Largest invasive species

The world's largest invasive species, remarkably enough, is currently the African hippopotamus (Hippopotamus amphibius) in Colombia, South America. The Colombian drugs baron Pablo Escobar stocked his huge estate with hundreds of exotic animals, including zebras, giraffes, elephants, and a lake of hippos. After he was killed by Colombian security forces in 1993, his estate passed into government hands, since when all of his animals have disappeared - except for the hippos. Originally four in number, over the years they have continued to breed until the current population numbers 19 in total, and they now roam the countryside at night in search of food. One was recently shot by a farmer several kilometres away from their lake. On account of their dangerous nature, there is now local concern that the hippos will attempt to colonise other lakes and rivers and thus spread further through the Colombian countryside.