Scientists have called hippos “one of the world’s greatest invasive species challenges”.
The Colombian government has had to sterilize dozens of hippos once owned by drug lord Pablo Escobar due to concerns about the impact they are having on wildlife and local people.
Known as the ‘cocaine-addicted hippos’, the herd has grown from a population of 35 in 2012 to 80 this year, and is believed to be the largest herd outside of Africa.
Researchers fear the herd could grow to 1,500 individuals over the next two decades, but if they breed, they are unchecked.
Previous plans to cull the herd received widespread opposition from locals, so now a local environmental agency has begun sterilizing them, using drugs from Washington.
Government group Cornare said it has already sterilized 24 of the animals using a contraceptive drug called GonaCon. Spaying hippos is made more difficult by the fact that they have internal testicles.
While most of Escobar’s exotic animals were sent to zoos after his death in 1993, the hippos were left free on his ranch before their offspring spread to the Magdalena wetlands.
But they have toxic urine and feces that cause algae blooms and have the potential to wreak havoc on the local ecosystem, pollute waterways and overpower other species because they don’t have no predators to control their numbers.
Earlier this year, scientists called for their sterilization in a scientific paper. The paper’s lead author, Nataly Castelblanco-Martínez, of the University of Quintana Roo, previously said she believes hippos pose “one of the greatest invasive species challenges in the world”.
The ecologist had called for the slaughter of 30 hippos per year.
Despite the call for “urgent” hippo population control in their study, published in the journal Biological conservationResearchers Noted that “proposal of a course of action may become controversial when the species has charismatic value to society, regardless of its ecological or social impact”.