Author: ANotiCiasabi

Este artigo é da Hakai Magazine, uma publicação online sobre ciência e sociedade em ecossistemas costeiros. Leia mais histórias como esta em hakaimagazine.com.

A arraia 12 está surpreendentemente calma para um animal que está sendo esfregado. A arraia, aproximadamente do tamanho de um prato de jantar, está submersa na areia de um tanque do tamanho de um freezer horizontal; até mesmo os olhos dourados no topo de sua cabeça estão enterrados no sedimento. Ela permanece imóvel enquanto o pesquisador Ben Perlman da Universidade Estadual da Califórnia, Long Beach (CSULB) empurra cuidadosamente a areia de seu corpo marrom manchado — o rodo oferece ao cientista um pouco de proteção contra os farpas de aparência perigosa que saem da metade da cauda da arraia 12.

“Desculpe incomodá-lo”, murmura Perlman.

Seis estudantes de graduação espiam por cima do ombro dele, e uma delas, Carly Brenner, dá um passo à frente segurando um pé humano de silicone impresso em 3D e colado em um cano de PVC.

“Um pouco mais perto, um pouco mais perto”, Perlman orienta enquanto Brenner traz o pé a centímetros do corpo da arraia. “Vá em frente”, ele diz, e Brenner mira na barbatana peitoral esquerda da arraia, pisando com o pé flexível.

O raio não se move.

“Nenhuma resposta”, diz Perlman. O resultado será registrado no estudo de seu laboratório sobre o que faz as arraias atacarem — ciência que Perlman espera que eventualmente ajude as pessoas a evitar picadas dolorosas dos farpas serrilhadas, cada uma do comprimento do dedão do pé de um humano adulto.

O laboratório de Perlman em Long Beach, Califórnia — apropriadamente chamado de STABB, para Stingray and Butterfly Biomechanics Lab (o projeto da borboleta está atualmente pausado) — explora como e por que as arraias se movem e se comportam da maneira que o fazem. Seal Beach, um dos pontos de surfe mais populares da cidade, a três milhas do laboratório, é coloquialmente conhecido como Ray Bay. As arraias adoram se reunir ali nas águas calmas e mornas da foz do Rio San Gabriel, e os salva-vidas documentam mais de 500 ferimentos dolorosos por facadas de arraias a cada ano. Estudar o comportamento das arraias e seu processo de picada pode abrir uma nova janela para as interações humanas com o que o laboratório chama de “panquecas perigosas”, diz Perlman.

A sua investigação centra-se em raios redondos—a espécie de arraia mais abundante que habita as águas da Califórnia. Seu comportamento também as torna as mais perigosas para os transeuntes desavisados. Enquanto outras arraias fogem rapidamente ao sinal de perigo, as arraias redondas ficam enterradas na areia e até prendem a respiração quando um predador, como um tubarão-branco juvenil — ou um predador percebido como um humano — passa, confiando em sua cor manchada para camuflagem. É esse comportamento protetor que as torna muito mais propensas a serem pisadas e explica por que a grande maioria dos ferimentos de arraias na Califórnia são atribuídos às arraias redondas, em vez das arraias-morcego ou arraias-diamante que também vivem na área.

Os farpas de arraia são um tipo de dentículo dérmico — como um dente — em uma cauda que pode ser chicoteada. Em um ataque, o animal libera uma toxina de células glandulares na base de uma das farpas. A toxina viaja ao longo de um revestimento mucoso e é envenenada — injetada — no receptor através da ferida perfurante. Algumas espécies de arraia têm farpas com entalhes serrilhados, o que pode fazer com que a farpa grude na pele do atacante.

Chris Lowe, um biólogo de tubarões que lidera Laboratório de Tubarões da CSULBestima que cerca de 10.000 pessoas por ano são feridas por arraias no sul da Califórnia. As arraias redondas são como hambúrgueres para tubarões brancos jovens, o que é uma das razões pelas quais Lowe e seus colegas cientistas de tubarões estão profundamente interessados ​​nas distribuições e populações de arraias. O Shark Lab, estabelecido na década de 1960, estuda arraias há anos, mas nunca sua mecânica de picada.

