The grey behemoth common hippopotamus (Hippopotamus amphibius), considered an invasive species 7,688 miles from their native habitat in sub-Saharan Africa, run rampant in Colombia. According to the African Wildlife Foundation, the common hippo is the third-largest land mammal (after elephants and white rhinos) native to lush sub-Saharan wetlands, marshes, and rivers. They have “four-webbed toes” to “adequately support them on land,” but “have adaptations to their semi-aquatic environments allowing them to move swiftly on both water and land” (“Hippopotamus”). The AWF measures hippos between two to five meters in length, and up to one-and-a-half meters tall, or about five feet, and weighing in at an absolutely massive one-point-four to five tons, a maximum weight of ten thousand pounds. In Africa, they graze on up to eighty-eight pounds of grass over about five hours every night, and their primary predators are lions, crocodiles, and hyenas. Humans also pose a very serious threat to hippos in Africa, and, according to the AWF, “the population of the common hippo declined more than 95 percent in the Democratic Republic of the Congo” since the beginning of the 21st Century, due to poaching efforts for their valuable fat and ivory tusks (“Hippopotamus”). 

But this report is not about hippopotamuses that live in Africa. In the 1980s, notorious drug lord Pablo Escobar smuggled in four hippos, three females and one male (Kaplan, “Invasion”) to his Hacienda Nápoles in Puerto Triunfo, approximately one hundred miles east of Medellín (“The debate”). According to the National Invasive Species Information Center, “human actions are the primary means of invasive species introductions” (“What are invasive species?”). The hippos were brought along with many other exotic creatures to create his own private zoo. When authorities killed Escobar in his final stand in 1993, many of the animals were sold off, but the hippos remained on the premises. According to Nataly Castelblanco-Martínez of the University of Quintana Roo, Mexico, moving the hippos was “logistically difficult, so the authorities just left them there, probably thinking [they] would die” (Edwards, “Drug lord”). But they didn’t die, and in fact, they flourished. According to a 2021 census by the Alexander Von Humboldt Biological Research Institute, Colombia housed one hundred and thirty-three hippos over two hundred square miles (Zea, “Colombia”). Ecologists estimate that the ecosystem’s carrying capacity of 1,418 hippos will be reached by 2039 if no action is taken to curtail their population (Kaplan, “Invasion”). Since there are no natural predators to these creatures in their adopted habitat, their population is poised for a boon, even perhaps exceeding the environment’s natural capacity for them. 

The hippos are “an extreme case” as they are “so big and destructive, and so obviously out of place” (“The debate,” 00:11:56-00:12:04). Invasive species, according to the National Wildlife Federation, pose a threat to the environment that is “second only to habitat loss and degradation” by “pushing many… native plants and animals to the brink of extinction” (“Combatting”). In fact, according to Castelblanco, hippos are “one of the greatest challenges of invasive species in the world” (Edwards, “Drug lord”). To scientists, these massive animals are an “ecological menace” (Kaplan, “Invasion”), especially due to their status as “ecological engineers” (Wilcox, “Could”), affecting their habitats so greatly simply as a result of their biological processes. As both terrestrial and aquatic animals, they double-dip in the environment, affecting not only the land but the water, too. According to Jonathan Shurin of the University of California, San Diego, nutrients in hippopotamus feces fuel billowing algal and bacteria blooms. The ecologist said, “we saw oxygen levels… where you would expect to see fish start to go belly up” (Kaplan, “Invasion”). In fact, according to Shurin and his partner Nelson Aranguren-Riaño from the Universidad Pedagógica y Tecnológica de Colombia, lakes that house hippos have an entirely different chemistry than lakes without their presence, including increased levels of Cyanobacteria, but “haven’t yet impacted the quantity or variety of invertebrates or zooplankton.” “If they have a detectable impact now - when they’re relatively rare,” they say, “then when they become much more common, that impact is certainly expected to increase” (Wilcox, “Could”). Most of the focus from scientists lies within the water, though there are concerns for the land ecology as well.

Environmentalists, ecologists, and the government alike have been scratching their heads trying to solve the problem of the invasive cocaine hippos. The answer, though each interested party insists on having the correct one, is not so clear cut. Across different disciplines, there are three main suggestions, boiled down to the following: (1) leave the hippos alone, (2) sterilize the hippos so that they can no longer reproduce, and (3) take drastic but necessary action to euthanize the remaining hippos in Colombia. 

Furthermore, the issue has been made more complex by the local population and government. Locals have taken to the hippopotamuses, seeing them as “an unofficial mascot” (Kaplan, “Invasion”) and as a gift that had been left by Escobar to bring in more money after his death (“The debate,” 00:06:35-00:06:45). And money they do bring, attracting upwards of 50,000 tourists to Hacienda Nápoles every year (Wilcox, “Could”). According to David Echeverri Lopez, from the environmental corporation Cornare, the hippos “have turned themselves into an emblem for a whole community of people. It’s not possible to just take them away.” While hippos can attack and kill dozens to hundreds of people in Africa every year, they have yet to kill any Colombians, and in 2009, it was outlawed to kill the hippos, even by government officials (Kaplan, “Invasion”). 

