Diego does it

You may have heard of prolific fathers like sperm donors Ed Houben and Trent Arsenault, but you may not know they have an animal counterpart. Meet "Diego" (above, another photo here), the senior sire at Galapagos National Park. By senior, I mean well over 100, and by sire I mean father of hundreds! Unlike "Lonesome George" (d. 2012) who was not able to reproduce, Diego is responsible for 40-45% of the 1,781 tortoises born in the breeding program. Rangers describe him as macho and say he has been central to bringing his breed back from near extinction.With Diego's sons and daughters reproducing in the wild, the population of giant tortoises has increased from a low of 3,000 in 1974 to a total of  20,000 today. Diego is an Espanola Island tortoise (Chelonoidis hoodensis) and after several decades at the San Diego Zoo - during which he was also very busy - he was returned to the Galapagos Islands in 1975. As the biggest and the oldest of the males, Diego is the most sexually active. Because the 176lb (80kg) tortoise bit, shoved, and bullied his rivals, he was placed in a pen with 5 females. Linda Cayot, herpetologist for the Galapagos Conservancy, explains, "In tortoises, the biggest dominates. It's not that the others aren't active. It's just that he's dominant."