Egg temp & gender probabilities

While I'm thinking about it I better ask haha. The sex of reptiles depends on temps while in the egg...I believe lower is prone for females (please correct me if I'm wrong) so if setting temps on my future clutches lower would give me a higher probability for females right? Does anyone do this?


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No. The gender of most if not all snakes is not determined by temps. That does however apply to several gecko species and crocs as well. Anything else not sure on

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Originally Posted by T&C Exotics

No. The gender of most if not all snakes is not determined by temps. That does however apply to several gecko species and crocs as well. Anything else not sure on

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^This. :gj:

So I did some more research and some breeders did document lower temps made more females and bigger and healthier babies. But like you guys said, temp doesn't determine sex of the snake. Though I think I will do temps lower like 87-87.5 because it's healthier on the babies. It will take longer but that gives the babies to cook longer ;) thanks for the inputs!


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Just remember that correlation does not equal causation! Just because clutches kept at lower temps occasionally have more females, or have produced healthy babies, it doesn't necessarily mean those things happened because of the lower temps. Let us know how the experiment goes!

If you incubate at low temps you will get a fully developed dead baby snake... If you incubate too high you get a possible skeletal deformity... So I would be careful if I were you.

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Thanks guys, you both have said some helpful things! One breeder said they keep theirs around 87-87.5. I def want to try this experiment out but I think I'll try it out on my second clutch, not my first :)


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pythons have sex-determining chromosomes.

in humans, men have "XY" and women have "XX", and half of the children will get the Y-chromosome, and its determined at the moment of fertilization.

its similar in pythons, except that the roles of the genders are the other way around. so we use different letters, to avoid confusion. males have "ZZ" and females have "ZW". half of the unfertilized follicles get "W", the other half gets "Z". when they get fertilized and each follicle gets another "Z", the gender is already determined.

its not like this in all reptiles, many reptiles do not have this mechanism.

i found this paper, it doesnt specifically mention pythons, but it really explains it all:

http://www.plosbiology.org/article/i...l.pbio.1001643

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Sex chromosomes have evolved from non-sex-determining chromosomes (autosomes) multiple times throughout the tree of life. In snakes, females are the heterogametic sex, in that they have two different sex chromosomes, Z and W, while males have two Z chromosomes. However, while in some snake species (e.g., boids) the Z and W chromosomes look identical (“homomorphic”), in others (e.g., vipers) they are very different in size and structure (“heteromorphic”); yet other species (e.g., colubrids) appear intermediate between these two states. This diversity makes snakes ideally suited for studying the evolutionary dynamics of sex chromosome differentiation.

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i found other sources that specifically mention pythons. the species of reptiles where temperature is the deciding factor lack this mechanism, males and females have the same genetics, and the difference between the genders is that different genes are switched on or off. but when such a mechanism is in place, sex determination is entirely independent of outside influence, it all happens in the female long before the eggs are fully formed.

Pythonfriend--that is really interesting, thanks for sharing! Clears up a lot of questions!


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Originally Posted by Scirlygirl

While I'm thinking about it I better ask haha. The sex of reptiles depends on temps while in the egg...I believe lower is prone for females (please correct me if I'm wrong) so if setting temps on my future clutches lower would give me a higher probability for females right? Does anyone do this?


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Works with some reptiles for example leopard geckos but not with Ball Pythons if it did no one would complain about their sex ratio ;)