The Diamondback may live as long as 50 years which is important considering its life cycle and low hatchling survival rate. By seven years old a male is considered mature, can weigh about a pound, and be four inches along the plastron, the underside ridge running front to back. The female terrapin matures later, by twelve years old and can weigh up to seven pounds, reaching lengths of nine inches long. Water temperatures and food supply play a role in growth rates, in warmer waters terrapins stay active, feed longer, and hibernate less. Mating occurs in May.
Female terrapins store sperm and thus can produce fertilized eggs up to four years after mating.
Light pink and leathery textured eggs, on average 13, are laid in nests during June and July on shore in sand or loam, then covered. Hatching occurs from August through October depending on temperatures. Once the eggs are in the nest, the female's obligation is complete. When the hatchlings emerge, they are only an inch long and on their own. Hatchlings are a favorite with herons.