As a newborn tadpole just hatching from its egg, a baby bullfrog relies completely on the yolk from inside the egg to sustain itself in those critical first days of life. But soon, the small tadpole must venture out into the pond and start fending for itself.
If you’ve ever wondered exactly what baby bullfrogs eat at each stage of their development, read on for a deep dive into bullfrog diets.
Newly Hatched Tadpole Diet
Yolk
When bullfrog tadpoles first hatch from their eggs, they survive entirely off of their yolk sac for the first few days of their lives. The yolk provides crucial nutrients and energy to fuel the tadpole’s early development and growth.
As the tadpole matures over the next several days, the yolk sac gradually gets absorbed into the body.
Algae
Once bullfrog tadpoles deplete their initial yolk stores, they must start seeking external food sources to survive. One of the first foods a newly hatched tadpole will start consuming is algae. Algae is abundant in the shallow, vegetated ponds and lakes where bullfrogs live.
The tadpoles will scrape tiny strands of algae off of surfaces like rocks and aquatic plants.
Algae provides an excellent source of nutrients for young tadpoles. It is rich in protein, vitamins, carotenoids, and omega-3 fatty acids – all key building blocks for the tadpole’s rapid growth and development. Algae also provides a sustainable food source since it continually regenerates.
As the tadpole grows over the next few weeks, algae will continue to form a major part of its diet.
Dead Plants
In addition to algae, newly hatched bullfrog tadpoles will also feed on dead and decaying plant material in their aquatic habitats. This includes fragments of leaves, stems, roots that fall into the water from surrounding vegetation.
The tadpoles will nibble and scrape these plant bits for additional nutrients.
The cell walls of dead plant matter contain cellulose and lignin that the tadpole’s digestive system can break down into usable energy. Though not as nutrient-dense as algae, decaying plant material is often abundant and supplements the tadpole’s diet.
This allows them to continue growing rapidly during the initial few weeks after hatching when they are still quite vulnerable.
Between the yolk sac remnants, algae, and dead vegetation, newly hatched bullfrog tadpoles are well fueled with diverse nutrients to power through their crucial early development. As they grow over subsequent weeks and months, their diet will continue expanding to include other food sources like insects, fish eggs, and even small crustaceans.
Older Tadpole Diet
Algae
As baby bullfrogs grow into older tadpoles, their diet expands to include more plant matter, especially algae. Algae are diverse photosynthetic organisms that live in water and provide an abundant source of nourishment for tadpoles.
Common types of algae that tadpoles feed on include green algae, diatoms, and cyanobacteria or blue-green algae. Tadpoles scrape algae off of rocks and other surfaces usingtiny teeth in their upper jaw called keradonts.
Algae provide tadpoles with carbohydrates, proteins, vitamins, and minerals needed for continued growth and development.
Aquatic Plants
In addition to algae, older bullfrog tadpoles will also begin grazing on aquatic plants. They use their keradont teeth to rasp plant material off stems and leaves. Some of the most commonly consumed aquatic plants are duckweed, elodea, and watermilfoil.
These plants provide nutrients like calcium that aid in tadpole bone development. The cellulose in aquatic plants also helps promote healthy digestion as tadpoles transition to bigger food sources. Grazing on plants teaches tadpoles to utilize vegetation as a key part of their diet, a behavior that will carry over into adulthood as bullfrogs.
Insects
As they grow larger, bullfrog tadpoles will start adding small insects and insect larvae to their diet. Tadpoles will eat mosquito larvae, mayfly larvae, dragonfly larvae, water fleas, and small aquatic beetles.
These protein-rich insects provide nutrients needed for the tadpole’s continuing growth and metamorphosis. Tadpoles capture insect prey by swimming up and sucking them into their large mouths. The number of insects consumed will increase steadily through the tadpole phase until insects become the mainstay of the adult bullfrog’s carnivorous diet.
Small Fish
In the later stages of the tadpole phase, some bullfrog tadpoles may even consume very small fish. Tadpoles drawn to shoals of fish fry may pick off small, weak, injured, or dead fish. While not all tadpoles exhibit this behavior, the protein and fat from fish tissue provide an excellent source of energy reserves that will help the tadpole through metamorphosis.
