An online resource based on the award-winning nature guide

Amphibians

Eastern Newts Dining On Hapless Dragonflies

eastern newt eating dragonfly 407Inevitably, as newly-emerged drying dragonflies and damselflies hang over the surface of the water on emergent vegetation, breezes blow and some of them lose their grip, falling into the water below.  At this stage, their bodies are soft and they are not capable of flight, which leaves them very vulnerable to aquatic predators such as Eastern Newts.  While amphibian eggs, aquatic insects, crustaceans, worms and small molluscs make up most of their diet, Eastern Newts are quick to make a meal of most invertebrates that end up in the water.

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Spotted Salamander Larvae Soon To Emerge From Eggs

spotted salamander eggs2  040Roughly a month after spotted salamanders participate in frenzied courtship dances, deposit spermatophores (males) and take the spermatophores into their bodies (females), the resulting eggs have developed into larvae.  These juvenile, gilled salamanders are still contained inside the gelatinous eggs, but the eggs are dissolving fast, and the larvae will soon be swimming free within the vernal pools where the eggs were laid.

Many spotted salamander larvae do not survive this long.  Eastern newts, caddisfly larvae, leeches, fly larvae and even turtles feed on the nutritious eggs.  Meteorological conditions also contribute to the fate of spotted salamander eggs.  Their situation is especially precarious because they develop in vernal pools, which often dry up by summer’s end, thus forcing a rapid metamorphosis for amphibious inhabitants.  Hot temperatures can evaporate the water before metamorphosis is completed, and cool temperatures can slow down their development.  Inevitably some will survive to adulthood, and  the inch-and-a-half to two-inch salamanders (see insert photo), having shed their gills and developed lungs, will adapt to a terrestrial life.

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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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Wood Frog Egg Matts

wood frog egg mass IMG_2760Now that normal spring temperatures have returned, the air around vernal pools is once again filled with the clacking/quacking calls of male wood frogs hoping to attract females. Once this has been accomplished, most paired wood frogs head to the same general area in the pool to mate.  The resulting egg masses, each consisting of several hundred eggs, form a communal cluster, or “egg matt,” on the surface of the water.  Eventually algae will start growing on the jelly-like substance surrounding the eggs, causing them to resemble pond slime – an effective camouflage.  The gelatin covering, the size of the communal cluster, and exposure to the sun all help the eggs to be warmer than the surrounding water and they develop quickly – a necessity if one is to metamorphose into an adult before the vernal pool dries up.

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“Big Night” Hazard

big night 2016 IMG_7612Every year in early spring on a rainy night spotted, blue-spotted, Jefferson and four-toed salamanders, wood frogs, and spring peepers leave their leaf litter and subterranean winter hibernacula and migrate to their ancestral breeding pools to mate.  Sometimes there are roads between these two sites.  Vehicles driving these roads inevitably kill thousands of salamanders, wood frogs and spring peepers every year.  Concerned citizens have set up teams to try to scoop up these nocturnal travelers and escort them to the side of the road in which they were headed.  While this action definitely helps, it is hard to find enough generous volunteers to man every crossing on every road all through a rainy night.

In Monkton, Vermont, Jim Andrews, Steve Parren and Chris Slesar, along with the Lewis Creek Association and the Monkton Conservation Commission, spear-headed an effort this past year to do something about the mortality of hundreds of migrating frogs and salamanders. Grants, plus a large number of organizations and citizens, provided the manpower and finances to construct two concrete culverts under a road in a location where the road separates the breeding pools of amphibians from their upland wintering grounds.

In the past, hundreds of migrating amphibians were killed in this location by automobiles during every spring and fall amphibian migration, and it is doubtful whether the population would have been able to sustain itself over time. (In the past month, 673 salamanders and 329 frogs have safely passed through the tunnel.  In addition, a few early migrators (16) have already started coming back up hill.) Hopefully, these will be the first of many such culverts in the Northeast. For further information on the Monkton underpasses, go to:  http://www.burlingtonfreepress.com/story/news/2016/03/28/hundreds-saved-new-vermont-salamander-crossing/82336084/.  (photo:  spotted salamander)        

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Wood Frogs & Spring Peepers On The Move

3-29-16 road frogs 015Although the temperature hovered around 32°F.  last night in central Vermont, wood frogs and spring peepers were on the move.  Usually it is above 40° or 45° before you see the earliest of our breeding amphibians, but a few hardy souls ventured forth to their breeding pools and ponds under cover of darkness and  rain yesterday.  Those that breed in vernal pools are in a hurry to take advantage of every day, as the eggs they lay must complete metamorphosis by the time their pool dries up, often in mid- to late summer.

Both of these species of frogs are freeze tolerant.  Wood frogs are coming out of a state in which they haven’t taken a breath and their heart hasn’t beaten for several months.  Prior to hibernation they convert glycogen in their bodies into glucose, a form of antifreeze that helps prevent the water within their cells from freezing, which would kill them.  However, the water outside their cells does freeze.  Amazingly, wood frogs can survive having up to 65% of this water frozen, yet when warm weather arrives, they thaw and move about in a matter of hours.

If you rescue these woodland amphibians that are crossing roads (where so many of them get run over at night) during their migration to their breeding pools, take note of the temperature of their body.  Often they are still quite cold to the touch — colder than the air, even – which fortunately makes it difficult for them to move fast enough to escape your helping hands. (Photo: Amorous wood frogs getting a head start as they cross a road to get to breeding pool.)

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Spring Peepers Peeping

12-16-15 spring peeper IMG_7853The sound of a peeping Spring Peeper in December (yes, this occurred in Vermont this week) conveys to one and all that climate change is not a figment of our imagination. Amphibians are extremely sensitive to small changes in temperature and moisture due to their permeable skin and shell-less eggs. Certain species, including Spring Peepers, Grey Tree Frogs, Wood Frogs, American Bullfrogs and American Toads, are emerging and mating earlier in the year than they did historically. Causal relationships have been found between irregular climate conditions (drought, increasing frequency of dry periods and severe frosts) and decreasing (extinction in some cases) of certain amphibian species.

Behaviorally and physically, warming temperatures are having an impact on amphibians. A recent laboratory study investigated changes in amphibian metamorphosis time due to pond desiccation and whether amphibian immune systems become compromised as a result of these changes. They found that amphibian immune responses became increasingly weaker and white blood cell counts were increasingly lower with higher desiccation. As a result of climate effects, immune systems are weakened, making it more difficult for amphibians to fight off diseases.

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