New Discovery About Crocodiles

My son asked for a current event about animals tonight, so here goes:

Article: We've long known that other animals besides humans use tools. The discovery was first made about chimpanzees, then about birds and even some fish. But scientists have recently discovered that crocodiles and alligators also use tools. Here's how it works: in swamps, twigs are pretty scarce. During nest building season, birds fight over the few twigs to build their nest. They build the nests high up in trees to keep their chicks safe from snakes and other predators. Recently, it was discovered that crocodiles swim under twigs and become motionless. When a bird goes to get a twig, the crocodiles snatches them and eats them up. They use the twigs as props/tools to catch their prey. And they appear not to do this practice once nest building season is over.

Discussion:

• How do you think this practice first developed? Did one alligator discover it and the rest copied? 
• Speak about natural selection and how it works -- survival of the fittest