Amphibians On The Move
According to Jim Andrews, Director of the Vermont Reptile and Amphibian Atlas Project (https://www.vtherpatlas.org), the recent warm rain triggered a significant movement of many amphibians in the Lake Champlain Basin as they left their hibernation sites and migrated towards their breeding grounds. Blue-spotted Salamanders (& hybrids), Four-toed Salamanders, Spotted Salamanders, Eastern Red-backed Salamanders, Eastern Newts, Spring Peepers and Wood Frogs were among those seen emerging from their hibernacula.
Keep your eyes peeled on warm (40°+), rainy evenings and see if you discover a popular amphibian road- crossing location. Check local resources to see if there is a local volunteer group that assists these slow-moving migrants across the road. If not, you could start one yourself – be sure to wear reflective clothing, have a flashlight and report your findings to a local nature center or conservation organization. (Photo: Blue-spotted Salamander by Erin Talmage)
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Eastern Red-backed Salamanders Still Active
The Eastern Red-backed Salamander is the most abundant terrestrial vertebrate in New England. Unlike many salamanders, it is terrestrial year-round – living, mating, laying eggs, feeding, and hibernating.
Eastern Red-backed Salamanders can occur in two color phases, lead-back and red-back. The lead-back phase salamanders are a consistent gray to black color while the red-back phase is characterized by an orange to red stripe down the length of their body and tail. In both phases, they are distinguishable by their mottled white and black undersides and five toes on their hind feet.
Due to its lack of lungs, this slender salamander must live in damp or moist habitats in order to breath. It is active into late fall, inhabiting rotting logs or living under moist leaf litter, bark, stones, etc. When cold weather really sets in, it will hibernate down to 15 inches in the soil, or in deep leaf litter or rock crevices. (Congratulations to Helen L., the first NC reader to correctly identify the latest Mystery Photo as an Eastern Red-backed Salamander!)
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Fall Amphibian Migration
The 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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Eastern Newts Dining On Hapless Dragonflies
Inevitably, 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
Roughly 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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Eastern Red-backed Salamanders Migrating Downwards
Eastern Red-backed Salamanders reside in the leaf litter throughout the Northeast during the summer months. Here they scent-mark their territories on the forest floor with pheromones and fecal matter in order to convey information concerning their body size and gender to other Red-backed Salamanders. If the temperature soars or the humidity drops, these salamanders do just what they do in the fall – seek deeper, moister protected areas such as beneath stones, under and within rotting logs and stumps, or underground in animal burrows.
Whereas they migrate downwards in summer to avoid the heat and dry air that would impair their ability to breathe through their skin, these salamanders are avoiding the approaching cold when they migrate downwards in the fall. Red-backed Salamanders are not freeze tolerant, and thus must avoid freezing temperatures. Once ensconced in a freeze-free hibernaculum, they usually remain there until snowmelt.
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Spotted Salamander Larvae Feeding
A few short weeks ago spotted salamanders gathered at vernal pools to breed and lay eggs. Since then their eggs have started hatching, and gilled spotted salamander larvae can now be found in these pools. The larvae are major predators and consume many insects and crustaceans, including mosquito larvae and fairy shrimp. During the next two or three months, these larvae will develop lungs, absorb their feathery gills and begin life as terrestrial amphibians, assuming the temporary pools they are in don’t dry up prematurely.
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Eastern Newts Dining on Wood Frog Eggs
Wood Frogs mate and lay their eggs in ponds and occasionally vernal pools before heading back to their terrestrial, wooded habitat. Amphibian eggs are subject to predation by numerous predators, including leeches, fish, aquatic insects and salamanders. Eastern Newts (aquatic as larvae and adults) are carnivorous and consume insect larvae, fingernail clams, leeches and amphibian eggs, among other things. At this time of year, Wood Frog eggs are plentiful and easily accessible, as the individual masses, each consisting of 1,000 to 2,000 eggs, are deposited adjacent to each other on submerged vegetation. Hungry newts can feed for hours without moving more than an inch, and many often do. After discovering an egg mass, a newt plunges its head into the clump of eggs, grabs one and, with great shaking of its head, separates an egg from the mass and quickly swallows it. Seconds later the newt repeats this process, and continues doing so until it is satiated.
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Spotted Salamander Spermatophores
After male spotted salamanders emerge from hibernation and arrive at their ancestral breeding (vernal) pools, they cluster in groups called congresses, await the arrival of females, pair up with one and then the pair performs a courtship dance.
Unlike some species of amphibians, the male spotted salamander does not fertilize the eggs as the female lays them. Rather, she collects his sperm into her body and internal fertilization takes place. When the female is sufficiently stimulated, the male deposits up to 80 spermatophores (pyramid-shaped plugs of mucus with a sperm capsule at the top), often on a submerged branch. The male maximizes the chances of insemination by depositing many scattered spermatophores, covering every spermatophore he encounters, even his own, with a new spermatophore. In so doing, he increases his spermatophore count, while simultaneously eliminating a rival’s spermatorphores. The female then crawls over a spermatophore and positions her vent, or cloaca, so as to allow the lips of her cloaca to detach the sperm capsule.
