1. Koalas
Mary Anne Forster, an Australian woman, was trying to protect her dogs in December 2014 when a koala bit her leg, refusing to let it go. He had to spread his jaws with his hands.
2. Beavers
In 2013, a fisherman in Belarus was killed by a beaver that bit his femoral artery .
3. Dolphins
In the 1990s, a group of male dolphins was responsible for killing other dolphins, including their own babies.
4. Prairie dogs
Prairie dogs compete with ground squirrels for resources. They routinely hunt down and assassinate their adversaries.
5. Swans
Hannibal the swan killed 15 other swans on the grounds of Pembroke Castle in Wales. It bit them, struck them with its wings, broke their toes and drowned them.
