(CNN) A womanizing tortoise whose rampant sex life may have single-handedly saved his entire species from extinction has retired from his playboy lifestyle, returning to the wild with his mission accomplished.

Diego's unstoppable libido was credited as a major reason for the survival of his fellow giant tortoises on Espanola, part of the Galapagos Islands, after being shipped over from the San Diego Zoo as part of a breeding program.

When he started his campaign of promiscuity, there were just two males and 12 females of his species alive on the island.

But the desirable shell-dweller had so much sex he helped boost the population to over 2,000. The Galapagos National Parks service believe the 100-year-old tortoise is the patriarch of around 40% of that population.

"He's contributed a large percentage to the lineage that we are returning to Espanola," Jorge Carrion, the park's director, told AFP. "There's a feeling of happiness to have the possibility of returning that tortoise to his natural state."

Diego's good looks made him a hit on the island.

A total of 15 tortoises took part in the breeding program to boost the island's population, but none played a big a role as Diego.

"About 1,800 tortoises have been returned to Espanola and now with natural reproduction we have approximately 2,000 tortoises," Carrion told AFP.

"This shows that they are able to grow, they are able to reproduce, they are able to develop," he said.

The Galapagos Islands are one of the world's premier destinations for wildlife viewing, and were visited by Charles Darwin as he worked on the theory of evolution.