What’s Hiding in Vernal Pools?

So much is hiding in vernal pools! A world of slimy salamander and frog eggs and ‘wee beasties’ – the strange world of vernal pool invertebrates, some of which could be cast in a horror movie!

On May 26, Matt Burne of BSC Group shared his deep knowledge of vernal pools, which he described as “small forest ponds that tend to dry up in the latter part of the year.”

The defining feature of vernal pools is that periodically, they dry up. This is key to their functions, because it means they don’t support fish – which would eat much of what lives in them.

Matt introduced us to mole salamanders, including the ‘bald eagle of vernal pools’ – the spotted salamander. They begin their breeding ritual in early spring, when temps hover around 40°, snow and ice are often still on the ground, and heavy rains fall. These are the conditions that trigger ‘Big Night,’ the night when amphibians begin to move to their breeding grounds, aka vernal pools.

Amphibians that breed in vernal pools have evolved to start early because their breeding ground will dry out. The eggs need time to mature and develop before the water disappears.

Wood frogs also breed in vernal pools in remarkable numbers. Close to the bottom of the forest food chain, the various stages of wood frogs are a key food source for snakes, birds, and many forest creatures.

Vernal pool invertebrates, practically unnoticeable to the naked eye, reveal a weird and wonderful world when viewed with magnification. Fairy shrimp, shrimp enclosed in a carapace, thumbnail-sized clams, hydra (relatives of the jellyfish).

And the invertebrate predators! Prehistoric-looking dragonfly larvae, predacious diving beetles, giant waterbugs, leeches. You would not want to encounter these creatures in a dark alley!

Why are vernal pools important? All sorts of reasons. The life in these pools supports (directly and indirectly) many of the so-called ‘charismatic mega-fauna’ (aka birds and mammals) we love to see.

The food web starts at the bottom. Invertebrates feed on leaf litter (and each other), amphibians and others feed on the invertebrates, mammals and others feed on the amphibians. The cycle of life.

Another benefit – salamanders are a key predator of mosquito larvae.

To learn more, watch Matt’s captivating presentation here. And head for a vernal pool next spring on Big Night to watch the flow of amphibians returning to their breeding ground.