Perlman, por sua vez, não se propôs a pesquisar raias — ele é um biomecanicista de peixes que estudou como a surfperca nada em florestas de algas e como peixes anfíbios nos trópicos usam seus músculos para se puxarem para fora da água. Ele também estudou como as asas dos pássaros podem mudar de forma durante o voo e como as rãs-touro carregam seus tendões para aumentar seu poder de salto. Em 2018, ele conseguiu um emprego na CSULB como professor e deixou a pesquisa por alguns anos.

Então, ele recebeu uma batida na porta no outono de 2021. Lowe tinha uma pergunta. Ele queria saber se Perlman poderia ajudar a testar um novo material para botas de surfe desenvolvido por um inventor cujos filhos tinham medo de raios e um colaborador com experiência em ciência dos materiais. As botas protegeriam contra ataques de arraias, conforme projetado? Depois de receber fundos de um doador anônimo amante do surfe, Perlman contratou um aluno e, juntos, eles coletaram arraias de Seal Beach para servirem como cobaias.

Para descobrir se o material poderia proteger contra ataques, Perlman primeiro teve que entender a dinâmica do comportamento defensivo da arraia. Seu objetivo inicial de pesquisa era capturar ataques na câmera e usar a filmagem para medir a velocidade e a aceleração, que ele poderia então usar para calcular a força. Ele comprou um pé desencarnado na loja Spirit Halloween, encheu-o com areia e o epoxiou em um pedaço de cano de plástico para imitar um pé humano para os testes. “Esse foi um ótimo ponto de partida”, diz Perlman.

Para aprender mais sobre o que faz uma arraia decidir atacar, ele projetou um experimento que divide o corpo da arraia em quatro regiões diferentes — corpo médio, nadadeira peitoral esquerda, nadadeira peitoral direita e focinho (basicamente equivalente a um nariz). Sua equipe usa o pé zumbi — que foi atualizado para um pé de silicone impresso em 3D em 2023 porque é mais realista — para “pisar” nas diferentes partes do corpo e registrar a reação do animal.

As descobertas iniciais são gritantes: as arraias só atacam se alguém pisar no meio do corpo delas, onde todos os seus órgãos estão localizados. Isso faz com que elas ataquem 85% das vezes. Pisar nas laterais delas apenas as faz nadar para longe; um tapa no focinho também não provoca uma reação. As descobertas são consistentes, independentemente do tamanho, idade ou sexo da arraia.

O laboratório também tem feito estudos do novo material que Lowe trouxe para Perlman — neoprene com um revestimento composto de borracha — para ver se ele pode suportar as forças de um ataque de arraia. Os pesquisadores cortam farpas — semelhante a cortar uma unha, já que as farpas à base de queratina voltam a crescer em poucos meses — e usam uma máquina para forçá-las a entrar no material com pressão crescente. Até agora, eles descobriram que o material resiste à força da maioria das arraias. (Outro empresa (na esperança de criar uma bota à prova de raios, está lançando um produto usando um material semelhante este ano.)

Além de seus farpas, algumas arraias têm dentículos grandes, espinhosos e semelhantes a escamas que fornecem proteção passiva, diz Chris Martinez, um biólogo de peixes da Universidade da Califórnia, Irvine, que estuda a morfologia das arraias. Os espinhos podem perfurar a pele e tornar a vida de um predador desagradável, ele diz, mas o ferrão é algo extra: uma arma direcionada que o animal pode controlar ativamente para infligir danos.

Martinez diz que o trabalho de Perlman é “realmente ótimo e é definitivamente muito relevante para atender aos banhistas do sul da Califórnia”. Ele está planejando colaborar com Perlman no futuro para investigar os fundamentos neuromusculares dos ataques.

