Pablo Escobar's hippos 'are a threat and must be culled' as population could reach 1,500 by 2035

A visitor feeds a hippo at the Hacienda Napoles Park in Puerto Triunfo, Colombia. Credit: AP

Scientists have called for a cull of hippos introduced to Colombia decades ago by drug lord Pablo Escobar.

The group has warned that the creatures are a major threat to biodiversity in the area. They also fear deadly encounters between humans and the hippos.

The hippos population was introduced to Colombia in the 1980's, when Escobar, a prolific cartel leader, established a private zoo of illegally imported animals at his estate, Hacienda Napoles Park.

Although he is long dead, the hippos have been flourishing in the fertile region between Medellin and capital city Bogota.

Government attempts to control their reproduction have had no real impact on population growth. The number of hippos has increased in the last eight years from 35 to somewhere between 65 and 80.

The scientists believe hippo numbers could reach around 1,500 by 2035 if no action is taken. They say some of the animals need to be killed.

“I believe that it is one of the greatest challenges of invasive species in the world,” said Nataly Castelblanco-Martínez, an ecologist at the University of Quintana Roo in Mexico and lead author of the group’s study.

Pablo Escobar with his wife and son Credit: AP

The idea of killing some of the animals has already drawn public criticism and is likely to see more. There was an outcry years ago when a hippo, who had wandered from the Escobar compound and was causing problems, was killed by hunters.

The animals have been embraced by local residents, in part because of the tourism money they reel in.

However, experts say the government’s attempt to keep down numbers by sterilising some hippos isn’t enough.

“Everyone asks, ‘Why is this happening?’ Well, imagine a town of 50 people and you perform a vasectomy on one man and in two years on another man, obviously, that is not going to control the reproduction of the entire population,” Castelblanco-Martínez said.

The scientists began studying the hippo population last year after one of the animals chased and severely injured a farmer. Their study was published in the journal Biological Conservation in January.

Last year, researchers at the University of California, San Diego, found the hippos are changing the quality of the water in which they spend much of their time.

Hippos float in the lake at Hacienda Napoles Park, once the private estate of drug kingpin Pablo Escobar. Credit: AP

As their population continues to grow, they could end up displacing native animals like the Antillean manatees, Castelblanco-Martinez said.After Escobar's death in a shootout with authorities in 1993, most of his exotic animals were relocated or died. However, the hippos were abandoned at the estate due to the cost and logistical issues associated with transporting the heavy animals, alongside the violence that plagued the area at the time.

“About 10 years ago, we realised that we have a giant population of hippopotamuses.

"We began to learn how the population was constituted, to see if there was an immediate solution,” said David Echeverri-Lopez, a researcher at the regional environmental agency that oversees the hippos.

“We really began to realise the dimensions of the problem.”

While Echeverri agreed that killing some of the hippos would be the best solution, he said the animals’ magnetic personality and government regulation may never allow it.

After the public criticism erupted more than a decade ago over the killing of the hippo by hunters the government instituted a ban on hunting hippos.