Cornelius' Corner:

"Vernal Pools Are Cool!"

Cornelius’ Corner: “Vernal Pools Are Cool!”

Vernal pool by the Millrace

Greetings friends!

I’m so excited that spring is almost here! For this blog, I’m going to talk about a special habitat in the park that many people walk right by without even noticing – the vernal pool. But March is the time when they really shine, so it seemed like a good time to spread the word of their importance.

Vernal pools are small seasonal wetlands that form in small depressions on the landscape. During winter, the rain and melting snow fill up these depressions to create little wetland pools. The pools are present during the late winter and early spring, but dry up as the weather gets warmer. In fact, the name “vernal pool” means “spring pool.” Another name for these wetlands is “ephemeral pool,” which references the fact that they are only present for a short period of time.

Their temporary nature is what makes them so special! Since the pools disappear every year, predatory fish are not able to establish populations. This means that frogs, toads, salamanders, and various insects are able to lay their eggs without the threat of those eggs being eaten! The animals that breed in vernal pools have to grow up very quickly, because they are in a race against evaporation. Once the water in the pool dries up, it won’t be refreshed until next winter.

Here in the park, we have several areas with both natural and man-made vernal pools. One such area is along the millrace closest to the dam. This location has always had one or two vernal pools, but they had filled in with plants over several years. In 2019, Girl Scout Troop 565 worked with our staff to begin the restoration of the bigger pool. They pulled out layers of dead plants and deepened the depression to help it hold more water. They also planted a variety of plants that support wildlife, including button bush, scarlet bee balm, and swamp milkweed.

Wood frog eggs

My coworkers ended up having to do more work on the pool after the floods in 2020, but the erosion damage provided the opportunity to add a clay liner to the pool to help it hold water for even longer in the spring! Right away, toads started using the repaired pool for breeding. On one night in April 2022, my coworkers counted over 40 toads singing and laying eggs in the pool!

In the future, we will be replacing the plantings that the floods destroyed. The goal is to add lots of flowering plants that support large insect populations for the local frogs to feed on, as well as providing shade to help keep the pools cool and evaporating more slowly. However, this work cannot be completed until after the silt remediation work in the millrace. So we’re working on planting plans and getting area all cleaned up and ready to go for when the time is right!

In the meantime, the wood frogs are enjoying the pool! There are already a few wood frog egg masses, and there are sure to be more added over the next few weeks. Please don’t disturb the pool looking for them though – we want to keep the growing tadpoles safe. If you want to check out wood frog eggs, you can also see some in the wetland adjacent to the Frog Pond, and there’s a trail right next door that you can use to observe them without disturbance!

Don’t forget to stop by my tank in the front room of the Visitor Center to say hi! I’m sure my next door neighbor Tommy Toad would love to hear your stories about the vernal pools, too.

– Cornelius

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Additional Note


The Bird Walk and Habitat Stewards programs scheduled for Saturday, 3/25 have been CANCELLED due to weather. We apologize for any inconvenience.