 An extensive search again in 1999 failed to find any iguanas.Military occupation of the island prior to the 1960s may have been responsible for its demise, or years of mining guano for fertilizer; the introduction of feral dogs, goats, and rats may have been to blame.Dr Robert Powell's research while at the Department of Natural Sciences, Avila College, Kansas City, Missouri, suggests that the iguanas disappeared before the introduction of feral species, as a result of habitat change or hunting by man.