By Dave Sigworth, Maritime Aquarium publicist
Spring has to come eventually. (EVENTUALLY, RIGHT?) And, when it does, one of nature’s seasonal creations will play its vital ecological role again in our woods.
We’re talking of course about … big puddles.
Well, they’re really called vernal pools, but essentially they’re big puddles of standing water in the woods; puddles sometimes big enough to be pond-sized.
Vernal means “spring.” Vernal pools are low areas in the woods where snow melt and spring rainwater collect in a big puddle. The vernal pool isn’t fed by a stream or creek. Nor does water flow out of the pool.
There are two other things that define vernal pools that are important:
A local vernal pool.
• Because they’re not connected to any other body of water – in or out – they don’t have fish in them.
• And, because it’s spring and not too hot yet, vernal pools won’t evaporate for many weeks.
Those two characteristics may not seem important to you, but they make vernal pools VERY appealing to animals that need to lay their eggs in water – our native frogs, toads, salamanders and newts. These creatures’ eggs don’t have a hard shell like a chicken’s. Their eggs are gooey and gelatinous, and would dry out if laid on land.
The same spot in summer, after the vernal pool has dried up.
These amphibians’ newly hatched young – think: tadpoles – need to be in water as well. There are things to eat in the vernal pool, like plant matter, fairy shrimp (a subject worthy of a whole other blog some day) and other tiny invertebrates. Leaf litter in the pool conveniently provides hiding places.
And, in one of those cool relationship things we often find in nature, vernal pools eventually dry up in late spring or early summer, right about the same time that the amphibians have grown up and are ready for life in the woods.
It doesn’t always work perfectly. A dry winter or a hot spring can mean the vernal pool doesn’t form at all or dries up too soon. And, although they lack fish, vernal pools don’t offer absolute safety for baby amphibians. Turtles, raccoons, birds and other animals can raid a pool for easy meals.
But the system generally works well enough to sustain the amphibian populations in our woods – populations that are struggling otherwise because of habitat loss and pollution. These amphibians are important creatures that eat a lot of the bugs that bug us. Species that are particularly reliant on vernal pools include wood frogs, fairy shrimp and three species of salamanders: blue-spotted, marbled and Jefferson. Thus, to help save the amphibians, state and local laws stringently protect vernal pools.
Some warm spring evening, if it has rained, watch for frogs and other creatures to be on the move, crossing roads. They’re heading to water – perhaps to a vernal pool – to lay their eggs.
And of course you can always find a fascinating collection of frogs, toads and salamanders in The Maritime Aquarium’s “Frogs!” exhibit.