A spring calendar of amphibian calls and egg masses in the National Capital Region

Amphibian season in the parks of the National Capital Region does not start in spring. It starts the previous autumn, with the marbled salamander. By the time March arrives, park staff beginning the Inventory and Monitoring program's March-to-July amphibian surveys can follow a sequence that runs from the first egg masses to the chorus of tree frogs.

The head start: marbled salamander

Marbled salamanders (Ambystoma opacum) breed in fall, and their larvae are among the first signs of amphibian life in early spring. NPS photo.

Most amphibians in the region lay eggs in ephemeral wetlands that dry up in late summer or early fall. Marbled salamanders lay theirs in the dry wetland beds on rainy fall nights, often on the underside of leaves or other debris. The eggs hatch after winter precipitation fills the beds, and the larvae can usually be found in dip-net surveys from March through late May. The adults have stout bodies and silver banding across a black back and live mostly underground, so they are not usually seen except during fall breeding.

First out in spring: spotted salamander and wood frog

Spotted salamander eggs are laid during mass breeding events on rainy nights in early spring. NPS photo.

These two species produce the year's first egg masses.

• Spotted salamander (Ambystoma maculatum): egg masses are oval, compact and wrapped in a cloudy jelly layer, laid in or near flooded wetlands during mass breeding on rainy nights. Courtship is an elaborate dance in which the salamanders nudge potential mates with their chins. Adults have bright yellow spots on dark purplish backs and are generally seen only at the large breeding events, spending the rest of the year underground.
• Wood frog: breeds in "explosive" events during early spring rains, shortly after the frogs thaw out of winter hibernation in leaf-litter burrows, where a natural antifreeze keeps their bodies from freezing. The circular, compact, clear egg masses can hold up to thousands of eggs. Adults, with a dark "robber mask" on the face, hop around the forest floor all through the breeding season.

A wood frog on the forest floor. NPS photo.

The choruses arrive

As temperatures rise, frog choruses become more common across the parks. The spring peeper (Pseudacris crucifer) is the one many people take as the sign that spring has come, with a "peep-peep-peep" chorus on warm spring nights.

As spring shifts toward summer, gray tree frogs (Hyla versicolor) join in with a rapid-fire musical trill that is easily mistaken for a bird call. Later, their tadpoles can be told apart in dip-net surveys by bright red tail tips, which develop when the tadpoles are stressed by predators, limited nutrients or falling wetland water levels.

A gray tree frog on a small tree branch. NPS photo.

Spring peepers and gray tree frogs are joined by cricket frogs, bullfrogs, toads and newts. Things slow down in July as summer temperatures rise and the ephemeral wetlands begin to dry up, and the cycle starts again the next year.

Sources

• National Park Service, National Capital Region Inventory and Monitoring, "Spring Amphibian Timeline," by Alex Wright, amphibian monitoring collaborator, Michigan State University (https://www.nps.gov/articles/spring-amphibian-timeline.htm). The article was inspired by a figure from a journal paper, which is not reproduced here; rewritten in hubnx's own words.