Tadpoles: What They Eat, How They Grow, and Unique Photos

Photographing 10,000 northwestern toad tadpoles in British Columbia

By William Drumm, underwater photographer and ocean ambassador

Of all the creatures I have photographed and shared on Instagram, tadpoles got one of the biggest reactions I have ever seen. People were stunned. The comments were full of variations of the same thing: I had no idea they looked like that.

That is the thing about tadpoles. Most people have never seen them up close. They are tiny, they live in water you cannot easily see into, and they exist in a stage of life that, for most species, lasts only a few weeks. Catching them at the right moment in the right water requires you to be in the exact right place.

I went looking for that exact right place in a remote area of British Columbia, on a small lake surrounded by forest. We camped on the bank and set up our gear on the shore. Each morning, we pulled on our wetsuits and walked into the water.

From above, the surface was glass calm. Quiet. The kind of stillness you imagine when you picture a wilderness lake at dawn.

Underneath, it was completely different.

Tens of thousands of small tadpoles – northwestern toad tadpoles, Anaxyrus boreas – were in the middle of their morning commute. Each day, the entire population would move from the deeper waters of the lake out to the shallow margins where the algae was thickest near the surface. Wave after wave moved past us. Some swimming alone. Most moving together in dense rivers of small bodies. The water was alive in a way you only really understand when you are inside it.

We shared the lake with leeches that occasionally came looking for a meal, with small fish that picked off stragglers, and with the geometry of the migration itself. Light filtered through the surface in shifting columns. The tadpoles cut across those columns of light by the thousands.

It was one of the most adventurous and rewarding underwater shoots I have done. Not because of any single dramatic moment, but because of the sheer scale and the rarity of seeing it. Most people who think about tadpoles imagine a few in a jar. The reality, in a healthy ecosystem, is a population so large you cannot count it.

What follows is what I have learned about these animals since that trip – their biology, their feeding, their development, and what they tell us about the freshwater systems they live in.

Quick facts about tadpoles

• What they are: the larval stage of frogs and toads, before they grow legs and lungs
• Where they live: ponds, lakes, slow-moving streams, vernal pools, and other freshwater habitats
• What they eat: algae and soft plant matter as young tadpoles, then small invertebrates and decaying matter as they grow
• How long they stay tadpoles: 4 to 14 weeks for most species, longer for some bullfrogs (up to 3 years)
• How they breathe: through external gills as young tadpoles, then internal gills, then developing lungs as they near transformation
• What they become: frogs and toads (collectively called anurans)
• Common predators: fish, ducks, dragonfly larvae, leeches, larger tadpoles, snakes, and birds
• Why they matter: tadpoles are key indicators of freshwater ecosystem health.

What is a tadpole?

A tadpole is the larval stage of a frog or toad. After amphibian eggs hatch in water, the young emerge with no legs, a long tail, external gills, and a body shape that looks more like a small fish than the adult animal it will eventually become. Over the following weeks or months, that tadpole undergoes one of the most dramatic transformations in vertebrate biology – a process called metamorphosis – and becomes a frog or toad.

The word “tadpole” comes from Middle English: “tadde” (toad) and “poll” (head). Together, roughly, “toad-head,” which is what they look like when you first see one – a wiggling head with a tail. “Polliwog” is another common name, more often used in North America, with a similar etymology (“poll” + “wiggle”).

All frogs and toads start life as tadpoles. There are about 7,500 species of anurans (the scientific group that includes frogs and toads) worldwide, and almost all of them follow the same basic pattern: aquatic larva, then transformation, then air-breathing adult. A small handful of species skip the tadpole stage entirely and develop directly inside the egg into miniature frogs, but they are the rare exceptions.

What do tadpoles eat?

Tadpoles eat different things at different stages of their development. Understanding what they need at each stage is the most common reason people search for tadpole information – usually because they have found tadpoles in a backyard pool or pond and want to know how to keep them alive.

