Scientists are warning that hippos descended from a group imported by drug lord Pablo Escobar are spreading through Colombia's waterways, posing a serious environmental threat. A study published in Biological Conservation journal calls for culling the animals to mitigate their impact.
The hippos were originally kept at Escobar's private zoo on his Hacienda Napoles estate. After his death in 1993, authorities left the hippos on the estate, believing they would die. Instead, the population has grown to an estimated 80–120 animals, making it the largest hippo herd outside Africa.
Biologist Nataly Castelblanco, co-author of the study, says the hippos are an invasive species with no natural predators in Colombia. Favorable conditions mean they reproduce earlier than in Africa, and the population could exceed 1,400 by 2034 without intervention. The study suggests culling or castrating 30 animals per year to control numbers.
The hippos are spreading along the River Magdalena, displacing native species like the manatee and altering water chemistry, which could affect local fisheries. Some experts oppose culling, advocating sterilization instead, but procedures are dangerous and costly—around $50,000 per animal. Only four sterilizations occurred between 2011 and 2019.
