Determining the sex of a snake can be tricky for novice and experienced herpetologists alike. With over 3,600 species of snakes in the world, encompassing a wide variety of shapes, sizes, and colors, there is no one foolproof method for sexing all snakes. However, with a basic understanding of snake anatomy and behavior, some simple techniques can help you identify whether that snake slithering through your yard is a male or female.
Look at the Length and Girth
One of the easiest ways to sex a mature snake is to look at its length and girth, as adult females are almost always longer and thicker than males of the same species. The reason for this size difference is that females must accommodate developing eggs inside their bodies. A female snake’s cloaca (the single opening for defecation, urination, and reproduction) also expands during the reproductive season to allow egg-laying.
So if presented with two adult snakes of the same type, the larger, fatter snake is most likely a female. For example, an adult female ball python may reach 5 feet long, while a male typically maxes out under 3 feet. The thickness of a female ball python during breeding season may be double or more the girth of a male’s mid-section.
This method isn’t foolproof, however, as some snake species don’t exhibit much sexual size dimorphism. Rat snakes, corn snakes, and king snakes, for instance, have males and females that are comparable in length and build. Younger snakes that haven’t reached full maturity can also be more challenging to sex based on size alone.
Check for the Hemipenes
The hemipenis is an external paired male sex organ exclusive to snakes and other squamates like lizards. All male snakes have two hemipenes, which are usually withdrawn into the base of the tail and hidden from view. When needed for mating, hemipenes become engorged with blood and everted, meaning turned inside out.
To identify hemipenes and confirm the sex of a snake, you gently press around the sides of the cloaca to push one or both hemipenes out. This may require applying firmer pressure than expected. If two spiky hemipenes emerge, the snake is definitely a male. The presence of hemipenes is the only surefire way to identify male snakes across all species.
Analyze Tail Length and Shape
While less reliable than probing for hemipenes, comparing tail length and shape can provide clues to a snake’s sex in some species. Males tend to have proportionally longer, more tapered tails than females to accommodate hemipenes. The tails of males may also appear blockier or club-shaped at the base compared to a slender female tail.
These differences help facilitate mating by allowing easier alignment of the male’s hemipenes with the female’s cloaca. For species like garter snakes and corn snakes, sexing by tail morphology can be upwards of 90% accurate. But researchers advise using this method in combination with other techniques to avoid mistakes, as some individual variation exists.
Look for Spurs on Each Side of the Cloaca
Many male snakes possess a pair of spurs, one on each side of the cloaca. These vestigial remnants of hind limbs are connected to cartilage inside the snake’s body. While they resemble claws, the spurs are not actually used for grasping or walking.
Spurs are present on males from birth and do not change in size throughout life. They are easiest to see on thicker-bodied snakes like pythons and boa constrictors. Spurs can help identify male individuals from birth in species that lack significant sexual size dimorphism as adults. However, the absence of spurs does not definitely indicate a female snake. Some male species like colubrids simply lack this trait.
Examine Scale Pattern and Color
Subtle differences in scale patterns, markings, and coloration between sexes provide additional clues about snake gender. These distinctions are often species-specific and may only be apparent to experts familiar with the snakes in question. Some examples:
- Male garter snakes usually have more vivid dorsal stripes than females.
- On brown snakes, the scales just below the cloaca are dark in males and light in females.
- Male northern water snakes possess dark crossband markings on their lips.
- Female copperhead snakes tend to have lighter copper heads than males.
So when presented with an unknown snake, an examination of its patterning and coloration may yield hints about its sex based on subtle sexual dimorphism. Combining this with other techniques helps confirm gender.
Analyze Behavioral Differences
Sometimes male and female snakes simply act differently in ways that reveal their sex:
- During the breeding season, male snakes actively search wide areas for females and engage in male-to-male combat.
- Receptive females stay in one area and release pheromones to attract males.
- When courting, males slither over and around the female’s body.
- Females become more defensive of their den when guarding eggs.
Observing a snake’s unique “personality” and interactions with other snakes can provide additional insight into whether the snake is exhibiting typical male or female behavior for its species. This further helps confirm gender when combined with physical and morphological evaluations.
Probe the Snake’s Cloaca (Popping)
One of the most reliable methods for determining sex in problematic snakes is to insert a small blunt probe into the cloaca to feel for the presence of hemipenes. This technique called “popping” should only be done by experienced herpetologists familiar with the risks.
Gently inserting and twisting a lubricated probe allows internal structures to be felt through the wall of the colon. Hemipenes have a distinct rubbery, spongy texture compared to other anatomy. This method may be needed for species that lack significant sexual size dimorphism and where hemipenes are challenging to invert for visual inspection. However, improper probing risks serious injury to the snake. It also causes significant stress that should be avoided unless necessary.
Use Lab Testing
For absolute certainty, a snake’s gender can be confirmed through laboratory testing. This involves collecting a small blood or shed skin sample and analyzing the DNA to identify the presence of male or female sex chromosomes. However, this method is expensive and primarily reserved for breeding programs requiring definitive sex identification. Simple physical examination combined with a knowledge of snake anatomy is still the most practical way to accurately sex pet snakes and snakes found in nature.
Conclusion
Identifying the sex of snakes relies on understanding the evolutionary adaptations that enable mating while accommodating egg development and birthing. While no single technique is foolproof, examining size, tail shape, hemipenes, spurs, scale patterns, behavior, and cloacal anatomy provides a toolkit for reliably determining gender. Equipped with this knowledge, the mystery of “is it male or female?” can be solved for any snake specimen crossed. Being able to properly sex snakes is an important skill for herpetology enthusiasts, breeders, and scientists seeking to understand these unique reptiles.
| Method | Reliability | Notes |
|---|---|---|
| Length and girth | High for mature snakes with sexual size dimorphism | Females larger than males. Unreliable for young snakes. |
| Hemipene probing | 100% accurate | Must everte hemipenes to confirm males; requires experience. |
| Tail length/shape | Moderate | Males have longer, tapered tails. Works best with other methods. |
| Spurs | High | Present on males from birth. Some species lack. |
| Scale patterns/color | Variable | Species-specific sexual dimorphism. Helps confirm other evidence. |
| Behavior | Moderate | Males search for females during breeding season. |
| Cloacal probing | High when done properly | Invasive; risks injury. Use with extreme care. |
| Lab testing | 100% accurate | Expensive; reserved for breeding programs. |
