This has got to be one of the strangest and most fascinating sagas involving an invasive species. In the South American country of Colombia, officials are working to control an invasive population of hippos. Seriously. 

The story dates back to the 1980s, when drug kingpin Pablo Escobar imported four hippos to one of his estates. After Escobar died in 1993, the hippos were left unattended on the estate—and soon, their population ballooned. 

Despite recent control efforts, including one controversial controlled hunt in 2009, there are now an estimated 169 feral hippos in Colombia, according to a recent government press release. Hippos, which are native sub-Saharan Africa, can reach weights of up to 4.5 tons and are known to be aggressive. Suffice to say, local officials are understandably worried about what the ecological impacts of an even larger feral population of the mammals would look like. 

According to the press release, if left unchecked, the “cocaine hippo” population could balloon to over 1,000 individuals by 2030. The country’s Minister of Environment and Sustainable Development Susana Muhamad announced that authorities will surgically sterilize 20 hippos this year. The government hopes to increase that number to 40 hippos per year going forward. Each sterilization costs around $40 million pesos, or $10,000 dollars. 

“This procedure is very dangerous since the veterinarian must be very skilled to sterilize [a hippo] in the shortest time possible, before it wakes up,” Germán Jiménez, a biologist at the Pontifical Javeriana University told the New York Times. The Colombian government is also considering two other management tactics: A plan to round up and relocate hippos to Mexico and India, and another that involves the “ethical euthanasia” of some hippos. 

Read Next: What It Feels Like to Catch a 19-Foot Foot Burmese Python…with Your Bare Hands

“We are in a race against time in terms of the permanent environmental and ecosystem impacts that are being generated and that is why we cannot say that only one strategy is effective for our objective, which is to control the population,” said Muhamad. “All three strategies [would] have to work together.”