The Debate About Pablo Escobar's Hippos : Short Wave Pablo Escobar had a private zoo at his estate in Colombia, with zebras, giraffes, flamingoes - and four hippopotamuses. After Escobar was killed in 1993, most of the animals were relocated except for the so-called "cocaine hippos." Authorities thought they would die but they did not and now, about a hundred roam near the estate. Conservationists are trying to control their population because they worry about the people and the environment. But some locals like the hippos and a few researchers say the animals should be left alone and are filling an ecological void. The controversy reflects growing debate in ecology about what an invasive species actually is.

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The Debate About Pablo Escobar's Hippos

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EMILY KWONG, BYLINE: You're listening to SHORT WAVE from NPR.

DAN CHARLES, HOST:

Hi, Short Wavers, it's Dan Charles here with science journalist and former SHORT WAVE intern Rasha Aridi. Hi, Rasha.

RASHA ARIDI, BYLINE: Hi, Dan.

CHARLES: So I hear we're talking about an invasive species today.

ARIDI: We are. But this isn't just any old invasive species. It's really big and incredibly dangerous.

CHARLES: So Burmese pythons in the Everglades?

ARIDI: Nope.

CHARLES: Feral hogs in Texas?

ARIDI: Also nope. They are common hippopotamuses - Pablo Escobar's hippos, in fact.

CHARLES: Pablo Escobar, the notorious drug lord, he had hippos?

ARIDI: Yeah, get ready for a wild ride. So Escobar started a private zoo at his estate in Colombia, about 100 miles east of the city of Medellin. And he smuggled hundreds of animals, like zebras, flamingos, giraffes and a handful of hippos.

CHARLES: Wow.

ARIDI: And after he was killed in 1993, most of the animals were relocated. But the hippos were left there. They're called cocaine hippos, and they were too difficult to move. So authorities just left them, probably thinking they would eventually just die.

CHARLES: So I guess they did not die.

ARIDI: They did not die. And what started as four hippos are now around 100.

CHARLES: Whoa.

ARIDI: Many have busted out of the estate and settled along the Magdalena River and nearby lakes. Conservationists are trying to control their population by sterilizing them, injecting them with contraceptives so they can't reproduce. That's because they're worried about what this booming hippo population may be doing to the environment.

GINA PAOLA SERNA: We have the majority of hippos. These lakes, they don't have fishes. They don't have another (ph) species like manatees or turtles. And second of all, the quality of the water is not so good because these animals are all day long in water, so the quality of the water go really, really bad.

ARIDI: Meet Gina Paola Serna. She's a wildlife veterinarian with Cornare, the region's conservation agency, and she's been working with hippos for about 10 years trying to control their population.

CHARLES: Oh, so she's trying to stop the hippo invasion.

ARIDI: She is, and so are other conservationists. People like Gina say the hippos are harming the native ecosystem. But, actually, there's an interesting debate going on. A few people are actually making the argument that the hippos belong, that they're filling a void left by large ancient herbivores that used to roam South America.

CHARLES: So these hippos, it sounds like, have lumbered into the middle of a big, fat controversy among conservationists.

ARIDI: Yeah. One that asks, are non-native species always bad? Do we always need to control them?

CHARLES: So today on the show, how Pablo Escobar's hippos are faring and the debate about how we handle invasive species. You're listening to SHORT WAVE, the daily science podcast from NPR.

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CHARLES: OK, Rasha, maybe I shouldn't find this invasive species story so hilarious, but I kind of do. There were four hippos, you said.

ARIDI: Yep.

CHARLES: Smart people thought they'd just die off, and instead, the population boomed to around 100 in less than 30 years. How did that happen? How did they grow so fast?

ARIDI: Yeah. Well, Gina told me it's because the hippos are just so happy to be there. Hippos spend most of their days, you know, chilling in fresh water, and these guys have the Magdalena River flowing through Colombia and lots of smaller lakes to live in. So they've got plenty of fresh grass to munch on, nice warm weather to enjoy pretty much year-round. And the predators that kill baby hippos in Africa, you know, like lions and hyenas, aren't present in Colombia.

