They are so secretive, most people don’t even know they exist. In their more than 30-year lives they have little or no contact with humans. If you were to tell your neighbors that 9-inch-long black salamanders with yellow spots live in the woodlands of their town, they might well be surprised.
Recently, I was walking by a vernal pool at a nearby state park and noticed a sign that salamanders had been there: a small, round egg cluster in the water. If you spy an egg mass in a vernal pool, it may be from a Spotted Salamander. Weeks ago, on a day when the first warm rain started and continued through the evening, 6- to almost 10-inch (15 to 25 centimeters) salamanders emerged from the ground and migrated en masse to shallow, often temporary, pools to mate. Most people don’t know about these amphibians, in a group called mole salamanders, because they are fossorial, spending most of their time below ground except when they emerge on rainy nights to mate or feed on crickets, spiders, slugs, and other invertebrates.
During the brief mating time, males arrive at the pools first and form a gathering called a congress. Jonathan Twining of Eastern Nazarene University has filmed this rarely seen underwater phenomenon (see his video here). When a female arrives, she and a male “court.” The male will rub the upper and lower surfaces of the female and she will nose the male’s back during the height of activity. This stimulates the male to deposit a sperm packet, a spermatophore, near her. She will pick up the spermatophore (or one nearby) with her cloaca to fertilize her eggs. A few days later, she’ll lay up to 200 eggs in that rounded cluster. The eggs will hatch in one to two months.
Spotted Salamander egg masses can be confused with the egg clusters of the Wood Frog (Rana sylvatica), which are also found in vernal pools. But the Wood Frog’s egg masses don’t have the clear jelly-like covering on the entire cluster like the eggs of the Spotted Salamander. Within the same pool, some Spotted Salamander egg masses can be clear, and some can be opaque. This is because of certain proteins in the clusters. Researchers are not clear what advantage one has over the other. I’ve often noticed green algae covering the egg masses. Scientists have discovered a symbiotic relationship between this alga, Oophila amblystomatis (the name means “loves salamander eggs”), and these eggs. This alga is found nowhere else in nature. It provides oxygen for the developing eggs, and the eggs in turn make carbon dioxide for the alga.
When the salamander larvae hatch they feed on small invertebrates in the vernal pool, like zooplankton, isopods, and amphipods. Two to four months after hatching, the larvae will lose their gills, develop lungs, and transform, or metamorphose, into young salamanders. They are then ready to live on the ground. It’s always a race to leave the water before the vernal pools dry up in mid to late summer. There are some years when the larvae don’t make it in time.
Many conservation issues surround these creatures. It is unclear how climate change might affect water levels in vernal pools through time. Habitat fragmentation, especially in places where salamander migration routes cross the asphalt roads that humans use, can be disastrous. A salamander that can live to be 32 years old may be killed in an instant by a passing car. Many amphibians are slaughtered each year by vehicles during warm spring evening rains. Some town residents, donning reflective clothing and flashlights, form “bucket brigades” and stop traffic temporarily to help crossing salamanders and frogs. In response to a local road kill area in Amherst, Massachusetts, in 1987 the Hitchcock Center for the Environment, Amherst Public Works, the Massachusetts Audubon Society with the help of volunteers created one of the first salamander tunnels in North America. Such tunnels funnel the amphibians under a road. The Amherst amphibian population seems to be holding steady.
Something perhaps for your own town to consider? At the very least, when driving near wetlands on a rainy, warm spring evening, please be extra cautious and slow down.