Following along with the largest bat migration in the world, where 20 million get together to fly from Mexico to Texas; the extraordinary migration of salmon in North America.
Alaskan salmon migrate upstream to the rivers where they were spawned.
Each year, millions of salmon instinctively fight their way back to their spawning grounds to lay eggs, but they are met by hungry grizzly bears and bald eagles with a plan of their own.
Each year, 40 million bats stream out of the `guano caves' near San Antonio, Texas, running a deadly gauntlet of hawks, falcons, snakes and raccoons.
After nesting in Antarctica all summer, young Adelie penguins must leap into the open oceans while predatory leopard seals lie in wait.
The migration of wildebeest across the Serengeti is thought to be the greatest movement of land animals anywhere on Earth, but at the Mara River, giant crocodiles guard the crossing points.
A million pink flamingos congregate on a steaming soda lake in Africa's Great Rift Valley, prey to baboons and fish eagles.
Billions of tiny sardines are on a collision course with thousands of dolphins.