Pablo Escobar smuggled 4 hippos into Colombia for his private zoo in the 1980s. When he was shot dead in 1993, the animals were abandoned at his estate. They bred freely in the Magdalena River, with no natural predators to slow them. Colombia now has an estimated 170 to 215 feral hippos - the largest population outside Africa - and is spending $10,000 per animal to surgically sterilize them.
