A hippo known as Pepa in Medellin, Colombia on July 15, 2018. Pepa was part of the initial batch of animals imported by drug lord Pablo Escobar back in the 1980s. Photo : Getty

Generally speaking, scientists are not down with Pablo Escobar’s hippos.

When the Colombian national police assassinated the cocaine kingpin in 1993, he left behind four fully-grown hippopotamuses. They are considered one of the world’s top invasive species. A January study showed that their shit was contributing to algae blooms and screwing with local lakes’ chemistry–the implication being that the animals are gross pests that could ruin local ecosystems.


But in a new study, published in Proceedings of the National Academy of Science on Monday, has a different view of the coke hippos. Specifically, the new research shows that the introduction of large non-native herbivores into ecosystems—like the hippos in Colombia—can actually restore ecologically beneficial traits to the area that may have been lost for thousands of years.


“While we found that some introduced herbivores are perfect ecological matches for extinct ones, in others cases the introduced species represents a mix of traits seen in extinct species,” study co-author John Rowan, a study co-author and biology researcher at the University of Massachusetts Amherst, said in a statement.

Pablo’s hippos, for instance, are similar in diet and size to the now-extinct giant llamas that once roamed the area. They’re also similar in size and semiaquatic behavior to another extinct species, notoungulates, which have been gone for thousands of years. That allows them to fill two long-vacated roles in the Colombian ecosystem they were introduced to after Escobar died and they began to roam the countryside.

In other words, Pablo Escobar is inadvertently responsible for rewilding his home country and bringing back ecosystem services that have been missing since these megafauna died out. That doesn’t necessarily mean Pablo’s hippos are good. But it does mean scientists should look at introduced species like the hippos without preconceptions that they’re negative, invasive pests (locals may beg to differ).

And this isn’t just about Pablo’s hippos. The researchers analyzed 72 cases of invasive—or “introduced,” as the authors say—herbivore species entering an ecosystem, comparing their ecological traits to those of the animals that populated the areas in the pre-historic, pre-human past.




In 64 percent of cases, the authors found introduced species resembled extinct species more than the ones currently populating an ecosystem. That means that more than half the time, these introduced species could potentially fill into ecological niches that have long been empty, which can variously affect many aspects ecosystem health, from what nutrients are dispersed in the water and soil to how often wildfires occur.

The hippos, for instance, have been thought to be harmful because their poop fertilizes lakes. But “in Africa, the fertilization of waterways that hippos conduct plays a keystone role in boosting fishery productivity,” Erick Lundgren, a Ph.D. student at the UTS Centre for Compassionate Conservation who led the study, told Earther. Indeed.


“We do not claim that hippos are beneficial or not—but that they should be studied without those types of labels, in the context of deep time,” said Lundgren.