These Tadpoles Migrate Every Day

Screenshot of western toad tadpoles from Tadpoles: The Big Little Migration

2 April 2021

Three weeks ago frogs were singing and laying eggs in the vernal ponds of southwestern Pennsylvania. Many of the eggs have hatched by now. What do the tadpoles do next? This video from a remote lake on Vancouver Island, BC, Canada provides a hint.

Maxwel Hohn spent four years filming a tiny migration we never see. Every morning western toad tadpoles (Anaxyrus boreas) swim from their nighttime shelters to feeding areas in the lake, then back again to hide at night. The result is his award-winning 8+ minute video: Tadpoles: The Big Little Migration.

Our eastern American toads (Anaxyrus americanus) are closely related to western toads so I wonder if they do this, too.

Meanwhile, if the video wasn’t amazing enough for you, here are two more amazing things about tadpoles and toads:

  • Don’t worry that our tadpoles won’t survive the freezing temperatures this morning in eastern North America. Even if the ponds freeze, tadpoles are able to overwinter under ice. See photos at What’s Under the Ice? Wow! Winter Tadpoles from Oakland Twp, Michigan.
  • Do you know where North America’s toads came from? South America. And they didn’t walk! “Based on DNA sequence comparisons, Anaxyrus americanus and other North American species of Anaxyrus are thought to be descended from an invasion of toads from South America prior to the formation of the Isthmus of Panama land bridge, presumably by means of rafting. — from the Wikipedia description of the American toad.

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