Category Archives: Frogs

Peepers: freeze protection strategies

When the temperature dropped below forty degrees, the frogs shut up. A few hours later, we hit the twenties, the pond was ice and the rocks from which the frogs had called were snow-covered.

The only sound was the creak of a Virginia pine’s knotty entrails, twisted by the weight of ice on its needles and branches. (Like other sounds on this blog, you’ll need to be on the website not the email summary, to hear.)

How do these crazy little frogs survive such temperature swings? Surely they’re all frozen to death by now?

A thermometer inserted just below the crust of snow and ice suggests the peepers’ first strategy. It is ten degrees warmer just an inch under the soil. By creeping into holes, bark crevices, and cracks in rocks the frogs find microclimates that, if not toasty, are more temperate.

2015-03-05 ice snow 010The peepers’ other defense is not so obvious. Their livers gush glucose into the blood, flooding their organs with sugary antifreeze. The bodies of these candied frogs can freeze without damage to their cells. Peepers can move in and out of this sugar-high within hours, making them well-adapted to the ill temper of the spring weather goddesses in eastern North America. After the last ice age, they were one of the first frog species to hop up north.

(For those wondering after my last post how a “spring pepper” might differ from a spring peeper, see here. Apologies for my many typos…)

Heck yeah: Peepers, peepers.

Rain + warmth = Pseudacris crucifer. The spring peeper.

Spring? Seriously? Appearing for one night only at a backyard pond in Tennessee. Tomorrow: the freeze returns.

2015-03-04 peepers hawkins lane 011

2015-03-04 peepers hawkins lane 007They are calling at an ear-ringing 85+ decibels. These frogs are so loud that birds have to adjust their songs near chorusing peepers. So crank this one to 11:

peeperspectroZoom in on the spectrogram (below) and we can see two call types: short upward sweeps and longer trilling sweeps. The short, untrilled sounds are the males calling to females; the zipped calls are aggressive signals to other males. Zip-a-dee-doo-dah. You can clearly hear each call type on the recording, minus Armstrong’s horn.

peeperspectro2Bonus: how many peppers can you spot in the photo below?

2015-03-04 peepers hawkins lane 001

Young treefrog

We’ve had a consistently wet summer in Tennessee, great for plants and even better for amphibians. Pools and streams that dry up in most years have remained wet, allowing many larval amphibians to grow up without their lives being cut short, as they so often are, by dry spells. Once metamorphosed and on land, the youngsters find a moist world. Most welcoming.

A careful eye will discern legions of young frogs and toads loping and bouncing in tangles of vegetation. Here is a young Cope’s Gray Treefrog (Hyla chrysoscelis) warming itself in the sun before plunging back under the shady leaves. The animal is small enough that it could sit comfortably on a penny. For photos of the adults and eggs, and sound recordings of the breeding males, see my previous posts here and here.

2014-08-24 Young Copes Gray Treefrog 0012014-08-24 Young Copes Gray Treefrog 004



Herp fest continues

Herpetological wonders continue to unfold. The Cumberland Plateau and the Southern Appalachians are among the most diverse places in North America (and the world) for amphibians and, to a lesser extent, reptiles. The last few weeks have not disappointed in encounters with this group.

We found this Seal Salamander during my Advanced Ecology/Biodiversity lab last week. The animal was in a creek in Shakerag Hollow. It was about five inches long. Seal salamanders spend most of their time in water, but will wander on land to feed, especially on wet nights.

Unlike its close relatives, the Seal Salamander has tough cornified toe tips, possibly to help it climb vegetation during its terrestrial forays. You can see the blackened tips through the ziplock bag.

This Slimy salamander was under a rock in the same creek. This species is usually found away from water, under logs or rocks, so this individual may have just been passing through. Slimy salamanders lay their eggs in moist places on land and their young never dip their feet in water. Young Seal Salamanders, on the other hand, are aquatic and have feathery gills.

I found this Marbled Salamander during Intro Biology class. It was hiding under a log in a dried up vernal pool. In a normal year, the salamander would wait for several more months before the pool filled up. This week’s phenomenal rains mean that the pools are now overbrimming. We’ll see whether or not the water stays. If so, this will be the earliest filling of these ephemeral wetlands that I know of in recent years.

Scott Summers, a freshman at Sewanee, found this spectacular Red Salamander last week under a log near Morgan’s Steep. Great find!

