Tour Stop 5: Vernal Ponds
If you’re standing here in August you’re on dry hard mud wondering, “What the heck am I suppose to be looking at?” That’s the nature of vernal ponds or, as some wetland scientists term them, “ephemeral bodies of water.” From the Latin “vernalis” the word vernal alludes to Spring, which is when these small depressions fill with water. They play an important role in the lives of many amphibians, which utilize them to fulfill the reproductive end of their life cycle. Because these temporary pools dry up in the summer they lack many of the predators that one might find in permanent waters. In this killer-free environment frogs, salamanders and toads can breed and lay eggs without fear of becoming lunch to hungry fish and predatory insects. The wood frog (Rana sylvatica) is especially fond of these pools.
In the Spring the ponds fill with rain and snow melt.
In Summer the “ponds” dry out.
With the help of Drew University we are in the process of determining what species are using our ponds. This biological inventory is being done in the hopes that we may find a population of blue-spotted salamanders. This species is a state endangered amphibian whose habitat structure closely resembles that which is found in this conservation area - Oak, Hickory and Beech trees with, yes, vernal ponds. I have surveyed four consecutive Springs at these ponds for the endangered blue-spotted salamander and have not found them.
Many vernal ponds had their origin during the last ice age, 150,000 years ago. As the Wisconsin Glacier retreated large chunks of ice remained and bored out these depressions through sheer weight. Wetland scientists refer to these as “kettle holes.” The following is a list of species you may find in vernal ponds. The first four are referred to as indicator species because of their breeding affinity for only vernal ponds:
- Wood frog (Rana sylvatica)
- Spotted Salamanders (Ambystoma maculatum)
- Blue-Spotted Salamander (Amystoma laterale)
- Fairy Shrimp (Eubranchipus sp.)
- Spring Peepers (Pseudacris crucifer)
- American Toad (Bufo Americana)
- Green Frog (Rana clamitans)
- Eastern Newt (Notophalmus viridescens)
Wood Frog
Wood frogs use vernal ponds to fullfill the breeding aspect of their life history.
Wood frogs in amplexis and the resulting egg masses. Later in the Spring these will be tadpoles.
Spotted Salamander
You will not find this species in any of the vernal ponds on our property. The habitat type that they prefer includes mixed deciduous forest leaning toward mesic soil types. Spotted salamanders prefer areas with slow moving streams and of course — vernal ponds. I have mentioned them here because I want people who have these temporary pools on there own property to be on the look out for them. If you can identify two vernal pond species (refer to the list under vernal ponds on the tour) breeding in your own vernal ponds then the area surrounding it is considered to be exceptional resource value and carries with it 150 foot buffers.
Spotted salamanders are in the same family as the Blue spotted salamanders, the Ambysitimids or mole salamanders
Blue-spotted Salamander
The word “philopatric” comes to mind when talking about Blue spotted Salamanders (Ambystoma laterale) and vernal ponds. This state-endangered species will breed in the same vernal ponds year after year. If you developed a property and a vernal pond hosting a breeding population of “blue spots” were paved over, you would sadly find adults walking over these same surfaces looking for the place they used to breed and lay eggs. In other words, a species that holds an innate propensity to use a specific location within its range to fulfill a specific life history component is said to be philopatric to that locale. This single aspect of a blue-spot's makeup has propelled it to state endangered status. Once their breeding ponds are gone, you have in effect, sterilized them in regards to breeding success.
With the aid of local universities we have surveyed all the vernal ponds on our properties and have yet to find a single blue-spotted salamander. We will continue this survey in the coming years in order to determine conclusively as to their presence or absence. What our surveys have shown is that these ponds contain a viable and vibrant population of breeding wood frogs.
If you own property within the Great Swamp watershed and are blessed with a vernal pond, it would be helpful to the State Non-Game Species Program if you surveyed for this elusive creature. Any warm March day go out to the pond and pull over any logs in the general vicinity of the pond. If you are intrepid put on a pair of hip boots at night, g o into the pond, and scan the water with a flashlight looking carefully for breeding adults. Report any findings to the Great Swamp Watershed Association at (973) 966-1900. If you find an adult please take a picture so that a qualified herpetologist can verify the sighting. Refer to the above picture for a visual cross-reference before you report your sighting.
Spring Peepers
I am far from a world traveler. I have yet to witness a hundred thousand hoofed ungulates foraging on the plains of the Serengeti, Replys sea turtles laying their eggs on the bleached shores of Costa Rica, Lemurs bipedling under Baobab trees in Madagascar, but that doesn’t matter to me as long as I can drive to the Great Swamp Conservation Area on a warm April morning to drown myself in one of natures greatest events — the cacophony of Spring peepers (Pseudacris crucifer) screaming their testosterone to the world.
The bombastic bird like shrills are emitted by males anytime the air temperature reaches 41 degrees or higher. This accounts for the fact I’ve heard them calling in the cool calm of January afternoons. When the temperature and humidity rise the males will call from higher perches. This gives them a strategic advantage over the predators that lurk in the marsh. Giant water bugs, fish, snakes, and water beetles are all looking to take advantage of peepers more concerned with love making then predator evasion. The calls of peepers are truly amazing when you think about the size of this animal. Imagine a creature no bigger then a minute (actually 1-1.5”) piercing a cry that can travel up to a half mile. That’s equivalent to a person belching a scream that carries sound over thirty-six miles — let me see Pavoratti do that! Even more intriguing is the fact that males can barely detect their own calls whereas female hearing is finely tuned to the male’s vocalization. It has been noted that a male spring peeper that is able to call louder and faster then other males, has a higher rate of breeding success. Age and size seem to factor into the equation, larger and older males are more successful than smaller and younger courtiers. But, wait, it gets better: up to 14% of males within a stable population of callers use tomfoolery in order to get the girl. Why blow out a perfectly good vocal sac when you can let your buddy do it. Just hang out by a calling male and wait for an enamored female to stroll by. Herpetologists call these charlatans “satellite males” — I love that one. Humans have a much harsher name for it. This is just another peek at the inner workings of evolution in action. Who knows how this strategy will play out for peepers? If the technique continues to work for these sexual parasites will the marsh become quieter in a hundred thousand years or might it be that it fails and becomes louder. I just hail the naturalist who had the patience to observe this behavior so that at the very least we have a starting point for further study.
I find everything about this animal intriguing, mystical and bizarre wrapped in one. If I was independently wealthy and had endless time on my hand the spring peeper would be the one member of the Great Swamp family of creatures I would love to study. Many questions about this denizen are left to be answered: what factors determine if a male will become a satellite, why are their populations so stable while other species of amphibians are declining? After the breeding season peepers disperse throughout the marsh and swamp, hardly ever observed by even the most astute of naturalists. They tend to be in the leaf litter or very low to the ground in shrubs. I would love to know what this gnome-like Lilliputian brings to the ecological table of the Great Swamp. A creature so abundant when breeding you can hardly complete a thought in light of their raucous vocalizations — surely this amphibian must play a major role in keeping the Swamps fabric intact. I am confident that the more we reveal about the spring peeper outside the breeding season this role will become visible.
American Toad