Colombia’s Magdalena River has an arterial quality, being the nation's largest river, cutting straight through its heart, pumping water into smaller channels, and eventually flowing into the Caribbean sea.
The river gives life to the nation. If you sailed down its smooth waters, as Columbus once did, you would see all levels of commerce, from massive freight ships from distant lands, to tiny family fishing boats chancing their luck.
If you continued further down its calm waters to a particular junction and arrived at the wrong moment, you’d see male hippos jousting for dominance.¹
They are the only wild hippos outside of Africa. They are also the largest invasive species on the planet. It is Colombia’s latest and most interesting ecological problem. There isn’t a consensus on how to deal with the hippos. There is even a growing argument that they aren’t a problem in the first place.
The hippos were an exotic pet
Colombia has long been trying to move past the legacy of Pablo Escobar. The drug lord was worth $30 billion at the time of his death and is tied to nearly 7,000 deaths.
After Escobar was killed by police in 1993, authorities began cleaning up his various estates and discovered one of the world’s largest private collections of exotic animals, spanning giraffes, monkeys, lions, and rhinos. A majority of them were shipped off to proper holding facilities.
However, there were four hippos at Escobar’s seven-square-mile Hacienda Napoles estate. True to their form, these megaherbivores were as cooperative as grizzly bears, proving too difficult to manage or ship off. The hippos were left to fend for themselves and, par for their hedonistic whims, the four began reproducing. By 2007, the four had multiplied into 16.
As the mansion fell into disrepair behind them, the hippos eventually left the estate, knocking down surrounding fences and wandering into local rivers.
Colombian Hippos lounging in the river. (Source: Wikimedia Commons)
Are they a problem?
Local environmentalists are advocating for the hippos to stay. They say the species could be good for the environment. In fact, the hippos are considered an accidental rewilding experiment that has captured the fascination of many ecologists.
A number of conservationists want to cull them, asserting they’ll pose a danger to otters, manatees, humans, and others. Additionally, their presence tends to alter the chemical state of the water they operate in. Though they could harm some wildlife, the hippos might be a net positive. Hippos eat their food on land at night and then excrete it in water during the day while they cool off and sleep.
A single hippo can excrete one ton of carbon and other nutrients into an aquatic system in a single year. This often causes plants, microorganisms, and fish, to flourish in the surrounding waters.
Jens-Christian Svenning, Professor of Ecology, at Aarhus University, believes the hippos could become a good addition to Colombia's wildlife.² Many herbivores have already been killed off and this has vacated room in the region’s evolutionary tree. The deliberate introduction of foreign animals is referred to as ‘trophic rewilding’. In plain terms, the animal a welcome invader. Beavers have frequently been used in this context, because of their ability to restore habitats, and survive in extreme temperatures.
Reducing Colombia’s hippo populations would be a violent solution, likely left to the hands of big game hunters and rangers. Alternatively, moving one live hippo costs a full $40,000, which is unappetizing in a country where more than a quarter of the population lives below the poverty line. Four hippos have been sterilized but the practice is also resource-intensive, costing $5,000 per hippo, requiring significant risk and man-hours.
So what next?
With no violent attacks or incidents to date, it would be hard to justify killing the hippos, particularly because the locals are mostly unopposed to their presence. Residents of Dorodal say they have been a boon for their tourism industry. Local children play on hippo statues and playgrounds. Their shops are filling with hippo shirts and memorabilia as people drive in from all over the region to see the area’s new tenants.
A regional environmental agency, Cornare, is tasked with managing the problem. They are tracking the hippos and doing something that seems counterintuitive: they are feeding them. This keeps the hippos mostly centralized at a specific location. The agency knows this solution is untenable and is using it more as a stalling mechanism to observe their behavior.
Today, there are an estimated 80–100 hippos in Colombian rivers. The hippo population is on track to double again in the next five to seven years. Even further, their primary residence in the Magdelena River is an aquatic highway to other channels throughout Colombia.
As a long-time resident of Florida, a state with one of the largest populations of exotic pets, and no shortage of invasive species problems, this story felt painfully familiar.
The decision to keep hippos in Colombia will be left to better minds and local authorities. But worth mentioning, human encroachment in Africa has hurt the hippo population for years. Additionally, human hunting nearly caused hippo extinction 10,000 years ago.
It’s also possible that I, like many in Colombia, am being a bit too bedazzled by the gentle, cute appearance of the ‘Hippopotamus amphibius’. We don’t tend to associate chubby, sleepy herbivores with extreme violence. The fact remains that they are indeed very dangerous. When it comes to wild animals in Africa, only mosquitoes kill more people.
We could see a future where thousands of hippos swim Colombia's waters, thriving as welcome guests by the locals. We could also see a much bloodier solution, as the reality of their presence strikes a dissonant chord with government authorities.
At the end of the day, humans have always been the ultimate invasive species. If we don’t manage illegal hunting and the exotic pet trade, we’ll be forced to rewild many more animals, or live with the fact that we’ll only be able to see them in zoos, if at all.
And no matter what comes of all this — don’t ever, ever, mess with hippos.
 J.D. Rockefeller (17 March 2016) Cocaine King Pablo Escobar: Crimes and Drug Dealings
 Subalusky (2019) Potential ecological and socio-economic effects of a novel megaherbivore introduction: the hippopotamus in Colombia.