Ambystoma Salamander Ecology

Adults and Breeding

In the spring, adult Ambystoma salamanders may be encountered in our area include Spotted, Blue-spotted and Jefferson Salamanders, and hybrids between Blue-spotted and Jefferson Salamanders. These hybrids can be very difficult to distinguish from either parental species, so we will refer to the whole group as the Jefferson/Blue-spotted complex. In western Pennsylvania in the fall one may also encounter Marbled Salamanders.

Spotted, Blue-spotted and Jefferson Salamanders emerge and migrate to breeding pools in the early spring, usually late March through mid-April, following several days of warm weather, heavy spring rains, and ground thaw. Males deposit spermatophores—small, whitish cone-shaped structures containing spermatozoa—on the pool bottom. These structures are often clearly visible scattered over the leafy bottom in shallow water, and are often concentrated in one area. A female will pick up spermatophores in her cloaca and fertilize her eggs internally.

Eggs

Within several days, the female will lay a number of egg masses, each attached to a stick or other submerged vegetation six inches or so beneath the surface. Egg masses begin somewhat transparent but may become whitish or greenish over the course of several weeks. Each egg within the gelatinous outer layer has its own individual membrane and is clearly visible within the mass. Spotted Salamander egg masses tend to be large, containing fifty to several hundred eggs, and can expand to a diameter of 4–10 cm. Blue-spotted Salamanders lay their eggs singly or in very small masses, containing a dozen or fewer eggs. Jefferson Salamander eggs form elongate clusters containing 20–30 eggs (rarely more.) In the Spotted Salamander the distance between the egg and its external membrane is about the width of the egg, while in the Jefferson and Blue-spotted Salamanders this distance is less than the width of the egg.

Larvae

By late April the salamander larvae should be clearly visible inside each individual egg. They typically emerge in May and hide in leaf litter on the bottom by day. They can be found foraging over the bottom or near the surface at night. During the day they may be captured with a fine-mesh dip net by running the net through leaf litter and vegetation at the bottom of the pool then carefully sorting through the debris by hand. The larvae resemble tadpoles but have four legs and external gills. They range in size from 0.8–1.4 cm at hatching to 4.0–7.5 cm at metamorphosis. The larvae remain in the pool through June and into August depending on water level, temperature, food supply and other variables. Although they may be difficult to find, they provide evidence of vernal pool obligates well into the summer after Wood Frog tadpoles have transformed into adults and left the area. As the larvae salamanders transform, they may be found under debris around the pool margins. Newly transformed larvae will be close to the waterÕs edge and will have gill remnants.