Although we always tend to label the big cats as the most dangerous creatures of the forest, when it comes to the actual figures, we get quite a shock! In Africa, the hippopotamus is considered to be the most dangerous mammal. Although herbivorous by nature, the hippos are known to kill more humans than any other African land species. The animals are known for their highly territorial and aggressive behavior. The sheer size of these animals (world's third-largest land mammal with males weighing around 3,300 lbs), the sharp teeth, and agility on land as well as water, makes them the most fearsome animals to be encountered. Male hippos fiercely defend their territories while females aggressively guard their babies. These animals can also run at speed of over 20 miles an hour.