Cocaine Hippos and Restoring Extinct Ecosystems.

Pablo Escobar is arguably the most infamous drug lord and narcoterrorist that has ever lived. In the 1970s, the "King of Cocaine" founded the Medellin Cartel and monopolised the North American cocaine industry; at one point in time they supplied nearly 85% of the world's cocaine. Widely considered to be the wealthiest criminal in history, Escobar had amassed an estimated net worth of £24 billion at the time of his death - approximately £47 billion today with inflation.

With all this wealth, Escobar developed a keen interest in both exotic wildlife and private menageries. His country estate, named Hacienda Napoles, covered 7.8 square miles of prime Columbian real estate and on this property, Escobar built his own personal zoo that featured antelope, elephants, giraffes, ostriches, a variety of exotic birds and hippopotamus.

When Escobar was shot and killed in 1993, the property became the subject of an intense legal dispute between the Columbian government and his family. Whilst the government eventually prevailed in attaining Hacienda Napoles, the maintenance of such a zoological collection forced them to sell nearly all of the animals that lived on the estate. The vast majority of animals were either transferred to the Columbia National Zoo or sold to oversees collections; however, four hippos were left behind in a pond on Escobar's ranch; they have since taken over the local waterways.

Today, there are between 80 and 100 hippopotamuses in the nearby lakes and canals of the Magdalena River, 40 of whom still live on the grounds of Hacienda Napoles itself. Their numbers have increased to the point where human intervention is required as without natural predators or managed culling, there could be between 800 and 5,000 hippos inhabiting northwestern Columbia by 2050.

The public has always viewed Escobar's hippos as invasive pests that do not have the right to run wild on the South American continent; however, new research from an international team of conservation biologists and ecologists is challenging this view in an intriguing way.

Over the past 100,000 years, humans have been decimating animal populations across the world, driving numerous species to extinction and drastically altering each particular ecosystem. At the same time as eliminating species from their natural habitat, many animals have also been introduced because of humans, whether on purpose or by accident. So, how do the invasive species that we introduced to areas compare to the native animals that became extinct by our actions?

This was the topic of a recently published article in the Proceedings of the National Academy of Sciences produced by a global team of researchers from the University of Technology Sydney, University of Kansas, University of California Davis, Natural History Museum of Los Angeles County, University of Sussex, University of Alcalá and Aarhus University.

The researchers wanted to compare the ecological traits of herbivore species from before the Late Pleistocene extinctions (126,000 years ago - 12,600 years ago) to the traits of those species that exist in the same locations today. Lead author, Erick Lundgren said, "This allowed us to compare species that are not necessarily closely related to each other, but are similar in terms of how they affect ecosystems. By doing this, we could quantify the extent to which introduced species make the world more similar or dissimilar to the pre-extinction past."

The researchers found that some introduced herbivores were perfect ecological matches for their extinct counterparts, whereas others represented a mixture of traits that had died out alongside species' thousands of years ago. In fact, 64% of the invasive species were more similar to the extinct animals than either the local native species or their closest-living native relatives.

This suggests that by introducing new species across the world, humans may have accidentally restored lost ecological traits to many ecosystems, making them more similar to their pre-extinction Late Pleistocene composition and 'counteracting a legacy of extinctions'.

With regards to our 'cocaine hippos', it appears that Escobar's animals not only have a similar body size and diet to an ancient species of giant llama, but also the semiaquatic lifestyle of the bizarre mammalian called a notoungulate - both of which once roamed South America in the Late Pleistocene. "While hippos don't perfectly replace any one extinct species, they restore parts of important ecologies across several species" says co-author, John Rowan.

Furthermore, there are other examples of animals that were introduced to the Americas that act as 'surrogates' for extinct species including feral horses, burros and hogs. "Many people are concerned about feral horses and donkeys in the American southwest because they aren't known from the continent in historic times," Rowan says. "But this view overlooks the fact that horses had been present in North America for over 50 million years -- all major milestones of their evolution, including their origin, takes place here." This research suggests that these human-introduced feral horses and burros, known for their well-digging behaviour, are replacing the original American horses that went extinct 12,000 years ago. Likewise, the hogs rooting behaviour increase tree growth which attracts bird flocks, parallel to their own extinct ancestors.

Whilst this is an amazing research paper, the scientists draw attention to the point that this is only at a preliminary stage of academic investigation. They emphasise that "our findings support calls for renewed research on introduced herbivore ecologies in light of paleo-ecological change."

For over 100,000 years, humanity has been responsible for the extinctions of numerous large-bodied herbivores across the planet, leading to cascading changes in each of those ecosystems. On the other hand, humans have also introduced animals that "in part, numerically compensated for extinction losses."

Researcher Arian Wallach quite elegantly articulated that "we usually think of nature as defined by the short period of time for which we have recorded history but this is already long after strong and pervasive human influences. Broadening our perspective to include the more evolutionarily relevant past lets us ask more nuanced questions about introduced species and how they affect the world."

Pablo Escobar was indeed a cruel cartel leader, a ruthless drug kingpin and an evil man who was responsible for the deaths of tens of thousands in Columbia and many more around the world; however, it is amazing that his wealth and subsequent purchasing of four hippopotamuses would have such a profound effect on evolutionary ecology and scientific research. The 'cocaine hippos' of Pablo Escobar may not be indigenous to the South American continent, but this animal's presence may one day restore their new home to its prehistoric ecological composition.

Reference:
Erick J. Lundgren, Daniel Ramp, John Rowan, Owen Middleton, Simon D. Schowanek, Oscar Sanisidro, Scott P. Carroll, Matt Davis, Christopher J. Sandom, Jens-Christian Svenning, Arian D. Wallach. Introduced herbivores restore Late Pleistocene ecological functions. Proceedings of the National Academy of Sciences, 2020; 201915769 DOI: 10.1073/pnas.1915769117