Key Takeaways The incubation temperature of turtle eggs determines their sex, with cooler temperatures producing males and warmer temperatures producing females.Male and female turtles can be distinguished by physical traits like plastron shape, tail length, and claw size.Sexual dimorphism in turtles, such as size and coloration differences, becomes more apparent as they reach sexual maturity.
Key Takeaways
The incubation temperature of turtle eggs determines their sex, with cooler temperatures producing males and warmer temperatures producing females.Male and female turtles can be distinguished by physical traits like plastron shape, tail length, and claw size.Sexual dimorphism in turtles, such as size and coloration differences, becomes more apparent as they reach sexual maturity.
Determining the gender of a pet turtle can be challenging, particularly if it was not bought from a breeder who used a controlled temperature environment during incubation. The temperature at which turtle eggs are incubated determines the embryo's sex: cooler temperatures yield males, while warmer temperatures result in females.1
Thankfully some types of turtles make it easier than others to distinguish a male from a female without knowing their incubation temperature. Red-eared sliders, for example, demonstrate sexual dimorphism and have distinct differences in size and appearance between the sexes.
Using Shell Size and Shape to Determine Gender
The size differences between most male and female turtles may not be obvious until the turtles reach sexual maturity (and the diet can also play a role in the size of a turtle). For male red-eared sliders, sexual maturity is about the time they reach 4 inches in length (and at about 2 to 5 years old). Females are sexually mature when they reach 6 to 7 inches in length (which may take 5 to 7 years). Females will grow larger than males in red-eared sliders and many other turtle species, but the size difference between males and females varies by species.
For example, in sulcata tortoises, the females can reach 100 pounds, and the males can grow to 200 pounds or more. In sea turtles, the males and females can both grow to the same size. To reliably use shell size as a factor in determining the gender of a turtle, the turtle must have reached its adult size.
The bottom of a turtle's shell (called the plastron) is also used as an indicator for determining gender. Male turtles have a concave (curved in) plastron while females have a flat one. These shapes enable male turtles to more easily mount a female during mating, and they give females more room to hold eggs internally.
Using Claw Length to Determine Gender
Female turtles often have claws on their front feet that are short and stubby. Males (and specifically red-eared sliders and other aquatic turtles) have much longer claws on their front feet than females. This is because males utilize their claws when they are attempting to woo females to breed. During mating, the males will also grab the female's upper shells by using their long claws.
Using Tails to Determine Gender
The most common way to determine gender in a turtle is to look at the length of its tail.2 Female turtles have short and skinny tails while males sport long, thick tails, with their vent (cloaca) positioned closer to the end of the tail when compared to a female. It is, of course, easiest to determine the gender of a turtle when looking at its tail length if you have multiple turtles of both sexes to compare.
Using Markings and Coloration to Determine Gender
All red-eared sliders have predominantly green bodies suffused with bright yellow streaking, which won't help distinguish males from females. But other color indicators may. The plastron is yellow with uneven, dark markings that are paired while the tail, legs, and head are green with thick yellow stripes. As red-eared sliders get older, many turn to a dark, almost black color and may obscure some or all of their yellow markings. This darker coloration is more common in male red-eared sliders.
Ornate box turtles are another type of turtle that is sexually dimorphic. Mature male ornate box turtles have red eyes while females' eyes are brown or yellow. Males also have greenish-colored heads with red or orange leg scales, and females have brown heads with yellow leg scales.