Hippopotamuses are an introduced species in Colombia. Four hippopotamuses were kept by Pablo Escobar in the late 1970s, and upon his death in 1993 they were allowed to wander his unattended estate. By 2019 their population had grown to approximately one hundred individuals, causing concerns they may harm the native flora and fauna in the area; as well as posing significant threat to human population in the area. History In the late 1970s, Colombian drug lord Pablo Escobar kept four hippopotamuses in a private menagerie at his residence in Hacienda Nápoles, east of Medellín, Colombia. They were deemed too difficult to seize and move after Escobar's death, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River. In early 2014, there were reported to be 40 hippopotamuses in Puerto Triunfo, Antioquia. The estimated population in December 2019 was around 90–120, with their range covering around and now extending into Santander; it is expected that the population will almost certainly increase to more than 150 individuals within a decade and could reach up to more than 200 hippos, while the range eventually could cover more than . Population projections estimate that there could be thousands within a few decades. The Colombian hippos reach sexual maturity earlier than African hippos. Conservation concerns Being non-native introductions, most conservationists considered them problematic and invasive in Colombia, as they have the potential to change the ecosystems, feeding heavily on plants and displacing native species like the West Indian manatee, Neotropical otter, spectacled caiman and turtles. The critically endangered Dahl's toad-headed turtle and Magdalena River turtle are largely restricted to the Magdalena River basin, as are many threatened fish. In 2020, a study showed that there was an increase in the nutrient levels and cyanobacteria in Colombian lakes inhabited by hippos. Cyanobacteria can cause toxic algae blooms and die-offs of aquatic fauna. Despite the limited magnitude of the observed change, it was noticeable since the species' population was still quite small. In contrast to the opposition by most conservationists, some ecologists have argued that they should remain and might even have a positive effect on the local environment. It has been suggested that the nutrients they introduce to the water and the occasional fish kills caused by them are overall positive, but this was based on a