In the 6.5 years since we last visited Pablo Escobar's hippo herd, it's become illegal to kill any member of the Colombian population, which is considered something of a country emblem. It's no surprise, then, that the non-native animals are breeding out of control in a population expected to reach the ecosystem's carrying capacity in the next two decades, according to a new study. The problem started when Escobar imported one male and three female hippos for a private zoo at his Hacienda Nápoles ranch in the 1980s. After his death in 1993, officials relocated most of the creatures to zoos, but let the aggressive 4,000-pound hippos be, per NBC News. Unencumbered by the droughts, disease, and predators of their native Africa, the animals have been expanding in reach—finding their way into the Magdalena River and surrounding lakes—and in number ever since.
A 2020 study found hippo feces were contributing to toxic algae blooms, per Smithsonian. Experts also worry that threatened Antillean manatees are being forced from their habitats, per the Washington Post. But this is nothing compared to what could come. With their numbers growing about 10% each year, the hippo population is expected to hit 1,418 by 2039, at which point the hippos will have utilized all the food and space available, per the study published in Biological Conservation. To prevent that outcome, study author Nataly Castelblanco-Martínez says officials need to start culling 30 hippos per year. "No other strategy is going to work," she tells the Post. Some see castration as an alternative. But castration is challenging, not least because male hippos have retractable testes. Indeed, one campaign to castrate hippos found it could only successfully do so to one hippo per year. (Read more Colombia stories.)