An online resource based on the award-winning nature guide

Frogs

Green Frogs’ Coloring

7-13-16  turquoise green frog 030Despite their name, Green Frogs are not always green.  They can be brown or tan, as well as many shades of green.  Usually Green Frogs in the Northeast are a combination of these colors, but occasionally one sees greenish-blue coloring on a Green Frog.  An understanding of what causes a frog’s green color sheds light on why sometimes all or part of a Green Frog may be close to turquoise than green.

Basically there are three types of pigment cells (chromatophores) which stack up on top of each other in a frog’s skin.  The bottom layer (melanophores) of pigment cells contain melanin, a pigment that appears dark brown or black.  On top of these cells are iridopores, which reflect light off the surface of crystals inside the cells.  When light hits these cells, they produce a silvery iridescent reflection in frogs, as well as other amphibians, fish and invertebrates. In most green frogs, sunlight penetrates through the skin to the little mirrors in the iridophores. The light that reflects back is blue. The blue light travels up to the top layer of cells called xanthophores, which often contain yellowish pigments. The light that filters through the top cells appears green to the human eye.

The pictured turquoise-headed Green Frog most likely lacks some xanthophores in the skin on its head, and thus we see reflected blue light there.

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Gray Treefrog: A Frog of Many Colors

7-28-16 young gray treefrog2 IMG_5078A Gray Treefrog starts life off as a ¼” yellow tadpole. Eventually it may reach 2 ½” in length, and its body will have turned olive green with a red tail. Upon metamorphosing into a frog, the Gray Treefrog turns a bright emerald green and gradually develops into a mottled greenish-gray adult which can change its color from green to gray in about half an hour to match its environment. The two color phases of the maturing frog (solid green of the young, and mottled gray or green of adult) are so different it’s hard to believe that they are the same species. (Photo:  young Gray Treefrog; insert- adult Gray Treefrog)

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Spring Peepers Dispersing

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If you live near a pond where you heard loud “peeping” in late April or May, now is the time to keep your eyes peeled for young subadult Spring Peepers in the woodlands near the pond, for they are just completing metamorphosis and moving onto land. Thanks to their enlarged toe pads, peepers are good climbers but are usually found on the ground or low in shrubbery. The best time to look for young peepers is in the early morning hours and in the late afternoon, when they tend to feed.  Even if your timing is right, it can be challenging to find one — a full grown peeper is only ¾” to 1 ¼” long, and recently metamorphosed individuals are not much longer than ¼”, about the size of your baby fingernail. You’ll know it’s young because of its diminutive size and  its snub nose!

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Young Wood Frogs Getting Land Legs

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Thank you all for your good wishes regarding my next book!

With the dry weather we’ve been having, there is reason to be concerned about vernal pool residents, especially those that need to undergo metamorphosis before the pools dry up.  Granted, those amphibians such as Wood Frogs and Spotted Salamanders which transform into terrestrial creatures have evolved to have very quick life cycles, due to the temporary nature of their aquatic environment, but were they quick enough this year?

A very young Wood Frog crossed my path yesterday and answered that question for me.  No bigger than a raisin, it had to have emerged from its aquatic home in the very recent past.  When you think about the changes that have to occur between egg stage and adulthood (a total of two months, and it takes three of those eight weeks for Wood Frog eggs to hatch), it is mind-boggling.  Gills disappear and lungs develop, tail is absorbed, legs develop, mouth widens, intestines adapt to a herbivore-to-carnivore switch in diet – all inside of five weeks.

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Eastern Gray Treefrog

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Congratulations to Naturally Curious readers for their familiarity with Eastern Gray Treefrog (Hyla versicolor) toe pads!  This is the easiest time of year to find these amphibians, mainly because of their habits.  During the fall, winter and spring treefrogs are usually silent, unlike the summer, when males can be heard calling their melodic trill from bushes and trees near bodies of water after the evening air temperature rises above 59°F.  Because they are nocturnal, well camouflaged, and hibernate in the winter, you don’t often come across one except for the warmer months when males are calling.  The colors of an Eastern Gray Treefrog (brown, green and pearl-gray) vary with the colors of its background and environmental factors such as season and humidity, but shades of gray are most common.  Their green color is more prominent during the breeding season and in young frogs.

When hunting insects, or when disturbed, treefrogs can leap great distances and, thanks to advanced toe pads, when they land they can cling to practically any surface, including vertical branches and leaves that are wet. A very low angle between the toe pads and substrate as well as mucous glands located in channels between the hexagonal pattern on a treefrog’s toe pads have inspired the design for treads on car tires.

You can listen to an Eastern Gray Treefrog’s call by going to http://langelliott.com/calls-of-frogs-and-toads-of-the-northeast/   (Sound recording © Lang Elliott – langelliott.com)

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Green Frogs Mating & Laying Eggs

6-14-16  green frogs 008The loose banjo string call of the Green Frog is a familiar sound near wetlands this time of year.  Males (to the right in photo, with bright yellow throat) have been busy serenading females (to the left in photo, with white throat), in an attempt to breed with one.  Female Green Frogs select their mate, a choice which is based partially on the suitability of the male’s territory (underwater plants are a plus).  After inspecting several males’ territories at night, the female chooses one and slowly approaches him, turning to face away from him as their bodies come in contact.  External fertilization takes place as he clasps her while she lays her eggs (known as “amplexus”).

Unlike Wood Frog eggs that are laid in clumps, or Spring Peepers’ individually-laid eggs, Green Frog eggs are laid in a loose cluster that often floats on the water’s surface (see photo) or is draped on underwater plants.  Each cluster usually consists of 1,000 to 5,000 eggs that hatch in three to five days.  Females sometimes return to breed a second time with a different mate, in which case the second egg clutch is usually smaller, consisting of about 1,000 to 1,500 eggs.

The larval, or tadpole, stage of a Green Frog lasts from 3 to 22 months, which explains why you might have already seen large Green Frog tadpoles this summer.

(Outstanding theories were submitted on yesterday’s mystery. Be sure to read comments!)

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Pickerel Frogs “Snoring”

4-28-16  pickerel frog IMG_9429Pickerel Frogs emerge early in the spring from their muddy, pond bottom hibernacula, and mate in April and May in the Northeast. As part of the mating ritual, males call to attract females, with the calls resonating inside their internal vocal sacs located between their tympanum (ear drum) and foreleg (unlike Spring Peepers and American Toads, whose vocal sacs are located directly under their mouths).

These low-pitched calls resemble short “snores.” Occasionally Pickerel Frogs call from under water, but even when they are above water, their calls do not carry very far, frequently making it difficult for human ears to hear them.  Their call is similar to that of the Leopard Frog’s but lacks the short grunts of a full Leopard Frog call.  You can compare these two calls (and several others) by going to http://langelliott.com/calls-of-frogs-and-toads-of-the-northeast/ (Sound recording © Lang Elliott – langelliott.com)

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