When the notorious drug lord Pablo Escobar was shot dead in 1993, the Colombian government took control of his luxurious estate in northwestern Colombia, including his personal zoo. Most of the animals were shipped away, but the four hippopotamuses—of which Escobar was especially fond—were left to fend for themselves in a pond. Now, there are dozens and dozens of them.

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. Indeed, the hippos could fill in for species that