How to sex green tree frogs
How can you tell a male from a female frog?
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- Author(s)
- Dr Jodi Rowley
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- Category
- Science
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- Published
- 23 February 2015
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- 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
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caustichumor
Very Well-Known Member
- #1
Just a quick question, can you tell the sexes of green tree frogs apart with a visual examination, eg any stand out differances that are noticable?
JandC_Reptiles
Suspended
- #2
Im not too educated on frogs so feel free to correct me if I am wrong guys,
but I think you can sex males by their nuptial pads on their feet.
I believe they are bigger than females so as to aid in holding a partner down when breeding?
PremierPythons
Very Well-Known Member
- #3
Yeah mate nuptial pads on the males - the males croak too...
DoofinFrog
Not so new Member
- #4
My Green Tree Frogs have recently bred, and I will be damed if I know which ones are the males and females.
As for the nuptial pads......hmmm....never found those!!! I looked and looked but saw nothing. On the otherhand, I have a White Lip Green Tree Frog and he has been croaking and croaking calling for a partner (Unfortunatly I only have the male), anyway, he HAS developed darker pads on his feet.
The only thing I can say for sure, was that my Green Tree Frogs got right into croaking when it was time to mate....they would sit on a rock and croak for Hours....and this went on for a good week or so. Eventually the female gave in. I think (only think ) that my female is the larger of the frogs??
But look, I am not expert on the subject, just sharing my experience.
JasonL
Almost Legendary
- #5
some males also develop a dark redish brown throat during the breeding period, and are usually alittle smaller than a female.
meshe1969
Well-Known Member
- #6
Yep females are slightly larger than the males, plus the croaking and nuptial pads (males), oh and some times the throat of the male will be darker because of the stretching of the throat while croaking.
Ann
http://frogs.org.au/community/
Biologists figured out why frogs are green
July 15, 2020 13:03 Anatoly Glyantsev
Scientists have unraveled the secret of the green color of frogs with transparent skin.
Photo by Santiago R. Ron.
A special biochemical mechanism gives frog tissues a pronounced green color.
Photo by Andres E. Brunetti.
What gives frogs with almost transparent skin their camouflage green color? Scientists have found the answer to this question by studying the amazing trick of evolution.
What gives frogs with almost transparent skin their camouflage green color? Scientists have found the answer to this question by studying the amazing trick of evolution.
The achievement is described in a scientific article published in the journal PNAS.
Shades of the inner world
A person can choose whether to be in the Green Party or not, but frogs have no such choice.
If they do not have camouflage coloration, they will simply be eaten. What gives these amphibians the color so prized by environmental activists?
The skin of most species of frogs is rich in special staining cells - chromatophores. So Ivan Tsarevich, picking up the frog skin shed by the bride, would surely be convinced that it was green.
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True, a frog with transparent skin would be difficult for Ivanushka to find in his native swamp. But there are many of them in the forests of South America, Southeast Asia and Madagascar.
These tropical amphibians are literally green on the inside. They have colorless skin, but soft tissues, lymphatic fluid and even bones are brightly colored. But what?
Turned green from poison
Experts have long known that biliverdin is present in the green tissues of frogs in huge concentrations.
This is a greenish pigment that is part of bile and is formed during the breakdown of hemoglobin. The characteristic greenish hue of some bruises is associated precisely with its presence.
It would seem that this is the answer: biliverdin gives the tissues an unusual color. However, not all so simple.
First, biliverdin itself is slightly greenish rather than bright green. How, then, do tissues rich in this substance get their rich color?
Secondly, this pigment has toxic effects when it enters the blood and tissues. Therefore, the body of most vertebrates (including humans) is designed so that biliverdin does not accumulate in it. Unless with liver diseases, an increased (and dangerous) concentration of this compound in the tissues is observed.
But in the green tissues of frogs, the content of biliverdin is four times higher than in humans even with the most severe liver pathologies, and two hundred times higher than in frogs stained with chromatophores.
How do amphibians survive with such a concentration of a poisonous substance in their bodies?
A special biochemical mechanism gives frog tissues a pronounced green color.
Photo by Andres E. Brunetti.
Repaint and decontaminate
To answer these questions, biologists studied in detail the composition of the stained tissues of the tree frog species Boana punctata living in South America.
Scientists have discovered a special protein in the animal, which they called biliverdin-binding serpin (BSS). By binding to the biliverdin molecule, BSS changes its shape. As a result, the wavelength of the light reflected by the molecule changes, and biliverdin becomes bluish-green. This color is superimposed on the yellow color, which is given to the tissues by some other pigments, and as a result, the same "frog" green is obtained.
Apparently, BSS also changes the chemical properties of biliverdin, making it less poisonous.
