Clad in waders and toting a jumble of nets, tubs, and empty tofu containers, we set out toward Lithia Springs. It was a raw, rainy day and early yet, but our spirits were high as we bushwhacked through the woods. Led by the ecologist Molly Hale, we, the members of the Hitchcock Center’s nature study group, were in search of vernal pools.
Vernal pools, by definition, are ephemeral, seasonal habitats. They range in size from small puddles to shallow lakes and are found across the Northeast wherever woodland depressions or kettle ponds collect rainwater or snowmelt. A key characteristic of these pools is that they are isolated wetlands; they are not connected to any other water source and, as a result, they dry out periodically and are unable to harbor any reproducing fish populations. This last part is important: because there are no fish in vernal pools, it makes them the perfect environment for amphibians and invertebrates to breed without the threat of predation—while they last, anyway.
When we reached our first pool of the morning, Molly gave us a rundown on the different critters that we might encounter: obligate and facultative, vertebrate and invertebrate, larval and adult. On this overcast morning, it was not easy to see through the dark water to the decaying leaves below, but there was plenty of life swimming around at our feet. Mosquito larvae galore, horsehair worms, leeches, and daphnia all came to life under our magnifying glasses.
Then, there were the caddisflies. Had I seen caddisfly larvae on my own, I would have dismissed them as merely clumps of leaves and pine needles. And they are that, in a sense…but in reality what I was looking at were the caddisfly larvae’s marvelously constructed protective cases. The larvae build their cases using the silk that they produce and a multitude of organic and inorganic materials, depending on the species. The ones we encountered (I think from the family Limnephilidae) had a preference for leaf litter, pine needles, and twigs; however, others use rocks or even snail shells! (Yet others, aided by humans, have developed a taste for semi-precious stones.)
Several species rely exclusively on vernal pools for reproduction and development, despite their impermanent nature. These obligate species include wood frogs, burrowing mole salamanders, and the first non-mosquito species that I netted myself: the fairy shrimp. Being a complete neophyte when it comes to vernal pools, I was delighted by the very existence of this tiny woodland crustacean. Shrimp! In the woods! Just swimming around on their backs! (Swimming around in my recycled tofu container, at that!) Their undulating swimmerets were mesmerizing. We were lucky enough to find both male and female fairy shrimp, with the female easily distinguished by her brood pouch, which looked like a tiny dark circle at the base of her abdomen. At the end of the shrimp’s lifetime, she will release hard-shelled eggs (or cysts) that then become embedded in the soil below and enter a period of dormancy. These hardy cysts can withstand both freezing and drying—and, in fact, actually require a period of drying out before being able to hatch in the spring once the vernal pools refill.
In terms of amphibious obligate species, other than a lone wood frog tadpole, our findings were mostly gelatinous.
On rainy nights in early spring, spotted salamanders migrate to vernal pools to mate and lay eggs, a journey that often involves perilous road crossings. In our area, the Hitchcock Center maintains special migratory tunnels—tiny underpasses, essentially—that allow the salamanders to reach the pools safely.
This is a freshly laid spotted salamander egg mass: round, firm, and glistening. Each egg mass is enveloped by an outer jelly that holds the individual eggs together and provides protection from predators. And after the ordeal that the adults undergo to reach their breeding grounds, any added protection is welcome!
Not far from this egg mass, we encountered another amphibian: the red-spotted newt, a facultative species that could very well have had salamander eggs for breakfast. We caught two of them in flagrante—or rather, in amplexus, with the male clasping his back legs around the female, rubbing his chin on her snout, and fanning his muscular tale to waft his pheromones her way. The bizarre twist was that the amplexus that we witnessed was between an aquatic adult male newt and what looked like a terrestrial red eft. Was this an eft that was reaching the end of its immature stage? But if so, why would the adult newt attempt to breed with it before it was sexually mature? Those questions are far beyond my knowledge, but it was fascinating to watch.
After three hours in the bitter rain, my hands were soggy and stiff from cold, my pants were soaked through, and my kneecaps had begun their involuntary dance. I think we were all ready for a hot drink or two. “If this doesn’t make you all naturalists, I don’t know what does,” said Molly. At this stage in my education, I don’t think I have enough knowledge to call myself a naturalist, but I hope that experiences like this will help me along the way. Because there is so much to learn! We’re lucky to have a place like the Hitchcock Center nearby, and I’m excited to see what the next 8 months of natural history study will bring.