This is a work in progress and will be added to when new pictures are available.
While probing seems to be the surest way to sex most species of snakes, many can be visually sexed with a reasonable degree of certainty. There are several ways to visually check for sex; some ways are better for one genus or spcies, some ways are better for others.
I do not plan to cover popping hemipenes or probing snakes here. That you should learn by watching and learning from someone experienced.
On most colubrids, checking the ventral area or checking for scent glands on the females is a good way. On sand boas and hognose snakes, tail size and length is good. On many boas and pythons, spur size is a good indicator. I find spur size to be a more dependable method than probing on some of my species, such as Dumeril's boas and Savu pythons. With many juvenile snakes, "popping:" for the presence of hemipenes is usually reliable, once you learn how to do it. Some people pop hemipenes on larger snakes, but I don't like to do it. They have more musculature than juveniles and I think there is a possibility of damaging the snake if sufficient pressure is applied.
Bear in mind that these are techniques that I like to use - others have their own techniques. Most of these methods I have learned from others over the years, some I have discovered on my own, even though they were already known by others.
This page will deal with American Colubrid snakes. Other genera will be linked as they are created.
Visual on Tail Length
These pictures are of neonate Mexican Hognose Snakes, Heterodon nasicus kennerlyi. The snakes are about 4-4.5" long. On adults sexing is easier, but it is readily evident even on hatchlings once you get used to it.
The picture on the left is of a female, on the right is the male. The female has a much shorter tail, somewhat stubbier in appearance. On the male the tail is much longer and not stubby.
From the side view on the ventral surface, the female may have a "dip" behind the cloaca, as is evident in the picture on the right. On males the tail goes straight back. This is noticeable on many colubrid snakes.
Owing to the small size of the tails of neonate nasicus, and the ease with which they can be visually sexed, I do not recommend either "popping" or probing as a method of sexing on them.
|Frequently female colubrids will "pop" or evert their cloacae. This may also be accompanied by a discharge of musk or urea. Two small red spots can be seen just aft of the cloacal scale on either side of the vent. These are the tips of her scent glands.
Males sometimes do this, but not nearly so often as females. With the males, there is occasionally a discharge of semen, which can be told from musk with a bit of practice or a sensitive nose. Also with males the tips of the hemipenes are often visible. This may be confused with the red spots on the females, which are the scent glands, but can be told apart with a bit of practice.
In adult or subadult females, the red spots (scent glands) can usually be exposed by pulling forward on the cloacal scale.