A esperança final, diz Perlman, é que a pesquisa se traduza em melhores práticas para as pessoas na praia. Por décadas, surfistas no sul da Califórnia têm usado uma técnica chamada “stingray shuffle”, onde eles dão pequenos passos no chão em vez de grandes passos — para avisar as arraias que podem estar enterradas na areia.

Perlman diz que seus experimentos respaldaram cientificamente o embaralhamento das arraias — quando alguém dá pequenos passos, eles não vão entrar em contato com a parte do meio do corpo da arraia, então não serão atingidos. As vibrações através da areia também podem dar ao animal uma chance de se mover para um lugar seguro.[The rays are] simplesmente escapar ou não responder”, diz Perlman.

Ele sabe exatamente o que está em jogo. No verão passado, ele estava segurando a cauda de uma arraia com uma rede enquanto usava um bisturi para fazer pequenos entalhes de identificação no corpo do animal — que precisam ser refeitos a cada poucos meses conforme os entalhes crescem — quando sua mão escorregou e a cauda do peixe girou e atingiu uma artéria em seu pulso. Sangue imediatamente espirrou para todos os lados, e a dor era “um 7 1/2 de 10”. Ele usou o único tratamento conhecido, que era submergir sua mão em água quente para desnaturar o veneno. Demorou quase duas horas para a dor desaparecer. Seu pulso ainda tem uma cicatriz.

O laboratório agora está envolvido em uma onda de atividades de pesquisa que pode manter Perlman e seus colegas de equipe ocupados pelo resto da década. Eles estão testando como o tamanho de um pé impacta a probabilidade de um ataque de arraia, para ver se alguém que é mais leve e menor tem menos probabilidade de ser picado. Até agora, o tamanho do pé parece não ter impacto em como uma arraia responde. Nos próximos meses, eles repetirão os experimentos de pisar no escuro e em diferentes temperaturas de água. O laboratório abriga 18 arraias, e os animais têm pelo menos dois dias de folga entre os experimentos para garantir que não sejam condicionados.

Os pesquisadores também estão estudando as raias enquanto elas se enterram na areia para entender por que e como os animais movem as partículas de areia. Eventualmente, o laboratório também usará imagens 3D de varreduras de microCT para observar a curvatura, nitidez e ângulo das serrilhas em diferentes farpas de raia redondas. Isso os ajudará a entender a variação dentro da espécie e até mesmo dentro de um indivíduo: às vezes, depois de ser aparada, uma farpa volta a crescer em um formato ou tamanho diferente.

Tubarões tendem a ser maiores do que arraias na consciência californiana, diz Martinez. “Arraias não recebem tanta atenção porque não são tão grandes, não têm dentes grandes como alguns dos grandes tubarões”, diz ele. “Mas é mais provável que você seja ferido por um desses do que por um tubarão grande.” As estatísticas comprovam seu ponto: em 2022, 57 ataques de tubarão ocorreram ao redor do mundo, e os ferimentos de arraias provavelmente chegaram a dezenas de milhares.

Após seu encontro com o pé de silicone, Stingray 12 tem uma pausa de dez minutos antes que sua outra nadadeira peitoral seja pisada. Perlman observa enquanto ela se enterra de volta na areia. É bom dar um passo figurativo para ajudar outros californianos a evitarem facadas e ferroadas, ele diz. No final das contas, se surfistas e nadadores puderem usar sua pesquisa para evitar panquecas perigosas, o tempo de todos na praia — arraias incluídas — será mais harmonioso.

Este artigo é da Hakai Magazine, uma publicação online sobre ciência e sociedade em ecossistemas costeiros. Leia mais histórias como esta em hakaimagazine.com.

