“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.

ghost glass frog

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.

eye color in frogs-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!


It’s real name is Duckweed – that scummy stuff that coats the surfaces of ponds and marshes and even the critters swimming around there.

mallards and wood ducks on a duckweed pond-

A mixed flock of Mallards and Wood Ducks floating on a pond of duckweed.

duckweed - Lemna species

From a distance, it just looks like scum covering the water surface.

duckweed - Lemna species-

Up close, it is only slightly more interesting. The “scum” is actually leaves of one or more species of Duckweed that float on the surface, attached to each other by slender threadlike filaments.

But it seems that Duckweed is highly nutritious and is even promoted as a supplementary feed for livestock.  Gram for gram it contains more protein than soybeans, and it grows incredibly fast — in fact, it is one of those species that exhibits exponential growth, doubling every so many hours.  With its high protein content (35-43%), low fat (5% poly-unsaturated fat), and low fiber content (5-15%), it is highly digestible, yielding more calories with less work.  Although it is regularly consumed in some cultures in southeast Asia, Duckweed is high in oxalates, which makes it potentially toxic to your kidneys, so it’s not high on my list of edibles.


From Off the Grid News: Feed your livestock AND your family with prolific, fast-growing Duckweed!  Use it instead of spinach in your salads…

Instead of eating it, Duckweed may prove valuable as a source of biofuels because it grows so fast, has so little fiber, and contains 5-6 times the amount of starch that corn does.

Duckweed is a primary food source for lots of wildlife, including Mallards, Wood Ducks, Canada Geese, Painted and Snapping Turtles (I thought they were carnivorous!), even Beaver. I’m going to add Trumpeter Swans to this list, because I saw them gobbling it up the other day.

Trumpeter Swans eating duckweed

A pair of Trumpeter Swans dabbling for duckweed on nearby Sucker Lake.

Trumpeter Swans eating duckweed

Strings of Duckweed dangle from their mouths as they gobble up their highly nutritious, protein-packed meal.

All in all, it seems that “Uck-weed” has a lot going for it, as a food source and a potential fuel source.  I’ll stop denigrating pond scum now.

Just the beginning

As nighttime temperatures dip toward freezing, the trees are starting to show a little color.  It’s just the beginning of the most colorful season of the year —

beginning fall color-

Warm days and cold nights signal plants to cease photosynthesis and begin breaking down the chorophyll pigment in their leaves to unmask other, colorful light-gathering pigments.

Fall weather and decreasing day length signal animals to begin making preparations for winter — either storing food (like the squirrels have been doing) or eating like crazy to get fat enough to migrate south.  Waves of warblers and other small songbirds have been moving through the Twin Cities recently, and some wind up in the backyard, looking for insects on late-blooming plants.

female or juvenile yellow-rumped warbler-

Large flocks of Yellow-rumped Warblers move quickly through the vegetation, but occasionally stop to pose for a photo.

showy goldenrod-

Only a few species of perennial plants are still flowering here, like this Showy Goldenrod that is buzzing with several species of insects.

showy goldenrod pollinators-

Pollinators looking for a late autumn meal of nectar and/or pollen crowd onto a Showy Goldenrod plant that stands out in a field of Little Bluestem grass.  In addition to the bumblebees, two species of hoverfly, a beetle, and a small wasp were foraging here.

sulfur butterfly on new england aster-

New England Aster was buzzing with Pink-edged Sulfur butterflies, bumblebees, and hoverflies.

Seed-eating migrants might find a banquet waiting for them too, as perennial plants put forth their seed crops.

canada goldenrod seed head

Canada Goldenrod seeds are buried in the wispy tendrils that help disperse the seed around the prairie.

indian grass-

Perennial grass seeds are ripe for the taking as well.

With all the rain late this summer, I hope this will be one of the most colorful fall seasons in recent years.  But that depends on the day-night temperature differences in the next few weeks.  So, stay tuned for more posts on fall color later.

I can’t eat another thing, not even a “wafer thin mint”

I think the squirrels have become satiated with all the walnuts and buckeye nuts falling on the ground this past week.  Here is what they left behind as I tried to clean up their messy harvest.

ohio buckeye nuts-

I raked up an entire mixing bowl full of buckeye nuts left behind by the squirrels at the base of the tree. A few of the nuts had a bite or two out of them, but most were unscathed.  They are so heavy and slick, they slide right into any crevice in the lawn and get more or less buried there — ready to germinate next Spring and create a little Buckeye forest.

Meanwhile the squirrels look like this…

gray squirrel-

“I’m so full — I can’t eat another thing, not even a wafer thin mint”.

