 Several waves of human exploitation of the tortoises as a food source caused a decline in the total wild population from around 250 @,@ 000 when first discovered in the 16th century to a low of 3 @,@ 060 individuals in a 1974 census . Modern conservation efforts have subsequently brought tortoise numbers up to 19 @,@ 317 ( estimate for 1995 – 2009 ) . 