Some scientists are wary of any attempt to address the issue with a heavy hand, or even to concede that the hippos pose an issue at all. According to Arian Wallach from the University of Technology in Sydney, the hippos are “deserving of protection” and “an expression of life’s resilience” (“The debate,” 00:09:20-00:09:51). Even further, some scientists believe that the hippos may even be beneficial to the ecosystem as a whole: Jens-Christian Svenning from Aarhus University in Denmark argues that the hippos may even provide “ecosystem services,” filling a niche of large terrestrial herbivores that disappeared from South America some-20,000 years ago (Wilcox, “Could”). However, critics assert that smaller animals like tapirs and capybaras have already filled that role (“The debate,” 00:11:30-00:11:43). 

More mildly, some scientists have focused their efforts on surgical or chemical castration of the hippos, putting them in a non-reproductive state. This, however, according to Echeverri, “was an almost Herculean task” (Kaplan, “Invasion”), including corralling, sedating, and performing surgery one at a time. Gina Paola Serna, a wildlife veterinarian working with Colombian hippos, “sit[s] and cr[ies]” “every time I do a surgery… because it’s so stress[ful]” (“The debate,” 00:05:40-00:05:10). Costs of each sterilization priced up to $50,000 and took months to complete. “It was horrible,” Echeverri said (Edwards, “Drug lord”). Even worse, Echeverri and his team have been able to, on average, sterilize one hippo per year, while their population grows by ten percent annually. To be effective, the pace would have to be thirty hippos per year, half of them being females (Kaplan, “Invasion”). While surgical sterilization has been largely ineffective, the proponents of this method have turned to chemical castration with the help of the United States government.  The USDA has donated for their efforts fifty five doses of the contraceptive GonaCon (Edwards, “Drug lord”), but that only lasts about nine months (Zea, “Colombia”). Scientists have embraced this method, injecting the hippos with blow darts, and were able to treat forty hippos with their first round of the drug within six months. They will receive their second dose in one year, and their third dose in nine years (“The debate,” 00:05:51-00:06:12). Still, each castration cost approximately $10,000 (Zea, “Colombia”).

Yet, some scientists feel this still is not effective enough. Castelblanco is a leading voice in the charge for “extraction.” “Nobody likes the idea of shooting a hippo,” she says. “But no other strategy is going to work” (Kaplan, “Invasion”). Making the issue stall are, of course, the local regulations and the local population. “Some people in Colombia can get very angry” when she calls the hippos an ‘invasive species.’ “People tend to understand much more… when we talk about plants or smaller animals, instead of a massive mammal that many may find cute” (Edwards, “Drug lord”). While physical extraction would be the prime choice, local and foreign zoos will not accept the hippos, nor will any African nation, citing worries about how they would fare with their own populations, bringing their “unknown behaviors.” “Relocation might have been feasible” when there were only four hippos in Colombia, Castelblanco continues, and “castration could have been effective if officials had provided sufficient resources,” but “now the sole remaining option is the most painful one” (Kaplan, “Invasion”). Residents aren’t so sure: “It would be unfair to [the hippos], it’s not their fault” that they’re in Colombia, Magdalena Torres says. The hippos, to her, “are now Colombians” (Zea, “Colombia”). 

Whatever the solution may be, it has become clear to Castelblanco and to others that Colombia faces a choice between “either preserv[ing] the hippos or the environment” (Zea, “Colombia”). In the end, humans “choose what we want the ecosystem to look like” when facing problems like this (“The debate,” 00:12:49-00:12:52). Do we reset the native environment to its pre-hippo days, or do we laud the fact that the hippos have been able to survive and thrive in a paradise when their African counterparts face endangerment and extinction? “I’ve worked for many years to understand the problem and find solutions,” Echeverri remarks. “But the problem keeps happening over and over again… The only thing that changes is the number of hippos” (Kaplan, “Invasion”). Whether or not the hippos will stay or leave South America, it has proven that humans and nature are inexorably linked, both contributing in ebbs and flows of the history - and the future - of the environment.

Works Cited

“The debate about Pablo Escobar’s hippo.” Short Wave from NPR, 14 Jan. 2022, www.npr.org/2022/01/13/1072903214/the-debate-about-pablo-escobars-hippos.

“Combatting invasive species.” National Wildlife Federation, n.d. www.nwf.org/Our-Work/Environmental-Threats/Invasive-Species

Edwards, Jonathan. “Drug lord Pablo Escobar smuggled hippos into Colombia. Officials are now sterilizing the invasive species.” The Washington Post, 18 Oct. 2021. www.washingtonpost.com/nation/2021/10/18/pablo-escobar-colombian-hippos-sterilization/. Accessed 23, Dec. 2022

“Hippopotamus.” African Wildlife Foundation, n.d. www.awf.org/wildlife-conservation/hippopotamus.

Kaplan, Sarah. “Invasion of the hippos: Colombia is running out of time to tackle Pablo Escobar’s wildest legacy.” The Washington Post, 11 Jan. 2021. www.washingtonpost.com/climate-environment/2021/01/11/invasive-hippos-escobar-colombia-castrate/. Accessed 23 Dec. 2022

“What are invasive species?” National Invasive Species Information Center, n.d. www.invasivespeciesinfo.gov/what-are-invasive-species

Wilcox, Sarah. “Could Pablo Escobar’s escaped hippos help the environment?” National Geographic, 31 Jan. 2020. www.nationalgeographic.com/animals/article/colombia-cocaine-hippos-rewilding-experiment-news. Accessed 23 Dec. 2022

Zea, Tibisay. “Colombia to declare hippos an invasive species.” The World, 14 Mar. 2022. www.theworld.org/stories/2022-03-14/colombia-declare-hippos-invasive-species. Accessed 23 Dec. 2022