Many people know that most frogs start their lives as tadpoles, which metamorph into mature frogs over time. Toads are a type of frog, so you may be wondering if they too have tadpoles. So, do toads have tadpoles?
Most toads lay eggs in water, which hatch into tadpoles. Over time, the tadpoles go through metamorphosis and transform into young toads. However, a few toad species do not have a tadpole stage – they lay eggs which then hatch into toadlets, or retain the eggs inside their bodies and give birth directly.
Toads are found on every continent, excluding Antarctica. With this wide distribution, they live in a very wide range of habitats, from humid forests, to dry regions.
Some toads live in areas with a shortage of surface water suitable for tadpoles to live in. For this reason, they adapted to their environment and developed breeding methods that are practical for the areas they live in.
Most Toads Have a Tadpole Stage
Unlike most frogs which lay their eggs in masses. Toads lay their eggs in long strings, usually one to three eggs wide. The egg strands are placed on submerged vegetation or rest on the pond’s bottom.
After a few days, to a few weeks, tiny tadpoles hatch from these eggs. Tadpoles are very different from adult toads; this is because they’re adapted for a fully aquatic life (life in the water), while adult toads are adapted for a mostly terrestrial life (life on land).
Tadpoles have external gills and a flat paddle-like tail fin for life in the water. They use their gills to breathe underwater, just like fish.
After anywhere from 9 to 16 weeks, these tadpoles will go through a process known as metamorphosis and transform into miniature toads that live on land.
During this process;
- They lose their gills and get well-developed lungs for breathing air
- The tail shortens and is eventually absorbed into the body
- They develop strong legs for moving on land
Once this process is complete, tiny toadlets (small toads), typically half an inch long will leave the water and live a fully terrestrial life.
These toadlets will grow into adult toads and once they mature, they will go back to the water to breed and lay their eggs.
Some Toads Do Not Have a Tadpole Stage
Some toads live in environments with low availability of undisturbed surface water suitable for tadpoles to live in. For this reason, they have developed unique breeding strategies to be able to reproduce in their harsh environments.
These toads do not have a tadpole stage. They lay eggs on land, often in most soil – which then hatch into toadlets, or retain the eggs inside their bodies and give birth to young fully-developed toads.
When toads (or other animals), retain their eggs inside of their bodies until they hatch, this is known as “Ovoviviparity.”
One study found that toads that do not have a tadpole stage almost always lived in environments with steep terrain and low availability of accumulated water sources. The lack of a tadpole stage is necessary for the survival of their species.
A few toads without a tadpole stage include the following:
- Kihansi spray toad (Nectophrynoides asperginis)
- Pseudo forest toad (Nectophrynoides pseudotornieri)
- Frontier forest toad (Nectophrynoides frontierei)
- Smooth forest toad (Nectophrynoides laevis)
- Minute tree toad (Nectophrynoides minutus)
- Tornier’s Tree Toad (Nectophrynoides tornieri)
- Morogoro tree toad (Nectophrynoides viviparus)
- Uzungwe Scarp tree toad (Nectophrynoides wendyae)
- Vestergaard’s forest toad (Nectophrynoides vestergaardi)
- Wide-headed viviparous toad (Nectophrynoides laticeps)
- Western Nimba toad (Nimbaphrynoides occidentalis occidentalis )
- Liberia Nimba toad (Nimbaphrynoides occidentalis liberiensis)
Frog Tadpoles vs Toad Tadpoles: The Differences
Frogs and toads often lay eggs in the same water bodies. While toad eggs are fairly easy to differentiate from frog eggs toads lay eggs in strings while frogs lay eggs in masses), that is not the same with the tadpoles.
Toad tadpoles look very similar to frog tadpoles and can be very difficult for the average person to tell apart. However, there are a few differences between the two.
Toad tadpoles |
Frog tadpoles |
|
| Body shape | Tend to be short and chunky | Tend to be longer and slimmer |
| Coloration | Are often plain jet-black (not always) | Often have markings (again, not always) |
Apart from these differences, frog and toad tadpoles can be difficult to tell apart. They have many similarities, they both have external gills (in their early stage) and a flat paddle-like tail fin for life in the water.
Also, both frog and toad tadpoles have very varied coloration, and can sometimes be similarly colored. Toad tadpoles are not always black, and sometimes even have markings.
The differences between frog and toad tadpoles can be compared to those of adult frogs and toads – toads are often shorter and chunkier than frogs.
Having a Tadpole Stage Has Disadvantages
The tadpole stage is the most vulnerable stage of most frogs and toad’s lives. Toads and frogs often lay eggs in temporary pools of water, and sometimes, these pools dry up before the tadpoles have had enough time to metamorph into adults.
Also, sometimes many frogs and toads lay eggs in the same pools, and when the eggs hatch, the pool will be crowded. This means the tadpoles have to compete for space and other limited resources.
Overcrowding often leads to cannibalism in which large tadpoles eat small, vulnerable tadpoles. For example, large cane toad tadpoles have been documented eating smaller tadpoles of their own species.
Tadpoles are also preyed on by fish, adult frogs and toads, salamanders, newts, birds, snakes and other reptiles, many mammals, and even predatory insects such as water boatmen and dragonfly larvae.
For these reasons, up to 95% of tadpoles never live long enough to undergo metamorphosis and transform into adult frogs and toads.
Some Tadpoles Can Defend Themselves From Predators
Due to their high vulnerability to predators, tadpoles have developed several ways to defend themselves.
When a predator has been detected, most tadpoles will dive to the bottom of the water and hide among aquatic plants. They then blend into their environment, escaping the notice of the predator.
Some tadpoles, like those of the American toad, also avoid predators by swimming in very shallow water, and by swimming close together in schools during the day.
Also, many species of tadpoles have potent toxins that make them unpalatable to some would-be predators. A predator that tries to eat a poisonous tadpole will get a foul taste in the mouth, and let go right away.
Some tadpoles, such as those of the European common frog and the Moor frog grow longer tails when in the presence of predators. With longer tails, the tadpoles swim faster and are better at avoiding predators.
Frequently Asked Questions (FAQS)
Do toads lay eggs on land? Most toads lay eggs in the water – these eggs are laid in long strings (usually one to three eggs wide). The eggs then develop and hatch into aquatic tadpoles. However, some toads such as the Ethiopian mountain toad lay eggs on land, usually in vegetation or occasionally under logs or in leaf litter.
How long does it take toad tadpoles to transform into toads? Generally, it takes about 9 to 16 weeks for tadpoles to develop into toads. However, exactly how long it takes a specific tadpole to develop into a toad will depend on many factors, such as the environmental conditions, availability of food, and the toad species.
What does a toad tadpole look like? Toad tadpoles are often jet-black and have short chunky bodies. This is in contrast to frog tadpoles which tend to be longer and Skinner, often with spots or flecking.
How many babies do toads have at a time? Toads lay anywhere from 2 to as many as 30, 000 eggs in a single breeding season. For example, the yellow-belied toad typically only lays 2 to 30 eggs at a time, while cane toads can lay up t0 30, 000 eggs in a single breeding season.
Conclusion
Toads are intriguing creatures that tend to capture the curiosity of many people. Now you know that the vast majority of toads have a tadpole stage, while a few species do not.
The toad species without a tadpole stage are very rare and are only found in a few parts of the world. So, if you ever see a toad, it most likely has a tadpole stage.
Photo credit: J. N. Stuart via Flickr (CC BY-NC-ND 2.0). Kat Avila via Flickr (CC BY-NC-ND 2.0). edhass via inaturalist (CC BY-NC 4.0)