The Marbled Salamander, Ambystoma opacum, is a stout-bodied amphibian found across the eastern United States, ranging from southern New England down to northern Florida and west to parts of Texas and Oklahoma. Adults typically measure between three and five inches in length and are easily recognized by their striking pattern of white or silvery-gray crossbands set against a dark black or purplish body. This species exhibits a change in diet as it undergoes metamorphosis, transitioning from a purely aquatic predator in its larval stage to a terrestrial hunter as an adult.
Larval Aquatic Diet
The larval Marbled Salamander begins its life cycle in temporary wetlands and vernal pools, acting as a highly opportunistic aquatic predator. Upon hatching, the larvae are small and initially focus on consuming microscopic organisms known as zooplankton, specifically small crustaceans like copepods and cladocerans. Their early arrival in the pond, often in the fall or winter, gives them a size advantage over other amphibian larvae that hatch in the spring.
As the larvae grow, their diet expands to include larger aquatic invertebrates. They actively hunt for insect larvae, such as mosquito larvae, as well as the nymphs of mayflies and damselflies. Larger larvae will also prey upon small crustaceans like isopods and fairy shrimp, and even oligochaete worms. Because of their size advantage, these voracious larvae are also known to consume the eggs and hatchlings of other amphibians, including wood frog tadpoles and the larvae of species like the Spotted Salamander, making them a dominant predator in their temporary aquatic habitat.
Adult Terrestrial Prey
Adults are effective carnivores, shifting their diet entirely to terrestrial invertebrates found in the forest floor environment after metamorphosis. They consume a wide array of small creatures they can overpower. Primary food sources include soft-bodied organisms such as earthworms, slugs, and snails.
The salamanders also consume various arthropods that inhabit the leaf litter and damp soil. Since they are relatively small, the species is limited to prey that can be captured and ingested whole.
Arthropod Prey
- Spiders
- Centipedes
- Beetles
- Ants and small crickets
Foraging and Predation Strategy
Adult Marbled Salamanders are secretive, fossorial animals, spending most of their time underground or hidden beneath debris. Their hunting activity is nocturnal, which helps them avoid predators and capitalize on high humidity. They are ambush predators, often waiting under cover for unsuspecting prey to pass by.
The primary method for locating prey in the dark, damp environment is through chemoreception, using smell and taste. They are attuned to movement and only consume live prey. Once a meal is detected, they employ a specialized feeding mechanism, rapidly projecting their tongue to adhere to and secure the invertebrate before retracting it. This quick strike allows them to efficiently capture the small, mobile prey.