Vernal Pool Fun

My spring semester wildlife students have been working hard for the past week learning all about vernal pools and the amphibians that call them home each spring. These ephemeral ponds in the woods are one my favorite topics to teach to high schoolers. It is one of the few instances in my Maine Fish and Wildlife course where we can learn in detail about a group of species and then march outside as a class and observe them in person. That is exactly what we did last week on Thursday (3/31).

Listening as a class for the duck-like chuckle of the wood frog.

Seasonal pond in the forest must satisfy three basic requirements before they can be classified as "vernal pools" and receive some extra protection. 

       1. Vernal pools are temporary bodies of water and typically dry up by late summer or early 

            fall.

       2. There must be no fish present. 

       3. Vernal pools should show signs of use by one or more of the indicator species listed 

            below.

              a. Wood frog (Rana sylvatica)

              b. Spotted salamander (Ambystoma maculatum)

              c. Blue-spotted salamander (Ambystoma laterale)

              d. Fairy Shrimp (Anostraca)

On our most recent visit, students got to witness two of the four indicator species in their natural environment. Wood frogs were both heard and seen floating around in the pool. Their softball sized egg masses were also visible clinging to vegetation in the water. A haul of a trap left overnight yielded two male spotted salamanders. The spotted salamanders are a real treat for the students as their size (up to 7") and striking coloration is unforgettable. These members of the mole salamander family are rarely seen outside of their springtime march to the vernal pool as they spend the remainder of the year deep underground in small mammal burrows or natural crevices in the forest. 

A close-up look at a wood frog, the first arrivals at vernal pools in the spring. 

A spotted salamander fresh from the vernal pool. 

The activity around the vernal pool as come to yet another screeching halt as winter refuses to release its grip on the landscape. The vernal pool ecosystems and their fragile amphibian inhabitants immediately come to mind whenever I see a springtime cold snap in the weather forecast. The good news is that wood frogs and spotted salamanders have existed on the Maine landscape for a lot longer than I have been worrying about them. They have evolved systems to handle brief dips in the mercury like the one we are currently experiencing. As long as temperatures don't get too cold for too long, they are able to wait out the snow and ice at the bottom of the pool or in nearby leaf litter before resuming their breeding activity again.