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Often mistaken for lizards, these moist-skinned, secretive creatures play a very important role in nature, especially in woodland and wetland habitats. They are much more abundant than most people realize, but are still very sensitive to changes in their environment. As a fundamental part of our natural heritage, it is essential that we ensure their survival.
Salamanders, along with the closely related frogs and toads, belong to the group of animals called amphibians. Like fish, reptiles, birds, and mammals, amphibians have a bony skeleton. But unlike their vertebrate relatives, amphibians typically have moist, smooth (or bumpy) skins, lay unshelled eggs in water, and hatch out as gilled fish like larvae that eventually undergo metamorphosis into a lung breathing, land living or semi aquatic adult. (A few kinds keep their gills, and live underwater permanently.) Twenty three species of amphibians have been recorded from the waters, wetlands, and woodlands of Michigan. Thirteen of the State's amphibians are frogs and toads, and the remaining ten species are salamanders.
The conspicuous (and seasonally noisy) frogs and toads are familiar to most people, but the silent and secretive salamanders are largely creatures of mystery. When salamanders are seen during their rare above ground migrations, many people mistake them for lizards, which they vaguely resemble. However, the thin skinned, moisture loving salamanders are not at all closely related to the lizards, which are scaly-skinned, warmth loving reptiles that lay shelled eggs on land.
Most native salamanders spend the majority of their lives hidden under forest soils and leaf litter, or (in the case of Mudpuppies and Sirens) on the bottoms of ponds, lakes, or streams. Salamanders can absorb water, and even take in oxygen and release carbon dioxide ("breathe") through their thin skins. Most adult salamanders also breathe with lungs, though the little Red backed and Four toed Salamanders lack lungs completely, and do all their breathing through the skin. Salamanders require cool, moist habitats, and they soon die if exposed to the hot sun, or confined in dry places.
Salamanders have some very unique breeding habits. In most species, the fertilization of the eggs takes place before they are laid even though the male and female never actually mate! To find out how this can be, let's take a close look at the reproductive habits of a common Michigan species, the Blue-spotted Salamander. In very early spring these salamanders leave burrows in woodland soil where they over-wintered and migrate to shallow, temporary ponds. (This migration often occurs with the first snow melting rain of the season, when the ponds are still partially covered with ice!) In the water, a male "blue-spot" will court a female by nudging her head and body with his snout and chin, and then grasping her behind the front legs with his own forelegs. Eventually, the male crawls ahead of the female and deposits a small cone-shaped glob of jelly like material capped with sperm, called a spermatophore. The female can then crawl over the spermatophore and take the sperm into her cloaca (an internal chamber near the base of her tail) through the anal opening. Her eggs are then fertilized inside her body, perhaps one to several days before being laid.
The Blue-spotted Salamander's eggs are laid in protective jelly like masses attached to underwater twigs or vegetation; each mass contains from one to a dozen or more eggs, and a large female might produce several hundred eggs. Salamander egg masses resemble the egg masses of frogs, but salamander eggs tend to be larger and fewer in number. Other differences with frogs show up soon after hatching the salamander larvae retain externally visible gills and soon develop their front and then hind legs. They feed on small aquatic animals like insect larvae, copepods, fairy shrimp, and even other amphibian larvae. In contrast, frog larvae (called tadpoles) soon hide their gills under the skin, develop their legs more slowly (back legs first), and feed mostly on algae, plankton, and decaying organic material.
Transformation of larval Blue-spotted Salamanders into the adult form takes place in mid to late summer. The gills and tail fins are absorbed, as lungs take over respiration and legs grow stronger. The juvenile salamanders then leave the water (often during rainfall) and hide in pondside leaf litter. They remain fully carnivorous, feeding on worms, insects, other invertebrates, and sometimes smaller salamanders! The young salamanders first breed when two or three years old.
The breeding habits of most Michigan salamanders resemble (with minor variations) those of the Blue-spotted Salamander, but there are exceptions. The adult Eastern Newt, despite lacking gills, is mostly aquatic, but their larvae transform into brightly colored, landing living "efts." The eft has fairly rough looking skin (for a salamander), and may remain on land for several years before returning to the water to become a greenish colored breeding adult.