Eating small fish signals the tadpole’s continuing transition to being a more active predator like the adult bullfrog.
Young Froglet Diet
Flies
Once bullfrog tadpoles metamorphose into froglets, they begin hunting for live prey instead of filtering organic matter from the water. Small flies make up a large portion of a young bullfrog’s diet. Froglets only measure about 1-1.5 inches long after metamorphosis, so they can only consume prey that is proportionate to their tiny mouths.
Common flies like houseflies, blowflies, and fungus gnats are perfect starter meals. Young bullfrogs snatch these insects out of the air with their sticky tongues when they fly or land close to the water’s edge. They need to eat lots of small flies each day to gather enough calories to fuel growth.
Worms
Earthworms and aquatic worms wiggle into the diet of many froglets. These invertebrates crawl on the mud at the bottom of ponds and streams where young frogs hunt. The protein and fat inside worms makes them a nutritious snack.
Bullfrogs may find worm hunting easier than fly catching since worms move slower. Worms also hang around the water instead of flying away. Beginning frog hunters likely appreciate wiggly worms that can’t zip out of reach.
Small Insects
Froglets gobble down any small insects within gulping range. Aquatic beetles, water striders, and mosquito larvae make tasty morsels. Grasshoppers, crickets, small butterflies and moths also end up as unfortunate frog snacks if they make the mistake of venturing too close to the water.
These small insects supply growing froglets with essential amino acids and micronutrients like calcium and vitamin A. Eating a wide variety of insects instead of just flies or just worms provides balanced nutrition.
Bullfrog parents do not watch over their offspring, so froglets must take advantage of any edible insect that crosses their path.
Tadpoles
Young bullfrogs may even consume smaller tadpoles of their own species. Bullfrog tadpoles sometimes turn cannibalistic when food becomes scarce. The hungry amphibian larvae bite off pieces of other tadpoles’ tails and feed on the protein-rich muscle tissue.
Tadpole cannibalism rates are higher when too many tadpoles are competing for limited food resources in crowded ponds. This cannibalistic tendency continues into the froglet stage. Tiny froglets discover defenseless tadpoles make easy pickings.
Gobbling up a few tadpoles gives a nutritional boost to froglets preparing for rapid juvenile growth. Eating other amphibian larvae also reduces competition. Consuming smaller members of their own species helps ensure the larger, stronger bullfrog froglets have enough food as they journey through the dangerous first weeks of life outside the egg.
Adult Bullfrog Diet
Adult bullfrogs are voracious predators that will eat just about anything they can fit in their large mouths. Their diverse palates and powerful jaws allow them to consume a wide variety of prey, including insects, snails, rodents, small reptiles, and even birds.
Insects
Insects make up a large part of the adult bullfrog’s diet. Their long, sticky tongues allow them to snatch up unsuspecting insects that pass by their perches near the water’s edge. Some of the bullfrogs’ favorite insect prey includes grasshoppers, crickets, beetles, dragonflies, butterflies, and moths.
Snails
Bullfrogs will also readily feed on aquatic snails and slugs. These slow-moving invertebrates are easily captured and consumed by hungry adult bullfrogs patrolling the margins of ponds and streams.
Rodents
If they can get their mouths around one, an adult bullfrog will eat small rodents like mice, shrews, and juvenile rats. Bullfrogs have even been documented consuming introduced mammals like muskrats and chipmunks in certain parts of their range.
Small Reptiles
In addition to mammals, bullfrogs will feed on smaller members of their own class. Hatchling turtles, juvenile snakes, small lizards like anoles, and even other tiny frogs and toads will get gobbled up by hungry adult bullfrogs.
Birds
Bullfrogs are also opportunistic predators of birds, especially their eggs and hatchlings. They have been documented preying on the chicks and eggs of ground-nesting species like ducks, rails, coots, gallinules, and other waterbirds.
Conclusion
As we’ve seen, a bullfrog’s diet changes dramatically as it grows from a tiny newborn tadpole to a massive adult frog. Key dietary staples evolve from egg yolks to algae to insects to small vertebrates.
Understanding what baby bullfrogs eat at each life stage gives us a deeper appreciation of how these incredible amphibians survive and thrive.