Russian tortoises grow up to 8 inches long, making them manageable pets throughout their 40-year life span. It's important to know the sex of your tortoise, as keeping two males together can spell injury or death for the weaker of the two. It's easy to tell a mature male from a female by the way he carries his tail and a spur on the end of it.
The Tail Tells the Tale
By the time Russian tortoises are 4 inches long, sex differences are easily noticeable. The male develops the telltale button, known as a spur, on the end of his tail. His tail is longer than a female's and he carries it to the side with it touching his hind leg. His anal opening on the underside of the tail is near the tail's end. A female has no spur, a shorter tail and her cloaca is closer to her shell than to the end of her tail. When kept outdoors and allowed to hibernate, she can begin laying eggs when she grows to about 6 inches long. Indoor tortoises that don't hibernate sometimes lose their urge to reproduce and can have significantly shorter lifespans.
If you can't wait until your Russian tortoise grows to 4 inches, take your pet to the veterinarian for an endoscopic exam. Your vet can easily see whether your tortoise has testes or ovaries.