Everything to Know About Frog Amplexus

There are numerous mating traditions and positions throughout the animal kingdom, and amphibians use one of the most interesting types: amplexus. The position in which frogs reproduce can be perplexing for many frog enthusiasts since the use and form of amplexus can differ depending on the species.

Amplexus is a reproductive position used by frogs, generally where the male is on the female’s back. There are 10 known amplexus positions at the moment, and the vast majority of frog species use an amplexus position for sexual, external reproduction.

While frogs generally use amplexus for mating, there are still many notable considerations and variations between species. Join me as I discuss what amplexus is, why frogs use this position to reproduce, and when these reproductive practices may differ between frog species. 

What Is Amplexus?

Amplexus is a sexual reproductive position taken on by frogs in order to reproduce externally. Generally, a male frog is on a female’s back, sometimes clasping her to stimulate the release of her eggs. Once she starts to release her eggs, the male begins fertilizing each one with sperm cells. 

When Does Amplexus Take Place?

Frogs generally mate in amplexus during the Spring, the Wet or Monsoon season.  Male frogs generally attract females with their species-specific croaks and calls during mating season and get into amplexus once in freshwater.

Once a male and a female are together and in water, the male climbs onto the female’s back to get into amplexus and start the reproductive process. Frogs generally need to be at least 3 or 4 years of age to reproduce properly. Most frogs reproduce in rainy and wet weather since rain presents ideal reproductive weather frog frogs that breathe and drink through their skin (CTNF).

Frogs typically reproduce in Spring within the Northern hemisphere and throughout the year in the Southern hemisphere. The Southern hemisphere often has humid and warm weather throughout the year, making it easier for frogs to reproduce. Frogs may also reproduce during rainy or Monsoon seasons depending on their location and the species.

Where Does Amplexus Take Place?

Most frogs select shaded, slow-moving, freshwater bodies for amplexus provided that the environmental conditions support the reproductive process and the development of fertilized eggs. 

Frog Lifecycle-min

Frogs commonly choose the following areas for amplexus:

  • Ponds 
  • Swamps 
  • Marshes 
  • Lakes 
  • Puddles 
  • Bogs
  • Fens

How Often Do Frogs Reproduce in Amplexus?

Most frog species, including many species within the Northern hemisphere, reproduce once a year during mating season. However, some frog species can reproduce 2 or more times per year. Such species include many frogs living in humid tropical parts of South America.

Depending on the species, amplexus can last a few hours to a few weeks. Some frog species can take a few minutes to reproduce, while it can take days or weeks for other species. Female frogs are stimulated to lay eggs during amplexus, and male frogs develop physical adaptions to aid the process. 

Males generally experience specific adaptions during mating seasons, such as enlarged thumbs (nuptial pad), or brightly colored skin. Developing enlarged thumbs helps the males maintain the assumed position during amplexus, ensuring that the reproductive process is efficient. Some frogs change color to make it easier to distinguish females from males.

Intersex Frogs Gender Reversal Change-min

The female frog can release hundreds to thousands of eggs depending on the frog species, and most frog species can release anywhere from 2 to 30,000 eggs at a time. The frog eggs are fertilized by the male sparking the beginning of their metamorphic journey from zygotes to mature frogs. 

Frog Amplexus Positions

There are 10 known amplexus positions including Inguinal, Axillary, Cephalic, Head Straddle, Glued, Gular, Lose, Scapular, Independent, and Dorsal straddle. However, the most common amplexus types are Inguinal and Axillary. 

Inguinal Amplexus

Inguinal Amplexus describes the process where the male clasps the female from behind with his forearms, using her waist as support. The name was gained since the waist section of a frog is known as the inguinal region. This position helps stimulate the female’s egg release.

Axillary Amplexus

Axillary amplexus describes the process where the male will grasp the female from behind using her forearms for support. The name was gained since the forearm section of a frog is known as the axillary region. This position also helps stimulate the female’s egg release (CTNF).

The remaining amplexus positions are less common and their use is generally dependant on the species. The use of other positions also depends on sexual dimorphism and intersexuality in frogs.

Do All Frogs Reproduce The Same Way? 

Although most frog species use amplexus as an aquatic reproduction method, some species have adapted and have begun using other approaches for reproduction. Many arboreal and terrestrial species do not use amplexus, and some frog species lay their eggs on land or keep their eggs inside their bodies. 

Frog SpeciesEgg LocationProcess
Solomon Island Leaf FrogsGroundThese frogs lay their eggs in moist ground, where the zygotes can absorb moisture from the surrounding soil. 
Poison Dart FrogsPuddlesThey lay their eggs in puddles throughout their habitats, returning to feed their tadpoles multiple times every day. 
Glass FrogsAbove WaterThey lay their eggs on leaves above rivers and streams so that the developed tadpoles can fall down into the water below. 
Darwin FrogsMale Vocal SacMales swallow developing tadpoles, carrying them in the vocal sac until they become froglets. 
Fanged FrogGives Birth to TadpolesThese frogs do not lay eggs and can support the development of tadpoles inside their bodies.

Some frog species may exhibit unusual or abnormal amplexus practices. Such cases include ‘breeding balls’, where multiple males clasp onto one female, or cases where males attempt to partake in amplexus with deceased females or inanimate objects.  This is common because most frogs use a trial-and-error process to find suitable mates.

More About Frog Reproduction And Amplexus

Learn more about frog reproduction and amplexus on our blog:

Sources 

Carvajal-Castro, Juan & López, Yelenny & Ospina-L, Ana & Santos, Juan & Rojas, Bibiana & Vargas-Salinas, Fernando. (2019). Much more than a clasp: Evolutionary pattern of amplexus diversity in anurans. Figure 1. 10.1101/854117. 

Sung, Y.-H.,  Lee, W.-H.,  Ng, H.-N.,  Crump, M. L., and  Karraker, N. E..  2021.  Novel reproductive behavior in an Asian frog: sex-reversed inguinal amplexus. Ecosphere  12( 3):e03407. 10.1002/ecs2.3407

Willaert, Bert & Suyesh, Robin & Garg, Sonali & Giri, Varad & Bee, Mark & S D, Biju. (2016). 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. Figure 4. PeerJ. 4:e2117. 1-21. 10.7717/peerj.2117.