Scientists say the animals, which have flourished after spreading from Pablo Escobar’s estate into nearby rivers, are an invasive species that could harm native wildlife, dubbing them an “ecological time bomb”.
In the 1980s, drug-trafficker Escobar illegally imported four African hippos for his private zoo, and after his death in 1993, the animals escaped to the Magdalena River, one of the country’s main waterways.
The creatures, which became known as “cocaine hippos”, reproduced at a rate that is considered unsustainable by ecologists who argued their numbers could grow to 1,000 by 2035.
As a row erupted over the hippos’ fate, the US-based Animal Legal Defense Fund filed a lawsuit against the Colombian government over its plans to kill them, arguing for a safe contraceptive instead.
Some locals appreciate the animals for the tourist money they bring to the region.
Now, after years of debate, ministers say they will try sterilising or exporting some of the herd, descended from Escobar’s imports, estimated at 169 creatures.
Environment minister Susana Muhamad said the first stage of the plan would be the surgical sterilisation of 40 hippos a year, beginning next week.
The procedure is expensive — each sterilisation costs about $9,800 (£7,936) — and entails risks for the hippopotamus, including allergic reactions to anesthesia or death, as well as risks to the vet, according to the ministry.
The hippos, which are dispersed over a large area, can be territorial and aggressive.
But ecologists say sterilisation alone is not enough to control the growth in numbers, so the government is arranging to export 60 of them to India.
Officials have also contacted authorities in Mexico and the Philippines, Ms Muhamad said.
“We are not going to export a single animal if there is no authorisation from the environmental authority of the other country,” she said. As a last resort, the ministry is creating a protocol to euthanise them, she added.
In 2021, an American court recognised the animals as “legal persons” – the first time in the US animals had received such recognition. But the ruling was deemed not to carry any weight in Colombia.