What Do Amphibians Eat? A Diet Breakdown by Group

Adult amphibians are overwhelmingly carnivorous, feeding mostly on small invertebrates like insects, worms, and spiders. That generalist appetite holds across all three major groups: frogs and toads, salamanders and newts, and caecilians.¹ But the details get interesting fast. Body size, habitat, life stage, and even gut bacteria shape what ends up on the menu, and a handful of species break the rules entirely by eating fruit, scavenging carrion, or cannibalizing their own kind.

Frogs and Toads

Frogs and toads (order Anura) make up the vast majority of amphibian species, and their diets reflect that diversity. Most adult anurans are sit-and-wait or active-pursuit predators of whatever small invertebrates they can fit in their mouths. Studies of the European common toad, for instance, show a diet dominated by insects, especially beetles and ants, with a long tail of other invertebrate groups eaten at much lower frequencies.² That pattern is fairly typical: a few insect orders form the core diet, and nearly everything else that crawls or flies nearby gets eaten occasionally.

What a frog eats depends heavily on where it lives and how big it is. Larger species take proportionally larger prey, and some of the biggest frogs regularly eat vertebrates, including other frogs. Body size is actually one of the strongest predictors of whether a frog species eats other frogs: for every millimeter increase in body length, a frog is about three percent more likely to include other frogs in its diet.¹ Invasive species are also about 40% more likely to eat other frogs than native species, which partly explains the ecological havoc caused by introductions like the cane toad.¹

In agricultural settings, native frogs can play a meaningful pest-control role. The Luzon wart frog in the Philippines, for example, eats far more rice pests than the invasive cane toad does, with pests making up over half of its diet.³ The cane toad, by contrast, tends to consume more beneficial arthropods, the ones that themselves eat pests. That dynamic is one reason conservation biologists worry about invasive amphibians in farmland.

From Algae to Insects: How Diet Changes During Metamorphosis

The most dramatic dietary shift in the amphibian world happens during metamorphosis. Tadpoles are primarily herbivorous, scraping algae off rocks, filtering suspended particles from the water, or grazing on decaying plant material. Their entire digestive tract is built for this: a long, coiled gut designed to extract nutrients from plant matter. During metamorphic climax, feeding slows and eventually stops, and the gastrointestinal tract remodels itself to accommodate the carnivorous diet of the adult frog.⁴ The gut shortens, stomach acid production ramps up, and the whole system switches from processing cellulose to digesting animal protein.

This transformation is not just anatomical. The gut microbiome overhauls itself in tandem. As tadpoles approach and enter metamorphic climax, bacteria associated with digesting chitin (the material insect exoskeletons are made of) and fat become more prominent, replacing the communities that had been helping break down plant carbohydrates.⁵ The surge in chitin-digesting bacteria appears to help the frog meet its nutritional needs during and immediately after metamorphosis, a period when the animal is not actively eating much but is burning enormous amounts of energy rebuilding its body.

Some tadpoles, though, do not stick to the herbivore script. Spadefoot toad tadpoles can develop into one of two drastically different body forms depending on their environment: an omnivore morph with a typical herbivorous tadpole body, or a carnivore morph with a wider head, larger jaw muscles, and a shorter gut suited to eating animal prey, including other tadpoles.⁶ Exposure to animal protein in the diet, especially other tadpoles, triggers the carnivore morph at significantly higher rates than a detritus-only diet.⁷ It is one of the more striking examples of diet-induced developmental plasticity in vertebrates.

Salamanders and Newts

Salamanders and newts (order Caudata) are almost universally carnivorous at every life stage, though aquatic larvae take smaller prey than adults. Their diet revolves around soft-bodied invertebrates: worms, insect larvae, snails, slugs, and small crustaceans. Terrestrial species forage in leaf litter and rotting logs, while aquatic species hunt along stream and pond bottoms.

Earthworms are a particularly important food source for many woodland salamanders. At sites where earthworms are present, they can account for over half of the total prey volume consumed by common salamander species, even though the salamanders eat fewer individual prey items compared to earthworm-free sites. The worms are simply large and nutritious enough to dominate the diet in bulk terms.⁸ In places where non-native earthworm species have invaded, salamanders have shifted their diets to take advantage of this new, high-quality food, consuming fewer individual prey items but gaining more total nutrition.

Larger aquatic salamanders are capable of eating vertebrate prey. Hellbenders, the giant salamanders of eastern North America, feed heavily on crayfish. They can discriminate between crayfish species by scent and show a preference for native crayfish over non-native ones, though in practice they often end up consuming more of the invasive species, likely because those are the ones most available.⁹ That disconnect between preference and actual intake illustrates a broader point about amphibian diets: what an animal wants to eat and what it ends up eating are often determined by prey availability and prey behavior rather than inherent food choices.

Salamander larvae can be voracious predators in their own right. Fire salamander larvae in streams and ponds drastically reduce the abundance of benthic invertebrates, cutting prey numbers by roughly 75-80% over a two-week period in controlled settings.¹⁰ That level of predation pressure means salamander larvae can reshape the invertebrate communities in small water bodies.

Caecilians

Caecilians (order Gymnophiona) are the least familiar amphibians, limbless and mostly burrowing, and their diets reflect a life spent underground or, for a few species, in water. Because they are hard to observe and rarely studied compared to frogs and salamanders, what we know about their feeding comes from relatively few detailed dietary analyses, but the picture is consistent: they are generalist predators of soil-dwelling invertebrates.

