Snake uses trick to avoid poisoning from toxic frogs

Snake uses trick to avoid poisoning from toxic frogs
mongabay.com
October 16, 2007

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."

CITATION: Ben Phillips and Richards Shine (2007). When dinner is dangerous: toxic frogs elicit species-specific responses from a generalist snake predator. The American Naturalist VOLUME 170 NUMBER 5 NOVEMBER 2007.

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