Diego, a 100-year-old tortoise, was retired from a breeding program after fathering 800+ children.
Diego lived at the San Diego Zoo until 1977, when he was sent to the Galápagos to save his species from extinction. Over the following 43 years, Diego almost single-handedly returned the Galápagos giant turtle population to acceptable levels. Diego has since retired to the island of Española, where he was initially found.