Baby dragons in Postojna cave, Slovenia

I’ve visited quite a few famous caves in the U.S., but the amazing caverns carved from karst limestone near Postojna in southwestern Slovenia are the most spectacular I’ve ever seen. They are definitely one of the Wonders of the Natural World.

We walked over the Pivka river bridge and uphill to the cave. This is the river that carved the caverns millions of years ago.
From this unassuming entrance a complex of caverns and passageways runs 24 kilometers (14.4 miles) underground. There are actually four caves, interconnected by the Pivka river, which drains through them.
5 km of the cave is open to the public, the first 3.5 of which is covered by train. The rail system was first installed in 1872, and electric lighting shortly after that. The cave became a tourist destination as early as 1819 with Archduke Ferdinand’s visit, but the cave has graffiti dating to the 1200s!
We followed a very well maintained path up and down through numerous passageways and huge ballrooms over a 1.5 km track to view a huge variety of cave formations. One such ballroom is noted for its exceptional acoustics and is so large it can hold 10,000 people. Symphony orchestras sometimes perform there.
Some of the massive rooms were several stories tall, decorated with all shapes, sizes, colors, and varieties of cave structures. The bridge in this photo was constructed by Russian POWs during WW1.
This is not an effect of multiple colored lights on the cave structures, but are multi-colored columns of stalactites and stalagmites that have fused together over centuries as mineral-laden water seeped through the porous limestone.
Pale white formations are pure calcium carbonate, and darker stained formations have manganese in them.
I thought this collection of stalagmites looked like little people.
A pure white column (called “the Brilliant”) stands right next to a chocolate brown column with thin rods that have gradually fused together. It’s fascinating to think about how the water must have dripped through here to create these shapes.

The Postojna cave system is notable because of all the animal life found there. Over 100 species have managed to survive in the dark, cold (45-50 F), mineral-rich water, including a cave beetle species, a jelly fish relative, crustaceans, pseudo scorpions, and a cave spider species. But the largest and most remarkable cave dweller in Postojna cave is the “baby dragon” or cave salamander or Olm (Proteus anguinus).

The Olm reaches 8-12 inches in length, with a worm-like body, feeble forelegs, and a short tail. It has bright pink, frilly external gills, and basically resembles the aquatic, larval stage of salamanders even when sexually mature (a condition called neoteny). They are completely blind (eyes covered by skin) but have sound and vibration detectors in their elongate head, as well as smell and taste receptors in their nose that help them find prey. (Photo from CNN travel, Dec 2021)

There was some excitement among the cave biologists several years ago when one of the large Olms began to lay eggs. It took quite a while but she eventually laid more than 50 eggs, about 20 of which hatched in about 5 months. The youngsters had normal eyes, but they regressed in size and skin eventually grew over them. When presented with small worms, Olms immediately go on the attack, hoovering them up (like a vacuum cleaner) with their elongate snout.

Photos of a few of other inhabitants of Postojna cave, from CNN travel, Dec, 2021.

Color me green!

When I went out to pick raspberries this morning, I found something much more delightful than a bunch of mating Japanese beetles (the scourge of the berry patch!) — a couple of 1-inch Gray Treefrogs hiding in plain sight on the green leaves of the raspberries.

From the side, this little one with its dark facial markings and dark lateral stripe was more obvious.

Although this species is named the Gray Treefrog, because they are quite gray with a dark blotchy pattern sometimes, in bright sunlight on a green background, they are well camouflaged as they match their background. In fact, this frog even matches the particular shade of green of the raspberry leaf on which it rests.

I wonder if they eat Japanese beetles? There are plenty of other insects resting on the raspberry leaves for these little guys to dine on. But these frogs are really only active at night, and usually seek shaded vegetation for their daytime rest.
The color matching camouflage is impressive in both the shade (this photo) and the sun (photo above).
How exactly does a gray treefrog become green?
Looking more like the gray treefrog, I photographed this maxi-sized (2.5-inch) adult in the early morning while it was sitting under an evergreen in the leaf litter.

Frog skin contains a stack of color-producing cells called chromatophores, and many frog species like the Gray Treefrog, have 3 sets of them: a deep layer called melanophores that contain a black/brown pigment called melanin, an intermediate layer called iridophores that lack pigment but contain particles that can reflect blue light, and an upper (most superficial) layer called xanthophores that contain yellow pigment.

Now, it should be more obvious how a Gray Treefrog can transform quickly from its gray color that is produced by the dispersion of deep-lying melanin pigment to a bright green color, produced by the interaction of blue-reflected light from the iridophores passing through the yellow pigment of the xanthiphores (i.e., blue plus yellow equals green to our eyes).