A la Monty Python’s sketch in “The Meaning of Life”


The strategy of satiating predators with an over-abundance of food ensures that some of the seed crop (or animal prey in the case of carnivores) remains unharmed, able to carry on the next generation.  Who said trees weren’t smart?

Syzygy — my new favorite word

Syzygy – the exact alignment of sun, earth, and moon with the earth in the middle so that the moon is caught completely in the earth’s shadow.

Almost complete lunar eclipse -- as full as I saw it in east-central Minnesota

Almost complete lunar eclipse — as full as I saw it in east-central Minnesota.  There was so little light coming from the moon, and so much light coming from street and house lights around me, it made it very difficult to get good focus on the moon.  This was a 3.5 second exposure — so there might have been some lunar movement that made the image fuzzy as well.


This diagram from The Hudson Valley Geologist blog shows the exact positioning necessary to create a full shadow of the earth on the moon.  

The transit of the moon through the full umbra shadow took almost an hour last night, while the partial shadow cast while the moon moved through the penumbra happened relatively quickly.

lunar eclipse-penumbra shadow-

The view before full lunar eclipse. The earth’s shadow moved from left to right across the face of the full moon.

lunar eclipse-penumbra shadow-

After full eclipse, the moon’s full brightness returned left to right. An hour and a half elapsed between the before- and after-full eclipse photos.

Why a blood red moon during the lunar eclipse?  The Hudson Valley Geologist explains that short (especially blue) wavelengths of light are scattered by the earth’s atmosphere, leaving the longer, orange and red wavelengths to be bent and focused on the moon.

I hope you all got a chance to see this somewhat rare event — another lunar eclipse of a super moon (at its closest distance to the earth in its orbit) won’t happen again until 2033.

Curious behavior

On a walk the other day I noticed several adult female grasshoppers on the edge of the asphalt walking path, probing the ground with the tips of their abdomens.

female two-striped grasshopper

This is mostly likely the common Two-striped Grasshopper, displaying some curious behavior as it spun around in a circle in front of me.  At intervals it touched the tip of its abdomen to the surface, poked up and down, and then continued to move around in a circle.

female two-striped grasshopper abdomen

A closer look showed that this was indeed a female grasshopper. Those shovel-shaped plates that make up her ovipositor at the tip of her abdomen dig into soft soil to create a long burrow in which she will lay her eggs.  Males, in contrast, have a blunt-ending abdomen.

A summer of eating and growing from the very tiny nymph that hatched last spring has matured this female into an egg-laying machine this fall.  She might be testing to see what lies under this rocky substrate, but a soft sandy soil would be the best type of soil for her egg-laying efforts.

female two-striped grasshopper abdomen-closeup

Those sturdy looking appendages at the tip of her abdomen are keratinzed plates that are moved by the actions of 10 sets of muscles in the two terminal segments of her abdomen.

Sets of opposing muscles open or close the plates together, protrude or retract the ovipositor, as well as moving it side to side and up and down.  As the ovipositor enters the soil, it opens, pushes soil to one side of the hole, and gradually lengthens to expand the depth of the hole.  Continued maneuvers of the ovipositor deepen the hole until it is sufficient for the egg mass she plans to leave there.

female grasshopper laying eggs in burrow-Thompson 1986

Who knew that a female grasshopper could extend its abdomen 3-4 times the length of its relaxed body length? But that is only part of what is amazing about this grasshopper’s reproduction. Apparently, the nerve control for this entire operation rests in a terminal nerve ganglion, not in the grasshopper’s small brain. This means even a beheaded grasshopper can still finish laying its eggs.

a mouse’s eye view

A walk around the pond in the way-back part of the backyard the other day revealed a few stray warblers (they all look alike in the fall to me), a pond full of molting Wood Ducks, a family of green herons obscured by a dense thicket, and a strange little mouse that was resting in a Wood Duck box.  Unfortunately, I disturbed his nap by opening the box, and he almost scampered out the hole…

white footed mouse in wood duck box-

This is either a Deer Mouse or a White-footed Mouse — they are difficult to tell apart.  I guess the mouse couldn’t decide whether to take a chance on staying where it could see me or hopping down where I might step on it.  

white footed mouse in wood duck box

The other half of the mouse, still in the box. The wire mesh in the box is there to help the Wood Duck nestlings get up to the edge of the hole before they fledge.  

The closely related Deer Mouse and White-footed Mouse species are nocturnal — hence the daytime nap in this unlikely resting place.  They have really large eyes (good for seeing at night), a buffy tan color to their fur coat, and long tails.  They inhabit forest woodlands as well as meadows and fields throughout much of the U.S., and subsist largely on a diet of seeds, although insects, spiders, and fruit are on the menu as well.

