“Eye” wonder

Last year I wrote about the possible basis for the many variations of eye color in birds (click here to read that post).  Unlike most mammals which sport a limited variety of pale blue, gray, green, to dark brown shades, I’ve noticed that frogs and toads, like birds, also exhibit a rich variety of eye colors.  And so, “eye” wonder why?

Leopard frogs have a golden-colored iris with some dark speckles running through it.

Similarly, Gray Treefrogs also exhibit that golden-colored iris with the darks streaks running through it.

But these highly colorful eyes are tame, compared to those of a couple of South American frogs.

Those are some mesmerizing eyeballs in this Ghost Glass Frog. Glass frogs have see-through skin, especially on their ventral surface, which is as transparent as glass permitting a view of their internal organs.  Are those wild purple lines etched on the silver background of its iris to captivate female glass frogs, or frighten potential predators?

Red-eyed Treefrogs sit quietly on the underside of leaves during the day. But if disturbed by a predator or nosy human, they flash their big red eyes, orange toes, and yellow and purple legs to startle and gain time to escape.  [Photo from Wikipedia, By Carey James Balboa via Wikimedia Commons]

The variety of eye color in frogs and toads is astounding, as captured in this collage by Jodi Rowley.

Just a sampling of the normal variation among amphibian species… From RealScientists.org

Surely all this ocular advertisement has purpose — beyond frightening would-be predators?  Any speculation from you, dear readers?

In addition to the flash of color provided by the wide-open frog eye, you may have noticed that frogs have the ability to project their eyes outward from their head, or retract the eyes inward level with their skull.

This leopard frog has staked out a calling site, hoping to attract females. But it’s broad daylight and he needs to be able to see approaching predators (and photographers). 

Extrinsic eye muscles that elevate the eye above the level of the head actually give the frog a 360 degree view of its environment.  Movement of the eyes downward presses on the roof of the frog’s mouth, helping to propel food down the back of the throat toward the stomach.  Eyes — the multiple use organ!

Frogs!

Off and on rainy days with warm(er) temperatures have really set the frogs in motion here.  I sat on an upended bucket by one of the ponds in the backyard and trained my binoculars on the pond’s edge, hoping to finally locate those tiny little creatures that were making that hugely loud racket.

Eventually, by trying to ignore the loudest chirpers, I could distinguish three different types of calls, all at different pitches, frequencies, and volume.  Finally, by staring at the water where I thought the calls were coming from (this takes sound localization ability, which apparently I am lousy at), I found the frogs making them.

Leopard frogs made very low intensity, low pitch calls, and call very infrequently.  I couldn’t really see where the sound was coming from (no obviously inflated pouches).

Wood frogs sit horizontally in the water, like the leopard frogs, emitting sort of a quacking call that sounds like it should be coming from a duck.  Dark bodies, striped legs, and a black mask over the eyes outlined with white stripes — make this frog quite attractive.

Here the wood frog has inflated its vocal sacs during its “quack” call.  When they do this, the water around them shows disturbances in concentric circles, making them a little easier to find in the pond (if you have bad sound localization ability).

Wood frogs are found almost everywhere in central and eastern North America; they are one of the first frogs out in the spring, as soon as the ice melts off the ponds.  They are unique in that they tolerate being frozen solid over the winter, as they “hibernate” in a state of suspended metabolism under the leaf litter.  Click here to view a short video of wood frogs calling (in Minnesota).  And here is an amazing video of Wood Frogs defrosting from their frozen winter state.

By far, the loudest, shrillest, and almost deafening calls were coming from the Boreal Chorus Frogs (Pseudacris maculata), which were almost impossible to find, mostly because I was looking in the wrong places.  They were sitting at least 3 feet from the shore, out in the submerged vegetation, oriented vertically, with their head, vocal sacs and abdomen out of the water.  Perhaps the volume of noise from multiple frogs confuses predators as well.  Are herons and egrets immune to this racket?

Even maximum telephoto didn’t bring these tiny, one-inch Chorus frogs into view.  

So, I moved to a better viewing spot, sat, and waited until they got used to my presence, and then got closer-up views of a calling Chorus Frog.  These frogs (once you see them) are easily distinguished by the three longitudinal stripes down their backs.

The cricket-like call is emitted through the larynx (voice box), but is amplified by vocal sacs. The body cavity of the frog swells when air is inhaled through the nostrils, and the vocal sac shrinks.

Then, the frog contracts its muscles to expel the air during exhalation through the larynx, enlarging the vocal sac, and producing a vibration that amplifies the sound.

If you haven’t had the pleasure of standing next to a group of calling Chorus Frogs, you can view a short video here.  These tiny frogs can emit sound at nearly 90 decibels, which is about as loud as the human ear can stand without damage, about the same as standing next to a truck without a muffler.  And, they call continuously for hours and days on end.  Now how is that for amazing!

For good photos and descriptions of MN frogs and toads, you can click here.

Prairie Spring

We took a field trip to Glacial Lakes State Park this weekend to take photos of the prairie wildflowers.  Hah!  Wildflowers are not fooled by a little warm weather in March.  They can monitor the daylength and “know” that the real spring weather (and rain) comes in April and May.  We unfortunately picked a rainy cold weekend to survey the prairie, but there were a few interesting highlights to see.  Just to give you an idea of the obstacles to our viewing pleasure, there was fog…

and a steady drizzle during one of our hikes (photo by Alison) …

with clouds threatening to pour down on us a lot of the time (photo by Alison).

The wildflowers made bright spots of color in the mat of taller grasses, like this Hoary Puccoon, which is almost orange  (photo by Alison).

Prairie Smoke is so-named for the structure formed by the maturing seed.  The flowers are a pretty magenta color but droop down, while the seed head will later be an erect wispy fringe on the flower stalk, resembling a plume of smoke.

Prairie Plum has low clumps of purple pea-like flowers that will later form an inflated orange-red pod lying close to the ground.  Apparently the pods taste much like fresh peas, which is logical since it is a pea family plant.

Another early bloomer is Golden Alexander, with its taller and erect flattened panicles of yellow flowers. 

Scattered throughout a wet, marshy field, we found Jack-in-the-Pulpit already well into its blooming phase.  The seed head of the central spike (Jack) will form a bright red cone of berries in the fall.  (see The Worm, the Pulpit, and the Thorn Plant, Nov. 29, 2011)

Even though it was rainy and misty most of the time, the were lots of birds out singing and flying around.  As we drove the backroads around the glacial lakes we saw a couple of Trumpeter Swans… (photo by Alison)

a small group of White Pelicans on Lake Minnewaska, (photo by Alison)

and the grandkids found a frog on the trail — it was very lethargic, either from the cold or having been injured earlier.

(photo by co-blogger Alison Mickelson)

As eldest grandson summed up at the end of our wet hike, “sometimes you find unexpected treasures in pretty boring places.”