The spotted salamander (Ambystoma maculatum) is a secretive amphibian found across the forests of Eastern North America. Adults spend most of their lives concealed underground or beneath damp leaf litter. As a small, terrestrial predator, the salamander’s diet changes completely between its aquatic larval stage and its terrestrial adult form, reflecting its environment.
Primary Food Sources of Adult Salamanders
The adult spotted salamander’s diet consists entirely of invertebrates found within its moist, forest-floor habitat. Since it spends much time underground, it preys opportunistically on organisms that share this humid environment. Earthworms are a staple, providing a soft-bodied and easily digestible source of nutrition. The salamander also regularly consumes slugs and snails, which are slow-moving mollusks common in damp areas.
The diet includes a wide array of arthropods inhabiting the forest floor ecosystem. These are encountered during the salamander’s foraging trips and include spiders, millipedes, and centipedes. Various insect larvae, such as those from beetles, are also consumed when discovered in the soil or under logs. Occasionally, an adult may even prey on a smaller salamander species, demonstrating its generalist carnivorous habits.
The Distinct Diet of Aquatic Larvae
The larval stage is fully aquatic and possesses a distinct diet. Larvae are aggressive generalist predators that feed on smaller, waterborne organisms in the temporary vernal pools where they hatch. Their initial diet consists mostly of microscopic prey, such as zooplankton and various microcrustaceans like copepods and cladocerans.
As the larvae grow, their prey size increases to include small aquatic insects and their larvae, such as chironomids and chaoborids. Larger larvae consume isopods and amphipods. When food resources become scarce, larger larvae may exhibit cannibalistic behavior, preying on smaller members of their own species.
Hunting Strategy and Feeding Habits
The spotted salamander primarily functions as an ambush predator, relying on a sit-and-wait strategy to secure its meals. They conduct most feeding activity at night, though they may venture out to forage more actively across the forest floor during wet weather.
Prey capture is accomplished using a specialized, highly effective tongue mechanism. The tongue is muscular and sticky, rapidly projecting outward to secure an invertebrate on contact. This quick, precise action allows the salamander to capture prey within striking distance. Feeding frequency is heavily influenced by environmental factors; adults may cease feeding during the spring breeding migration and feed heavily in the fall to build up fat reserves before winter hibernation.
Diet in a Captive Environment
For spotted salamanders kept in captivity, the diet must mimic the variety and nutritional content of their natural invertebrate prey. Cultured earthworms should form the basis of the diet due to their high moisture and protein content. Other appropriate feeder insects include:
- Crickets
- Mealworms
- Waxworms
- Nightcrawlers
Feeder insects must be “gut-loaded” with nutritious food before being offered to ensure the transfer of vitamins and minerals. To prevent nutritional deficiencies, especially Metabolic Bone Disease, all feeder insects must also be dusted with a calcium and vitamin D3 supplement. Food items must always be appropriately sized for the salamander’s mouth to prevent injury.