Green Turtle Gender: Spotting The Difference

Green turtles are fascinating creatures, and telling them apart by gender is a tricky task. While juvenile green turtles have no distinguishable external differences, there are some features that can help identify their sex once they reach sexual maturity. Male green turtles develop a long tail, which may extend past the hind flippers, while females have shorter tails that don't extend more than 10 cm beyond the carapace. Male turtles also have elongated, curved claws on their front flippers, which they use for grasping during mating. Another distinguishing feature is the shape of the plastron, the underside of the shell. Male turtles have a concave plastron, curving inwards, while female turtles have a flatter plastron, providing more room for growing eggs.

Shell size and shape

The shell, or carapace, of a green turtle differs slightly between males and females. An adult female turtle has a slightly longer shell than an adult male. However, it is difficult to determine the gender of a turtle based on shell size and shape alone, as there is an overlap in size between large males and small females. Therefore, it is important to look for other clues as well.

The bottom of the shell, called the plastron, is another indicator of gender. Male turtles have a concave (curved inwards) plastron, while females have a flat one. This shape difference enables male turtles to more easily mount a female during mating, and it gives females more room to hold eggs internally. However, it is important to note that the turtle must have reached its adult size for this to be a reliable indicator of gender.

In addition to shell size and shape, other factors such as claw length, tail size and shape, and species-specific markings can also be used to distinguish between male and female green turtles.

Tail length and thickness

Male turtles have longer and thicker tails than females. The male's genitalia are located within the tail, which houses the reproductive organ. The tail may extend past the hind flippers. The female's tail is shorter and thinner, generally not extending more than 10 cm (4 inches) past the edge of the carapace.

The vent or cloacal opening is also located differently on the tail depending on the gender. The female's cloaca is rounder and more star-shaped, found at the base of her tail where it joins her body, almost disappearing into the shell. The male's cloaca is longer and more slit-like, located in the last third of the tail, towards the tip.

Determining the gender of a turtle by examining its tail is not as easy for beginners as some other methods, but it is a good indicator when distinguishing between male and female turtles.

Vent/cloaca position

The position of the cloaca/vent is one of the most consistent indicators of a turtle's sex. Both male and female turtles have a vent/cloaca, but its position differs between the sexes.

The female's cloaca is rounder and more star-shaped than the male's. It is found much closer to her body, at the base of her tail where it joins her body, almost disappearing into the shell.

The male's cloaca is longer and more slit-like. It is located in the last third of the tail, towards the tip.

The male's genitalia are located within the tail, and the position of the vent/cloaca is related to this. The female's vent/cloaca is closer to the base of the tail because her reproductive organs are inside her body.

The position of the cloaca/vent is not always a definitive way to determine the sex of a turtle. Some turtles, such as the Kemp Ridley species, show no external signs of their gender. In these cases, a veterinarian specialising in marine animals would be needed to determine the sex of the turtle.

Additionally, it is extremely difficult to determine the sex of a baby turtle. It is recommended to wait until the turtle is older and has reached sexual maturity before attempting to determine its sex.

Plastron shape

The plastron is the underside of a turtle's shell, covering the turtle's belly. The shape of a turtle's plastron differs between sexes. Male turtles have a concave plastron, meaning it curves inwards, whereas a female's plastron is flat.

The concave shape of the male turtle's plastron allows it to fit over a female's shell during mating without rolling off. The female's flatter plastron gives her more room to grow eggs internally.

The plastron is a reliable indicator of a turtle's gender, but it is not the only factor to consider. The turtle must also be fully grown, as there can be an overlap in size between a large male and a small female.

In addition to examining the plastron, you can check for other physical differences between male and female turtles, such as tail length and shape, shell size and shape, claw length, and cloaca position.

In terms of behaviour, male sea turtles are known to be more aggressive and territorial, often displaying courtship behaviour towards females. Female sea turtles, on the other hand, are more focused on nesting and laying eggs.

Eye and shell colour

The eyes and shell colour of a turtle can be used to determine the gender of the turtle, although this method is more effective for certain species of turtles.

Ornate Box Turtles

Mature male ornate box turtles have red eyes, while female ornate box turtles have brown or yellow eyes. Male ornate box turtles also have greenish-coloured heads with red or orange leg scales, while females have brown heads with yellow leg scales.

American Box Turtles

Male American box turtles are usually characterised by red or orange irises, while female American box turtles have brown or yellow irises.

Sun Turtles

Male sun turtles have blue colouring on their underbellies, while female sun turtles do not.

Red-Eared Sliders

Male and female red-eared sliders have predominantly green bodies with bright yellow streaking, which does not help to distinguish between the sexes. However, as they get older, males tend to turn a darker, almost black colour, which obscures their yellow markings.

Other Turtle Species

The shell colour of a turtle is more heavily influenced by external, environmental factors than by gender. For example, poor nutrition and lack of calcium may lead to "terracing" or ridges within individual scutes.

Frequently asked questions