In the steamy heat of the afternoon, Yamit Diaz Romero steered our motorised longboat around overhanging bamboo branches and islets in the Claro Cocorná Sur River in Colombia. Red howler monkeys swung from the cables of a footbridge and screeched in the jungle. Herons, snowy egrets, brown pelicans and parakeets darted across the coffee-coloured water and soared over our heads. The river is known as a destination for whitewater rafting. But these days it’s also become the scene of a more unsettling natural phenomenon.
Joining me on the vessel was Alejandro Mira, a veterinarian from Medellín, and Joshua Wilson, an American jiu-jitsu champion and world traveller who had hitched a ride with Mira and me and was sharing the experience with his followers on social media. Fishers motoring from the opposite direction gave warnings to Romero about what lay ahead. After an hour, the Claro Cocorná spilled into the Magdalena River, the longest in Colombia, which originates in the Andes and flows north for 1,600km before emptying into the Caribbean Sea.
Romero, a solid man with black-framed spectacles and a pink camouflage shirt, scanned the river and pointed straight ahead. Near the opposite bank, about 250 metres away, three pairs of grey ears flicked, and beady eyes darted above the water line. The boatman circled cautiously, then winced when Wilson suddenly launched an aerial drone and banged on the boat’s gunwale to get the animals’ attention. One raised a gigantic, bulbous head and opened its mouth, exposing a sharp set of canines. “Tourists think this is cute,” Romero told me in Spanish. “But it’s a sign of aggression.”
You might not expect to encounter wild hippopotamuses, the huge, semiaquatic mammal native to sub-Saharan Africa, in the rivers – and ponds, swamps, lakes, forests and roads – of rural Colombia. Their increasingly ubiquitous presence here is an unlikely legacy of Pablo Escobar, the infamous drug baron from Medellín. Decades ago, Escobar spent part of his vast fortune assembling a menagerie of exotic animals, including elephants, giraffes, zebras, ostriches and kangaroos, at his hacienda outside Doradal, a town about 10 miles west of the Magdalena. After he was shot dead in Medellín by Colombian police in 1993, local people poured on to the property and tore apart Escobar’s villa in search of rumoured caches of money and weapons. Afterward, the hacienda sank into ruin. In 1998, the government seized the property and eventually transferred most of the animals to domestic zoos. But several hippos – most sources say three females and one male – were considered too dangerous to move. And that’s how Colombia’s current trouble began.
The hippos multiplied. (Once they reach maturity, female hippos can produce a calf every 18 months, and they can give birth 25 times during a lifespan of 40 to 50 years.) Males cast out of the herd by the dominant male migrated elsewhere, started their own herds and took over new territory. Today nobody knows how many hippos inhabit the rivers and lakes of the Magdalena Basin, which covers roughly 260,000 sq km and is home to two-thirds of Colombia’s human population. As of late 2023, the official government count was 169. David Echeverri López, chief of the Biodiversity Management Office of Cornare, a regional environmental agency, says there could be 200. Colombian biologists recently predicted that by 2040, if nothing is done to control their breeding, the population will grow to as many as 1,400. The hippos will use the Magdalena River as their primary expansion route, says Francisco Sánchez, an environmental official in the riverside municipality of Puerto Triunfo, which includes Doradal. “They’ll get all the way to the sea, because they will just follow the river.” He calls the situation “completely out of control”.
The presence of these beasts in the heart of South America, waddling at night down rural paths and staring into the headlights of jeeps and motorcycles, might be comical if it weren’t so deadly. In Africa, hippos are thought to kill about 500 people a year, making them among the most dangerous animals to humans, according to the BBC and other sources. And while, for now, violent encounters in Colombia have been limited, unsettling incidents are increasing. The beasts have attacked farmers and destroyed crops. Last year, a car struck and killed a hippo crossing a highway. (Hippos tend to spend daytime hours in the water and move around land at night, adding to a menacing sense of danger striking in the dark.) This wasn’t long after a hippo lumbered into the yard of a school, sending frightened teachers and children running for cover. The animal munched on fruit that had fallen from trees before shuffling off to nearby fields. Although nobody was hurt, the incident was widely covered in the Colombian media, increasing pressure on the authorities to do something.