SERNA: This is like hippo paradise. They're having newborns really, really fast - not normally how they do it in Africa. So every time you're going to see the hippos, you'll see newborns.

ARIDI: I asked Gina what she thinks might happen in 10 years if they didn't control the population.

SERNA: I think it's going to be like 500, something like that.

CHARLES: Five hundred hippos, and there's really nothing to stop them.

ARIDI: Yeah, and it's illegal to kill them. And, you know, that applies to wildlife authorities, too.

CHARLES: It's illegal. Why?

ARIDI: Well, in 2009, authorities killed a hippo that lived in the wild because it was deemed dangerous, a threat to the community, and there was a huge public outcry after the hippo was killed. So because of that, the government ultimately instituted a ban on killing the hippos, even in light of the safety concerns and environmental concerns.

CHARLES: (Laughter) This story gets weirder by the minute.

ARIDI: Yeah.

CHARLES: So what is the current plan now? Do they have a plan?

ARIDI: So they do have a plan. You know, controlling the hippo population has been an ongoing issue for years. And since the hippos can't be killed, conservationists came up with a plan to surgically sterilize them like we do for our pets.

CHARLES: Well, yeah, but with a cat, you just put it in a little cat carrier and drive it over to the vet. I'm trying to visualize what you do with a hippo, and it's not exactly clear to me.

ARIDI: Yeah. Well, imagine trying to sedate a very vicious, incredibly territorial, roughly three or four thousand-pound animal that you cornered into an enclosure and then trying to perform surgery on this giant animal in the middle of a swamp.

SERNA: Every time I do a surgery, when everything's over, I sit and cry. I don't know why - because it's so stressing.

CHARLES: So much work and probably so much money, too.

ARIDI: Yeah, exactly. It costs thousands of dollars per hippo and, you know, a ton of time. So Gina and her team have turned to administering contraceptives through blow darts. Since October, they've injected about 40 hippos with their first round of a drug. After their first dose, they'll give a second about a year later and a third dose in nine years just to make sure the hippos are fully sterile.

CHARLES: Wow. Like, a 10-year process for each animal. So, Rasha, I'm curious, how do the locals feel about these giant animals?

ARIDI: Well, Dan, like in every good conservation story, they're split. A lot of the people love the hippos. I mean, you know, they're objectively pretty cool, and they bring in big bucks from ecotourism. Gina told me that some people even see them as a gift that Escobar left them to bring their communities more money after he was gone.

CHARLES: So there really are pro-hippo people.

ARIDI: Yeah.

CHARLES: But what about the people who actually live and work around the rivers where those animals are kind of taking over?

ARIDI: Yeah, Gina tells me that fishers in particular have an issue because they don't catch as many fish as they used to. And they're worried about hippos flipping their boats. They also can't boat around the river as they like. You know, hippos are dangerous. There have been reports of them attacking people in Colombia, showing up in town or on people's property. In their native Africa, they kill hundreds of people a year.

CHARLES: Wow. So they are really quite deadly.

ARIDI: Mmm hmm.

CHARLES: You know, Rasha, I've covered, you know, other invasive species stories in the past, and there's often the issue of what they're doing to people's livelihoods. You know, like, the spotted lanternfly in Pennsylvania, it's, you know, attacking vineyards. But there's also the scientific consideration of, you know, what is this animal doing to the ecosystem, right?

ARIDI: Yeah, exactly, and this is where things get dicey. Even scientists are divided about the hippos and their impact on the environment.

CHARLES: Like how?

ARIDI: Well, in Africa, hippos are called ecosystem engineers because they shape their environment in such a profound way. A study from a couple of years ago found that hippos are also engineering their environment in Colombia in very similar ways to Africa, like how they eat a lot of grass on land and make a lot of poop in the water.

CHARLES: Oh, so they're sort of moving nutrients around from the land to the water, fertilizing the water.

