How Frogs Reproduce: Everything There is to Know

It may seem confusing as to how frogs reproduce. It looks like they just sit there, hugging each other, waiting for some strange miracle to happen. But there is a lot more than just sitting and waiting going on when frogs mate.

As a general rule, frogs reproduce by amplexus through external fertilization. The female frog releases her eggs (ovum) into the water while the male frog simultaneously fertilizes the eggs by releasing sperm.

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However, not all frog species reproduce in this exact way. We’ll discuss what is considered the general way in which frogs breed (external fertilization in water) as well as ways that some specific frog species reproduce, lay their eggs, or care for them differently.

Frogs Reproduce During Mating Season

Frogs reproduce during their mating season which may take place during the early Spring in the Northern Hemisphere, during the Wet or Monsoon seasons, or at any time of year in humid, tropical locations.

Frogs generally like to reproduce and lay eggs when it is rainy and wet. Rain water replenishes dried ponds, lakes or bogs, providing more space for them to lay their eggs and for their tadpoles to thrive. Depending on where the frogs are located, Monsoon or Rainy Seasons may dictate when frogs reproduce.

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Most frogs can reproduce once they are over the age of 3 or 4. When the Mating Season begins, adult males find the pond where they were born, or an ideal location to reproduce, and call out to attract female partners of the same species.

They fill their vocal sacs with air and expel loud sounds that can be heard up to 1 km away depending on the species. Each frog species has a unique call to attract females of the same species. You can watch a Spring Pepper call out for mates in the video above.

Most Frogs Reproduce Sexually

Frogs reproduce sexually (meaning a male and a female are involved in reproduction) in a position called amplexus. If there are too few females in the group, some frog species are known to be able to experience gender change in order to facilitate sexual reproduction.

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Once the male frog has attracted a female mate, the couple will generally get into an inguinal or axillary amplexus position in order to reproduce. Most often, the male frog climbs onto the female’s back and clasps her around the waist.

Frogs have several amplexus postions but here are the two main types of amplexus frogs may use:

• Inguinal Amplexus: Occurs when a male frog clasps the female frog around her waist (inguinal region) using his forearms.
• Axillary amplexus: Occurs a male frog clasps the female behind her forearms (axillary region).

Male frogs generally develop large thumbs during mating season which help them remain in this position for the time it takes to lay and fertilize the eggs. Amplexus stimulates the female to lay eggs and can last a few hours to a few months depending on the species of frogs.

Male frogs may seem to try to reproduce with other males, dead females, other species such as fish, and inanimate objects in amplexus, but are trying to find a suitable partner. Male frogs generally quickly realized what they have grabbed is not a female they can reproduce with and move on.

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Once male and female frog of the same species are in amplexus, and in water, the female releases her unfertilized ovum into the water while the male simultaneously releases sperm cells to fertilize them, rendering the eggs zygotes, or newly fertilized eggs.

Most Frogs Reproduce in Water

Most frog species lay their eggs in water and choose shaded, shallow areas in ponds, marshes, swamps, vernal pools, or bogs to reproduce. Some frog species such as Spring Peeper chose to reproduce in water where there are no fish present.

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If you’ve ever found a mysterious patch of slime with dots in them, maybe you wondered if those were frog eggs. Frogs lay their eggs in a variety of different bodies of water including lakes, ponds, marshes, bogs, swamps and even in temporary puddles. This is because frog eggs require water to develop and survive.

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While most frogs do lay their eggs in water, some frogs can lay their eggs on the land or in trees. Some frog species may try to lure the females in trees and away from heavily male-populated areas in order to increase the male’s probability of fertilizing the eggs.

“Biologists noticed an apparent linear progression toward more terrestrial reproduction throughout frog evolution and proposed that frogs avoid putting their eggs and tadpoles in streams or ponds because they would be more vulnerable to aquatic predators.”

Rayna Camille Bell on Phys.org

This quote suggests that some frog species are evolving to lay their eggs on land. Laying eggs on land provide frogs more hidden areas to hide from predators (CTNF). These unique adaptations often take place in locations where water is harder to access or is more scarce, for example in the desert or other arid locations.

How Many Eggs Can Frogs Lay Per Reproductive Cycle?

Female frogs can lay 2 to 30,000 eggs during reproduction depending on the climate and species. Frogs lay a large amount of eggs to increase their chances of survival since few will become tadpoles and many will be eaten by predators or die of external or natural causes.

Here is how many eggs frogs can lay during reproduction depending on the species:

A group of frogs eggs is called frogspawn, spawn, or a clutch. How many eggs a frog can lay per reproductive cycle varies depending on the species, the frog’s health, and the climate.

For example, a healthy the Northern Leopard Frog can lay up to 5,000 eggs whereas American Bullfrogs can lay as many as 20,000. These frogs generally live in climates that have a Winter and so they hibernate part of the year.

Poison Dart Frogs generally live in tropical climates where they can be active all year and reproduce more frequently. However, they lay much less eggs than most species. Let’s have a look at how often some frogs reproduce.

How Often Do Frogs Reproduce?

Most frogs in the Northern Hemisphere including American Bullfrogs, Spring Peepers, and Common Frogs reproduce once per year and hibernate during Winter. However, many Poison Dart Frogs in humid and Tropical climates reproduce 3 or more times per year.

Here is a chart detailing how often certain species of frogs reproduce per year:

How often frogs reproduce is influenced by climate, temperatures, humidity, and seasons. Where there is a long Winter, frogs tend to reproduce less often because they spend a good part of the year hibernating.

