Signs of Spring 5: Waterfalls and Frogs!

Two Penn State professors at Ohiopyle, PA

Photo by D. Sillman

Rob, Michele, Deborah and I went to Ohiopyle last Saturday to see if there were any new (or different) signs of spring down there. In particular we wanted to see if the wood frogs that we saw two years ago (on a warm afternoon in late March 2013) might be back!

Frogs help to sing in the spring all over western Pennsylvania. The Spring Peepers (Hyla crucifer) will begin their group choruses as soon as we have some warm evenings, and the gray tree frogs (Hyla versicolor) will start their resonating trills soon after. The tree frogs may even continue to call through the rest of the summer! The first frog of spring, though, and the one we are looking for down in the cool, wet woods of Ohiopyle, is the wood frog (Lithobates sylvaticus). This frog neither peeps nor trills. Instead, it announces the start of spring by quacking like a duck!   Have a listen:

We walked out onto the Ferncliff Peninsula at Ohiopyle. The day was almost warm, and it felt good when the sun occasionally came out from behind the clouds. The first part of the hike was over the far shore’s rocks and boulders along the Youghiogheny River right at the Ohiopyle Falls. The picture above shows Rob and I working our way along the rocks and debris. The water level had recently been quite high! The debris layer extended well up onto the shoreline and made each footfall a bit of an adventure. The gray-green water was rushing past us and roaring as it went over the rocky falls.

Last week an unfortunate person slipped off of the rocks on the shore just across from us. He had climbed over a guardrail to pose for a picture not realizing that the rocks were covered with ice. He fell into the river, went over the falls, and has not yet been found. We stayed well away from the edge!

Back in the 1880’s this peninsula was the site of a large hotel and a thriving tourism/resort industry. In addition to the Ferncliff Hotel there had been a boardwalk, a dance pavilion, a bowling alley, tennis courts and ball fields all nested into the rocky terrain. Some of the foundations of these buildings are still visible up along the Fernwood Trail, but the peninsula has returned to a remarkably pristine, natural state. Fifty years ago the Western Pennsylvania Conservancy purchased the property of the peninsula and the surrounding hills and then sold it to the state of Pennsylvania to make the Ohiopyle State Park.

The isolated pools up and around the shoreline rocks were all barren of life. There were no insects, no amphibians and no growing algae. No signs of spring along the shore just the accumulated, plastic debris from the long winter.

Photo by D. Sillman

Photo by D. Sillman

The trail climbed up away from the rocks and headed out along one side of the peninsula. The deciduous trees were all bare, but the rhododendrons, hemlocks and the scattered white pines were a welcome green. Evergreen wood fern was scattered about in the undergrowth, too. It added a rich, green highlight to the overwhelming brown of the scattered, dead leaves.

We walked for a couple of hours around the peninsula but saw very little in the way of “spring.” No colt’s foot was blooming, no comma butterflies fluttered around the dense stands of rhododendrons. Everything was very quiet.

Just before the trail junction where Fernwood Trail split off from the Ferncliff Trail there was a ten meter by ten meter fenced off area designed to keep white tailed deer away from the developing tree seedlings. Inside the fence margin poplar and birch seedlings grew in incredibly dense clusters. There must have been two hundred, three and four foot tree seedlings growing inside the fence (there were hardly any outside the fence)! The woods would look very different if there were no white-tailed deer!

Michele and Deborah took the Fernwood Trail while Rob and I continued on the Ferncliff Trail, but everything was very quiet until we got the end of the trail. Deborah and Michele were waiting for us (they walk a lot faster than Rob and I!). They had found frogs!

Photo by D. Sillman

Photo by D. Sillman

We climbed up to the Great Allegheny Passage Trail and followed it back toward the town. Near the trail parking area a small, vernal pool was alive with a couple of dozen wood frogs. They splashed and quacked and made us feel very welcome!

The wood frog is found from northern Georgia all the way up to far northern Canada. In fact, it is the only “cold blooded” vertebrate known to live north of the Arctic Circle! They utilize temporary pools formed by spring rains and snow melt as breeding pools and then spend most of the rest of their active season away from standing water. Adult wood frogs feed opportunistically and extensively on small insects and other invertebrates. They use their long, sticky tongues to capture prey and are said to eat “anything that they can fit into their mouths.”

The ability of the wood frog to survive in high latitude ecosystems depends upon a number of specialized physiological adaptations that include the presence of specific proteins in the blood that regulate ice crystal formation, circulatory controls that shunt blood preferentially into critical organs (heart, liver, brain), and a liver response that releases huge amounts of glucose into the blood stream and organs. These high levels of glucose act as a cryoprotectant which reduces the amount of ice formed in the protected tissues and cells.

During hibernation, 60 to 70% of a frog’s body fluids may be frozen. Cardiac function stops and blood ceases to circulate. As their bodies thaw, their hearts resume contractions and their livers rapidly clear the high levels of glucose from the blood even before all of the body’s ice is melted. Thawing frogs display some short term movement and behavioral difficulties but are soon fully functional.

We watched a couple of frogs jump out of the dense piles of leaf litter that surrounded the pool. It was like they were catapulting themselves out of hibernation! They flung themselves into the increasingly crowed water, and you could almost hear them shouting, “I’m back!!”

In the mating pools, males call to females with their “duck-like” songs. An attracted female enters the pool and is quickly grasped on the back by the smaller male (this is called “amplexus”). The male may remain in place on the female’s back for 24 to 72 hours. The male releases sperm into the pool water as the female ovulates and thus externally fertilizes the forming egg mass. A typical egg mass contains 1000 to 2000 eggs. The female moves the floating egg mass into the shallow areas of the pool in a large, communal raft. Counting these rafts in an area’s pools is an accepted, and highly efficient, way to determine the population density of the wood frog in a particular region.

Both the fertilized eggs and the developing embryos can withstand even prolonged sub-zero temperatures. The ”jelly” that surrounds them and holds the great floating masses of eggs together helps to pull water out of the egg or embryo when it freezes. This prevents freeze damage to the delicate cells. It will take quite a while (two and a half months) for the embryos to develop into tadpoles!

So, spring IS happening out in the woods! Just ignore the snow that’s in tonight’s forecast!

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