Within a short period of time the salamanders retreat back to the woods, rarely to be glimpsed until next spring’s breeding season. (Photo: spotted salamander spermatorphores, with sperm capsule missing on far left spermatophore)
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Juvenile Eastern Newts Leaving Ponds
Eastern newts, those four-inch long, red-spotted, olive-green, aquatic salamanders that inhabit most ponds, breed throughout the summer and well into the fall. Their eggs hatch in three to five weeks and the aquatic larvae are equipped with gills with which they breathe for the next three months or so. By late summer and early autumn the inch-and-a-half-long larvae begin to reabsorb their gills and develop lungs and a rough-textured skin. These tiny, young salamanders start to emerge from ponds and live on land, gradually turning reddish-orange. We refer to the juvenile eastern newt salamander during its terrestrial stage as a red eft. After spending two to five years on land, red efts return to the water, regain their green coloration and live the rest of their life as aquatic eastern newts. (Photo: A juvenile eastern newt that just emerged from a pond and has yet to attain the reddish-orange color of a red eft, on a quarter for scale. The darker patch on its neck just before its foreleg is where gills were once located.)
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Eastern Red-backed Salamander Eggs Hatching
If you make a habit of looking under (and carefully replacing) rotting logs lying on the forest floor, sooner or later you will be rewarded with the discovery of an eastern red-backed salamander. These three to four-inch salamanders can be completely gray, gray with a reddish stripe down the center of the back or bright orange-red. The color of a redback is often related to elevation. Those with a stripe down the back (pictured) are usually found at upper elevations, while the gray phase often inhabits lowlands.
Eastern red-backed salamanders are entirely terrestrial, mating in the spring and fall and laying their eggs in rotting logs (particularly conifer) and leaf litter. Females remain with their eggs, defending them from predators. The larval stage of a redback is quite long –two months– and most of it takes place inside the egg, so when the eggs ( laid in the spring) hatch in the fall, the young, three-quarter-inch salamanders are within days of completing metamorphosis and transforming into adults. (This strategy eliminates the need for eastern red-backed salamanders to find standing water to complete their larval stage.)
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Dragonfly Eclosure: A Vulnerable Time
Dragonfly larvae reside in ponds until the time comes for them to climb up stalks of emergent vegetation or adjacent rocks, split their larval skin and emerge as adults (a process called eclosure). Before it can take flight, a dragonfly has to cling to the substrate long enough to expand its wings by pumping fluid into them, and dry its exoskeleton as well as its wings. During this time the dragonfly is extremely vulnerable – not only can it not fly, but it is usually situated directly above the water. The slightest breeze can blow it from its precarious perch into the water below, where opportunistic predators such as this Eastern Newt are at the ready and make quick work of their helpless prey.
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Determined Spotted Salamanders
It’s rare to get a glimpse of a Spotted Salamander – these secretive amphibians spend most of their lives hidden under rocks or logs or in the burrows of other forest animals, emerging only at night to feed and during spring mating. In central Vermont, the annual mass migration of Spotted Salamanders to their ancestral breeding pools began two nights ago, when the rain-soaked earth and rising temperatures signaled that it was time to emerge from hibernation. Unfortunately for the salamanders (and frogs) that answered the calling, temperatures dropped relatively early in the evening, and the rain turned to snow. Undaunted, these stout salamanders continued their trek through the woods, plowing their way through new-fallen snow, all in the name of procreation.
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Tracks Reveal Spotted Salamander Defense Mechanism
Red Foxes have a very diverse diet – birds, small mammals, snakes, frogs, eggs, insects, fish, earthworms, berries, fruit — the list is endless and this diversity is part of the reason that foxes thrive in almost any habitat. However, the fox whose tracks I was following recently passed up a meaty meal – that of a Spotted Salamander. The story the tracks tell suggests that the fox dropped the salamander after unearthing it from its hibernaculum and carrying it some distance. It’s likely that it had detected the sticky white toxic liquid that Spotted Salamanders secrete from poison glands in their skin when they are threatened. Unfortunately, detection did not occur in time to save the salamander’s life. Either its experience with the fox and/or freezing temperatures killed the salamander, preventing it from going back into hibernation. (Note red fox tracks to right of salamander.)
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Eastern Red-backed Salamanders Headed for Hibernation
Unless you spend time looking beneath rotting logs or sifting through the leaf litter, you’re not apt to see an Eastern Red-backed Salamander, even though they are prolific in our woods. Studies have found over 1,000 of these salamanders inhabiting one square acre of woodlands. Eastern Red-backed Salamanders are not freeze tolerant so they must spend the winter in locations that don’t freeze if they are to survive. Once the temperature drops to the 30’s and 40’s, they migrate downwards and hibernate in deep leaf litter, under rocks or in rock crevices, and as much as 15 inches under the ground in animal burrows.
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Spotted Salamanders Emerge From Hibernation
Under the stealth of a rainy night, subterranean-dwelling spotted salamanders migrated to their ancestral breeding pools this week. Groups, or “congresses,” of males gather, followed by females. Once a female locates a congress of males, she eventually pairs up with one of them. The pair of salamanders then engages in a courtship dance ending with the male depositing a tiny white packet of sperm called a spermatophore on the bottom of the vernal pool. If he has sufficiently stimulated the female, she picks up this packet into her cloaca, or vent, and fertilization takes place. The next morning the only sign that spotted salamanders have been and gone are the unclaimed spermatophores scattered on the leaves that lie on the pool bottom.
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