Answer:
Males have long, thick tails that stick out quite a bit from their shells. Females have shorter, thinner tails that are less noticeable. When looking at male vs female red-eared turtles, the slider with the thicker tail is likely to be a male.
Step-by-step explanation:
For male red-eared sliders, maturity is about the time they reach 4 inches in length (and at about two to five years old). Females are mature when they reach 6 to 7 inches in length (which may take five to seven 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.