What is the deadliest animal on earth? This countdown contains a reptilian monster with deadly dribble, an octopus with spit that's 10,000 times more deadly than cyanide, and a killer snail that injects its prey with a cocktail of toxins.

From Texan caves containing 20 million bats and a 300 foot pile of bat guano, to Christmas Island where each year there's a stampede of 120 million red crabs. Never mess with the mob when swarms are taken to the extreme!

You can pump iron as much as you like, but you'll never build a body like the unique physiques of the natural world. How would you like to be able to clean your ears with your tongue? Or have eyes the size of a beach ball?

Get ready to discover that bathroom etiquette means nothing in the animal kingdom. See Hippopotami spray their droppings and spotted hyena turn their anal pouches inside out. Come join us as stench warfare is taken to The Most Extreme.

Some animals possess surprising powers of perception! Starring in this countdown are pocket-sized primates with eyes bigger than their brain, elephants that can hear with their feet, and pigs with over 20,000 taste buds!