Reptiles and Amphibians

Salamander Migration

Salamanders in Massachusetts are threatened by many man-made circumstances: loss of habitat, highway mortality, acid rain, and pesticides. Understanding salamander behavior has led to methods that lessen the impact of humans on salamanders. These include the creation of special tunnels that allow them to cross under roadways, closing specific roads on the first warm rainy nights of spring, and the definition and preservation of critical salamander habitat.

MASSACHUSETTS SALAMANDERS

Spotted salamander by Leo Kenney, www.vernalpool.org

There are four different families of salamander species in Massachusetts including newts, mudpuppies, and lungless salamanders. One of our most common species, the spotted salamander, belongs to the fourth family, the mole salamanders.

LIFE CYCLE OF SPOTTED SALAMANDERS

Adult spotted salamanders are mostly nocturnal, reside mostly underground, and can live over 20 years. They grow up to nine inches long and are blackish with yellow spots in patterns unique to each individual. They eat earthworms, slugs, and small insects. After spending the cold months underground, they emerge in late winter to migrate to their aquatic breeding sites, most likely the very site where they were born.

Breeding

Most individuals in the area arrive at the breeding site on the same night. The specific trigger for this coordinated migration is determined by a combination of factors including ground and air temperature, humidity, barometric pressure, and darkness. In general, the first rainy night over 45 degrees Fahrenheit, after the ground has thawed, is sufficient to trigger the migration.

Eggs and Larvae

Once they have arrived at a wetland pool, the males gather in groups of 12 to 200 called congresses. They then entice the females with an elaborate courtship dance. The males deposit gel-like structures with sperm packets attached, on the twigs and leaf litter in the pond. The females then pick these up and use them to fertilize their eggs internally. A few hours to days later the female will deposit 100 to 300 eggs in a clear mass about the size of a tennis ball on a rock or twig below the pond's surface. The adults then leave the pond on the next wet, warm night and travel to their summering ground - usually in an abandoned rodent hole or under a rock or log.

In a couple of weeks the egg mass becomes greenish due to the growth of algae which may provide oxygen for the developing embryos. In drought years the water levels may drop low enough to expose and kill the eggs. Other factors affecting water quality, such as acidity, will also determine survival. Those that survive will hatch into 1/4-inch larvae in a month or two, depending mostly on water temperature.

The babies have head, body, and tail sections, and after only a few days, begin to form limbs. They generally eat small animals such as zooplankton and insect larvae, but sometimes will eat other salamander larvae as well. But no matter what they eat, the important thing is to find enough food to metamorphose before the pond dries up.

The other big trick is to avoid predators, which include diving beetles and dragonfly nymphs. If they manage to survive this early stage of life, however, the young salamanders then lose their tail fin and gills, develop lungs, and crawl out of the ponds by mid-summer to late fall. They won’t return to the pond until they mature in 2 or 3 years, at which point they will start the process all over again for the next generation.

PROTECTING SALAMANDERS DURING MIGRATION

Hundreds of salamanders are killed each year by traffic, as they attempt to cross roads on their migration route. In towns across Massachusetts, wildlife enthusiasts wait for the night of the big migration and get out there to help. This involves identifying the roads that cause a problem, and temporarily closing them, or physically carrying the salamanders across.

Although not a solution to the loss of critical habitat, tunnels under roads (a.k.a. amphibian migration corridors) have been successful in some areas as well.

VERNAL POOL IDENTIFICATION AND PROTECTION

Half of all Massachusetts salamanders species breed in vernal pools, temporary ponds which are created by spring rains and snowmelts and will dry up by mid summer. Vernal pools are suited for breeding salamanders because they lack fish and turtles, which would prey on the developing larvae. Because they only exist for part of the year, many vernal pools are overlooked when wetlands are identified and not encompassed by the regulation of the Wetland Protection Act. In addition, preservation of the surrounding uplands is critical to the survival of many of the vernal pool species, because these amphibians spend most of their lives in the woods, not in the water.