The dispersion of pigment in frog skin is controlled by nerves and hormones, which act on the chromatophores to aggregate (condense) or disperse pigment. Physiologically, in a matter of seconds, when melanophores aggregate their pigment to uncover the iridophores and xanthophores disperse their pigment, a gray frog turns green!

Color changes can even happen while frogs are sitting in the dark in my covered water tank. It just depends on their physiological state, the temperature of their environment, and the amount of hormonal or nerve stimulus they are experiencing.

Above the rainforest canopy

A series of 14 bridges carry you from big tree to big tree at the Explorama canopy walk just a short walk from Napo lodge on the Napo river, one of the Amazon tributaries.

Explorama canopy walk, Napo lodge, Peru

Successive walkways gain height until you reach a height of 117 feet above the forest floor.

Explorama canopy walk, Napo lodge, Peru

Netting strung between cables provides hand holds for a shaky bridge. The floor of the walkway is two side-by-side boards covering ladders laid horizontally end to end. Longer bridges shake noticeably, but are safe, and checked every day.

Few birds were active in the middle of the day when we did the canopy walk, but the views were magnificent.

Explorama canopy walk, Napo lodge, Peru

Bromeliads covered the top one third of the tree trunks. These “air plants” capture rainfall in the canopy and provide breeding sites for frogs, lizards, spiders, and insects, which the birds then feed upon.

Black-bellied Cuckoo, Amazon, Peru

A Black-bellied Cuckoo rested in the shade at tree top, escaping the mid-day heat.

White-tailed Trogon, Amazon, Peru

A White-tailed Trogon alternately panted and looked around from his high altitude perch in the canopy.

Canopy lizard, Amazon, Peru

This canopy lizard would have made a nice meal for the cuckoo, but the birds were too hot to hunt. And so were we!

Into the rainforest

We left the delightful warm weather in Lima for the steamy jungle in northeastern Peru, where plants thrive, insects diversify to eat them, and birds that eat both the insects and or the plants adopt outlandish colors and decorative feathers to show off.  In other words, we are immersed in DIVERSITY.

Explorama lodge, Amazon river

Explorama lodge on the Amazon river

We headed down the Amazon river about an hour from Iquitos (in northeastern Peru) by motor boat, to Explorama Lodge, where we would stay in non air-conditioned lodging, with cold showers to cool us down after trekking through the steamy jungle. Boat trips out on the river and walks through the rain forest provided opportunities to see some of that diversity.

Passion flower butterfly

Passion flower butterfly

Heliconia flower

Heliconia flowers, a relative of banana, are actually colorful, waxy bracts, in which the actual flowers hide. They advertise their sweet nectar to hummingbirds with bright red and yellow colors.

Scarlet macaw

Scarlet macaw, really up-close, a family pet of river villagers

White-cheeked Jacamar, Explorama lodge, Amazon

The White-chinned Jacamar is shades of iridescent teal and green with a chestnut cap and a white chin of course.

Poison dart frog, Amazon forest

Poison dart frogs are tiny but bright and can be found in the moist forest floor or lower vegetation.

Are you seeing a pattern here of vividly bright colors of tropical flowers and animals?  I wonder why that is?  Your thoughts?

Mug shots – take 1

It’s great when you can get really close to the wildlife, i.e., right in their “faces”, to grab a “mug shot”.  I didn’t get many this year, but there were a few opportunities, assisted either by my extremely long (600 mm) telephoto lens or my trusty macro, to get up close and personal with the local wildlife on our travels and in my backyard.

hoverfly-on coneflower

Hoverfly gleaning pollen and/or nectar from New England Asters.

american-painted-lady-on sedum

American-painted-lady-on fall-blooming Sedum; they came through by the dozens to congregate on late-blooming flowers

honeybees-on-new-england-aster

Honeybees foraged on New England Aster; I saw more of them this year than in the last 5 years combined.

small-carpenter-bee-ceratina-spp

A tiny carpenter bee feasting on pollen from newly opened anthers on a coneflower.

bullfrog-

We found a Bullfrog calling in a desert oasis in Arizona. Kind of ugly, but beautiful eyes…that might be a mosquito on his upper lip trying to get a meal.

chuckwalla-

A Chuckwalla was sunning itself at the Sonora desert museum in Tucson. Dark pigmented scales on its underside help it soak up heat from rocks. Chuckwallas love to hide in rock crevices and resist being pulled out from their hiding place by puffing up their body with air, expanding into any empty space in the crevice.

snapping turtle-

Snapping Turtles have large jaws and long necks, but this one was protecting itself by withdrawing into its carapace.  My what beady little eyes you have, Mr. Turtle.

