By Don Lyman
The Boston Globe, March 24, 2021
A spotted salamander photographed in Needham. TIMOTHY BEAULIEU
The first warm rains of spring, usually around the end of March or the beginning of April, coax an assortment of amphibians from their winter dormancy.
Wood frogs, spring peepers, and a variety of salamanders make their way to vernal pools – small, temporary ponds that form from snowmelt and rain in forested areas. Amphibians arrive by the hundreds to breed at these ephemeral wetlands. Among these amorous amphibians is the spotted salamander.
“At first I was blown away by how cool they are,” said Bryan Windmiller, director of conservation at Zoo New England. “They’re huge! Big black things with yellow spots. Very dramatic animals.”
Windmiller, who studied spotted salamanders in the Concord area for his doctorate at Tufts University in the 1990s, said they are part of a family of salamanders called the Ambystomatidae, or mole salamanders.
Spotted salamanders are the most common of the mole salamanders, and at up to 8 inches long, they are the largest mole salamander species in Massachusetts. They can be found in almost every city and town in the state, said Windmiller.
Spotted salamanders spend about a week breeding in vernal pools before heading back to their burrows in the surrounding forest, Windmiller explained. Males deposit little packets of sperm called spermatophores along the bottom of vernal pools, and females pick up the spermatophores in their cloaca, a multipurpose opening at the base of the tail that’s used for excretion and reproduction.
The females lay eggs that are contained in a gelatinous mass. The number varies, but typically averages around a hundred eggs, said Windmiller. The females prefer to attach their eggs to the branches or stems of submerged vegetation, like buttonbush or sedges, but they’ll plunk their egg masses on the bottom of a vernal pool if there’s no vegetation. The ideal place to lay their eggs is a sunny spot because warmer eggs hatch faster.
Spotted salamander eggs in a vernal pool in Dracut. TIMOTHY BEAULIEU
Interestingly, a symbiotic species of algae, Oophila amblystomatis, grows on spotted salamander egg masses. Windmiller said the algae has a positive effect on the eggs because as the algae photosynthesizes it produces oxygen, which boosts the rate of development of the salamander embryos.
A number of animals, including spotted turtles and newts, will eat spotted salamander eggs, so the faster the eggs hatch, the better, Windmiller said. The eggs usually hatch about six weeks after they’ve been laid.
Once they hatch, the tiny salamander larvae, about half an inch long with feathery gills, face a gantlet of potential predators, mainly aquatic invertebrates such as giant water bugs, backswimmers, predacious diving beetles, and dragonfly nymphs, said Windmiller. They also face the danger that their pools may dry up before the larvae develop into salamanders.
The larvae feed on tiny crustaceans, like daphnia, initially. As they grow bigger they eat various aquatic insect larvae and other amphibian larvae, Windmiller said.
The larvae metamorphose into 2- to 3-inch long salamanders by August, when they leave their aquatic home before their pools dry up, said Windmiller. They make their way to surrounding upland forests where they will spend much of their lives, most within several hundred feet of their breeding pools.
A larva of a spotted salamander. LEO P. KENNEY
Aside from spring breeding season, spotted salamanders don’t get out much. Being amphibians, they need to stay moist, so they spend most of their time underground. They usually live in the burrow systems of small mammals, especially short-tailed shrews, Windmiller explained.
This is pretty remarkable, considering shrews are voracious little carnivores with a high metabolic rate, a big appetite, and eat pretty much anything they can catch. And short-tailed shrews are venomous. Although they don’t pose any danger to humans or other large animals, these 5-inch-long predators produce toxic saliva that can paralyze prey such as mice, frogs, and insects. So, how do spotted salamanders survive living with such creatures?
“Spotted salamanders have glands on their backs that produce toxic skin secretions,” said Windmiller.
Those bright yellow spots on the salamander’s back are warning colors, what scientists call aposematic coloration, explained Windmiller. Warning colors tell potential predators to stay away. So, the spotted salamanders’ toxic secretions keep the venomous shrews at bay.
“I’ve handled hundreds of spotted salamanders,” said Windmiller. “Getting the toxin on your skin is no problem, but be careful not to get it in your eyes. And don’t eat spotted salamanders if you get lost in the woods!”
Some animals, including garter and ribbon snakes, great horned owls, red-shouldered hawks, and raccoons, eat spotted salamanders in spite of their toxic secretions, Windmiller said.
Spotted salamanders feed on invertebrates like millipedes, insects, and spiders, said Windmiller. They spend most of the summer hunkered down but occasionally pop their heads out of their burrows on rainy nights and wait for a potential meal.
Spotted salamanders shuffle around a lot in the fall, said Windmiller, and on warm, wet nights in October and November, you can find them moving from one burrow to another, likely looking for a good spot to spend the winter.
Windmiller said spotted salamanders can live more than 30 years, but one major threat is automobiles. MassWildlife advises motorists to watch for migrating amphibians and to use caution while driving on rainy spring nights.
Windmiller said one of the most amazing things about spring amphibian migrations is how the seemingly empty forest suddenly comes to life.
“You walk around the woods and see nothing,” said Windmiller. “Then you get a rainy night and suddenly there are thousands of wood frogs and spotted salamanders and they swarm down to the vernal pools and congregate together. It’s really dramatic. It shows the link between vernal pools and the forest. And then when the pond dries up, the whole thing just disappears.”
Mass Audubon offers several ways to explore vernal pools in person. Learn more about them here, here, and here.
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