When drug kingpin Pablo Escobar died in 1993, having built a billion dollar cocaine empire, he left behind a zoo.
While his rhinos, giraffes, elephants and kangaroos were re-housed, the hippos were left in Escobar’s abandoned ranch in the Colombian countryside.
In 2007 they started turning up 100 kilometres away.
Vet Carlos Valderrama was called in to tackle the problem. He describes his experience of castrating a hippo in the wild.
Listen to more on this story from Witness History.