For most reptiles, sex is determined by environmental factors, most notably, temperature. This process varies greatly from how sex is determined for mammals, which is purely based on chromosomal pairs.
However, bearded dragons have a unique combination of chromosomal determination and environmentally-induced sexual reversal. This means that as an embryo, bearded dragons have a set of chromosomes that determine their sex, but temperature can change the overall outcome before they hatch.
This article will dive into how bearded dragons change their gender, and what that means for reptile owners caring for beardie eggs.
How Is The Sex of a Bearded Dragon Determined?
As we mentioned, there are two primary ways that the sex of a bearded dragon is determined: chromosomes and temperature. The chromosomes for bearded dragons form the baseline for how their sex is determined, but temperature can reverse the pre-determined sex of a bearded dragon.
Human sex is determined via chromosome pairs, with XX representing male and XY representing female. Bearded dragons have a similar chromosome structure, with ZZ representing male beardies, and ZW representing female beardies.
In the correct environmental conditions for bearded dragons, embryos will develop based on their assigned chromosomes. But, as temperatures start to deviate from the norm, RNA protein chains act differently, resulting in temperature-dependant sex determination.
Temperature-Dependant Sex Determination
Temperature plays a crucial role in determining the sex of bearded dragon (Pogona spp.) hatchlings, as in many reptiles. This phenomenon is known as temperature-dependent sex determination (TSD).
The sex of bearded dragon offspring is influenced by the temperature at which the eggs are incubated during a critical period of development.
At normal incubation temperatures (below 32 degrees Celsius), bearded dragon embryos will develop naturally. This means that ZZ pairs will be male, while ZW will result in females.
But, as temperatures rise above 32 degrees Celsius, ZZ embryos will begin to develop as females instead of males. This is known as sex reversal, and these female dragons are referred to as ZZ-reversed.
Bearded Dragon Sex Reversal in Nature
Temperatures fluctuate greatly in the desert climate that bearded dragons prefer, so sex reversal is a common part of the beardie development process.
Biologists from the University of Canberra’s Institute of Applied Ecology indicated that near the end of the breeding season, “it could be more advantageous to be male” because of their faster development to sexual maturity. But females born near the end of the breeding season must wait until the next season to rear eggs.
Taking this consideration in stride, female bearded dragons are able to manipulate the sex of their offspring in response to environmental conditions. Keeping eggs warmer, for example, would produce ZW hatchlings.
But, because of rising global temperatures, TSD in bearded dragons is seen as a risk factor for the species as a whole, as it is for other creatures like turtles and crocodiles. High temperatures in the bearded dragons’ natural habitat indicate that the population might become female-dominant, since ZZ-reversed females are more common when incubated at higher temperatures.
Bearded Dragon Sex Reversal in Captivity
Using the information uncovered about RNA protein switching and sex reversal, breeders can engineer conditions that change the sex of their bearded dragon eggs while in captivity.
However, it’s important to note that the specific temperature ranges and critical periods for sex determination can vary between different species and populations of bearded dragons. Additionally, extreme temperatures can be harmful or lethal to developing embryos, so it’s essential to maintain stable and appropriate incubation conditions.
It’s important to follow ethical guidelines for reptile breeding and care and ensure that the temperature manipulation is done responsibly to avoid harming the animals.
First-time reptile owners should avoid attempting to change the sex of their bearded dragon embryos, and instead focus on proper beardie care.