20. Hippopotamus

The portly hippopotamus may look cuddly, but leave your first impressions at the door. Hippos are believed to be the most dangerous land mammal in Africa, and are known to have a short fuse and a tendency to capsize boats. The animal’s combination of sheer power, unpredictability, and aggression leads to an estimated 500 deaths a year, though some experts believe the number could be as high as 3000.