Vernal Pools: Tiny Ecosystems, Big Impact

The spring amphibian migration is about to begin. [Note: This was posted to Front Porch Forum on April 14.] This week, many frogs and salamanders will be trekking back to the vernal pools where they were born. Watch for them on warm, rainy nights.

Wood frogs and spotted salamanders rely on vernal pools to breed successfully. These seasonal wetlands dry out in summer, which prevents predatory fish from living in them and eating amphibian eggs. Several fairy shrimp species also depend on the fish-free conditions. Their egg-like cysts can lie dormant for decades, waiting for the right spring conditions to hatch. Fairy shrimp live only a few weeks, breeding and producing new cysts before dying off in mid-May. Fingernail clams thrive in vernal pools too, burrowing into the soil during dry periods and emerging in spring to feed on plankton and detritus. Clams and shrimp both filter nutrients out of the water, but clams suck water through their gills using siphons and shrimp use their feathery legs to fan water into their mouths.

Vernal pools are sensitive to disturbance—and so are the surrounding forests, where frogs and salamanders spend most of their adult lives. These areas are sometimes called “amphibian life zones.” Amphibians need moist, shady forests with plenty of dead wood on the ground, so clearing or intensive logging in these zones is discouraged.

Because vernal pools are small and seasonal, they’re easy to overlook—and easy to destroy through development, trail building, and logging, often without anyone realizing. That’s why it’s so important to identify and map them. In Calais, 131 potential pools have been mapped using aerial photos, but only 34 have been confirmed by visiting them during the spring breeding season. You can explore them here: https://drive.google.com/file/d/1efZmb1MiGOTm6b28mpOrSkg-2VdZkSHr/view?usp=sharing.

We try to visit a few pools each spring—and only with landowner permission. If you’d like to help with the inventory, contact Neal at nealmaker@gmail.com. Some training is required, but it’s a great way to meet your slimy neighbors!