Diego is thought to have been hatched on Española Island, one of the Galápagos Islands, before 1920. He was captured and transported to the United States as a young adult sometime between 1928 and 1933 as part of a shipment of tortoises from the Galápagos Islands sent to American zoos.
Breeding programme
The Hood Island giant tortoise was threatened by hunting for food and competition from goats and was declared critically endangered in the 1960s. A breeding programme was set up in 1976, at which point there were only 12 females and 3 males remaining on the island. Only two of the males proved suitable for breeding, so the programme searched for Española tortoises held in captivity. By this point Diego had been at the San Diego zoo for 30 years, but his species was unknown. DNA testing proved that he was a Hood Island tortoise, and he was transferred to Santa Cruz Island, Galápagos to join the programme in 1977. The three male tortoises were placed into breeding pens with different females and the offspring released onto Española as juveniles, once or twice a year. The survival rate of the offspring on the island was around 50%. During this time Diego fathered around 900 offspring, some 40% of the programme's output. A second tortoise, known as E5, fathered most of the remaining 60%, with the third male, E3, producing very few offspring. Despite E5's being more successful at reproducing, Diego has received the majority of media attention and has been said to have "had so much sex he saved his species". This is believed to be because E5 had a more reserved character, a less interesting name, and was seldom witnessed in the act of mating. Diego, by comparison, has been described as aggressive, active and vocal in the act of mating, which in turn made him popular with the female tortoises.
Retirement
Diego remained with the breeding programme until it ended in January 2020. By this time the programme had increased the number of tortoises on Española to 2,000 individuals, considered to be self-sufficient without new influxes of juveniles from the programme. Diego and 14 other tortoises from the programme were released on Española on 15 June 2020. It is thought that he could live to reach 150 years old. At the time of his release he weighed and measured in length at in height at full stretch.
