The Colombian government is planning to declare that a herd of hippopotamuses descended from animals imported illegally by drug lord Pablo Escobar in the 1980s are an exotic invasive species.

People from the town of Puerto Triunfo have grown accustomed to living near the herd, and many are opposed to any measures to control the population.

Within weeks, the government plans to sign the declaration, meaning it must come up with a plan for how to control the hippo population, which has reached 130 and is projected hit 400 within eight years.

Among the strategies being debated are castration, sterilization or even a cull.

Colombian environment minister Carlos Eduardo Correa said many strategies are being discussed on controlling the hippos, but no decisions have been made.

Local communities will be consulted about any plan to control the hippos’ population, he added.

“They talk of castration, sterilization, taking the life of some hippopotamuses,” he said. “What is important is the scientific and technical rigor with which the decisions are made.”

Most people interviewed in Puerto Triunfo, some 120 miles from the capital, Bogota, say they can get along with the hippos.

Local resident Alvaro Molina has had his run-ins with the burly creatures, who showed up about a decade ago along the river in front of his house in Colombia’s Antioquia province.

But he has learned to live with them and says he is worried about them coming to any harm under the government plan.

The 57-year-old says he supports the hippos even though he is one of the few Colombians to have been attacked by one.

He was out fishing one day when he felt a movement beneath his canoe that spilled him into the water.

“The female attacked me once – the first pair that arrived – because she had recently given birth,” he said.

Isabel Romero Jerez, a local conservationist, said of the government: “They make laws from a distance. We live with the hippopotamuses here, and we have never thought of killing them.

“The hippopotamuses aren’t African now; they are Colombians.”

Escobar’s sprawling estate, the Hacienda Napoles – and the hippos – have become a local tourist attraction in the years since the kingpin was killed by police in 1993.

When his ranch was abandoned, the hippos survived and reproduced in local rivers amid favorable climatic conditions. They began showing up around Puerto Triunfo a decade ago.

However, scientists warn that the hippos do not have a natural predator in Colombia and are a potential problem for biodiversity since their feces change the composition of the rivers and could impact the habitat upon of manatees and capybaras.

An analysis by the Alexander Von Humboldt Biological Resources Research Institute said that climate change and “an increase in equatorial conditions, the ideal climate for the species” could increase the hippos’ dispersion across Colombia, potentially “overlapping with the geographic and ecological niches of native species, increasing the risk of possible competition for resources”.

Hippos can also cause damage to crops because they are mainly herbivores and seek food in large quantities at night.

While hippos are considered one of the most dangerous animals for humans in Africa, there have been only a few injuries recorded so far in Colombia.

Locals say the hippos sometimes come out of the water and walk through the streets of the town. When that happens, traffic stops and people keep out of their way.

“The human animal is the one that invades their territory, that is why they feel threatened and attack,” said Ms Romero Jerez.

“Human beings should be prudent, respectful and keep their distance.”

Scientists warn that hippos are territorial and weigh up to three tonnes.

Daniel Cadena, a biologist and dean of sciences at the Universidad de Los Andes, said they are aggressive animals and not as gentle as people imagine.

“There are estimates in Africa that hippos kill more people each year than lions, hyenas and crocodiles combined,” he said.

When the document declaring them an invasive species in Colombia is signed, hippopotamuses will join species such as the giant African snail, coqui frog, black tilapia and lionfish.

The declaration will allow the government to allocate resources to control the hippo population, one of the main obstacles.

There is currently an experimental program of immuno-castration with a drug donated by the United States. Surgically sterilizing them requires sedating them, transporting them to a safe place and cutting through their thick skin.

Any population control process promises to be costly and complex because it requires finding the hippos scattered along the Magdalena River.