What tadpoles eat in the wild

In their natural habitat, young tadpoles are primarily herbivorous. They feed on:

• Algae growing on rocks, plants, and pond surfaces
• Soft aquatic plant matter and decaying vegetation
• Biofilm (the thin layer of microorganisms coating underwater surfaces)
• Tiny floating organisms like protozoa and bacteria

As tadpoles grow larger and approach metamorphosis, their diet shifts. They begin eating:

• Small invertebrates like mosquito larvae and tiny aquatic worms
• Decaying animal matter in the water
• Sometimes, in crowded conditions, smaller tadpoles or damaged tadpoles of the same species

That last one is uncomfortable to read but biologically real. When food is scarce or populations are dense, cannibalism happens. It is not aggressive – tadpoles just eat what is available, and a damaged sibling is protein in the water.

What to feed tadpoles you have rescued or are raising

If you have found tadpoles in a backyard pool or are raising them as a school project (always check local laws first – some species are protected and cannot be kept), the safest foods are:

• Boiled lettuce (romaine or spinach), chopped into small pieces
• Algae wafers sold for aquarium fish (sinking pellets work best)
• Frozen and thawed lettuce or spinach (the freezing breaks down cell walls and makes them easier to eat)
• Fish food flakes in moderation, especially as they grow
• A small piece of cucumber or zucchini

Feed small amounts. Tadpoles do not eat much per individual, and uneaten food fouls the water quickly. A pinch of food per day for a small group is usually enough.

Foods to avoid

Some foods seem reasonable but cause real problems:

• Bread – swells in their stomachs, has no nutritional value
• Meat or processed foods – can cause digestive issues and water pollution
• Tap water that has not been dechlorinated – chlorine and chloramines kill tadpoles
• Fatty or oily foods – foul the water immediately

The water itself is as important as the food. Tadpoles need clean, oxygenated, dechlorinated water at appropriate temperature for their species. A gallon jar in direct sun is not survivable. A shaded outdoor container with aged rainwater or dechlorinated tap water, partial shade, and aquatic plants is much closer to what they actually need.

How long does it take a tadpole to turn into a frog?

The time from hatching to fully formed frog varies dramatically by species, temperature, food availability, and habitat conditions. Here are typical ranges:

• Toad tadpoles (most species): 4 to 8 weeks
• Tree frog tadpoles: 6 to 12 weeks
• Common frog tadpoles: 12 to 16 weeks
• Bullfrog tadpoles: 1 to 3 years (yes, years)

That bullfrog timeline surprises a lot of people. American bullfrog tadpoles in cooler northern climates can take 2 to 3 years to fully metamorphose, overwintering in ponds as tadpoles. In warmer southern climates, they finish in a single season. The same species, completely different timelines, depending on where the population lives.

Within any single species, the variables that speed up or slow down metamorphosis are:

Water temperature: warmer water generally accelerates development. Tadpoles are ectothermic, so their metabolism tracks the water temperature directly.

Food availability: well-fed tadpoles develop faster than starving ones. This sounds obvious but matters in the wild, where food availability is often the limiting factor.

Population density: crowded populations grow more slowly. There is even research suggesting tadpoles secrete chemicals that suppress the growth of other tadpoles when populations get too dense.

Pond size and stability: tadpoles in temporary ponds (vernal pools that dry up each summer) tend to develop fast as a survival strategy. Tadpoles in stable lakes can afford to take their time. Northwestern toads, the species I photographed in BC, sometimes use temporary pools and have to race the drying.

Predator pressure: in some species, the presence of predators actually accelerates metamorphosis – tadpoles that detect predator chemicals in the water sometimes leave the water sooner, even at smaller sizes.

A “big tadpole” is not necessarily one that is doing well. Sometimes a large tadpole is one that has delayed transformation because conditions are not right – water has gotten too cold, food is scarce, or the population is too dense. Size is not always the same as success.

The tadpole life cycle, stage by stage

The transformation from egg to frog happens in roughly six stages, though they blend continuously:

Stage 1: Egg. Frog and toad eggs are laid in water, surrounded by jelly that protects them from predators and dehydration. Frog eggs are usually laid in clusters; toad eggs in long strings. The eggs develop for several days to weeks depending on species and temperature.

