Along the Magdalena River in Colombia, something enormous has been happening in plain sight. A population of animals has been spreading through wetlands and tributaries for decades, growing faster ...

Colombia is taking aim at its invasive hippopotamus population. This week, the government announced plans to euthanize dozens of the hulking animals, which are causing ecological and safety issues in ...

Hippos might seem harmless from a distance, but their poop plays a surprisingly dangerous role in river ecosystems. Here's how this natural waste can choke out fish, alter water quality, and even ...