Woodcock Nature Center Column: The Great Amphibian Migration

GOOD Morning Wilton is thrilled about one of our newest features, a column contributed by the environmental educators at Woodcock Nature Center. They’ll be bringing you news and information about what’s happening seasonally in nature where we live and answering reader questions about our local environment and wildlife. (Email questions directly to Woodcock Nature Center.) 

Written By:  Jennifer Bradshaw, Environmental Educator

Why did the frog cross the road? To breed on the other side, of course. If you have ever been driving down the road on a rainy spring night and encountered dozens of frogs on the pavement, then you have witnessed one of nature’s most remarkable phenomena–the Great Amphibian Migration!

During early spring in Connecticut, several native species of amphibians, such as wood frogs and spotted salamanders, begin their migration to the wetlands. Some species rely only on vernal pools, which are ephemeral wetlands that are seasonally flooded and isolated from any sort of stream system. They need temporary pools for two important reasons:  they do not contain fish that would happily make a meal out of amphibian eggs and tadpoles, and because the stillness of water prevents the eggs from washing away.

There are 11 species of frogs and toads in Connecticut, and 13 species of salamanders. The five amphibians that are spotted most frequently during migration are the Wood Frog, Spring Peeper, Grey Tree Frog, American Toad and the Yellow Spotted Salamander. Between the months of March and April, when things begin to thaw and temperatures start to rise, these amphibians begin to emerge from hibernation. Most people will not see them starting to appear, but you can certainly hear them. They each have a distinct call that is easy to recognize and, when several call at the same time, the chorus that these tiny creatures make is absolutely incredible.

Once breeding takes place, frogs, toads and salamanders will lay their eggs in the water. The egg masses are quite different depending on the species:

  • Wood frogs generally lay 500-2000 eggs and groups of them often will lay their eggs in close proximity, also known as a “communal mass,” usually on vegetation or submerged tree branches. Their eggs hatch after 15-20 days.
  • Spring Peeper eggs turn into tadpoles anywhere from two days to two weeks, depending on water temperature.
  • Grey Tree Frog eggs hatch in 4-5 days.
  • American Toads lay their eggs in a long string. Each strand can contain up to 20,000 eggs, depending on the size of the female.
  • Spotted Salamander eggs are usually attached to sticks, branches or aquatic plants. Their egg masses, which are made up of 50-250 eggs, are surrounded by a dense, firm layer of gel. Their eggs take the longest to hatch–between 30 to 60 days.

Often these temporary pools have an explosion of tadpoles with slowly dwindling amounts of water which can leave the pools looking like a giant swarm of insects.

In about 1-3 months, these amphibians will complete their metamorphosis. This is the process of transformation from an immature form to an adult form in two or more distinct stages. They lose their gills and grow their front and back legs, and frogs also absorb their tail into their body. The fully-formed adults now leave the water for life on land.

My love for frogs, toads and salamanders started at a very young age. I spent hours pond-side catching frogs, scooping eggs and looking under logs for salamanders. When I was 10 years old, I became so obsessed that I used all of my grandma’s good dishes and pots to hold the hundreds of tadpoles and frogs I caught–I was in trouble that day!

As an adult, my love for them has not wavered. I recently became a FrogWatch USA Volunteer and I’m in the process of starting a chapter here at the Woodcock Nature Center. This nationwide program created by the Association of Zoos & Aquariums is one of the first citizen science programs ever created and is in its 21st year.

If you are interested in seeing some of the nature center’s currently bustling vernal pools, please join us for our Earth Day Celebration, “Peepers, a Vernal Pool Walk” on Saturday, April 27 at 10:30 a.m..

For more information about the amphibian migration, vernal pools or general nature and wildlife questions, please feel free to email me.