Stage 2: Newly hatched tadpole. When tadpoles first hatch, they have external gills and a yolk sac for nutrition. They cling to plants and rocks and barely move. This stage lasts a few days.

Stage 3: Free-swimming tadpole. The yolk sac is absorbed, external gills are replaced by internal gills covered by a flap of skin (the operculum), and the tadpole begins actively feeding on algae and plant matter. This is the iconic “tadpole” stage that most people picture.

Stage 4: Hind legs appear. Tiny back legs sprout first, often appearing as small buds before becoming functional. The tadpole continues swimming with its tail but now has the beginning of its frog body.

Stage 5: Front legs and lung development. Front legs emerge, lungs develop, and the tadpole begins occasionally surfacing for air. Internal anatomy is reorganizing rapidly – the long herbivore intestines shorten, the mouth shifts from a small algae-grazing mouth to a wide carnivore mouth, eyes migrate to the top of the head.

Stage 6: Froglet. The tail begins to shrink, absorbed back into the body as a nutrient source rather than falling off. The young frog or toad climbs out of the water for the first time. Over the next days to weeks, the tail disappears entirely and the animal is fully metamorphosed.

The whole process, from egg to functional frog or toad, typically takes 8 to 14 weeks for most temperate species, but as noted above, can take much longer for bullfrogs or in cold climates.

Toad tadpoles vs frog tadpoles

Telling toad tadpoles apart from frog tadpoles in the field is harder than telling adult toads apart from adult frogs, but there are reliable differences:

Color and size: toad tadpoles are typically smaller and darker – often nearly black. Frog tadpoles are larger and often more variable in color, ranging from olive green to brown to gold-flecked.

Behavior: toad tadpoles often school densely and move together in groups – this is exactly what I saw with the northwestern toad tadpoles in BC, where the migration moved as a coordinated mass. Frog tadpoles tend to be more dispersed, more independent, and more solitary in their movements.

Eggs (the easiest tell): before they hatch, toad eggs are laid in long strings or chains. Frog eggs are laid in clumped masses. If you see eggs in a pond and they are stretched out in a line, you are looking at toad eggs. If they are in a clustered jelly mass, you are looking at frog eggs.

Toxicity: many toad tadpoles are mildly toxic or unpalatable to predators – they have skin chemistry that makes fish and other predators reject them. Frog tadpoles are generally palatable. This is why toad tadpoles can school in dense, visible aggregations: they have less to fear from predators.

The schooling behavior of the northwestern toad tadpoles I photographed is a direct expression of this toxicity defense. They do not need to hide. The chemistry of their bodies handles that. So they aggregate in the most food-rich shallows, in plain view, by the tens of thousands.

What eats tadpoles?

Despite some chemical defenses, tadpoles are a major food source in freshwater ecosystems. Their predators include:

• Fish – many species, especially predatory ones like bass, perch, and pike. This is why tadpoles often do best in fishless ponds and vernal pools.
• Aquatic insects – dragonfly larvae are particularly aggressive tadpole predators. So are giant water bugs, diving beetles, and backswimmers.
• Birds – ducks, herons, egrets, and kingfishers all eat tadpoles when they can catch them.
• Snakes – several aquatic snake species specialize partially in tadpoles.
• Other amphibians – larger frog and salamander larvae will eat smaller tadpoles, including their own siblings in some species.
• Leeches – I saw plenty of these on my BC trip. They feed on tadpoles, occasionally on amphibian eggs, and on injured aquatic animals.
• Mammals – raccoons, otters, and even some shrew species will take tadpoles when easy to catch.

A common question: do goldfish and koi eat tadpoles? Yes. Both will readily eat tadpoles if given access. This is why backyard ponds with goldfish or koi rarely host frog populations – the fish eat the tadpoles before they can metamorphose. If you want frogs and toads in your garden, a fishless water feature is the move.