The danger is hardly limited to people. Colombian scientists are sounding alarms about the impact on the region’s ecosystem. For example, a single hippo produces up to 9kg of faeces a day. In Africa, the dung long provided nutrients for fish populations in rivers and lakes, but in recent years, perhaps as a consequence of warming temperatures, water-intensive agriculture and increasing drought, the dung has accumulated to toxic levels in stagnating pools, killing off the same aquatic life that once benefited from it. Experts fear the same thing could happen in Colombia. And competition for food and space could displace otters, West Indian manatees, capybaras and turtles. “If I lived in Colombia, I would be worried,” Rebecca Lewison, an ecologist at San Diego State University’s Coastal and Marine Institute, told me. “Colombia has great biodiversity, and this is not a system that has evolved to support a mega-herbivore.”
This bizarre problem is compelling Colombian conservationists to search for unusual solutions, which is one reason I found myself with Mira on the Magdalena, staking out unsuspecting hippos. Mira is a member of a newly formed, first-of-its-kind animal control programme, which seeks not to capture or “cull” the hippos, but to sterilise them in the wild. The procedure, an invasive surgical castration, is medically complicated, expensive and sometimes dangerous for hippos, as well as for the people performing it. After successfully piloting the programme last year, the team sterilised seven hippos in three months – a considerable achievement, but short of the estimated 40 castrations a year that they believe will be necessary to control the population. “There have been sterilisations in zoos, but no information was available about doing this in the wild,” Mira told me. “We basically had to learn it as we went along.”
As we circled the hippos, Romero, the boatman, kept a judicious distance. Mira and I had come, during a hiatus in the castrations, to see for ourselves the growth of the population, but viewing hippos in the wild can be risky. Half an hour into our excursion, the boat engine abruptly died. Romero yanked on the pull cord. The motor responded with a sputter. He yanked again – nothing. With mounting frustration, and sweat pouring down his face, the boatman tugged and pulled the rope. Meanwhile, we drifted towards the hippo pod. The creatures turned toward us, watching. Wilson returned the stare. Then he muttered: “Uh-oh.” Finally, with a powerful jerk, Romero brought the engine back to life, and we slowly motored back in the other direction toward the Claro Cocorná.
When Pablo Escobar appeared in Puerto Triunfo in 1978, the government had just built a two-lane asphalt highway between Medellín and the Magdalena River, making the jungled region far more accessible. The 28-year-old Escobar identified himself as a “businessman” and announced that he was looking to buy property. “There was very good tree cover and good water resources,” Sánchez, the local environmental official, said, as we sat in Puerto Triunfo’s riverfront town hall, where he has worked for more than three decades. “It was the perfect place to build a retreat.” After a search, Escobar bought a 2,000-hectare property near Doradal.
The drug baron installed a runway, a villa, heliports, aircraft hangars, horse stables, 27 artificial lakes, a dinosaur theme park and a bull ring. He also hired a staff of more than 1,000 people to run the hacienda. In the early 1980s, inspired by other Latin American drug traffickers and drawn to the symbolic power of wild beasts, he reportedly paid exotic animal breeders in Dallas $2m in cash for the first animals in his menagerie. Many more, including the hippos, were procured from other dealers and possibly zoos. Sánchez told me that he examined the records of Escobar’s transactions in the archives at the town hall, but the documentation was destroyed when the Magdalena River flooded the town in the 1990s.
Escobar was picky about his animals. “He would not buy lions, tigers or other big cats,” Sánchez said. “Taking care of carnivores is very complicated. Just keeping them fed is a tremendous amount of work.” Escobar had also decided to open his menagerie to the public, and he didn’t want predators roaming freely around the grounds. Giving ordinary Colombians access “was a way of making himself popular”, Sánchez said. In the early 80s, crowds stood in line for hours in the heat at the hacienda gates, waiting to board electric vehicles and bounce over the property past elephants, ostriches and other wild beasts. Sánchez did the tour himself in 1982. “There was a female elephant that would put her trunk inside the cars, and people loved her,” he recalled.
Escobar’s days at Hacienda Nápoles didn’t last long. After he was publicly identified as a leader of the Medellín cartel, he went into hiding. In 1984, he dispatched a hit squad to assassinate Colombia’s minister of justice. Five years after that, an unwitting courier carried a bomb on to a Colombian airliner, which blew up mid-flight, killing all 107 people on board. Escobar’s intended victim, presidential candidate César Gaviria Trujillo, had missed the flight; he was later elected president and made the capture or killing of drug traffickers a priority. As Colombia’s security forces hunted the narcotraficante, violence spread across the region. Rightwing death squads known as autodefensas formed an alliance with drug cartels – offering the cartel members protection in return for a cut of their profits – and declared war on the Revolutionary Armed Forces of Colombia (Farc), a Marxist guerrilla group, and its sympathisers. Puerto Triunfo became a centre of the violence, with many people kidnapped and murdered during the late 80s and 90s.
