Colombia's cocaine hippos are all descendants of the animals imported by Pablo Escobar.
In Clomobia, descendants of "cocaine hippos," which drug lord Pablo Escobar once owned, represent a major threat to both people and nature.
Researchers had underestimated the size of the invading hippo population in Colombia, which is now posing a threat to the country's native wildlife and plant life. To lower the population, the government wants to take extreme steps.
The cocaine baron Pablo Escobar brought a small number of African beasts to Colombia in the late 1980s. But after his death in 1993, the animals were left to roam freely in a hot, marshy area of the Antioquia department, where environmental authorities have been helpless to curb their numbers.
According to Nature magazine, after Pablo Escobar died, the hippos (Hippopotamus amphibius) escaped from his estate and established themselves in the Magdalena River. Without the natural predators or droughts of their native Africa to keep them in check, the giant herbivores have bred rapidly to form the largest population of the animals outside that continent.
Colombia had tried a sterilisation programme to control the population, but it failed. The environment ministry declared the hippos an invasive species last year, which opened the door to an eventual cull. But the hippo transfer plan is seen as a life-saving measure.
In their homeland in Africa, they are responsible for more human deaths than almost any other animal, but in Colombia, hippopotami have become beloved members of the local community and a tourist attraction.
But the hippo numbers exploded, and there are now around 200 of the two-tonne beasts wandering freely in northwestern Colombia.
A few years ago, researchers estimated how fast the animals were reproducing and projected that about 98 hippos would be living along the country's Magdalena River and its tributaries in 2020. But the new study, for which a research team counted the animals in person, by drone, and using other tracking methods, estimates that there are 181-215 of them residing in Colombia.
"Before, one argument against dealing with the hippos was that our information was limited and our arguments were theoretical," says ecologist Rafael Moreno, who participated in the study while at the Alexander von Humboldt Biological Resources Research Institute in Bogota.
"But we have put that argument to bed now. This study shows that this is a real issue and that the state must act urgently."
A study by the National University estimated that the local population of hippopotami could rise to 1,000 by 2035.