A female ball python that seems to be a male...

Dear VPI,

I have a question regarding the sex of a pied female that I own. I have been placing the female in with one of my male lemons but have not witnessed any breedings. She always reminds me of a male for some reason--for instance, she is a much more sporadic feeder than any of my other females, and she has a leaner build than other females.

I was so unsure that although she had been in with males I probed her which appeared to be female. When I withdrew the probes there were sperm plugs on the probe, my friends popped her and he was sure that she was female. I have not seen any combating with the males she was placed in with to indicate that she is female something just does not seem right.

Is it likely that the plugs on the probe from the female were left in from a male breeding her?

Also I have noticed that when my other males breed a lot the scales covering the vent become folded over. She, too, has the folded scales. Does this happen in females to when they have been breeding? Maybe it is just that I have not noticed before. I did check a different female that had been breeding today and there was no rolled vent scale.

I am tempted to put her in with another female for a few days to see if anything happens. Have you had any females that turned out to be males even after repeated sexing?   Regards, Colin. 


Dear Colin,

If you sexed this snake with a probe and did it correctly and there was some of what is (incorrectly) referred to as a "sperm plug" on the probe when you withdrew it, then I would say there is a strong probability that this animal is a male. A python "sperm plug" is better referred to as a "hemipenial cast" and is comprised of shed hemipenial skin and dried mucus, with probably a dash of the reptilian equivalent to smegma. We've never seen it form in a female python.

No species of python has or makes sperm plugs. A sperm plug is a waxy deposit that a male of some species of snakes (gartersnakes, for example) leaves in the gonadal openings of a female after copulation--the sperm plug blocks the sperm of other males from getting into the oviducts.

The rolled edge of the cloacal scale is a good observation on your part. I have never paid attention as to whether or not that is diagnostic of sex during the breeding season.

Male ball pythons rarely combat, so the absence of combat in non-informative. The build of your snake sounds like that of a male.

I don't think that is a girl. Of course, I cannot see the snake, so take my opinion as just that. But I've never heard of or encountered a female that has hemipenial casts. Maybe your breeding male is the female and this animal is the male?  Good luck with her/him,  DGB