After Escobar was shot dead and his property abandoned, the hippos survived on their own, eating the grass, fruits and other plants. Over the years, the population established new pods beyond the hacienda. Reports trickled in that the animals were trampling farmland, attacking cattle and menacing fishing boats.
By 2008, the population had reached about two dozen, and Colombia’s ministry of the environment decided it was time to act. Echeverri López, who had recently graduated from the University of Antioquia in Medellín with a botany degree, was hired to help search for solutions. One of his first initiatives was to seek advice from wildlife experts in South Africa, who visited Doradal to investigate. “They told me: ‘You have a problem,’” Echeverri López said, as we sat in a restaurant in Doradal, a lively tourist town four hours east of Medellín. “They said: ‘The only solution is to kill them.’”
The next year, the government hired a hunter to begin culling the hippos, but when a photograph circulated in the media showing the corpse of a male called Pepe, who had wandered 60 miles from Escobar’s hacienda, pro-hippo protests erupted across Colombia. Echeverri López found himself puzzled by the response. “I was saying to myself: ‘Think about how many people are murdered in Colombia every day.’” This was a time when the ongoing civil war was still claiming the lives of more than 1,000 civilians a year. “And then there’s this outpouring of sentiment to protect the hippo. I couldn’t explain it.” In the face of public outrage, the minister of the environment resigned, and hippo killings were put on hold.
Echeverri López was obliged to search for other methods. “I had nothing in my background to suggest I could handle this,” he admitted. Conservation teams prowled the region near Escobar’s hacienda at night, looking for hippos to shoot with tranquilliser darts while they grazed. But it took an hour for the tranquilliser to have an effect, by which time the animal had returned to the water. In 2011, veterinarians managed to anaesthetise and castrate one hippo named Napolitano, 50 miles from Escobar’s former ranch. A military helicopter then transported the unconscious beast in a cage back to the hacienda. But the helicopter’s engine overheated, and the pilot barely made it down safely.
To contain the hippos, Cornare tried cordoning off the hacienda with bushes, barbed wire and electric fences, but the animals kept finding escape routes. The agency approached zoos in India, the Philippines, Ecuador and other countries about adopting the animals, but the plan was criticised by the Hippo Specialist Group of the International Union for Conservation of Nature (IUCN), a Switzerland-based committee of biologists and animal conservationists. A zoo relocation programme, IUCN declared in 2023, “would be extremely costly, have no conservation benefit, and represents a poor use of conservation resources that are critically needed to protect common hippos” in Africa. Cornare’s initiative has yet to result in a single transfer.
“Most captive facilities can’t accommodate them,” says Lewison, the San Diego State University ecologist, who also serves as the co-chair of the IUCN hippo specialist group. “Hippos are difficult to keep, they’re huge, and water filtration” – necessary to account for all the poop – “is expensive. Most zoos that want a hippo have one already, and if they don’t, they don’t have the capacity for it.”
Staffers also tried chemically castrating the animals with darts, a procedure used successfully in zoos around the world. But hippos require multiple shots, months apart from each other over two years, and it proved impossible to tag and track the free-ranging animals that had received the first dose. Inside the park near Doradal, they surgically castrated a dozen juvenile hippos, which are more docile and easier to manoeuvre than adults. But that still left an adult population scattered across the Magdalena Basin.
I followed Echeverri López in my vehicle through the gated entrance of Escobar’s former hacienda. In 2007, the Puerto Triunfo municipal government partnered with a private company to turn it into a zoo and safari park – with an all-new animal population – and it’s now Doradal’s main tourist attraction. Garishly painted statues of dinosaurs, hippos and other beasts, some left over from Escobar’s time, loomed along the shoulder of an asphalt road that wound through the rolling pastureland. We walked down a steep slope toward what was once one of Escobar’s artificial lakes, now located outside the grounds, where a dozen hippos lolled in a cluster. “They found a quiet habitat here, with plenty of food, and they settled in,” Echeverri López said. The hippos, on seeing us, moved closer to the shore. “Don’t worry,” he reassured me. “We are halfway up the slope, so we have a certain advantage if one attacks.”