Where the climate is tropical and consistently warm, frogs can generally be active and reproduce more frequently throughout the year.

Exceptions to How Frogs Reproduce

Not all frogs lay their eggs in water, reproduce by amplexus or use external fertilization. For example Bombay Night Frogs lay eggs in trees, and female Fanged Frog reproduce internally.

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Here are some exceptions to how most frogs reproduce:

• Solomon Island Leaf Frogs lay their eggs in clutches in the ground for example. The older a female Solomon frog is, the more eggs she produces for the clutch.
• Poison Dart Frogs lay their eggs in a bunch of different puddles in the rainforest and return to them to feed their tadpoles. They remember exactly where they left all their tadpoles and feed them multiple times a day.
• Glass Frogs, which live in Central and South America, lay their eggs above the river and streams so once the tadpoles develop, they can drop down into the water.
• Male Darwin Frogs swallow the developing tadpoles and carry them in his vocal sac until they are fully formed. When they are ready, he regurgitates them. This keeps the eggs safe from natural forces and predators.
• Fanged Frog can give birth to live tadpoles. This is a surprising discovery for scientists because the rest of the frog species either lays their eggs or give birth to fully formed froglets.

So the way in which frog eggs are produced, laid and protected can be quite unique to the frog species.

Frog Eggs Are Vulnerable to Many Predators

Frogs generally lay thousands of eggs per reproductive cycle since survival rates can be very low and or even decline. A scientific study found that of over 8,000 tadpoles, only 14% became adult frogs in 1999, and of over 16,000 tadpoles, only 8% became adult frogs in 2004.

Frogs lay thousands of eggs because some of them may not get fertilized during reproduction, others will be eaten by predators, and many will die of natural or external causes.

Climate change and urbanization are important external causes that is threatening frogs. Diseases and lack of water cause tadpoles to die or become stunted in their growth due to lack of space.

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Most frogs do not stay with their eggs to protect them, leaving them vulnerable to predators.

Frog egg predators include:

• Leeches
• Birds
• Dragonflies
• Salamanders
• Diving Beetles
• Large Water Bugs
• Large spiders
• Fish
• Snakes

Frog eggs have no self defence mechanisms compared to adult frogs that have sophisticated ways to avoid predators. Predators attack and eat frog eggs that are very nutritious and easy to find.

Questions Related to How Frogs Reproduce

How do Frogs Reproduce? Frogs reproduce through external fertilization meaning that male frog’s sperm fertilizes female eggs outside of the female’s body. The female releases her eggs into the water and the male frog simultaneously releases sperm cells which then fertilize the eggs.

How Can You Tell if a Frog is Pregnant? Frogs do not get pregnant since they reproduce externally. Female frogs naturally carry thousands of ovum that they release into water during amplexus for a male frogs fertilize. Frogs do not carry their offspring inside their bodies like most mammals so they cannot get pregnant.

Why Do Frogs Hug Each other? Frogs “hug” each other in amplexus, a position in which frogs reproduce. Once mating season begins, a male frog will call and attract a female frog, climb onto her back and clasps her around the waist to start the reproductive cycle.

What are Frog Eggs Made Of? Frog eggs are made of a female frog’s embryo that is fertilized by a male frog’s sperm. Most frog egg are laid in water that they quickly absorb to form a protective jelly around them that allows them to cluster together.

How Long Does it Take for Frogs to Reproduce? Generally it can take frogs a few hours to a few days to reproduce. Some frogs were found to take 5 seconds to 2 months or more to reproduce, although during longer periods amplexus but little fertilization may take place.

What Does Frog Spawn Look Like? Frogspawn looks like a big jumble of clustered, round, jelly-like chia seeds balls with a black dot in the middle. The black dot is a future tadpole and the cluster is a clutch of frog eggs generally found in small bodies of water.

Do Frogs Reproduce Sexually or Asexually? Frogs reproduce sexually meaning a female and a male frog must be involved. A female frog is required to lay eggs and a male frog is required to fertilize them with sperm.

Sources

Nussbaum, Ronald A. (1980). “Phylogenetic Implications of Amplectic Behavior in Sooglossid Frogs”. Herpetologica.  ISSN 0018-0831. JSTOR 3891845.

Chesne, Corinne. La Grenouille. Artémis éd., 2009.

Parsons, Harry. L’univers Des Grenouilles: Amphibiens Poseurs. Éditions Du Trécarré, 2000. 

De Vecchi, S. Caratozzolo. Grenouilles, Crapauds Et Rainettes: Morphologie, Comportement, Alimentation Et Reproduction, 2008.

A Novel Reproductive Mode in Frogs: A New Species of Fanged Frog with Internal Fertilization and Birth of Tadpoles. PLOS ONE e0119988. https://doi.org/10.1371/journal.pone.0119988.

Kendell, Kris. Northern Leopard Frog Recovery Program, Year 6, 2004.

Willaert, B., Suyesh, R., Garg, S., Giri, V.B., Bee, M.A. & Biju, S.D. A unique mating strategy without physical contact during fertilization in Bombay Night Frogs (Nyctibatrachus humayuni) with the description of a new form of amplexus and female call. PeerJ, 4: e2117. 2016

Robertson, J.G. Female choice, male strategies and the role of vocalizations in the Australian frog Uperoleia rugosa. Animal Behaviour, 34(3): 773-784. 1986