With his long leathery neck, dull-yellow face and beady eyes, there’s just something about Diego.

A tortoise more than 100 years old, Diego has had little trouble mating.

A member of Chelonoidis hoodensis, or the giant tortoise species from Española Island in the Galápagos in Ecuador, he was one of 15 tortoises in a captive breeding program at the Fausto Llerena Tortoise Center on the island of Santa Cruz.

Among the males, Diego displayed an exceptional sex drive, so much so, he’s credited with helping save his species from extinction.

Now, with the future secured, he gets to retire.

In a statement Friday, Galápagos National Park announced the end of the breeding program, saying an evaluation showed it had met its conservation goals.


The program began in 1965, with efforts first dedicated to saving the tortoise population on Pinzón Island, another island in the Galápagos. In 1970, researchers began saving the Española Island tortoises.

At the time, there were 14 tortoises left: 12 females and two males, according to the Galápagos Conservancy. In 1976, a third male was introduced to the tortoise restoration breeding program, Diego, who had lived at the San Diego Zoo in the United States for 30 years.

The breeding program helped increase the tortoise population to 2,000 from 15, Jorge Carrión, director of Galápagos National Park, said in a statement.

Paternity tests indicate that Diego is responsible for about 40 percent of the offspring produced, said James P. Gibbs, a professor of environmental and forest biology at the State University of New York in Syracuse.

“Another more reserved, less charismatic male — ‘E5’ — has generated about 60 percent,” he said. “The third male — ‘E3’ — virtually none. So Diego has been critical.”

What was it about Diego? Why did he attract so many mates and garner such international attention, especially if another male was more productive?


Gibbs says Diego has “a big personality — quite aggressive, active, and vocal in his mating habits, and so I think he has gotten most of the attention.”

“But it clearly is the other, quieter male that has had much more success,” he added. “Maybe he prefers to mate more at night.”

Gibbs said it was all about who the females select.

“It might come as a surprise to many, but tortoises do form what we would call ‘relationships,’ ” he said. “The social hierarchies and relationships of giant tortoises are very poorly known.”