Great Blue Heron-

Eye to eye with a Great Blue Heron

molting mallard ducks-

Male Mallard Duck before molting a new set of showy feathers

Black-capped Chickadee-

Chickadee with an attitude…

green on green

Hiding in plain sight by matching the color of your skin to the color of the background is useful for predators stalking their prey or prey trying to escape predation.  It’s also useful in confusing photographers about where to aim their cameras.  Case in point: I saw the bushes moving, wondered if it was a bird, thought it might be a chipmunk, but stared right at the little critter for a full minute before I figured out what it was.

gray tree frog-

A gray tree frog in green phase hiding in plain sight.  It wasn’t this obvious without the zoom on the camera to help pinpoint its location.

gray tree frog-

It’s scientific name gives a hint to its ability to change colors: Hyla versicolor. Usually it appears mostly gray with green splotches.

Many species of fish, amphibians, and reptiles have the ability to change color and outward appearance by contracting or expanding the chromatophore (pigment-containing) cells in their skin.  This chameleon-like ability can assist them in better regulating their body temperature, or as suggested, in achieving the kind of camouflage that helps them evade their predators or fool their prey. It is thought that the animals’ eyes perceive the color spectrum of their environment and send neural signals to skin chromatophores to effect the appropriate color changes.

In cases where there doesn’t seem to be a clear message about the color of the background, Gray Treefrogs are often mottled gray and green, or just remain gray, as illustrated below.

gray-tree-frog-

Hmm… water in a bird bath? Not sure what color to be.

gray-tree-frog-

Gray treefrog sitting on the side of a dish pan, next to green vegetation — again, it’s confusing about what color to be.

gray-tree-frog-

Gray treefrog sitting on an orange dahlia — no possibility of a match here.

gray-tree-frog-green-phase

Green-colored Gray treefrog on the ledge of a wooden door? Clearly a bad match.

Toxic toads

I heard a few faint, froggy croaks coming from the dying perennials in the garden.  It seemed a little late in the season for the local amphibians to be active.  But wind and coolish temperatures didn’t deter an appearance by this little American Toad — hiding in the litter under the aging peony vegetation.

American Toad

It’s not much bigger than the chunk of mulch it was sitting on (about 2 inches long). 

American Toad

Not the most attractive skin with its lumps and spots, but those large lumps right behind the eyes (called parotid glands) are the toad’s secret weapons.

Amphibian skin is really quite special.  It can absorb water like a sponge when its owner is dehydrated, and it can secrete a variety of chemicals its owner might use for defense.  Poison dart frogs aren’t the only amphibians to use toxic chemicals to deter predators; several Toad species (in the genus Bufo) secrete a combination of chemicals called “bufotoxin”, which induce a variety of debilitating reactions in animals that try to eat them.  Although concentrations of bufotoxin vary from species to species, one website claims that “the skin of an average-sized toad can cause significant symptoms and even death in humans and other animals”.

Pet owners beware — don’t let your dogs lick any toads.

“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 FROG-

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

GRAY TREE FROG-

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_tree_frog_

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.

leopard-frog-swimming

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!

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.

Fotogenic Frog

gray tree frog

A dahlia flower fell down into some yews, and a shy tree frog decided it was a fine place to rest.

The Eastern Gray Treefrogs are most often found on vegetation, usually high up in the trees, rather than near water, as their name implies.  Actually, I most often see them in the outdoor tank we use to water potted plants.

gray tree frog

I picked up the lid of the water tank to see if it needed filling, and found this little guy waiting for me. I don’t know how they get in, and I wonder how they get out.

gray tree frog

They are adept at climbing vertical surfaces, even slick ones, using their sticky, enlarged toepads.

Their skin has a warty appearance, like that of toads, and they manage to stay hydrated without taking refuge in pools of water, even during hot days.  Gray Treefrogs tend to hunt at night, often near an outdoor light fixture where they can capture insects coming to the light.

gray tree frog

Interesting eye color in this individual, and you notice patches of green in the otherwise gray skin.

Skin color in these frogs is highly variable (hence their scientific name — Hyla versicolor).  Three layers of chromatophores in the skin (color-producing cells) combine to produce the color pattern, which can change (very slowly) from near white to very dark brown, with variations of mottled green and gray in between. Treefrogs don’t match their environment perfectly the way a chameleon does, but their color changes do help camouflage them in their environment somewhat.  More on how this is accomplished in the next post!  Stay tuned.

gray tree frog

oops, there are no red-orange pigments in those chromatophores, so color matching this dahlia would be tough.