The drug kingpin Pablo Escobar smuggled four hippos into his compound in Colombia, but they escaped into the wild after he was killed. Their population has now ballooned to around 140, leaving authorities grappling with a very big invasive species. We hear more from Luke Taylor, a freelance journalist in Bogotá, Colombia; and Gina Paola Serna, a veterinarian who has been helping track and sterilize the animals.