Signs of Spring 4: Wood Frog Day (year #6)!

Photo by D. Sillman

(if you would like to listen to an audio version of this blog, please click here!)

I am sitting at my writing desk on this first day of Spring watching the snow pile up in my back yard. It is very difficult to keep track of what should be happening as winter fades away, but I don’t think that five inches of snow is at all normal. But is it unexpected?

We live in a climate zone that is subject to all sorts of swings and shifts in weather. Some of these shifts actually occur with some regularity and are referred to as “weather singularities.” We even have common names for some of these weather twists and turns. In the Fall, for example, after the first frost and the initial onset of cold temperatures, the weather often moderates and the days become warm and hazy. We refer to this singularity as “Indian summer.” Also, almost every January we have a stretch of days or even a week when temperatures climb above freezing sometimes all the way into the 50’s or 60’s F and the air starts smelling like Spring. We all think “this is unusual!” but, actually, it is typical. We call this weather singularity the “January thaw” (what an incredibly logical name!). We also get snows in late March or early April and think, “how strange,” but actually we regularly get these late snows. Here in Pennsylvania we call this weather singularity an “onion snow” because it occurs along with the sprouting of the spring planted onions out in our gardens.

We each have very hardwired ideas about our climate and about what the weather should be at any particular time of the year. When the weather we observe differs from our mental models we feel that there is something odd going on around us, something strange. It is very difficult to keep a mental track of the 365 days of each year, year in and year out!

Cliff swallow. Photo by I. Taylor, Flickr

The habits and movements of animals help us focus on a particular year and compare it to our previous experiences. Migrating cliff swallows in California don’t always return to San Juan Capistrano on March 19, but their return a week before or a few days after is a good index on what kind of year (weather-wise) it has been! The turkey vultures don’t always return to Hinckley, Ohio on March 15, but their earlier or later arrival helps us to focus on the features of the winter to spring transition that we are experiencing.

There are many celebrations of the return of migrating birds all around the world. In Ketchikan, Alaska they watch for (and celebrate) the return of the Rufous Hummingbird. Aborigines in Australia celebrate the return of the migrating sand pipers (or some would say via their dances and rituals they actually call the sand pipers to them!) in order to mark the onset of the wet season with its life-giving and sustaining rains.

Phenology is the scientific study of these cyclic patterns of animals and plants. A phenologist might observe the return of some migratory species or the emergence of some hibernating animals. They might observe the timing of the flowering or leafing out of certain plants. They might observe the activity of certain insects. You can imagine all of the phenological data collected feeding into an intricate matrix of a vast number of variables which then generates a mathematical function that clicks its way through the ecological events of each and every year. Phenology is a very precise way to make year to year comparisons of seasonal transitions and phenomena.

And, that’s why we have invented “Wood Frog Day!”

Photo by B. Gratwicke, Wikimedia Commons

Some background: The wood frog (Lithobates sylvaticus)(formerly Rana sylvatica) is found from northern Georgia all the way up to the Arctic Circle. 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. Wood frogs spend the winter hibernating in a frozen state deep in the litter and soil near their vernal pools and emerge en mass in the spring to mate. For the last six years, Deborah and I and Rob and Michele Bridges have gone down to Ohiopyle, Pennsylvania in mid-March to check on these glorious frogs. Our phenological observations on these animals and their surrounding ecosystems have given us some insights into our pulsating climate and the differences between each of the passing years. Each date, by the way, is a link to the original blog post about the “frog walk!”

Photo by D. Sillman

March 16, 2013: Coltsfoot is blooming in sunny spots along the Youghiogheny River. Comma butterflies are flying about up in the rhododendron thickets. Wood frogs are abundant (and croaking loudly!) in the vernal pools along the upper hiking trails.

March 14, 2015: No coltsfoot blooming yet. No butterflies. Water in the Youghiogheny is very high. Pools along river don’t have any frogs or insects. Wood frogs are active in the vernal pools along the Great Allegheny Passage Trail and around the parking lot of the trail. Frogs are catapulting themselves out of their soil and leaf litter hibernaculae into the active

Photo by D. Sillman

pools. Lots of frog “quacking” and mating!

March 19, 2016: Low water levels on the Youghiogheny (a very dry winter and spring!). Pools along Yough, though, are full of tadpoles, and egg masses and adult wood frogs. A salamander is seen in the Yough pools and water striders are abundant. Wildflowers blooming along upper trails (red trillium, sessile leafed bellwort, star chickweed). Red maples and Yellow poplars just starting to leaf out. Pools up along Great Allegheny Passage Trail are very shallow and full of litter and debris (no frogs or tadpoles or eggs seen).

Photo by D. Sillman

March 18, 2017: Very little winter snow and a very dry spring. Coltsfoot blooming. Pools along Yough are alive with wood frogs (large females and smaller males all actively quacking). Large egg masses. An eastern newt is seen in one pool. No other wild flowers along upper trails. No wood frogs in pools along Great Allegheny Passage Trail. Pools are very shallow and full of trash and debris.

March 18, 2018: It has been a cold spring but there has been abundant winter snow and lots of recent rain. We were hopeful that there would be water in the vernal pools down at Ohiopyle. It was sunny and in the upper 40’s when we headed out on

Photo by D. Sillman

our hike. No coltsfoot blooming yet, no other spring wildflowers. No butterflies. The pools along the Yough are partially covered with slushy snow. There are ring shaped markings in this pool snow (each ring is about 2 inches in diameter). The rings are very regular and very abundant. Possibly they are formed by decomposition gases (carbon dioxide? methane?) rising up from the warming sediments of the pools? The covering ice is slushy enough to be shaped by the rising  gases, but solid enough to hold the new shapes? There are no frogs, no egg masses, no tadpoles in the Yough pools. No salamanders. No water striders. One adult caddisfly was seen next to one of the pools. The upper trail pools along the Great Allegheny Passage Trail are very shallow in spite of all of the rain and snow melt. They are clogged with debris and look as though they have been used as branch and log disposal sites. No frogs at all.

Our Wood Frog Days have not always had any wood frogs, but they give a point of time focus for the onset of Spring. We do see that the mating pools on the rocks along the Youghiogheny River have become very important for these wood frogs and that the pools up along the Great Allegheny Passage have been degraded by human activity and neglect. These upper trail pools are being drained too rapidly to be useful to the frogs and are being used as wood and debris disposal sites.