Even though this little mouse is 1/3 the size of a chipmunk, it doesn’t hibernate but stays active all winter, venturing from its nest among rocks or tree crevices each evening to search for something good to eat.  It’s amazing that they can withstand the frigid nocturnal temperatures of the Minnesota winters!

white footed mouse in wood duck box

There was so much reflection coming from the mouse’s eye, I took a closer look — and sure enough you can see me standing in the bottom center of his eye, right beside the nest box.

It’s not often you get to see the mouse’s view of the world.

The buckeye harvest

Our Ohio Buckeye tree is rapidly being harvested by the local gray squirrel population.

gray squirrel eating buckeye nuts

Gray Squirrels make quick work of this large nut, by stripping off the outer spongy hull to get to the larger brown seeds inside.

A half dozen squirrels race up and down the trunk and branches, cutting the nuts from the terminal parts of the branches, then quickly de-hulling them, and carrying the brown seeds off to their hidden caches.

gray squirrel eating buckeye nuts

It takes some acrobatic maneuvers to get to some of the nuts on the tree.

gray squirrel eating buckeye nuts

A young squirrel copying the example of his elders — but going the wrong direction (up the tree) with his prize.

Nuts of the Ohio buckeye

1-3 shiny brown nuts can be found within the spongy hull of the buckeye.  Carrying buckeye nuts around in your pocket is supposed to bring good luck….  (Photo by H.Zell, from Wikimedia Commons.)

It’s somewhat surprising that the squirrels place such value on these toxic nuts, which are so poisonous to domestic animals and pets.  Indians apparently found a way to detoxify their high tannic acid and alkaloid content by roasting, grinding, and leaching the nuts before pounding the extract into a powder for a nut-bread concoction.

gray squirrel eating buckeye nuts

Those are some sharp lower incisors that can chip through the tough outer shell of the nut.

gray squirrel eating buckeye nuts

The aftermath of the harvest is a big pile of leaves and hull debris on the lawn, which is pretty difficult to rake up.

gray squirrel eating buckeye nuts-

Enjoying the fruits of the harvest. I’m just glad these squirrels prefer buckeye nuts to my Honeycrisp apples!

Color me green, or gray, or brown…

Gray Treefrog, Hyla versicolor

The ever-changeable, Gray Treefrog.  How does it do it?

Green is a popular color for frogs, and birds too, but that lovely green color doesn’t come from a green pigment as you might expect, but from the interaction of multiple layers of specialized color and light-reflecting cells in the upper layers of their skin.

Frogs have three layers of chromatophores (color-producing cells) in their skin. The deepest layer are melanophores that produce melanin pigment giving skin a brown to black color. The middle layer are iridiphores which contain no pigment but instead have mirror like plates capable of producing iridescence, or when viewed from a certain angle, reflect blue light. The most superficial layer of chromatophores are xanthophores that contain a yellow pigment.  When the middle layer of iridophores interact with the top layer of yellow-pigment containing xanthophores, you get what elementary school students have learned:  yellow paint + blue paint = green color.

gray treefrog color

A closeup look at the skin of Gray Treefrogs reveals a mottled pattern of color — the result of different stimuli to those color producing cells in the skin.

Animals that change their skin color (like some frogs and reptiles) not only can change the shape and size of the chromatophore but the dispersion of the pigment within the cells.  Thus, tightly contracted chromatophores with no dispersion of pigment might appear white, and the opposite pattern would look black. Moderate dispersion of melanin pigment in the deepest layer of chromatophores looks gray. Dispersion of pigment in the xanthophores coupled with dispersion of light-reflecting particles in the iridophores produces variation of yellow, blue, and green colors in the skin.  Combination of all of the above produces the mottled pattern of coloration the animal uses to blend in with its background — a protective camouflage.

gray treefrog color-closeup

An even closer, close-up look at the skin of the Gray Treefrog.

Color change seems to be temperature dependent:  warmer frogs are lighter in color to reflect incident light; darker frogs are generally cooler and the darker skin helps them absorb heat.  Skin color becomes lighter when these frogs are placed on a brighter background, and darker when placed on a dark background.  This color matching is part of the effective camouflage protection.  And lastly color change may reflect the mood of the animal — e.g., sexual display, territorial display, etc.  The stimulus for all of this change begins in the brain, is transmitted by hormones, and carried out by the actions of the chromatophores — all in a matter of seconds to minutes.

A really detailed and fascinating discussion of how color change is achieved in animals (in this case a Chameleon) is shown below.