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Frogs

Green Frog Tadpoles Maturing

green frog with tail 127When you think about the structure and form of a tadpole, a plant-eating, streamlined creature designed for aquatic life, and that of a meat-eating terrestrial frog which is adapted for jumping on land, and know that they are one and the same organism, one can’t help but be impressed. The visible changes in this transformation are dramatic enough – legs emerging, head shape changing, tail being absorbed – but the internal changes a tadpole undergoes are just as dramatic. Research has shown that everything from a tadpole’s respiratory (gills replaced by lungs), urogenital and sensory systems to its digestive system (intestines becomes much shorter due to change in diet) is undergoing significant changes.

The length of time these changes take varies according to the species of amphibian. Most Green Frogs (Rana clamitans, pictured) undergo metamorphosis within the same breeding season or they overwinter as tadpoles and mature the following summer. (There are records of Green Frog metamorphosis taking up to 22 months). Biologists in Michigan found that eggs deposited before roughly June 25 were capable of developing in one season, whereas eggs deposited after roughly July 10 remained as tadpoles until the following year.

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Male Pickerel Frogs Snoring

5-18-15 pickerel frog IMG_3937Next to the Green Frog, the Pickerel Frog is the most abundant frog in New England. It is often confused with the Northern Leopard Frog, which it closely resembles. The spots on a Pickerel Frog’s back are squarish and aligned in rows, whereas the Leopard Frog’s spots are rounded, and randomly scattered over its back. In addition, the male Pickerel Frog has bright orange on the inner surface of its hind legs, which the Leopard Frog lacks.

Recently male Pickerel Frogs have started calling to attract mates. Each species of frog, just like each species of bird, has its own distinctive call. Spring Peepers “peep, “ Wood Frogs “quack” and Pickerel Frogs “snore.” Their snore isn’t long – it only lasts a second or two — but it is unmistakable. Pickerel Frogs call from under water, as well as on top of mounds of vegetation, so if you hear one, and then search for it, you may not find it. To hear a Pickerel Frog, go to http://langelliott.com/mary-holland/pickerel_frog_VA.mp3. (Sound recording © Lang Elliott – langelliott.com & miracleofnature.org)

Starting with today’s post, my blog will occasionally be enhanced with the sound recordings of Lang Elliott. For those of you who may not be familiar with his work, Lang Elliott has made world-renowned recordings (that are commercially available) of the vocalizations of birds, mammals, insects, frogs and toads. If you’ve ever wondered what out-of-sight creature was singing, screaming, trilling or buzzing, his CDs and books will give you the answer. To learn more about the work of this author, speaker, cinematographer, sound recordist, and nature poet, visit http://www.langelliott.com.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Aquatic Frogs Hibernating in Ponds

1-9-15  green frog IMG_0181Most aquatic frogs such as this Green Frog have been deep in hibernation for several months. A common misconception is that frogs spend the winter the way aquatic turtles do, dug into the mud at the bottom of a pond or stream. In fact, hibernating frogs would suffocate if they dug into the mud for an extended period of time. A hibernating turtle’s metabolism slows down so drastically that it can get by on the mud’s meager oxygen supply. Hibernating aquatic frogs, however, must be near oxygen-rich water and spend a good portion of the winter just lying on top of the mud or only partially buried. They may even slowly swim around from time to time.

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September Snub-Noses

9-1-14  juvenile amphibians IMG_5078Frogs and toads that hatched from eggs laid this past spring are now two to four months old, and are growing rapidly. Like snakes, frogs and toads shed their skin as they grow — unlike snakes, they eat their skin. Periodically toads and frogs stretch their bodies and then pull their loosened skin off in one piece, much like we pull off a sweater. Using their feet, they then stuff their skin under their tongue and swallow it. When frogs and toads are young and growing fast, they usually shed their skin more often than when they are older and their growth slows down. Not only is their skin a valuable source of nutrients and protein, but if it’s eaten, there is no sign left behind for predators to find.

Most young toads and frogs, with the exception of the Gray Treefrog, look like miniature adults. (Gray Treefrogs are emerald green in their youth, unlike the mottled gray/green adults they will become.) There is one characteristic at this stage that they don’t share with their elders, however, and that is their snub noses. If you’re wondering if the frog or toad you saw is a small adult or a youngster, take a closer look at its nose! If it’s unusually short and blunt, there’s a bit of growing left to do.

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Common Gartersnakes Giving Birth

8-15-14  common gartersnake 082Common Gartersnakes mate soon after emerging from hibernation in the spring, in March or April, and four months later the females give birth to live young. The newborn snakes are 5 to 9 inches long at birth and from day one have to fend for themselves. Their diet at this early stage consists of earthworms, insects, slugs, tadpoles, small frogs and fish. If there is an abundant supply of food, the young snakes can grow as much as 1 ½ inches a month during their first year. Earthworms are their preferred diet and gartersnakes are known for their ability to find them, even underground. It turns out that earthworms produce a chemical substance in their skin that is easily detected by (and attractive to) Common Gartersnakes. (Thanks to Eli Holland, who located the worm-eating newborn Common Gartersnake in the photograph.)

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Gray Treefrogs Calling

gray treefrog 021At this time of year, bird-like trills are often heard in wetlands, where male gray treefrogs (Hyla versicolor) are calling to potential mates. The chorus ramps up at night, but the songsters can be hard to find during the day, when they often hide in tree cavities or high up in the canopy. (Their large toe pads produce mucous which allows them to adhere to smooth bark.) The colors of a gray treefrog vary with the colors of its background and environmental factors such as season and humidity, but shades of gray are most common, with black blotches on the back. Variations of brown, green, and pearl-gray colors have been noted, with green being more prominent during the breeding season. Warm, humid weather seems to elicit calls from these well-camouflaged amphibians. To watch and hear a calling gray treefrog, go to http://www.youtube.com/watch?v=2kd5c4p8-0M. (Thanks to Rachael Cohen for photo op.)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Wood Frogs Awakening and Thawing

4-17-14 wood frog IMG_1377The duck-like quacking of recently-emerged, courting wood frogs is slightly miraculous considering that only days ago these amphibians were frozen practically rock solid. At some point in late fall or winter, as temperatures drop, they flood their bodies with blood sugar that acts as antifreeze in their circulatory system. Activity in their brains stops, their heart stops, and 45 – 60% of their body can freeze. Yet within hours of being exposed to the spring’s warming temperatures, wood frogs thaw out and start moving towards a body of water to breed.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


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