When the Colombian National Police killed cocaine kingpin and narcoterrorist Pablo Escobar in 1993, they seized his enormous estate, including his sculpture garden, car collection, small airports, and personal zoo. They shipped most of the zoo animals off to other zoos, but they left dude’s four hippos to fend for themselves.
But then those hippos had a lot of sex, and now there are more than 80 of them roaming around Colombia. They’re now considered one of the world’s top invasive species. And they’re causing problems, roaming into towns and generally being two-ton nuisances. According to a new study in the journal Ecology, they’re also wreaking havoc on the local ecosystem.
Researchers spent two years studying the water quality and microbiomes of Colombian lakes with hippo populations and compared them to hippo-free ones. They found that the animals are changing the water’s chemistry in pretty gross ways.
Hippos are nocturnal. They spend their days eating off the land and their nights cooling off in the water—and, uh, crapping out large amounts of waste. It turns out their poop is changing the water’s chemistry and oxygen levels, and fertilizing harmful algae and bacteria, which can lead to algae blooms that make people and animals sick. For some places like East Africa’s Lake Victoria, ecosystems have evolved with copious amounts of hippo poop. In fact, some species even need the nutrients in it to survive. Though even there, some research suggests that all that poop may be too much of a “good” thing.
In comparison, Colombia’s waterways and the species that live in and around them have never had to contend with copious amounts hippo crap or the other disruptions the huge ungulates can cause. The researchers also note Colombia sees more rainfall than East African lakes and streams with hippos researchers have studied, creating another confounding factor.
Stress is only likely to grow. The animals are expected to keep reproducing, and Colombia has none of the constraints or threat of predators hippos traditionally have to contend with. The researchers expect the hippo population will grow dramatically. Like really dramatically.
“If you plot out their population growth, we show that it tends to go exponentially skyward,” Jonathan Shurin, a UC San Diego Biological Sciences Professor who worked on the study, said in a release. “In the next couple of decades there could be thousands of them.”
That could make the problem much worse, and create new problems. No one knows, for instance, how the hippos will interact with other local animals, like manatees and giant river turtles. The researchers recommend that Colombian officials figure out to do about their hippo problem, fast.
That won’t be easy. Hippos might seem pretty chill, but they’re really fast runners and are notoriously difficult and dangerous to catch. They’re also really violent so actually catching up to them comes with serious risks. Attempts to get rid of Escobar’s hippos haven’t gone too well to-date. Over the past few years, local government authorities sent biologists out to try contain and castrate them, but that saw little success. They only managed to get a handful of hippos under the knife.
The researchers aren’t sure what to do about this either, but they are sure that more hippos aren’t going to make it any easier. And the surrounding ecosystems could suffer.