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In the steamy heat of afternoon, Yamit Diaz Romero steered our motorized longboat around overhanging bamboo branches and islets in the Claro Cocorná Sur River, in western 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-colored water and soared over our heads. The river is known as a destination for white-water 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 jujitsu champion and world traveler who had hitched a ride with Mira and me and was sharing the experience with his followers on social media. Fishermen 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 950 miles 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, 300 yards away, three pairs of gray ears flicked, and beady eyes darted above the water line. The boatman circled cautiously, then winced when Wilson, the jujitsu champion, suddenly launched an aerial drone and banged on the boat’s gunwale to get the animals’ attention. One animal raised a gigantic, bulbous head and opened its mouth, exposing a sharp set of canines. “Tourists think that 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 ten miles west of the Magdalena. After he was shot dead in Medellín by Colombian police, in 1993, local people poured onto the property and tore apart Escobar’s villa in search of rumored caches of money and weapons. Afterward, the hacienda sank into ruin. In 1998, the government seized possession of 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 life span 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 100,000 square miles 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 the number 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 serious. In Africa, hippos are thought to kill some 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 kids 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 authorities to do something before the problem spins out of control.

And 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 20 pounds of feces 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 program, which seeks not to capture or “cull” the hippos but to sterilize them in the wild. But 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 program last year, the team sterilized seven hippos in three months—a considerable achievement, but short of the estimated 40 castrations a year they believe will be necessary to control the population. “There have been sterilizations 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 toward the hippo pod. The creatures turned toward us, watching. Wilson, the jujitsu champion, 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.

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When Pablo Escobar appeared in Puerto Triunfo in 1978, the government had just constructed 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 5,000-acre property near Doradal.

The drug baron installed an airplane 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 $2 million 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 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 1980s, 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 fled into hiding. In 1984, he dispatched a hit team to assassinate Colombia’s minister of justice. Five years after that, an unwitting courier carried a bomb onto a Colombian airliner, which blew up midflight, 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. Right-wing 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 sympathizers. Puerto Triunfo became a center of the violence, with many people kidnapped and murdered during the late 1980s and 1990s.

After Escobar was shot dead and his property abandoned, the hippos survived on their own, eating the grass, fruits and other plants that proliferated on the land. 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, a bearded, 40-year-old biologist 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 a thousand civilians per 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 to me. Conservation teams prowled the region near Escobar’s hacienda at night, looking for hippos to shoot with tranquilizer darts while they grazed. But it took an hour for the tranquilizer to have an effect, by which time the animal had returned to the water. In 2011, veterinarians managed to anesthetize 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, to regather the wandering hippos at their point of origin. 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 criticized 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 program, 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 maneuver than adults. But that still left an adult population scattered across the Magdalena Basin.

After lunch, 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 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 darted with tranquilizers, 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.

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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 an 800-pound male—relatively junior sized—pacing inside the enclosure. A team member fired three tranquilizer 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 onto 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 signaled 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 anesthetics—into the veins on his ears and tongue. Administering the anesthetic 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 15 inches inside the body, they can be difficult to find. Buitrago made a two-and-half-inch 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 theorize, that can help stave off infections from the animals’ frequent tussling—as well as from castration.

Throughout the fall 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 1,500 pounds, among the largest they had encountered. Tying ropes around the feet to pull the animal onto 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 toward the makeshift operating theater. 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 percent 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 1,500-pounder was a success. But, at the end of 2023, Cornare’s contract with the government expired, and there was some question about when the program 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 program 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 euthanized, although she also said that both castrations and attempts to move the beasts to overseas zoos will continue.

But the sentiment for a hard-line solution is growing. After years of searching for a viable alternative, Echeverri López now acknowledged to me that a cull will probably have to happen. Indeed, more and more hippo experts around the world say that a controlled killing program is inevitable. “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.”

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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 1970s 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 told me. But, she went on, “We see him every single 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 realized when I visited his hacienda. The drug lord’s restored villa on the property grounds 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 airplane that Escobar first used to fly cocaine to landing strips in the United States. Colombian tourists moved somberly 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 favorite cafés, some of those same tourists were posing for photographs alongside a life-size Escobar mannequin and browsing for coffee mugs, T-shirts and refrigerator magnets emblazoned with his portrait. Those looking for more menacing mementos 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 program, wide-scale sterilization, targeted translocation or some combination, even in the best of circumstances Colombians will likely have to live with a vestige hippo population. Of some 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.”