If you follow me either virtually or in reality, you know that during April and May I spend a lot of time beside vernal pools. And this year is no different. Thankfully, I also get to take others along on the journey, from school children to their parents, and members of the public, plus colleague naturalists in the form of Greater Lovell Land Trust’s volunteer docents.
And so it’s been that this particular pool on a land trust property has received tons of attention this year. We’ve always known it to be special because it’s home to Fairy Shrimp, which just the occurrence of one makes it significant by State of Maine standards.
Vernal pools provide essential breeding habitat for certain species of wildlife, including salamanders and some frogs species. At the same time, juvenile and adult amphibians associated with such a pool provide an important food source for small carnivores as well as large game species. Many of these amphibians are pool specific in that they must return to their natal vernal pool to breed, thus making them and the surrounding habitat important and the loss of such would lead to loss of local amphibians, a decrease in biodiversity, and a decline in food available to others who inhabit the surrounding natural community.
Upon visiting this past week, the pool had taken on a new sheen, appearing at first glance to resemble ice. But it was much too warm for that to be the case.
Floating upon the pool’s surface were male Red Maple flowers, the oval items at the ends of slender, threadlike stalks the pollen producing anthers dangling on their filaments and the release of said pollen the cause of the ice-like presentation.
So the exciting thing about this particular pool is that though It has long been a breeding ground for Fairy Shrimp (and mosquito larvae), this year we spotted more of the former than ever swimming along on their backs as they filtered the water and sought a mate.
Though the pollen on the pool may give it a look of being polluted, the presence of Fairy Shrimp actually serve as an indicator of good water quality.
Where a month ago we were scooping up hundreds of these tiny crustaceans, this past week we found only a few, which served as one sign that this is a pool in transition. Their life cycle isn’t long, but if you checked in recently with the post entitled Peering Into the Pool, you’ll have learned a cool fact or two about their existence.
Back to now. Wood Frog tadpoles had suddenly emerged and their egg masses began to disintegrate, though still adding a source of food in the symbiotic relationship with an algal form.
Mosquito larvae and pupae, though still present, were not as prevalent, given that their flying, biting form had begun to hatch.
And then there was another change to note. And it’s a major change in my book of these habitats. Large Bullfrogs had taken up residence.
The wee bit smaller but similar Green Frogs had as well.
How does one decipher between a Bullfrog and Green Frog? First, as you approach a pool and you hear a squeal as a frog jumps from the edge into the water, you know that Green Frogs are in the midst.
And if you finally get to spy one, look for the line behind the eye. If it follows along both edges of the frog’s back, called dorsal lateral folds, it’s a Green Frog.
If, however, the line extends from the back of the eye and wraps around the round disk, or tympanum membrane (think ear), it’s a Bullfrog.
Also, Bullfrogs don’t leap away quite a suddenly as Green Frogs. In fact, they can stay quite still for hours on end.
Once human eyes adjust to the surroundings, shadows may pretend to be frogs, but they aren’t. The real deal, however, lurks at the surface, often only its eyes making its presence known.
Hemlock needles and maple flowers decorate it, and much to my surprise don’t frustrate it. Though some frogs may seem super sensitive to us, they also exhibit a patience not to be matched as they sit and wait.
Oh, did I mention that they were everywhere? Literally.
The thing is. these two frog species weren’t in the pool to breed like the Wood Frogs had been. They, after all, need a permanent water source because their tadpoles take two years at a minimum to morph into adults and a vernal pool that dries up each year would not be suitable. This tadpole was spied at a nearby pond, indicating that perhaps the Bullfrog came from that source to the vernal pool.
So what were the Bullfrogs and Green Frogs doing at the pool? Predating all that live within. Remember what I said earlier, that vernal pools provide food for small and large predators. These would be on the smaller size, though not the smallest.
Perhaps that’s why we weren’t seeing as many Fairy Shrimp this past week. And given the prevalence of these two frogs, who knows what will hop or crawl out of the pool, but we suspect some Wood Frogs and Spotted Salamanders will make it to adulthood so that they can carry on the tradition of returning to their natal pools to breed.
The thing about visiting a pool such as this with the younger set is that they are bound to make exciting finds. And so one did, locating a Spring Peeper swimming about.
And in the surrounding uplands, another found a Pickerel Frog. We could hear their snoring chorus, so this discovery wasn’t unexpected. But still it was special.
How to tell a Pickerel Frog from a Leopard Frog (the latter a species I’ve only seen a few times): by the spots on its back. The Pickerel’s spots are more symmetrical than the randomness of a Leopard’s and the Pickerel’s spots are outlined while a Leopard’s are not.
And then there was this teeny, tiny American Toad covered with warts and suddenly the ground was hopping with these wee creatures and Spring Peepers and one had to be careful where one stepped.
The final find of the week, an adult Wood Frog with its robber mask making for a sure ID. This one was a poser.
As the vernal pool turns, so do its inhabitants and I give great thanks for the opportunity to learn from it and share it with so many others who add to the lessons.
Dedication: This one is for Nancy Hogan Posey cuze I was going to write about something completely different today and your question turned the page to this one. Thank you.