Reptile & Amphibian Forums

I believe I have read of this happening before, maybe on this forum. But I have a female butter corn, whom I thought was to small to breed this year, so she was not put with any males. Absolutely, positively not with any other snakes, males or females. So I noticed that she was carrying eggs several weeks ago, and she was not very heavy, so she had an egg box, and yesterday laid 9 infertile duds as expected, and 1 good looking, nice, healthy egg. I have not candled it, but it is healthy and fertile from looks. She is an unusual corn anyway, as she seems to be developing a calico pattern as she is aging, becoming more and more white. She did not breed last year, as she was only a year old, this year she is almost 2 years (of course) and maybe 34 inches. Thoughts?

Spontaneous fertilizations aside, there is simply no way for a corn snake to lay a fertile egg without having been exposed to a male.

There have been supposed cases of a female holding back sperm from one year to the next, thereby producing fertile eggs without being exposed to a male THIS year...but even those reports are undocumented, and it is far mroe likely that the keeper simply made a mistake. It doesn't take very long at all for a determined corn to inseminate a receptive female, and having them together for even a minute or two while feeding or cleaning can definitely get the job done.

It may also be that the egg you see is not really fertile, but only appears that way. It's sometimes hard to tell, and if one looks dramatically different than the others, the distinction between fertile and infertile may be even more strained.

However, one thing upon which I can firmly stand is this. No corn snake lays a fertile egg without SOME exposure to a male for SOME period of time.

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Darin Chappell
Hillbilly Herps
PO Box 254
Rogersville, MO 65742

Cases of parthenogenisis are really rare in vertebrates. I think there might have been some documented cases in pythons or some such thing, but I've never heard of it in colubrids. I concur with Darin's hunch that some male snuck in that cage when nobody was looking. lol.

I recommend that you wait another week to candle that egg. There'll be more veins by then and it'll be easier to determine if it's fertile or not. I get lots of eggs that look good, but upon candling, don't have embryos.

IF (big IF) it turns out to be a nonconceived creation, it'll be a female and an exact clone of the mother. Hence, it will have the same markings right down to the scale. So since no two corns are the same (unless they're clones), the proof'll be in the markings.

Good luck.

Don
www.cornsnake.NET
South Mountain Reptiles

i agree that the egg is most likely infertile or that a male did somehow get in but as far as being identical in every respect, it just isn't the case. Yes it will be genetically identical but many factors other than genetics determine the overall appearance of an animal. Different temperature fluctuations or amounts of air and water available to the egg at different times during development can have an effect as to the extent of different features. The pattern will be VERY similar and it will be female but the pattern will not be identical

If we were working with mammals, I would agree that a parthenogenic offspring would be female. But colubrid snakes have the bird pattern of sex chromosomes. Males have a pair of large Z chromosomes, and females have a large Z chromosome paired with a smaller W chromosome. So I would expect a male from the egg instead of a female.

If a butter comes out of the egg, it might be virgin birth, or it might be the luck of the draw. But if a caramel, amelanistic, or normal baby turns up, there was a male in there sometime. Good luck.

Paul Hollander

Paul, why would you suspect the snake may be a male? Could not the "clone" baby snake inherit the W or the Z chromosome and be male or female and either way be infertile? Do the whiptail lizards that produce with parthenogenesis have the same WZ female chromosome makeup?
The egg still looks good tonight, I will candle it in a couple more days, thanks for the interesting conversation.