My children and I first learned about vernal pools a couple of years ago while visiting a local nature preserve. I noticed it labeled on the trail map and it piqued my curiosity. When we arrived, we thought it was an interesting spot but it didn’t look any different from a small pond. Why was this called a “vernal pool”? What exactly is a vernal pool any way? We had to find out.
What is a vernal pool?
Vernal means ‘of or relating to spring’ (the April nature word of the month). So… how is it a spring pond? Vernal pools are typically formed in shallow depressions from spring rains or melting snow (although they can also start filling in the fall). But there’s more to defining vernal pools. Vernal pools:
- only hold water for part of the year, typically spring through fall
- are not fed by a permanent water source
- do not have an inlet or outlet
- do not support fish life
- are an important wetland habitat with key indicator, or obligate, species
And that last tidbit is the fun part to explore – the indicator species found there and the ecological importance of the habitat.
Indicator species are plants and animals that define a characteristic of an environment and are often used to measure the conditions of that environment. The indicator species of vernal pools require this temporary habitat for continuing their cycle of life. These species include:
- Spotted, Blue Spotted, Jefferson, and Marbled salamanders – Salamanders migrate to vernal pools in early spring to mate and lay their eggs, where they will develop and hatch.
- Wood frogs – Wood frogs also return annually to vernal pools to lay their eggs.
- Fairy shrimp – Fairy shrimp are very small crustaceans that have specialized for a short life cycle. Eggs remain embedded in the mud once the pool has dried up and freeze over the winter. They hatch once the spring rains return and the pool fills up again.
Many places host a “big night” in early spring to observe the mass migration of salamanders and frogs and to even give them a helping hand in areas where they cross roads. Early spring is a very exciting time for vernal pools but the activity continues through the spring and summer and even into fall.
Vernal pools can be easily overlooked as they may seem like a large puddle or because upon first glance there may not seem like much is happening. If you take your time and look closely, however, you will begin to notice a very active and interesting habitat.
There are eggs and newly hatched life to spot, other animals that come to take advantage of this special environment, and unique plant life. Watch predacious diving beetles feed on newly hatched young. Keep an eye out for different types of frogs, turtles, dragonflies, and birds. Look for tracks that indicate a mammal has been visiting.
If you have access to a vernal pool, a great activity is to observe it throughout the seasons and record your observations. We like to bring our net and a clear container for some closer observations. Does the water level remain constant? What plant life do you notice? What animals are you noticing at the different times? Sketch your observations in your nature journal or take photos during each visit and compare them.
Here are some resources that we have used to help further our vernal pool studies…
Books about vernal pools:
The Secret Pool by Raye & Ridley
Frog Heaven: Ecology of a Vernal Pool by Doug Wechsler
Big Night for Salamanders by Sarah Marwil Lamstein
Salamander Dance by David Fitzsimmons
Happy exploring! Let us know what you discover at your local vernal pool.
Have a wonder-filled weekend.