What to do if you find tadpoles

Every spring, kids and adults alike find tadpoles in puddles, swimming pools, garden water features, and stock troughs. The instinct to “save them” is good. The execution often makes things worse.

First, check your local laws. In some regions and for some species, collecting tadpoles is illegal. Native amphibian populations are declining globally, and many jurisdictions protect them. A quick search for your state or country plus “amphibian collection regulations” tells you what you can and cannot do.

If the tadpoles are in a pool that will be drained: transferring them to a nearby natural pond, stream margin, or wetland is usually the kindest option. Use water from their original source if possible. Move them in cool conditions (early morning or evening). Do not drop them suddenly into much warmer or colder water – acclimate them by floating their container in the destination water for 10-15 minutes first.

If you want to raise them as a learning project: a 5-10 gallon container with shaded position, dechlorinated water, aquatic plants, smooth surfaces (no sharp gravel), and a daily feed of small amounts of boiled lettuce or algae wafers can work. As they develop legs and approach metamorphosis, add a sloped surface or rocks they can climb out onto. They will drown if they cannot leave the water once their lungs develop. When they are fully metamorphosed (no tail, frog body), release them at a natural water source nearby.

If you find tadpoles in a swimming pool with chlorine: they will not survive long. Move them to dechlorinated water immediately – rainwater, well water, or treated tap water. Time matters with chlorine exposure.

What you should not do: release tadpoles into water bodies far from where you found them. Amphibians can spread diseases (chytrid fungus is a serious global problem), and moving them between locations risks introducing pathogens to new populations. Local water sources only.

Why tadpoles matter as ecological indicators

Amphibians are among the most threatened groups of vertebrates on Earth. According to the IUCN, more than 40% of amphibian species are currently threatened with extinction. The reasons are familiar: habitat loss, pollution, climate change, invasive species, and chytridiomycosis (a fungal disease that has driven multiple species to extinction).

Tadpoles are particularly sensitive to changes in their environment. Because they breathe through their skin and gills, they absorb whatever is in the water – pesticides, fertilizers, hormones, microplastics, all of it. A pond full of healthy tadpoles is a pond with healthy water. A pond where tadpoles are dying or developing deformities is telling you something about that water that fish and bird counts might not yet show.

This is why amphibian biologists use tadpole populations as bioindicators – early warning signs of ecosystem stress. The tadpoles tell you what is happening before it shows up in larger animals.

When I photographed the northwestern toad tadpoles in BC, the lake was full. Tens of thousands of healthy, dense, migrating tadpoles. That is what a functioning freshwater ecosystem looks like. Many lakes I have visited over the years no longer have populations like that. Documenting the ones that still do, and showing what they look like up close, is one of the small ways underwater photography contributes to conservation. You cannot care about what you do not know exists.

Frequently asked questions about tadpoles

What do tadpoles eat?

In the wild, young tadpoles eat algae, soft plant matter, and biofilm. As they grow, they add small invertebrates and decaying organic matter to their diet. If you are raising tadpoles, the safest foods are boiled lettuce, algae wafers, and small amounts of fish flakes. Avoid bread, meat, and chlorinated tap water.

How long does it take a tadpole to turn into a frog?

Most temperate frog and toad species complete metamorphosis in 8 to 14 weeks. Toad tadpoles are typically the fastest at 4 to 8 weeks. Bullfrogs are the outliers – their tadpoles can take 1 to 3 years, especially in cooler climates. Temperature, food, and habitat conditions all affect the timeline.

Do toads have tadpoles?

Yes. Almost all toad species go through a tadpole stage just like frogs do. Toad tadpoles tend to be smaller and darker than frog tadpoles, and they often school densely in groups. The easiest way to tell toad eggs from frog eggs is shape: toad eggs are laid in long strings, while frog eggs are laid in clumped masses.

What is the difference between toad tadpoles and frog tadpoles?

Toad tadpoles are usually smaller, darker, and often move together in dense schools. Frog tadpoles are typically larger, more variable in color, and tend to be more solitary. Toad tadpoles are also often mildly toxic or unpalatable to predators, which is why they can school in plain view without much defensive behavior.

