Similarities between the two systems (island populations, highly venomous snakes, reliance on sessile prey) clarify the circumstances under which the loss of vision does not reduce an organism's viability. This result is strongly counter-intuitive, but mirrors an earlier report of congenital blindness (without ill-effects) in American viperid snakes. Thus, destruction of a major sensory modality had no detectable effect on these predators. Blind male snakes trail-followed females, and mated successfully.
This loss of vision did not reduce the snakes' body condition (mass relative to length), or their rates of growth or survival (measured over a 12-month period).
Many adult tiger snakes have had their eyes destroyed, apparently during nest defence, by silver gulls ( Larus novaehollandiae). Our behavioural and mark-recapture studies provide the first ecological data on this population, and reveal a surprising phenomenon. Large (to >1 m), diurnally active tiger snakes ( Notechis scutatus) are abundant on Carnac Island, near the coast of Western Australia.
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