Outdoor Encounters

By Nathan Bolls on November 7, 2019

The loud, thumping trill from the woods booms against our ears. I’m reminded of James Thurber’s “things that go bump in the night.” What Phantom of the Forest with such auditory might lurks therein and calls from the night? Or... “what rough beast...slouches toward Bethlehem to be born?” (W.B. Yeats poem “The Second Coming”) Numerous societies across our world speak of a mysterious local monster, but the existence of none, as of yet, has been proven. We hear most often of the Himalayan Yeti, the north American Sasquatch (Bigfoot), or of Scotland’s Loch Ness Monster.  

   Not to be outdone, we have one of those “things that go bump in the night:” the Beast of the Loud Thumps (Thank you, Sharon) that we know as the—Treefrog, or Tree Toad, as they sometimes are called! Reason for second name later. They are all around us, just waiting to burst—our eardrums! For two reasons, humans rarely see them. It is the only amphibian in Kansas capable increasing its camouflage, of changing somewhat both the pattern on and the color of its skin to match the substrate on which it happens to be sitting or clinging.

   Although the treefrog skin’s ground color usually is some shade of gray, both species possess the ability to change through a range of colors to green. But regardless of the ground color, there is an irregular dark pattern on the back outlined in black. I was only eight to nine years old when I first held one in my hand—and was intrigued with watching its skin color change gradually from greyish to brownish, a reaction that is hormone driven. 

   And then there’s the matter of size: snout to rump, they usually are in the mighty range of  1 1/4th to 2 1/4th inches in length!  Everyone who has heard that loud, thumping trill, and knows the frog’s size, wonders how the critter manages to create that magnitude of sound.

  We have two species of treefrogs in Kansas: Cope’s gray treefrog and the eastern gray treefrog, so similar that one has to use the diameter of their red blood cells or the number of their chromosomes to tell them apart. For example, Cope’s treefrog has half as many chromosomes as does the eastern gray. 

  Both are highly arboreal (far more than any other KS frogs), inhabiting trees and low shrubs in woodland and woodland edge areas. But the Cope’s gray treefrog is more arboreal, and apparently can tolerate a less humid habitat. Both species possess enlarged adhesive toe pads that enable them cling to surfaces, even to a vertical glass plate!

  They are active in Kansas from early March to early October, their trills growing slower and

shorter in cooler weather: below 60 degrees. One mid-October I once heard one give but a single loud “thump;” probably the Cope’s treefrog because of the harshness of the “thump,” which sounded more like a bark.  Their normal breeding season is from mid-March to mid-July in permanent, semi-permanent, or temporary pools with mud bottoms, or weedy vegetation in or nearby wet woodlands. The males often “sing” in choruses within the same breeding area, and they do this either on the ground at water’s edge or from low overhanging vegetation. 

The most robust choruses have been recorded between 10 p.m. and 3 a.m. The mating call for both sexes is a loud trill that lasts one to three seconds. The gray treefrog’s call is slower and more melodious than the harsh call of Cope’s treefrog. They are nocturnal and are active even on hot, but humid, summer nights, when they can often be heard calling from tree tops.  Listen for them; it makes the humidity more bearable.  

  As cold weather approaches, they find shelter under loose bark, among the tangle of roots of trees, beneath leaf litter, under logs, or in hollow trees. They are freeze tolerant, forming a glycerol in their blood, and are able to withstand temperatures as low as minus 20 degrees Fahrenheit. Amazing! When inactive during warm weather they hide in some of these same sorts of spots.

  Our treefrogs feed on beetles, ants, flies, moths, insect larvae, spiders, and other small invertebrates. Around human habitations, they often forage near porch lights, windows, and other sources of light. Look closely while enjoying your porch in the evening. 

  Usually, but not always, their skin is rough and warty, like that of a toad. But, like other frogs, the skin always a bit moist. The skin of other frogs is smooth, but highly permeable, making it a route via which water may be either easily lost from or taken up by the body.  The treefrog skin surely is less permeable than that of other KS frogs. Otherwise, these animals would not be able to travel so far, and stay so long away from a body of water. 

  These marvelous creatures represent yet another fly in the out-of-date jar of ointment that is labelled Bigger-is-Always-Better.