Wood Frog Tadpoles

wood frog tadpole, Rana sylvatica

wood frog tadpole, predator induced morphology

After hatching from eggs, wood frogs (Rana sylvatica or Lithobates sylvaticus) remain in a tadpole stage for eight to twelve weeks before metamorphosing into small froglets. The wetlands that woodfrog tadpoles inhabit vary greatly from year to year. In some years they may be full of predatory insects, but in other years they may have few predatory insects. The video below shows wood frog tadpoles interacting with predatory dragonflies in a woodland vernal pool.

Wood frog tadpoles change their development and behavior in ways that improve their survival across variable environments. Tail shape is one example of this developmental flexibility. When faced with predatory insects, tadpoles develop deep tails that improve their ability to survive attacks. But when predators are missing, tadpoles develop smaller tails, allowing them to conserve energy for growth. The pictures above illustrate this. The top tadpole was raised in an environment without predators, and so developed a shallow tail. The bottom tadpole was raised in an environment with predators, and so developed a deep tail.

All text and photographs Michael F. Benard
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Some more pages on herps and natural history:
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