This allows amphibians to withstand unprecedented concentrations of a dangerous substance, carelessly croaking.
Interestingly, evolution repeated this invention over and over again. According to the calculations of the authors of the scientific article, in the evolutionary history of frogs, BSS independently arose more than 40 times in 11 different families.
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science animals biology news
Scientists have confirmed the existence of a population of the Far Eastern tree frog in Shikotan. Sakhalin.Info
12:05 10 October 2016
Ecology, News of the Kuril Islands, Yuzhno-Kurilsk
Yuri and Larisa Sundukov, the scientists of the Kurilsky Reserve, conducted special studies and finally resolved the issue of the habitat of the Far Eastern tree frog on Shikotan.
The Far Eastern tree frog (Hyla japonica) is a small cute green frog with suction cups on its fingertips, thanks to which it is able to climb the leaves of trees, shrubs, and grass stalks. It is widespread in the nemoral zone of East Asia, occurring from Buryatia and the Sino-Tibetan Mountains in the west to the Japanese Islands in the east. It also lives in the Southern Kuriles.
But if in Kunashir this frog is quite common and was found by scientists almost throughout its entire territory, then the question of the Shikotan tree frog is almost a detective story, in which several stages are distinguished.
So, in the Japanese period, tree frogs from Shikotan were not indicated.
The first information about its habitation on the island appeared in 1949, when the Leningrad zoologist Andrey Strelkov caught two frogs in Tserkovnaya Bay, which are still kept in the collection of the Zoological Institute of the Russian Academy of Sciences in St.
Petersburg.
A young tree frog basking on a butterbur leaf in Tserkovnaya Bay
Tree frogs move well along grass stalks; Tserkovnaya Bay
Adult tree frog from Cape Ivanovsky, Kunashir
Over the next 60 years (1950-2012), no new information about the tree frogs of Shikotan has been received, although scientists have repeatedly visited this island, including to study its herpeto- and batrachofauna. For example, in 1972, a well-known amphibian specialist Lev Borkin (ZIN, St. Petersburg) worked in the vicinity of Malokurilsk. Another leading Russian herpetologist, Nikolay Orlov (ZIN, St. Petersburg), also visited Shikotan. At the request of Borkin, Sakhalin herpetologist Anatoly Basarukin repeatedly came to Shikotan in 1980-1990 and was specifically looking for a tree frog.
But his attempts were unsuccessful, the species was excluded from the fauna of this island. In 1995, in the article "How many species of amphibians and reptiles live on Sakhalin and the Kuril Islands? (Rumors and reliability)" Anatoly Basarukin concluded that a certain number of tree frogs were brought to the island by Japanese amateurs, but they gradually died out, and now the existence of these frogs on the island is doubtful.
During field work on Shikotan in the summer of 2012, Yuri and Larisa Sundukov noted the singing of males and met three adult tree frogs in Tserkovnaya Bay and one young frog in the upper reaches of the Gorobets River. But, not possessing the above information, they did not attach due importance to this. Only in June of this year, information about these findings was transferred to Borkin, as a result of which it became necessary to re-examine Shikotan in order to confirm these data, a more detailed examination of the island and biotopes in which amphibians are found.
Not all tree frogs are green. On a forest lake near the Tyatina River in Kunashir, scientists encountered an almost completely brown frog
Tree frogs develop in such reservoirs in the area of Tserkovnaya Bay, Shikotan
Therefore, when the opportunity arose to go to Shikotan in August, in addition to the planned seal counts and insect collection, experts decided to examine the island for the presence of tree frogs.
On August 12, a significant population of tree frogs was found in Tserkovnaya Bay in small coastal waters. On this day, we managed to see at least 50 frogs and 1 adult tree frog. In the following days, the "song" of a single male was heard in Malaya Tserkovnaya Bay and tree frog tadpoles were found in deep puddles on an old road in the middle reaches of the Gorobets River.
Thus, the habitats of the tree frog, found in 2012, were confirmed, and the issue of tree frog habitat on Shikotan Island was finally resolved in its favor.
This is how the tree frog biotope in Tserkovnaya Bay looks like from the slope of Mount Brusilov, Shikotan
In conclusion, it should be added that the tree frog was probably brought to Shikotan by the Japanese, and its population lived in the Tserkovnaya Bay for a long time in an oppressed state. That is why for more than half a century nothing was known about her, and A. Basarukin was never able to find her. As the latest survey showed, at present, after a period of acclimatization to new conditions, there is an active increase in the number of this frog in Tserkovnaya Bay and its resettlement in neighboring territories - in Malaya Tserkovnaya Bay and the Gorobets River basin, Sakh.com news agency reports with a link to the Kurilsky Reserve.
