Amphibians
Marbled Salamander
Ambystoma opacum · also called marbled salamander, banded salamander
The marbled salamander is a stocky, boldly banded amphibian of the eastern American woods that runs its life on a different schedule from every relative it has. While other mole salamanders wait for spring and lay in water, the marbled salamander breeds in autumn, on dry land, and the female stays with her eggs — guarding them in the dust of an empty pool until the rain comes.
Overview
Marbled salamanders live in deciduous and mixed forest with vernal pools — woodland depressions that fill seasonally and dry out — across the eastern United States. Adults are 9–12 centimetres, black with striking silver-white or grey crossbands, and they spend almost the whole year underground or under logs, emerging only on wet nights and to breed.
Breeding out of season
Most Ambystoma salamanders migrate to full spring pools and spawn in the water. The marbled salamander breeds in September and October, and the female lays her 50–200 eggs on land, in the dry basin of a pool that will not fill for weeks or months.
The guarding mother
She then stays with the clutch, curled around it in a cavity under cover, keeping it moist and deterring small predators, for days to weeks. When the autumn and winter rains flood the pool and the water reaches the nest, she leaves and the submerged eggs hatch within days.
A head start, and a gamble
Hatching in autumn or winter means marbled salamander larvae are already large when the spring breeders’ eggs hatch. They out-compete and often eat the smaller, newly hatched larvae of spotted salamanders and wood frogs. The risk is the pool not filling at all — a dry autumn can wipe out an entire cohort of eggs.
Status
The marbled salamander is Least Concern, common and widespread, but tied to the survival of small seasonal woodland pools, which are easily lost to drainage, filling, and development.
Marbled Salamander: common questions
Why does the marbled salamander breed in autumn on dry land?
Most mole salamanders (genus Ambystoma) migrate to seasonal woodland pools in early spring, when the pools are full, and lay their eggs in the water. The marbled salamander does the opposite. It breeds in September and October, and the female lays her eggs on land, in the dry, leaf-littered basin of a pool that will not fill until the autumn and winter rains. She then guards them. When the rains finally flood the depression, the eggs hatch. This timing gives the larvae several months' growth before the spring-breeding species even lay their eggs.
Does the female really guard her eggs?
Yes, which is unusual for a salamander. After laying, the female marbled salamander stays curled around or on top of her clutch in a hollow beneath a log, a rock, or matted leaves. She keeps the eggs from drying out — partly by her body contact and the moisture of her skin — and her presence deters some small predators and may reduce mould. She typically stays for one to several weeks, until the rising water of the flooding pool reaches the nest, at which point she leaves and the eggs, now submerged, hatch within days.
What is the advantage of hatching so early?
A big one — a head start in the arms race of the vernal pool. By hatching in autumn or winter, marbled salamander larvae spend the cold months growing slowly in the pool, so by the time the eggs of spotted salamanders, wood frogs, and other spring breeders hatch, the marbled larvae are considerably larger. Larger larvae are stronger competitors for the pool's limited food, and marbled salamander larvae are also directly predatory on the smaller, newly hatched larvae and tadpoles of the spring breeders. The gamble is that the pool fills at all — in a dry autumn, a whole cohort of marbled salamander eggs can fail.
How do you tell a marbled salamander from other salamanders?
The pattern is distinctive — a chunky, black-bodied salamander with bold, irregular crossbands of silvery white (in adult males) or grey to silvery (in females and juveniles) running across the back and tail, giving a marbled or banded look. It is smaller and stockier than the spotted salamander, which is black with two rows of round yellow spots, and it lacks the spotted salamander's slimmer build. Marbled salamanders are also almost never seen in the open — they spend most of the year underground or under cover and only surface on wet nights and to breed.