Another notable exception is the common woodland Red-backed Salamander. Female "red-backs" do not lay their eggs in water instead the eggs are typically deposited (and are attended by the female) in a cavity under a rotting log or stump. The "larval stage" is completed within the egg, and the baby salamanders hatch out looking like miniatures of their parents. Without free swimming larvae, Red-backed Salamanders are able to live in woodlands that lack vernal ponds.
Some salamanders lack a land living stage and spend their entire lives in water. Mudpuppies reproduce with spermatophores in the usual manner, but retain gills throughout life. Living in deep lakes or rivers allows them to remain active all year. The reproductive habits of the eel like Lesser Siren (possibly extirpated from Michigan) are poorly known; it is possible that they have external fertilization. In some places, salamanders that normally have a land living adult stage may fail to transform, and instead become sexually mature and breed in their aquatic, gilled form. A few population of Tiger Salamanders in northern Michigan reportedly have this habit.
Many predators will eat salamanders and their larvae, including fish, frogs, snakes, birds, and small mammals such as shrews, raccoons, and skunks. Large salamanders sometimes eat smaller ones even their own siblings! Most salamanders (once they become terrestrial adults) spend the vast majority of their time hidden in soil or forest debris, and are vulnerable to enemies only during the brief spring breeding season.
Our native salamanders are generally harmless creatures which appear to be almost defenseless, but they do have a number of defenses against predators. Many species have skin glands that produce distasteful or even poisonous substances to repel predators. The skin toxins of the terrestrial "eft" stage of the Eastern Newt are poisonous enough that small animals may be sickened or killed by eating them though few actually try, having been warned off by the eft's bright red or orange color. The red color phase of the Red backed Salamander (a relatively non toxic species) may gain some protection by mimicking the eft's bright colors. The "mole" salamanders (genus Ambystoma) have concentrations of poison glands on their tails, which may be lashed at an attacking predator. Salamander skin glands also produce a protective mucus covering that can make the animals very difficult to hold on to. The aquatic Mudpuppy is a prime example trying to grasp this creature in hand has been likened to gripping a wet bar of soap!
If attacked by a predator, the smaller salamander species can drop portions of their tails. The lost tail piece will continue to wriggle, perhaps confusing the predator long enough to allow the salamander to escape. Later, they can re-grow a new tail. Some scientists are studying about the ability of the salamanders to regenerate new arms, legs and tails.
Despite being secretive and inconspicuous, salamanders play important roles in nature, especially in woodland and wetland habitats. They are predators on smaller creatures, such as insects, spiders, and worms, and in turn are eaten by a variety of larger animals, from song birds to bears. Several studies in moist forests show that the numbers and biomass (living weight) of salamanders can equal or surpass that of other vertebrates, such as birds and mammals a strong indication of their ecological significance. The little Red backed Salamander was the most abundant species in Michigan studies, with estimates of up to 3600 salamanders per acre (9000 per hectare) of woodland reported.
Many human activities can harm salamander populations. Their eggs and larvae are threatened by the destruction of shallow ponds and wetlands. (Many people fail to realize the critical importance of wetlands that may be dry for half the year!) When forest trees are harvested by humans, the resulting higher ground temperatures and lowered humidity can quickly eliminate most or all of the resident salamanders. Contamination of habitats by pesticides, fertilizers, sewage, or industrial and farm wastes are additional threats.
Recent concerns about the decline of amphibian populations in many parts of the world have been mainly focused on frogs and toads which are often relatively easy to detect and survey, due to their distinctive breeding voices. Salamanders are affected by the same environmental factors as their noisier relatives, but are more challenging to find and study. It will be well worth the extra effort to monitor the health of salamander populations, as these skulking creatures can tell us much about the health of our woodland and pond environments.
Amphibians and Reptiles of the Great Lakes Region. By J. H. Harding. University of Michigan Press, 1997.
Key for the Identification of Wisconsin's Larval Amphibians. By D.J. Watermolen and H. Gilbertson. Wisconsin Endangered Species Report 109, Wisconsin Dept. of Natural Resources, 1996.
Michigan Frogs, Toads, and Salamanders. By J.H. Harding and J.A. Holman. Michigan State University Extension, 1992.
Salamanders of Ohio. Edited by R.A. Pfingsten and F.L. Downs. Bulletin of the Ohio Biological Survey, 7(2), 1989.
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