What eats tadpoles?

Tadpole predators include fish (especially bass, perch, and pike), dragonfly larvae and other aquatic insects, ducks and wading birds, snakes, larger amphibians, leeches, and some mammals. Both goldfish and koi will readily eat tadpoles, which is why backyard ponds with these fish rarely host frog populations.

Do tadpoles eat each other?

Yes, occasionally. In crowded conditions or when food is scarce, larger tadpoles will eat smaller or injured ones. Some species are more cannibalistic than others. It is not aggressive behavior – tadpoles eat what is available, and a dead or damaged tadpole is protein.

Are tadpoles fish?

No. Tadpoles look fish-like and live in water, but they are amphibians – the larval stage of frogs and toads. Unlike fish, tadpoles undergo dramatic metamorphosis: they grow legs, develop lungs, lose their tail, and leave the water as adults. Fish never make this transition.

Can you keep tadpoles as pets?

In some places yes, in some places no. Many regions have laws protecting native amphibians from collection. If keeping tadpoles is legal where you live, they can be kept short-term as a learning project, but you should release them as froglets at the same water source where you found them. Long-term frog keeping requires very different care than keeping tadpoles.

How do tadpoles breathe?

Tadpoles breathe in three different ways depending on their developmental stage. Newly hatched tadpoles have external gills (visible as feathery structures behind the head). As they grow, internal gills replace the external ones and are covered by a skin flap called the operculum. As metamorphosis approaches, lungs develop and the tadpoles begin surfacing to breathe air, transitioning from water-breathing to air-breathing animals.

Why are some tadpoles so big?

Two main reasons. First, some species are simply large – American bullfrog tadpoles are massive, often 4-6 inches long. Second, individual tadpoles can grow large when they delay metamorphosis. If conditions for transformation are not right (temperature, food, the absence of safe land nearby), tadpoles can pause their development and continue growing as larvae. A big tadpole is sometimes one that has been waiting for better conditions, not one that is necessarily thriving.

What is a polliwog?

Polliwog and pollywog are alternate names for tadpoles, used especially in North America. The words come from Middle English “poll” (head) and “wiggle.” Tadpole, polliwog, and pollywog all refer to the same thing – the larval stage of frogs and toads.

Where can I see tadpoles in the wild?

Tadpoles live in freshwater habitats: ponds, lakes, slow-moving streams, vernal pools, ditches, and even temporary puddles in some species. Spring is the best time to look in temperate climates. Look in shallow, sun-warmed water near aquatic vegetation. Many tadpoles cluster in the warmest parts of a pond – margins, shallows, or warm pockets between rocks.

Why I keep photographing the small stuff

A lot of underwater photography is dramatic by default – sharks, whales, schooling fish, predators in action. Those subjects deserve the attention they get. But some of the most meaningful underwater work I have done has been at the other end of the size scale: thousands of small bodies that almost nobody has bothered to look at carefully.

Tadpoles are one of those subjects. They live for weeks, transform completely, and most people never see them up close. Bringing those images to people who would never get in the water themselves is exactly the kind of work that justifies all the cold mornings, the wetsuits, the camping on muddy lake banks. The ocean is worth saving. So is everything that lives in the freshwater systems connected to it. The tadpoles know that better than we do.

If you enjoyed this story, you might also like exploring some of my other underwater and conservation-focused work:

• If you are interested in underwater photography take a look a look at my How to Take Underwater Photos blog.
• Explore my Ocean Worth Saving series, where I document marine ecosystems and the species most affected by environmental change.
• See my underwater photography work featuring manta rays vs string rays, , and big-bull sharks.
• Browse my collection of underwater photography prints and t-shirts.

The farther I travel, the more convinced I become that every body of water is connected. The health of remote lakes, wetlands, rivers, and oceans is part of the same story. Sometimes that story looks like a breaching whale. Sometimes it looks like 10,000 tiny tadpoles moving through the morning light.