An Australian snake employs a special feeding behavior to avoid
poisoning by toxic frogs, reports The American Naturalist. University
of Sydney scientists Ben Phillips and Richards Shine found that the
northern death adder not only distinguishes between different species
of toxic frogs, but modifies its feeding behavior to enable it to eat
species that rely on different poisons and defensive strategies.
First the adder bites and waits for its prey to die. Depending on the
species, the snake then waits a specific length of time for the
frog's toxins to degrade: 12 minutes for the marbled frog, the toxins
of which lose potency after about 10 minutes, and 30-40 minutes for
the Dahl's aquatic frog, which is rendered harmless about 30 minutes
after death. The behavior, which takes place only after the death of
a frog, is highly effective from an evolutionary standpoint, write
the authors.
"In evolutionary terms, the snake's strategy of 'bite, release, and
wait' is unbeatable by the frogs. Although prey often evolve ways of
overcoming predator tactics, the frogs can't do so in this case -
because the snake's strategy only becomes effective after the frog
has died. Natural selection ceases to operate on an individual after
that individual's death, so frogs will probably never evolve toxins
that last longer in response to the snake's tactic. Thus, this
waiting strategy is likely to be stable and unbeatable over
evolutionary time."
