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Field Notes: Know your salamanders

An adult mudpuppy found during a snorkeling survey over the summer. Surveys consist of flipping rocks until locating a mudpuppy. After all data is collected, mudpuppies are released back under the rock that they were originally found.
Wisconsin DNR
An adult mudpuppy found during a snorkeling survey over the summer. Surveys consist of flipping rocks until locating a mudpuppy. After all data is collected, mudpuppies are released back under the rock that they were originally found.

From late March to mid-May, the road into Presque Isle Park in Marquette, MI is closed from dusk to dawn. Now why would they do that? To discourage hooligan teenagers with spring fever? No, it is to make sure that salamanders can cross from the wooded areas where they live most of the year to the temporary ponds where they mate and lay their eggs.

Salamanders, newts and mudpuppies are amphibians, and they are all salamanders, but not all salamanders are newts or mudpuppies. Unlike reptiles, amphibians do not have scales and must lay their eggs in water. Unlike other amphibians such as frogs and toads salamanders keep their tails throughout their lives and have long slender bodies. They also have short legs designed for walking and swimming whereas frogs and toads have legs meant for jumping. They must keep their skin moist so they generally live in damp woods or near a pond or creek.

Salamanders are all around us, but they are secretive and hard to find unless you know where to look. We have seven species in Wisconsin, and the most common species, the Blue spotted salamander, is most often found in damp woods under logs or rocks. Like most of Wisconsin’s salamanders they live most of their life in woodlands but, like their Marquette buddies, must get to a fish-less wetland to reproduce. Some salamanders, including the mudpuppies and newts, are aquatic.

But, then that isn’t quite right either because the newts spend some time on land. Nature is very messy.

When the eggs of terrestrial salamanders, such as the blue-spotted salamander, hatch they look like small adults, except that they have external, frilly-looking gills for breathing underwater, a strong tail and relatively weak legs. The larvae eat small invertebrates such as mosquito larvae and small crustaceans. The larvae metamorphose into adults and lose their external gills and may grow to be about 5-6” long. These terrestrial salamanders breathe through their skin, which must
always stay moist, even though they do not actually live in the water. Adults eat mostly invertebrates such as earthworms and slugs and in turn are prey to snakes, wading birds and racoons. In the fall, they find a burrow below the frost line where they will spend the winter.

Newts have a different life history, physical features and physiology than other salamanders. Newt larvae are aquatic and have webbed feet and the fluffy external gills typical of the terrestrial salamanders. When newts metamorphose, they lose their external gills and develop lungs and no longer breathe through their skin. These juveniles move onto land and at this point are known as “efts”.

They must return to water to reproduce, and some remain aquatic while others become largely terrestrial. Eastern newts produce an extremely toxic neurotoxin on their skin, tetrodotoxin, a toxin much more poisonous than cyanide, which deters predators from chowing down on what must seem like an appealing snack.

Now, I am a biologist but even I blushed reading about the newt sexual shenanigans. Males and females get it on with hula dances and rubbing of different parts on other parts. The male drops some sperm-containing droplets called spermatophores which the female picks up with her cloacal lips. And if you don’t know what cloacal lips are, I suggest you use your imagination.

The third group of salamanders is the mudpuppy. Mudpuppies are Wisconsin’s largest (they are often about a foot long) and only fully aquatic salamander. They never lose their frilly external gills. They will eat anything they can fit in their mouths, including each other. Mudpuppies don’t mature until they are about six years old and typically live about 11 years in the wild. They are quite adorable, but they are very slimy. They love the cold and are most active in winter. Perhaps for this reason, ice fisherman will often catch mudpuppies. They are much less active in summer and mostly hide under rocks.

Now for a slight diversion to freshwater mussels: You may know that freshwater mussels release their fertilized eggs near a fish, so that those eggs will take up residence and develop in the fish’s gills. (I recommend you look this up on YouTube – it is absolutely amazing). Only the Salamander Mussel infects the mudpuppy instead of a fish. Since the mudpuppy retains its external gills throughout its lifetime, the mussel development will not be interrupted by untimely salamander metamorphosis.

So grab a flashlight tonight and turn over a rotting log or two and hunt for salamanders. There is no end to entertainment opportunities here in the Northwoods.

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Susan Knight works for the University of Wisconsin-Madison’s Center for Limnology at Trout Lake Station and collaborates closely with the Wisconsin Department of Natural Resources. She is involved in many aspects of aquatic plants, including aquatic plant identification workshops and research on aquatic invasive plants. She is especially fond of bladderworts.
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