Frogs are incredible creatures that can change their gender in natural settings. Frogs have been shown to be intersex, hermaphrodite, or to reverse their sex in polluted as well as pristine waters.
Many frog species are known to include intersex individuals that have changed gender or reversed their sex from male to female, or female to male. Generally, the number of individuals having experienced sex reversal represents 2 to 16% of the observed frog population.
Sex reversal is not uncommon in nature and fish and turtles are known to also be able to reverse their sex.
A frog’s gender is generally set by its genetics but scientists believe it can be changed, reversed, or influenced by pollution, weather, and temperature.
Frogs Can Be Intersex or Change Their Gender
For humans, sexual identity is a personal internal, external, or psychological sense of gender and can include identification as a female, a male, or as both, intersex, or non-binary (neither male nor female). Some people may transition from one sex to the other (transgender) to best represent who they are.
For frogs, they can be male, female, or intersex (display traits of both sexes). Some frogs can experience sex reversal based on water contaminants as well as weather and temperature in pristine conditions.
Although many studies have found that sex reversal in frogs is linked to pollution and is “unnatural” (Hayes et al, 2010), other studies have found that sex reversal in frogs be a natural occurence (Lambert et al, 2019).
“While sex reversal and intersex are often considered aberrant responses to human activities and associated pollution, we found no such associations here. Our data perhaps begin to suggest that, relative to what is often suggested, sex reversal may be a relatively natural process in amphibians.”Lambert et al (2019)
Some frogs may be hermaphrodites, intersex, or experience sex reversal. This can happen due to the presence of pesticides (Hayes et al, 2010) but may also be “a relatively natural process in amphibians” (Lambert, 2019).
Many Frog Species Can Change Their Gender
Intersex frogs and cases of sex reversal have been observed in a wide variety of frog species in scientific studies, from Common Reed Frogs (Grafe et al 1989), to Cricket Frogs (Reeder et al 1998), African Clawed Frogs (Hayes et al 2010), and Green Frogs (Lambert et al 2019, Skelly et al 2010) for example.
The African Dwarf Frog is a species where the males and females look so similar it is difficult to tell them apart. However, there are key features that can help you figure out the genders:
- When mating or when excited, the males of this species hum or sing.
- The females are generally larger and when they are ready to mate, exhibit more of a pear shape, indicating they are laden with eggs and ready to mate.
- If you look closely at the back of the male’s front legs and hands, there is a small white bump or black patch that is a gland thought to be helpful during mating.
- Males are generally smaller and have slimmer bodies than females.
African Dwarf Frogs are known to be either born hermaphrodites, intersex, or experience sex reversal. This is one of the reasons why they are often studied by scientists when it comes to gender in frogs (Hayes et al 2010).
However, it is difficult to observe intersexuality in frogs without scientific intervention, dissection (do not do this yourself) or observing African Dwarf Frogs over a certain period of time and looking for male or female traits (CTNF).
Why Frogs Can Change Gender
Overall, frog gender reversal and intersexuality in frogs are fairly novel to scientists with few studies on the topic, notably in pristine environments.
Scientists are still trying to understand why and how and why frogs may change their sex.
Although some speculate it is due to weather or temperature in pristine conditions, others believe it may happen to facilitate reproduction for survival (CTNF).
Overall, sex reversal in frogs is an incredible phenomenon that also occurs naturally in many other species such as fish, birds, reptiles, and rodents.
More About Frogs And Gender Reversal
Learn more about intersex frogs and the difference (and amalgamation in media) with “gay frogs,” in our articles below:
- How to Know a Frog’s Gender
- Are Frogs Gay? The Answer May Surprise You
- How Do Frogs Mate?
- Everything About Frog Aesthetic
Questions About Frogs And Gender Reversal
Are frogs male or female? Frogs can be male, female, or intersex (display traits of both sexes), and some frogs can experience sex reversal based on water contaminants as well as weather and temperature in pristine conditions.
Are frogs unisex? Frogs do not have to be strictly unisex since as much as 2% to 16% of given frog populations can be represented by intersex or sex-reversed individuals.
Are frogs asexual? Frogs reproduce sexually by amplexus through external fertilization, meaning a male and female frog are required for reproduction. The female frog releases her eggs into the water and the male frog simultaneously releases sperm cells to fertilize the eggs.
What is it called when a frog changes gender? When a frog changes gender it is generally called “sex reversal.” Some frogs may naturally be hermaphrodites, intersex (display traits of both sexes), or experience sex reversal.
Which frogs can change gender? Intersex frog and sex reversal have been observed in a wide variety of frog species from Common Reed Frogs (Grafe et al 1989), to Cricket Frogs (Reeder et al 1998), African Clawed Frogs (Hayes et al 2010), Green Frogs (Skelly et al 2010), and Wood Frogs (Lambert et al 2019).
Are all frogs both male and female? Frogs can be male, female, or intersex (display traits of both sexes). Therefore, not all frogs display both male and female traits as could frogs that are intersex or have experienced sex reversal.
Grafe, Ulmar & Linsenmair, K. Eduard. (1989). Protogynous Sex Change in the Reed Frog Hyperolius viridiflavus. In: Copeia (1989) 4, 1024-1029.. 1989. 10.2307/1445989.
Hayes, Tyrone B et al. (2010) “Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis).” Proceedings of the National Academy of Sciences of the United States of America vol. 107,10: 4612-7. doi:10.1073/pnas.0909519107
Lambert, Max & Tran, Tien & Kilian, Andrzej & Ezaz, Tariq & Skelly, David. (2019). Molecular evidence for sex reversal in wild populations of green frogs (Rana clamitans). PeerJ. 7. e6449. 10.7717/peerj.6449.
Max R. Lambert, Geoffrey S. J. Giller, Larry B. Barber, Kevin C. Fitzgerald, David K. Skelly. Proceedings of the National Academy of Sciences Sep 2015, 201501065; DOI: 10.1073/pnas.1501065112
Reeder, A., Foley, G., Nichols, D., Hansen, L., Wikoff, B., Faeh, S., . . . Beasley, V. (1998). Forms and Prevalence of Intersexuality and Effects of Environmental Contaminants on Sexuality in Cricket Frogs (Acris crepitans). Environmental Health Perspectives, 106(5), 261-266. doi:10.2307/3434013
Skelly DK, Bolden SR, Dion KB. Intersex frogs concentrated in suburban and urban landscapes. Ecohealth. 2010 Sep;7(3):374-9. doi: 10.1007/s10393-010-0348-4. Epub 2010 Sep 23. PMID: 20862600.
ISNA, Use of intersex vs hermaphrodite