Earthworms, termites, and ants are the main foods. In Central Africa, one species of caecilian eats primarily earthworms (about 54% of its diet by frequency and volume), while a co-occurring species in the same habitat leans more heavily on mole crickets and ants.¹¹ In southern India, a burrowing caecilian switches seasonally between earthworms and termites depending on monsoon timing, with termites dominating in mid-monsoon and earthworms contributing the most mass earlier in the rainy season.¹² Researchers have rejected the idea that these caecilians are dietary specialists; they eat whatever soil invertebrates are locally and seasonally abundant.

Aquatic caecilians have a somewhat different menu. The Rio Cauca caecilian, an aquatic species that has established non-native populations in Florida, appears to eat primarily soft-bodied prey, and at least one specimen contained fish bones in its stomach, suggesting it also scavenges vertebrate carrion.¹³ That combination of active predation and scavenging is unusual among amphibians and highlights how different caecilian ecology is from what most people picture when they think of this group.

Unusual Feeding Strategies That Break the Rules

The generalist-carnivore template holds for almost all amphibians, but a few species have evolved feeding strategies that would surprise anyone who thinks of frogs as simple bug-catchers. The most remarkable outlier is a small Brazilian treefrog called Xenohyla truncata, which regularly eats fruit, flowers, and nectar. Studies have confirmed that fruits are an intrinsic part of its diet, not an occasional accident, and the frog has been observed using suction-like movements to consume nectar from flowers.^{14 15} Pollen grains found stuck to the frog’s back suggest it may even act as a pollinator, making it perhaps the only known amphibian to provide that ecological service. Nectar consumption during the breeding season could supply extra energy when the frogs are under heavy metabolic demand.

Poison frogs of the family Dendrobatidae have taken dietary specialization in a completely different direction. Rather than broadening their menu, many species have narrowed it. Their defensive skin alkaloids are not produced internally; they are acquired directly from the ants and mites the frogs eat.¹⁶ Researchers have found a strong correlation between how specialized a poison frog’s diet is and how toxic its skin alkaloids are, suggesting that the evolution of chemical defense and dietary narrowing have gone hand in hand across the family.¹⁶ These frogs also show genuine prey preferences: given a choice, they select among arthropod prey based on type and alkaloid content, not just availability.¹⁷

How Frogs Actually Catch Their Food

The tongue of a frog is one of the fastest and stickiest biological structures known. Researchers have shown that frog tongues work through a combination of extreme softness and unusual saliva properties. The tongue itself is viscoelastic, meaning it deforms like a shock absorber on impact with an insect, spreading over the prey’s body rather than bouncing off.¹⁸ The saliva is shear-thinning: it flows easily during the high-speed strike and spreads across the insect on impact, then thickens and grips firmly during tongue retraction, and finally loosens again inside the mouth to let the prey slide off and be swallowed.¹⁸ Close-up observations of tongue detachment from surfaces also reveal thin fibrils that maintain contact even as the main body of the tongue peels away, functioning somewhat like adhesive tape.¹⁹

Not all frogs rely on tongue projection. The tongueless frogs of the family Pipidae, which are fully aquatic, capture prey by suction feeding. Species like the African clawed frog generate a drop in pressure inside the mouth by rapidly opening the jaws, creating a water current that pulls prey inward. Some pipid species supplement this with forelimb scooping, using their front legs to direct food toward the mouth, but all can capture prey with suction alone.²⁰ Tadpoles of some frog species also use a form of suspension feeding, filtering algal cells from the water through structures in the mouth, though very young larvae may reduce their filtering rate at low food concentrations rather than feeding continuously.²¹

When Offspring Eat Their Parents

Some of the strangest feeding relationships in amphibians involve parents provisioning their young with their own bodies. Certain caecilian mothers develop a thickened, nutrient-rich outer skin layer after their eggs hatch. The hatchlings, equipped with specialized teeth, peel and eat strips of this modified skin in a behavior called maternal dermatophagy. This form of parental care has been documented in at least two distantly related caecilian lineages, one in Africa and one in South America, suggesting it evolved independently or dates back over a hundred million years to a common ancestor.²² The mother’s skin regrows between feeding bouts, making this a renewable food source for the young during their most vulnerable period.

Poison frogs take a different approach. Female strawberry poison frogs deposit their tadpoles in small pools of water held in the leaf axils of bromeliads or other plants, then return regularly to lay unfertilized eggs for the tadpoles to eat. These trophic eggs are the tadpoles’ sole food source throughout development. Experimental removal of tadpoles from their mothers’ care in captive colonies has shown that the investment pays off increasingly as the tadpoles grow, which may explain why mothers maintain the behavior over such an extended period rather than cutting their losses early.²³ Both skin-feeding and egg-feeding represent unusually high levels of parental investment for amphibians, a group more commonly associated with laying eggs and leaving.

Amphibian Diets and Agriculture

The appetite of frogs for insects has not gone unnoticed by agricultural researchers. In rice paddies across Asia, frogs naturally consume pest insects, and the idea of leveraging this as biological pest control has been studied repeatedly. The results are more nuanced than the simple “frogs eat pests” narrative suggests. In field experiments in rice paddies, the effect of frog predation on pest abundance was not statistically significant at either high or low frog densities, and at lower frog densities, the frogs actually reduced the abundance of beneficial arthropods (the predatory insects that also eat pests).²⁴ In other words, frogs in rice fields may eat both the pests and the pest-eaters, and the net effect on crop damage depends on the specifics of the system.

That said, not all frogs are equal in this regard. Native frog species tend to consume a higher proportion of actual pest insects compared to invasive ones. As mentioned earlier, the native Luzon wart frog’s diet consisted of over half pests, while the invasive cane toad in the same system preferentially ate beneficial arthropods.³ The lesson for farmers and conservation managers is that maintaining native frog populations matters more than simply having lots of frogs around. An agricultural landscape dominated by invasive amphibians could actually lose pest-control services even as total frog numbers remain high.