The population in this lake, where the animals spend the daylight hours, had reached about 50 – the densest concentration outside the park, and became the initial target of the new surgical castration campaign. Echeverri López pointed to a corral a few dozen yards from the lake, one of three strategically placed enclosures built using a metal alloy that is all but unbreakable, even by huge, angry mammals. The team uses a trail of carrots, cabbages and fruit to lure hippos into the enclosure; a spring-trap door then slams shut. Once lured, the animals are shot with tranquilliser darts, allowing the scientists to castrate them where they rest. Cornare observers conduct spot checks every evening, and if they encounter a trapped hippo, they quickly summon the surgical team to the scene.
Alejandro Mira got the call to assist in his first surgical castration of a hippo last October. “I was nervous,” he told me one evening, as we were driving along a rural road, keeping a wary lookout for hippos on the highway. In the predawn darkness last year, Mira arrived at the lakeshore to confront a 350kg male – relatively junior-sized – pacing inside the enclosure. A team member fired three tranquilliser darts into the hippo’s buttocks. Then the group waited outside. After 45 minutes, the animal sank into a seated position – “like a dog,” Mira said – then rolled on to its side in a pool of mud.
Mira had castrated many horses, dogs and cats, but this was different from the usual neutering. “The surgery is taking place in a wild environment, with a dangerous animal, with the testicles hidden deep inside the body,” he told me. To verify that the hippo was in a deep state of unconsciousness, a team member tickled his ears. When they didn’t twitch, he signalled to the others. The veterinarians tied a rope around the animal’s feet, then dragged him a few yards to a sterile canvas sheet on which the surgery would take place. The team donned surgical scrubs and raised a canvas tent to shield themselves and the animal from the rising sun. Then they swabbed the hippo with sterile wipes and inserted intravenous drips – antibiotics, anti-inflammatories and anaesthetics – into the veins on his ears and tongue. Administering the anaesthetic is a dangerous part of the procedure. For unclear reasons, hippos, like other marine mammals, are highly sensitive to sedation and, in zoos, have sometimes had fatal reactions.
The lead veterinarian, Cristina Buitrago, knelt and palpated the hippo’s abdomen to feel for his testicles, located in the inguinal canal. Because they are retractable and can reside as deep as 40cm inside the body, they can be difficult to find. Buitrago made a 6cm incision, cutting with difficulty through thick skin and layers of fat. Mira knelt beside her, handing her surgical instruments. Then, slicing delicately around the blood vessels, she pulled out the mango-sized testicles, “about the size of a horse’s balls”, Mira told me. The vet snipped them off, sutured the wound and sewed the incision shut.
As the animal slept, the team hurriedly removed the equipment and exited the corral, monitoring the hippo until it returned to consciousness and shambled through the gate and into the lake. From darting to awakening, the procedure had lasted seven hours. The team had tagged the animal’s ears during the surgery, though it is difficult to monitor hippos in the wild. Still, they were confident it would recover well. “They have a strong immune system, and there’s no reason to believe that they can’t survive,” Mira told me. In fact, biologists have discovered a pigment in hippo skin that absorbs ultraviolet light and may prevent bacteria from growing; it’s a natural antibiotic, they theorise, that can help stave off infections from the animals’ frequent tussling – as well as from castration.
Throughout the autumn of 2023, the Cornare team refined the procedure to as close to a science as possible. Then, in December, Mira and his colleagues faced a male hippo weighing almost 700kg, among the largest they had encountered. Tying ropes around the feet to pull the animal on to a sheet wouldn’t work with an animal of this size. Instead, Mira and his six colleagues stationed themselves around the hippo’s hind legs, forelegs, backside and head. After a count of “uno, dos, tres”, they pushed, tugged, yanked, dragged and inched the sleeping behemoth a few yards towards the makeshift operating theatre. With a final heave, they raised the animal just enough to slide the canvas sheet beneath his bulk. (Two of the animals they operated on in 2023 were female, a fact that became known only after the hippos’ sedation. “It’s 200% more complicated with females,” Mira told me. “You have to access the ovaries through the flanks, cutting through thicker skin and several layers of muscle. You have to go much deeper and really use your hands.”)
The operation on the big hippo was a success. But, at the end of 2023, Cornare’s contract with the government expired, and there was some question about when the programme would continue. By April, however, the veterinary team was back in the field, and had castrated three more hippos. Meanwhile, Colombia’s ministry of the environment has apparently decided that the catch-and-castrate programme isn’t sufficient to handle the hippo problem. Susana Muhamad, the minister of the environment, says that of 169 hippos so far confirmed to be roaming the Colombian countryside, “some” will have to be euthanised, although she also said that both castrations and attempts to move the beasts to overseas zoos will continue.
