1.   The ground squirrel is another mammal that has adopted the practice of throwing things - primarily at its main predators, snakes.

2.   A robust thick-billed parrot can easily outfly goshawks and red-tailed hawks, its main predators, and sometimes even a peregrine falcon.

3.   The study also showed that in the areas where main predators were sharply reduced, the numbers of rodents increased, then fell again.

4.   Which explains why they suffer the treacherous journey and hostile conditions to return thousands of kilometres to places they believe to be safe from their main predators, humans.