“I like it when a flower or a little tuft of grass grows through a crack in the concrete. It’s so [expletive deleted] heroic.”—George Carlin
I looked hard for a better description of how I feel about chorus frogs but couldn’t find one. It did prompt me to check the definition of heroic: “behavior or talk that is bold or dramatic, especially excessively or unexpectedly so.”
How else could you describe a creature that freezes more than half its body fluids every winter, stops its heartbeat, stops breathing, stays like that through the winter, thaws back to life, finds an ephemeral pond and some food, and may continue calling for—and hopefully find—a mate from March through late May. The full life span of a chorus frogs is around 5 years, and they will go through this death defying feat every winter and spring of its life. Bold and dramatic—especially excessively or unexpectedly so!
But, to most of us warm-blooded, well-dressed, and well-sheltered primates, it’s just a sign of “awakening” spring. We hear the “creeeek – creeeek – creeek” rising pitch comb-like call of the chorus frog, and think “oh—that’s nice—it really is spring.” Delving just a bit deeper though: springtime, and the many life forms that awaken at this time, is a great reminder that within the Arboretum, out our back doors, and within our own skin and between our own ears, mysterious and mind-blowing, amazing things are happening.
Scientist can measure and observe that the frog’s outside skin in winter starts to get icy, which stimulates adrenaline production, that in turn triggers production of a kind of antifreeze of alcohol, glycerol, and glucose that will permeate the frog’s blood vessels and bodily fluids. The glucose concentrations in these frogs are about 200 times more than what would cause a human being to enter a coma and die. This winter-to-spring heroic feat occurs similarly in wood frogs, gray tree frogs, and spring peepers that are commonly found around this area.
How do these little thin skinned fellas survive this? How do all the delicate organs and blood vessels, nerves, etc. survive this? Other than adrenaline, what are all the hormonal and chemical changes that instigate and play their parts in the orchestra of events that propel our heroes through this yearly cycle? By the way, didn’t mean to leave out the females—who also become frogsicles in the winter, and, on average, live one year longer than their male counterparts. They lay between 500–1,500 eggs per year in gel-like sacs of 20–300 eggs per sac. The eggs will hatch in about 2 weeks. And, the tadpoles will mature into small frogs in two to three months.
This happens quickly by design. The frogs are often mating in temporary or ephemeral ponds that will likely dry up in the summer. These ephemeral ponds are unlikely to have fish and other overwintering predators, so that is why laying eggs and having tadpoles develop there gives them a better chance of survival. Still, snakes, birds, mammals, other amphibians and just about anything larger than they are will prey on the eggs and tadpoles. Some studies put the chances of tadpole becoming a frog at about 14 percent. And, the first year of the frog’s life is also precarious and has a similarly high mortality rate.
You are much more likely to hear chorus frogs than to see them. Full-grown, they are about 1½ inches long with smooth skin, and are various shades of greenish-grey, reddish, olive, or brown in color. Typically, they have three dark-brown or grey stripes extending down their back. Hence, one of their common names: striped chorus frog. They also are referred to as the western chorus frog. The binomal or scientific classification is: Pseudacris triseriata. They are very sensitive to being approached and will duck under the water or vegetation and stop croaking/creeking when they sense any danger. So, best chance to see them is approach slow, stay by the water, bring your binoculars and look along vegetation and shallow water and wait for the chorus to begin. To send out their call, the males fill up a flexible sac of air in their throat that when full of air is about as big as they are.
You could probably spend and hour and a half listening and looking for frogs, but we didn’t. Some of the wildflowers this time of year are a bit hard to spot as well. However, once they start growing they won’t hop away. I knew some of the earliest wildflowers would be performing their own heroic chemical orchestra and emerging amongst the leaf litter. On our way through Gallistel Woods and toward the Icke Boardwalk we spotted emerging Virginia bluebells (Mertensia virginica) and toothwort (Cardamine concatenata). At this time, they are miniatures of their full-grown selves, but we could make out the shapes and passed around a great book for identifying these characters in the spring wildflower show that is just beginning (but goes pretty fast): Spring Woodland Wildflowers of the University of Wisconsin–Madison Arboretum by Andrew L. Hipp.
On the front cover of this book is a photo of flowers that are so unusual—they are actually late winter/early spring wildflowers—in a class of their own around here: skunk-cabbage (Symplocarpus foetidus). We crossed over the road and into Wingra Woods and headed toward the namesake of this interesting flower: skunk-cabbage bridge. The reddish-brown mottled part of this plant will emerge as early as February. It looks like a pointy hood and can grow to about the size of a cupped hand. This hood-like structure helps conserve the heat that the skunk-cabbage generates and also protects the male and female flower parts from the ice and snow. This hood, called a spathe, is spongy and has air pockets. Inside the spathe is a golf-ball shaped structure with tiny whitish, almost translucent flowers. As the plant respirates, the spathe keeps the flower parts warm. In fact, as long as the outside air temperature is above freezing, the temperature inside the spathe will remain fairly constant at around 70 degrees.
Another function of warming the space inside the spathe is that it vaporizes and carries the scent of the skunk-cabbage flower. I don’t think it smells like a skunk; it is a bit more subtle to me—kind of like an old smelly gym shoe. Not a very strong smell, but with a gentle breeze across the stream and the muck all around the bridge, we got a good whiff of the prolific crop of skunk cabbage all around the area.
With all the trees and shrubs yet to leaf out, early spring is a great time to hear and see birds too. In Gallistel Woods we saw a hairy woodpecker and chickadees. We heard two sandhill cranes. Cranes have been nesting off Icke Boardwalk for several years. We did not see them land there or anywhere else though. Before the group went through, I heard a barred owl in the same area. When we crossed over to Wingra Woods we heard a great crested flycatcher and got a glimpse of its tail high up in the trees. We also heard a red-bellied woodpecker and a cooper’s hawk in Wingra Woods. Walking back through Longenecker Horticultural Gardens we saw a large troop of robins probing the ground for worms, etc. We heard the resonant spring time songs of several bright red male cardinals. And the ever-reliable flocks of turkeys—males getting some red and blue coloration on their heads and neck, and starting to flip up and display tail feathers. It must be spring!
If you want to watch some of the frogsicle process, here are two short videos on YouTube: