Marauding Salamanders: Earliest Sign of Spring
by Jeremy Feinberg
Article first published in Trail Walker, March/April 2009
When most people think about spring, they probably envision the arrival of warm weather, bright sunshine, birds calling, and flowers blooming. However, if you consider things from a slightly different perspective, there is an alternate universe of spring awakenings that people are seldom aware of. While the idea of thawing ice, rainy nights, and temporary puddles of waist-high water (known as "vernal pools") may not sound spring-like or exciting to most people, to some, especially herpetologists, these conditions are ideal for observing one of the first true signs of spring. A herpetologist is someone who studies reptiles and amphibians, and if you find one (or more) of them out in conditions such as these, they are likely to be searching for one thing in particular - salamanders.
There are approximately 15 species of salamander living in the New York-New Jersey metropolitan area. Some species breed over extended periods of time and in unique habitats, such as the redback salamander (Plethodon cinereus), which breeds on land, or the spring salamander (Gyrinophilus porphyriticus), which breeds in isolated springs and small tributary streams. However, most of the largest, well known salamanders in our region are members of the genus Ambystoma, commonly referred to as "mole salamanders." There are four members of this group in our region (or five depending on the outcome of a debate over two species that hybridize). These salamanders are characterized by explosive breeding migrations during the first few nights of thawing spring rain, usually in March.
Explosive migrations involve a mass terrestrial movement of adult salamanders to their breeding wetlands, often the same pond where they themselves were born. Male salamanders may arrive before females, and leave behind a sperm packet known as a spermatophore. Females will follow in search of spermatophores. After fertilization, the female deposits a jelly-like egg mass. Within a few hours to a few days, the adult salamanders disappear and return to their subterranean upland habitats.
Aquatic salamander larvae (similar to tadpoles) emerge from the eggs after several days. The predatory larvae develop quickly, and if lucky, survive to lose their gills and venture onto land as young adults after several months, hopefully before their pond dries during summer.
Mole salamanders are typically associated with vernal pools and other temporary wetlands (e.g. wet meadows, agricultural wetlands, ditches) where predatory fish are not an issue. In addition to this essential aquatic breeding habitat, adjacent terrestrial upland habitat is also critical for nearly all the remaining non-breeding needs of the adults. Salamander populations cannot persist in one habitat without the other.
Depending on where you are in our area, there may not be any habitat for salamanders or there may be dozens or even hundreds of different breeding wetlands scattered within a particular area. At night, people with a little knowledge, care, and keen eyesight, may even witness a breeding migration over a roadway. While roads make it easy to see a breeding migration, they are usually catastrophic for the salamanders, as cars rarely if ever stop for slithering salamanders. Juveniles may meet the same crushing fate as they migrate away from their pond later in the year. Some towns have constructed special passageways or have enacted road closures on heavy migration nights.
Vernal pool; photo by Jeremy Feinberg
One of the earliest species to breed is also one of the rarest amphibians in the mid-Atlantic region. The eastern tiger salamander (Ambystoma tigrinum), endangered in both New York and New Jersey, is also the second largest terrestrial salamander in North America. Primarily restricted to pine barrens habitats in our region, this species will breed on any warm, rainy night, even as early as November, December, or January.
The spotted salamander (Ambystoma maculatum), follows on the heels of the tiger. However, they are much more common and widely distributed in our area, especially throughout deciduous forests. Many people have encountered these black, yellow-spotted salamanders at least once in their life.
No discussion of our regional mole salamanders is complete without mentioning one last species that is a bit of a rogue among the others. Marbled salamanders (Ambystoma opacum) follow many of the same rules as the other Ambystoma except for the fact that they breed in the fall, when the wetlands first fill with water after the summer drought, instead of spring. They probably do this to get a jump on the other salamanders they compete with. Marbled salamanders are the smallest of our Ambystoma, so if they were to breed at the same time as the larger species, they would not stand a chance. By breeding in the fall, the aquatic larvae are already well-developed when the other species arrive the following spring.
Other species in our area include: the blue-spotted salamander (Amybstoma laterale) and Jefferson salamander (Ambystoma jeffersonianum) hybrid group as well as the two-lined salamander (Eurycea bislineata), longtail salamander (Eurycea longicauda), northern dusky salamander (Desmognathus fuscus), mountain dusky salamander (Desmognathus ochrophaeus), northern red salamander (Pseudotriton ruber), mud salamander (Pseudotriton montanus), four-toed salamander (Hemidactylium scutatum), red-spotted newt (Notophthalmus viridiscens), and slimy salamander (Plethodon glutinosus).
Explosive migrations! What a great excuse for an evening hike in early spring!
Jeremy Feinberg is a herpetologist and doctoral candidate in the Graduate Program in Ecology and Evolution at Rutgers University. He is interested in understanding the specific factors that lead particular species to become rare or extinct.