The Waters of Lathrop #2: Vernal Pools

by Barbara Walvoord

“Vernal” means spring, which is a long way away. But Lathrop’s vernal pools are in their winter garb, covered with ice, and very beautiful.

A vernal pool by definition has no outlet above ground. It fills with water in certain seasons, especially spring, and then is generally (but not always) dry by late summer.

On the east campus, if you start at the blue shed and walk down the wide path into the woods a few hundred yards, you’ll see a vernal pool through the trees on your left.

Another vernal pool, pictured with this article, you can find by walking along that wide path all the way to the meadow, and then crossing the meadow and going to the far left hand corner. Just a few yards into the woods, you’ll see the vernal pool.

The big thing about vernal pools is, no fish can survive because the pool dries up. Fish eat small amphibians and their eggs. So a vernal pool is a haven for any creature creative enough to use the vernal waters for only part of its life cycle. Some, like fairy shrimp, live a very short life, while the pool is wet, and then die, leaving behind eggs that can stand drying and freezing at the bottom of the pool. If you want a longer life, you have to lay your eggs in the pool in the spring, and then, when the pool dries up, you and your tadpoles, now grown, must hop out to the surrounding woodland, like wood frogs do, or back into your burrows on the forest floor, like mole salamanders do. So our vernal pools are full of eggs, and the surrounding woods are full of creatures hunkered in, waiting, as we do, for spring.

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