ARIDI: Yeah. Another study found that hippo-filled lakes tend to have more organic matter in them than non-hippo lakes, and that isn't necessarily a bad thing to an extent. The researchers were concerned that if a population grew to hundreds or even thousands of hippos, their poop could fuel the growth of algal blooms and toxic bacteria in the water, which can cut off oxygen and lead to die-offs. And the concern is that if the hippo population keeps growing and growing unchecked, it may ultimately be too late to do anything about it.

CHARLES: Interesting. So these are the ecological risks. But despite that, you were saying there's this other school of thought among scientists that the hippos should be just left alone.

ARIDI: Yeah. I talked to Arian Wallach about this. She's an ecologist at the University of Technology Sydney. I reached her at her home in Queensland, Australia, where it's summer and the cicadas are buzzing. Arian takes a very different approach to invasive species, which she says should be called introduced instead of invasive.

ARIAN WALLACH: The difference between my ideological background and that of most of my ecologist colleagues is that I regard species that are typically referred to in terms like invasive species as wonderful, as deserving of protection, as an expression of life's resilience, as a story of wonder rather than a story of harm.

ARIDI: She says hippos actually fill an ecological niche that's been vacant for thousands of years. Giant plant-eating mammals like giant llamas lived in South America for millions of years before humans even migrated into the continent and helped contribute to their decline. So she says that if we're going to use pre-human civilization as this ideal standard for nature, what the world should look like, then we have to go back to the Late Pleistocene, which ended around 12,000 years ago.

WALLACH: We can therefore describe what is happening in the world as a rewilding of the world to a state that is more similar to the Pleistocene.

CHARLES: This is really interesting. I mean, when - she was talking about her ideological background, so there is ideology in science, different ways of seeing things. She's saying that hippos are actually a great thing, and they're doing things in the environment that are good and, quote-unquote, "natural."

ARIDI: Yeah, exactly. Arian doesn't believe that any animal is invasive.

WALLACH: What makes the hippos a bad thing in South America is not so much the hippos themselves but the fact that they were moved there by post-industrial humans. And therefore, they become part of the category of not-nature rather than nature.

ARIDI: And she thinks these hippos should be able to stay and roam free.

CHARLES: You know, did you raise this with Gina or other scientists? How do they react to that point of view?

ARIDI: Well, they say that a lot has changed since the Pleistocene and that critters like tapers, which look like a small elephant crossed with a pig, and capybaras are taking care of that role now. And, you know, there's the ongoing concern that keeping the hippos around could lead to worse effects on Colombia's wildlife down the road. And Gina says people who advocate for the hippos aren't always seeing what she sees.

CHARLES: You know, these hippos are kind of an extreme case. You know, they're so big and destructive and so obviously out of place. But there is a version of this argument that happens a lot in ecology where scientists are increasingly pointing out that this idea of a, you know, natural world is often a fallacy, you know, how we humans have been shaping ecosystems for so long, you know, for millennia, especially now, you know, with the climate changing. And there's this really profound question - can you really say what species belongs in a particular place, you know, and which one doesn't?

ARIDI: Yeah. And it's this massive ethical conundrum, too. Like, if the hippos die off, we could be helping the native wildlife. Or if we keep the hippos, we could put native species at risk or we just see what happens and the ecosystem rewires itself a little bit. Either way, we choose what we want the ecosystem to look like. It begs the question, who are we to decide that?

CHARLES: What is next for Colombia's hippos?

ARIDI: Yeah. Well, Gina will continue with the surgeries and injecting contraception, and she'll start working with surrounding municipalities the hippos have trudged into. And she's hoping to relocate some hippos to zoos, maybe even send some back to Africa.

SERNA: I really love hippo because they are so amazing animals. I really don't want to hurt them. I just only want one to do, like, the best for the animals, for our environment and for the people.

CHARLES: Thanks so much for bringing us this story, Rasha.

ARIDI: Yeah, thanks for having me, Dan. And a huge thanks to Gina Paola Serna and Arian Wallach for speaking with me.

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CHARLES: This episode was produced by Berly McCoy, edited by Gisele Grayson and fact-checked by Margaret Cirino and Katherine Sypher. The audio engineer for this episode was Stu Rushfield. I'm Dan Charles. Thanks for listening to SHORT WAVE from NPR.

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