Amphibians are a diverse group of cold-blooded vertebrate animals known for their ability to live in both aquatic and terrestrial environments. The term “amphibian” itself originates from a Greek word meaning “double life,” reflecting this dual existence. Their diet is varied and plays a significant role in their survival and ecological contributions.
General Feeding Habits
Most adult amphibians are carnivorous, primarily preying on a range of invertebrates. Their diet commonly includes insects such as crickets, flies, and beetles, along with worms, slugs, and spiders. Larger amphibian species can expand their diet to include small vertebrates like fish, mice, or even other amphibians.
Dietary Shifts by Life Stage
Amphibians exhibit significant dietary changes as they progress through their life stages. Larval frogs and toads, known as tadpoles, are typically herbivorous, feeding on algae, decaying plant matter, and detritus found in their aquatic habitats. As tadpoles undergo metamorphosis, their diet gradually shifts; their long, spiral intestines, adapted for plant digestion, shorten to accommodate a carnivorous diet. Once they transform into froglets and adult frogs, they become primarily insectivorous. In contrast, larval salamanders are carnivorous from hatching, consuming small aquatic invertebrates. Their early diet includes microcrustaceans and later, mosquito larvae and small worms. As they grow, their prey size increases, and they may consume larger aquatic invertebrates, maintaining a predatory lifestyle similar to their adult forms.
Diet Across Amphibian Groups
Dietary preferences vary considerably among the three main orders of amphibians: Anura (frogs and toads), Caudata (salamanders and newts), and Gymnophiona (caecilians). Frogs and toads are largely insectivorous, though bigger species can prey on small vertebrates. Their diet includes a wide array of insects, worms, and slugs.
Salamanders and newts are predominantly carnivorous, consuming worms, insects, snails, and aquatic invertebrates. Larger salamander species may also eat small fish, crayfish, or even small mammals like mice. Their prey selection can be influenced by their habitat, with terrestrial species focusing on soil and leaf litter invertebrates and aquatic species preferring water-borne prey.
Caecilians, which are limbless and often burrow underground, primarily feed on subterranean invertebrates. Their diet includes earthworms, termites, and other insects found in the soil. A unique aspect of some caecilian species is maternal dermatophagy, where young caecilians feed on a specialized fatty outer layer of their mother’s skin.
Unique Feeding Adaptations
Amphibians employ various specialized methods to capture their prey. Many frogs and some salamanders utilize a projectile tongue, which is rapidly extended to snare prey. The frog’s tongue is remarkably soft and coated with non-Newtonian saliva, allowing it to adhere strongly to prey upon impact and then release it easily for swallowing.
Aquatic amphibian larvae and some adult aquatic salamanders use suction feeding to draw prey into their mouths. They rapidly expand their buccal cavity, creating a negative pressure that pulls water and the prey inward. This method is highly effective for capturing elusive prey in water.
Ambush hunting is a common strategy for many amphibians, where they rely on camouflage and stillness to wait for prey to come within striking distance. Once prey is close, they can quickly lunge to capture it. Amphibians typically possess small teeth in their jaws, which are primarily used for holding captured prey rather than chewing.