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Frogs

Male Green Frogs Defending Territories

6-25-18 green frogs2 _U1A9296Male Green Frogs are extremely territorial. During June, July and August they establish a series of territories, often claiming each one for less than one week before moving on.

The desirability of a given territory is of utmost importance – the better the quality (amount of vegetation) of your territory the more likely it is that a female will choose you to fertilize her eggs. The more time a male spends in a high quality territory the greater the number of mates he will acquire.

Considerable aggression is displayed against other males when an individual is claiming and maintaining a territory. When a competing male arrives, a wrestling match often ensues (see photo).

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Wood Frogs Mating

4-23-18 mating wood frogs2 0U1A0777Wood Frogs have emerged from their hibernacula and migrated to their ancestral woodland breeding pools, or vernal pools, to sing (males), mate and lay eggs (females). A chorus of duck-like quacking reveals where these hidden temporary bodies of water are located. The male Wood Frog in this photograph is on top of a female, grasping her behind her front legs in a hold referred to as “amplexus.” They will remain in this position until she lays her eggs and he then fertilizes them externally. Note that even though he has attracted a female and is in the process of mating with her, the male is continuing to sing (one of his two vocal pouches is inflated on the near side of his body).

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Young Spring Peepers Appearing

8-24-17 SPRING peeper 049A3399Every year in late July or August a young Spring Peeper crosses my path and I cannot resist photographing it. At this time of year they are roughly the size of a Japanese Beetle, and during early mornings and late afternoons can be found in shrubbery where they intermittently rest in the shade and feed on insects even smaller than themselves. If you live near a pond where it sounded like sleigh bells were ringing last spring, keep an eye out for these irresistible frogs that are no bigger than your tiny finger nail.


Leopard Frogs – Too Little, Too Late

leopard-frogs-in-puddle-by-kelly-maginnis-northampton-ma-12-10-16At this time of year one would expect to find Leopard Frogs lying on the bottom of a pond, partially but not completely covered with leaves or mud as they hibernate their way through winter. Because of the depth of a pond, and the fact that in winter the water temperature is around 39°F., ice isn’t an issue at the bottom of a pond, and the frogs and turtles that overwinter there don’t usually freeze.

However, sometimes ponds freeze over before amphibians or reptiles that overwinter in them arrive at their hibernacula. Apparently this is what happened to these Leopard Frogs, and they took refuge in the only open body of water they could find – a large but shallow puddle about 10’ wide by 20’ long in a dirt road. Shortly after they arrived temperatures dropped and the frogs were trapped under (and eventually will be encased in) the ice. Unlike Wood Frogs, Spring Peepers and Gray Treefrogs, Leopard Frogs are not freeze tolerant, so their demise is inevitable. (Thanks to Kelly Maginnis for photo, and Jim Andrews for his herpetological expertise.)

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Fall Amphibian Migration

10-24-16-red-backed-sal-089The migration of amphibians from the woodlands where they overwinter to their breeding pools in March is a familiar spring phenomenon to most. However, some of these amphibians engage in a fall migration as well. Amphibians (and reptiles) need to find a good overwintering spot, where they won’t freeze. In some cases, that might be a few feet upstream or into a seepage area, and in others it is a few hundred yards uphill. The extent of the migration and the species participating vary in different parts of the state.

In western Vermont, Jim Andrews, Director of the Vermont Reptile and Amphibian Atlas(http://vtherpatlas.org), has observed Blue-spotted and Four-toed Salamanders moving down into wetlands in the spring, staying close to the wetland for moisture and feeding during the summer, and then moving uphill back to wintering areas in the fall. On the other hand, he has found that most Spotted and Jefferson Salamanders, as well as Wood Frogs, move down in the spring to breed, and then head back uphill in stages soon after they are done breeding.

Eastern Red-backed Salamanders (pictured) migrate as needed during the summer to maintain their body moisture, and in the fall, search for an animal burrow or crevice to hibernate in. Migration often occurs at night, while it’s raining, so as to prevent their skin from drying out. (Amphibians need to have moist skin because a large portion of the frog’s “breathing” occurs via oxygen diffusing through the skin. Oxygen will not diffuse through a dry membrane.) After the very dry summer we’ve had, a large number of amphibians were observed taking advantage of the recent rain and migrating.

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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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