Pablo Escobar’s Hippos, Friend or Foe for Colombia’s Ecosystem?

Image: Shurin Lab / UC San Diego

While many of us have probably read about Pablo Escobar’s hippos that escaped his zoo, it’s been unclear to biologists what sort of impact the hippos have had on Colombian ecosystems. There are currently 80-100 animals in the Magdalena River and researchers estimate that in 20-40 years there could be thousands.

As NatGeo explained, for over a decade the Colombian government has been pondering how to best curb the growing population, a strategy largely supported by conservation experts. But not everyone is on board. Without direct evidence that the animals are doing harm, some ecologists argue that there’s no reason to cull or relocate them. 

However now, UC San Diego biologist Jonathan Shurin who has been working with the Universidad Pedagógica y Tecnológica de Colombia has been measuring the hippos’ impact on their new realm and has some new insights to report. Mainly, that it’s complicated!

What’s Happening: Shurin found that most locals aren’t too concerned about the hippos–they leave them be and tourism to see them hasn’t picked up in any significant way. However, hippos eat A LOT. They spend most of the nigh grazing on grass and spend most of the day eliminating their “organic material.” As the LA Times explained, this “organic material,” fuels algae blooms, alters oxygen levels and may lead to fish die-offs. If the hippo pods continue to grow at their current pace, there’s also the danger that they’ll deplete local grasslands.
Around Hacienda Nápoles, Shurin and his colleagues took water samples from 14 small lakes, two with hippo populations and 12 without.

“The effects of hippos on the aquatic environment that we observe,” the researchers wrote in the journal Ecology, “suggest that sustained population growth poses a threat to water quality in lakes and rivers as they expand their range throughout Magdalena Medio watershed and potentially colonize new regions on the Caribbean slope of Colombia.”

Additionally, David Echeverri, a researcher with the Colombian government’s environmental agency Cornare, which is overseeing management of the animals, explained to NatGeo that he has no doubt they act like an invasive species. If allowed to remain unchecked, they will displace endemic animals like otters and manatees, he says. They also pose a danger to local residents since they can be territorial and aggressive, though no serious injuries or deaths have occurred as yet.

What’s The Plan: As the LA Times noted, at present, though, there is no strategy to keep this population in check. Colombian officials told Shurin there was no money to fund a sterilization campaign, and the locals are opposed to culling the herd.

Why This Matters: Smaller invasive species are generally viewed as disruptive (or even disastrous) to local ecosystems, but we’re still learning about the impacts that larger invasive species have on their new homes. In the case of Australia’s camels, their herds have been slated for culling by the government, but it’s hard to assess this decision as the Australian government has overestimated kangaroo populations to justify cruel “roo culls.” Humans have altered the distribution of nature so profoundly that it’s difficult to know what’s what. The best we can do is use data and science to help manage nature in a good-faith way.

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