Tracing ancient paths, wildebeests become a moving feast. But the biggest threat is the gauntlet, the saltwater crocodile filled Mara River crossing.

When you've got it all, why give it up? We expect animals to choose the easiest option for food and comfort, but that's not always predictable.

Once a year land bound Christmas Island red crabs are called back to the sea to birth their young, encountering obstacles in the forest along the way.