A Pickerel Frog in Shakerag Hollow. Note the squarish spots on the back. The similar Leopard Frog has rounder spots that are more randomly scattered over the back.

A Green Frog snuggled underwater with an acorn. Also in Shakerag Hollow. Note the nice clear water — thankfully, not all streams have been impacted by silt runoff into the hollow.

And from an entirely different habitat, located just a stone’s throw away from the vernal pool: a fence lizard enjoying the baking sun on a sandstone outcrop near Piney Point. These outcrops are incredibly dry and blazing hot. Fence lizards love the heat.

In closing, a frission of danger. This Timber Rattlesnake was on the trail in the northern Smoky Mountains where I was botanizing with the TN Native Plant Society last weekend. The botanists stopped briefly to admire the snake’s freshly molted shine, then returned their attention to petioles, leaf margins, and floral structure. The snake had thirteen rattles, so it has molted thirteen times. They molt two or three times a year, so this one is relatively young. They live up to twenty years.

Toad song

Click below to hear…

…the sweet trill of amorous American toads (Anaxyrus americanus). Half a dozen males have been chorusing in the small pond at our house for the last week or so. For a warty ol’ amphibian, they sure make a nice sound. The recording has several individuals calling, some sweeter than others. Female toads, I’m told, prefer males that can produce low-pitched trills over many hours. I’m not that fussy. Any trill will do: the song of these toads is one of my favorite sounds. Winter is done. The acoustic world expands.

Last night, the male toads were joined by a couple of females. Amplexus ensued and now the pond is festooned with long strings of eggs.

I’m pretty sure the female in the photo above is the same one that has been here the last several years – she’s a rich chestnut color, quite unlike most local toads. She is also about twice as big as the males, a dream-mate because size correlates with egg number, and egg number correlates with numbers of toadlings, and toadlings are what natural selection cares about, and dreams are made by brains, and brains are made by natural selection. Happy slumbers.

The eggs are neatly lined up in jelly strands. Usually these strands are coiled, but they straighten out when pulled out of the water for a photo. The eggs hatch in about a week (depending on temperature) and the tadpoles graze on algae underwater for a couple of months before emerging onto land.

The future.

Dick Cove

My Field Investigations in Biology class ventured into the old growth forest in Dick Cove (aka Thumping Dick Hollow, apparently named for a former inhabitant who built an ingenious corn-pounding device). In addition to measuring trees to quantify how the forest community is changing, we found some interesting creatures in the undergrowth.

First question, thanks to Ruffin: can you spot the animal?

Camouflage on leaves

How about now, when it sits on a rock?

Spring peeper, Pseudacris crucifer. The scientific name derives from the cross on the animal's back.

Another cryptic creature, this time an unknown Hemipteran bug:

...and Mary demonstrates how to "picture-bomb."

Allie found an archaeological artifact (or, trash, depending on your perspective). After some debate, we left it in place. The mini-terrarium inside was remarkable — soil had accumulated over the years, then moss spores somehow found their way in.

Bryophytes in a bottle

Another world inside; like the Sewanee Bubble.

Last, Jeff found a spectacular Philomycus under some bark of a downed log. These native gastropods are “mantleslugs” and they are as big as cigars.

Philomycus with the fecal remains of its fungus dinner.

Treefrogs in amplexus

The heavy rains have brought amorous Cope’s gray tree frogs to the garden. It seems that embracing pairs of tree frogs are everywhere.

In the trees... the water...

... and on land.

Their camouflage can be impressive. These frogs change the color of the skin to match their background.

A previous post describes their eggs and calls. This morning there were about fifty small rafts of eggs on a pond that is a little over a meter across.

Cope’s Gray Tree Frogs

Despite the lack of rain, the tree frogs have been calling every night from our small pond.

The croak calls are the tree frogs; the sweeter trill is an American toad.

In the morning, about a dozen small clutches of eggs were floating on the water surface.

Cope's gray tree frog eggs. The whole cluster is about as big as a my thumbnail.

The eggs will hatch in less than a week, then the tadpoles will take another month or so to develop. To make sure that the ducks don’t destroy all the eggs, I have scooped some of the eggs masses out of the pond. I’m keeping them in a bucket until they hatch, then I’ll return the tadpoles to the pond. Ducks don’t seem to be good at catching tadpoles.