of the world.
Impressive. Stereo vision fore and aft. I wonder about up and down. Don't see any mention of that, though I've not gone back to the original source.

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