Can you tell the gender of a snake just by looking at its tail?
Q. What do you think about the claim of a U.S. snake seller that he can sex snakes with complete accuracy just by looking at their tails? I bought rat snakes and kingsnakes from him, and I don't think he even knows what a sexing probe is. The funny thing is that he was 100-percent correct about the ones he shipped to me. I probed them myself. He said the tails have different shapes that can be easily seen, but they look the same to me.
Roelf Van Der Schaaf
A. The ability to visually sex snakes, especially adult specimens of Elaphe (rats) and Lampropeltis (kings), is easily accomplished by someone with experience – that is true. Males have longer and thicker tails than do females. The difference is not hard to see once you've had a few examples of known sexes to study for a moment.
To approach the task the first time, ask a friend to hold an adult male rat snake (any species) in the right hand and an adult female rat snake in the left. Have your friend stand about 10 feet away from you. The lower halves of each snake should hang down freely with the snakes' bellies facing you. Have your friend line them up vertically so the cloacas are side by side. Study their profiles for girth and length comparison.
It should be a cinch to distinguish which tail is longer and thicker at the base. That will be the male. The hemipenes swell the first 2 or 3 inches below the cloaca in males. Hemipenes also make that part of the tail appear the same girth as the cloacal region before tapering further down toward the tail tip. Any person can see the bulge if they know what they're looking for.
About 20 years ago, an old pal of mine (not a herper) swore he couldn't see any difference when staring at a sexed pair of corn snakes that were perfect models of the features I'm trying to explain. I was incredulous that he couldn't immediately see the difference between the male and female. Then I realized he was looking for a bold, obvious disparity of sizes that doesn't actually exist. He was looking for a glaring difference, not a subtle one.
If people can determine human gender from hundreds of feet away, their eyes are more than sharp enough to spot the sexual difference in tail sizes of mature colubrid snakes. Boosted by that reality, my friend recalibrated his expectations and instantly saw the tail differences between males and females without further difficulty.