But the sentiment for a hardline solution is growing. After years of searching for a viable alternative, Echeverri López acknowledged to me that a cull will probably have to happen. Indeed, many hippo experts around the world agree. “Castration can slow population growth down a bit, but it’s not a solution,” Jan Pluháček, a Czech biologist and hippo specialist, told me. Culling, he said, is “the only thing that makes sense”.
On one of my last days in rural Colombia, I drove with Mira to a guest house called Villa Sara, a couple of miles from Hacienda Nápoles. The caretaker had notified Cornare that a hippo had moved into a pond behind the property, and Mira had been called to assess the situation. Reports like these have become more common in the last couple of years, Mira told me.
We drove up the long driveway to a Spanish colonial-style villa where Escobar is reported to have lived in the 70s while hunting for a ranch. The caretaker, a young woman named Flor Daza, led us to the back garden. “There he is,” she exclaimed, pointing to a pair of eyes and a snout protruding beyond the shoreline. Mira said the animal was probably a young male who had been cast out of a herd by the dominant male and forced to live on his own. “When he first looked at me in the eye, I was terrified,” Daza said. But, she went on, “We see him every day, and we are no longer afraid of him.” The owners of the villa, however, who live in Bogotá, remained concerned, and Daza could not rule out the possibility of violent run-ins between the hippo and unwitting guests.
Daza’s ambivalence about the hippo reflected the perspective of many people I encountered in Colombia, who couldn’t help but feel a mixture of affection and even protectiveness, along with a twinge of fear. In this beleaguered part of the country, which has suffered decades of violence, turmoil and civil war, many people see the hippos as a potential economic lifeline. At a grocery store just outside Escobar’s former hacienda, the owner has turned the top floor of his establishment into a “tourist hotel”, and he posts videos to social media showing groups of four or five hippos – “our pets”, he calls them – wandering past the shop to graze in the bush at night. Isabel Romero, who runs a nonprofit that breeds endangered river tortoises on the Claro Cocorná Sur River, recently opened a hippo-viewing concession, offering lunch and a boat ride to the Magdalena for about $100. It’s doing a brisk business among both Colombian and foreign tourists.
This pragmatic embrace of Escobar’s hippos was not so unlike the response to his legacy itself, as I realised when I visited his hacienda. The drug lord’s restored villa is now a memorial museum to his victims, just down a path from the pond where his original hippos once resided. (Today, the pond is home to a female hippo named Vanessa, the park’s mascot.) A high arch stands at the entrance, topped by a replica of the single-engine Piper Super Cub plane that Escobar first used to fly cocaine to landing strips in the US. Colombian tourists moved sombrely through galleries displaying portraits of politicians, policemen and ordinary citizens killed in car bombings and crossfire, and yellowing newspaper clippings and magazine covers documenting Escobar’s atrocities. Billboards near the museum saluted the “triumph of the state” against “the worst criminal in our history”.
On Doradal’s main drag a mile away, however, I encountered a different kind of commemoration. At Pablo’s Shop, which opened on the former site of one of his favourite cafes, some of those same tourists were posing for photographs alongside a lifesize Escobar mannequin and browsing for coffee mugs, T-shirts and refrigerator magnets emblazoned with his portrait. Those looking for more menacing mementoes could take their pick from display cases filled with replica pistols and AK-47s. The owner conceded that he had been nervous about opening the boutique – friends had warned him that he might face a backlash – but he’d had no trouble at all. In fact, business was booming. Escobar’s charisma, his extraordinary wealth and his flamboyant notoriety had conferred on him the status of permanent celebrity.
Despite a recognition among Colombian officials that the hippos will have to be managed, whether by a culling programme, wide-scale sterilisation, targeted translocation or some combination, even in the best of circumstances Colombians are likely to have to live with a vestigial hippo population. Of 3,500 invasive animal species introduced by humans into new, unsuitable biomes around the world, few have been eradicated. Whether the intruders are Burmese pythons imported by exotic pet collectors and abandoned in the Florida Everglades, or lionfish from the Indo-Pacific eating up crustaceans, snappers, groupers and other aquatic animals along the East Coast and Gulf of Mexico, or giant African land snails devouring native plants across Asia and Latin America, there is no realistic way to turn back the clock. Colombians may have no choice but to make their peace with this reality.
At dusk, as we watched the hippo behind Villa Sara leave the lake and begin a search for food in the adjacent woods, Daza said: “I’ve accepted him, and I’ve come to view having him here as a privilege.”
This article was first published in the Smithsonian Magazine