Responses of predatory fish to lures

The evolution of bright “warning” colours in nontoxic animals often is
attributed to mimicry of toxic species, but empirical tests of that
hypothesis are elusive. Populations of a harmless sea snake species
(Emydocephalus annulatus) in New Caledonia exhibit colour polymorphism,
with around 20% of individuals banded rather than melanic. Stability in
that proportion over 20 years has been attributed to Batesian mimicry of
deadly snake species by banded morphs of the harmless taxon. This
hypothesis requires that banded colours reduce a snake’s vulnerability to
predation. We tested that idea by pulling flexible snake-shaped models
through the water and recording responses by predatory fish. Black and
banded lures attracted similar numbers of following fish, but attacks were
directed almost exclusively to black lures. Our methods overcome several
ambiguities associated with experimental studies on mimicry in terrestrial
snakes, and support the hypothesis that banded colour patterns reduce a
non-venomous marine snake’s vulnerability to predation.