A few questions about Red Eared Sliders

I have 2 RES. they are about a year old and are aproximately the same size. However one of the turtles has a tail about 4 times as large as the other turtles tail. Does this indicate he is a male and the other is a female?

And if so, when do they start reproducing?

The male *Trachemys scripta * is usually smaller, with a much longer, thicker tail. The males also develop longer claws.

Males become sexually mature at around 3 to 5 years of age, females at 5 to 7 years.

I have two RES that are around 3 years old. I found tons of helpful information about them here.