How to sex green tree frogs


How can you tell a male from a female frog?



  • Author(s)
    Dr Jodi Rowley
  • Category
    Science
  • Published
    23 February 2015
  • Read time
    2 minutes



Calling male Eastern Dwarf Tree Frog (Litoria fallax), with inflated, yellowish vocal sac. Image: Jodi Rowley
© Jodi Rowley


As a biologist, when I spot a frog, the first thing I try and figure out is what species is it. Relatively quickly after that, I want to know if it’s a male or a female. Below are some pointers in distinguishing male from female frogs- some rules are pretty stricly adhered to in the frog world, while others are a little less definitive.


  • Male frogs call

    Male frogs are the ones you hear croaking away all night from your backyard pond or local stream. Male frogs call from potential breeding sites to attract female frogs- females decide which calling male of her species sounds the most attractive and then approaches him. This is not to say that female frogs can't make any noise- they certainly do (for example, if a snake grabs a female frog you’ll generally hear a ‘scream’), but they don’t advertise themselves all night- they leave that to the males!

  • Male frogs have vocal sacs

    When male frogs call, their throat region usually expands as their vocal sac fills with air, amplifying their call. Because of this, when not calling, males tend to have obviously thin, baggy skin on their throat. This skin is also usually a different colour to their belly (often yellow or black).


A tiny male Odorous Frog (Odorrana sp.) from Vietnam in amplexus with a large female of the same species. Image: Jodi Rowley
© Jodi Rowley


  • Female frogs are generally bigger than males

    Although there are exceptions to the rule, female frogs are generally bigger and heavier than males. This makes sense, as females are the ones responsible for holding the eggs, and bigger females can hold more eggs (which potentially translates into having more offspring). Sometimes the size difference can be subtle, but sometimes it's dramatic, with females three times larger than males (Odorous frogs [Odorrana sp.] from Asia are prime examples of this). There are exceptions, though. Particularly where male frogs fight with each other (such as the Australian Tusked frog [Adelotus brevis] and Asian fanged frogs [Limnonectes sp.]), males have become larger than females.


The hand of a male Giant Burrowing Frog (Heleioporus australiacus). Males sport a large conical black spine on their thumb and smaller spines on their fingers during the breeding season. Image: Jodi Rowley
© Jodi Rowley


  • Males and female frogs often have slight differences on their hands and feet

    Male frogs often have small differently coloured and/or more roughly textured patches on their hands, especially on the insides of their thumbs. Often tricky to see, in the breeding season they often turn dark and become raised. Most Australian frogs have very subtle nuptial pads (slightly darker and more textured bits on the inside of their thumb), but male Giant Burrowing Frogs (Heleioporus australiacus) sport some pretty serious spikes on their hands in the breeding season. In a few species, it’s females that have the hand or foot adornment, but it’s generally in the form of fringes on the fingers or toes (the fringing is generally used for whipping up their eggs into a foamy nest).


Female (left) and male (right) toads (Bufo sp.) from China. Female frogs are generally smaller and weigh less than males. Males also often have larger and more muscly arms. Image: Jodi Rowley
© Jodi Rowley



  • Male frogs sometimes have thicker arms

    Male frogs sometimes have thicker, more muscly arms, making them look a little like they’ve been working out (a lot). Muscles probably come in handy when wrestling with other males or when holding on to the females as they carry them to a suitable breeding spot.


  • Male frogs are sometimes brighter than females

    Usually male and female frogs are roughly the same colour. But not always. In a handful of species, males are vastly different than females all the time. In others, males match the females most of the time, but get more colourful in the breeding season. One of the best examples of this is the Australian Stony Creek Frog (Litoria wilcoxii), with males turning from a relatively dull brown to a vivid yellow in the breeding season (especially when they are actually in amplexus).


Male (smaller and bright yellow) and female (larger and more dull in colour) Stony Creek Frogs (Litoria wilcoxii). Male frogs sometimes brighter than females, especially in the breeding season (particularly when in amplexus). Image: Jodi Rowley
© Jodi Rowley



  • Male frogs sometimes have rougher skin than females

    Sometimes there’s a difference in skin texture between male and female frogs. Most often, males have the rougher or spikier skin than the females. One of the best examples of this is the recently discovered Thorny Tree Frog (Gracixalus lumarius) from Vietnam. Males of this species have conical spikes running down their backs, while females are smooth.


Dr Jodi Rowley,
Amphibian biologist


More in this category

Archive by Category
  • AMRI (480)
  • At the Museum (267)
  • Education (98)
  • Explore magazine (28)
  • Museullaneous (463)
  • Science (784)

You may also be interested in.

..
Striped Rocket Frog

The Rocket Frog gets its name from its long pointed snout, but it could equally have got it for its impressive leaping ability.

Litoria nasuta

Read more
Crucifix Frog

This odd-looking frog is found in the black soil plains areas and semi-arid grasslands of New South Wales and Queensland where it burrows into soil to wait for the infrequent summer and autumn rains.

Notaden bennettii

Learn more
Frog sex

The amazing diversity of frog mating strategies.

No two frog species take the same approach to mating.

Read more
Eastern Dwarf Tree Frog

This little frog is usually a green colour but it can change colour to be brown or a mix of the two colours.

Litoria fallax

Find out more
Wanted! Eavesdroppers on Red Tree Frog conversations to better understand effects of urbanisation

Recording frog calls with the FrogID app may let us know how they are coping in urban areas.

FrogID
Frog calls

Read more
Australia's Lost Frogs

In the early 1980s, frog researchers noticed the sudden disappearance of two frog species from streams in southeast Queensland.

Discover more
The Aussie Green Tree Frog’s disappearing act from Sydney

FrogID reveals that Green Tree Frogs, once common throughout Sydney, are now few and far between

Read more
Two new Horned Frog species found on Vietnam’s highest peak

Two new, and likely highly threatened, frog species have just been revealed.

Horned frogs
New species
Herpetology

Read more
Robust Bleating Tree Frog

The Robust Bleating Tree Frog sounds more like a cicada than a frog.

Litoria dentata

Learn more
Great Barred Frog

This large frog lives in moist forests. It hides during the day, camouflaged beneath fallen leaves or burrowing into the loose soil.

Mixophyes fasciolatus

More details
Vampire Flying Frog

Vampire Flying Frog

Rhacophorus vampyrus

More details
Jervis Bay Tree Frog

Despite its name, this tree frog is known to live on most of the south-eastern coast of New South Wales.

Litoria jervisiensis

More details

Sex of green tree frogs

caustichumor
Very Well-Known Member