Hybrids can be bizarre and they can be deadly. We look at two hybrid animals that owe their existence to human interference – the pizzly bear (a cross between a polar bear and grizzly), which has come into being because of global warming, and the killer bee brought into existence because of the transfer of African bees to South America.

Can animals count? This is a question that has intrigued and fooled investigators for a long time. Just over a hundred years ago, a German horse called Hans was declared a mathematical genius but all was not as it seemed. And strangely, some bamboos around the world flower exactly at the same no matter where they are – are they counting down the years?

The Siamese Fighting Fish is so aggressive it will fight its own reflection until it is exhausted. Recent research shows that the fighting behaviour varies and depends on the personality of the fish! Male kangaroos were once pitted against humans in the boxing ring – the most impressive male kangaroos are solid blocks of muscle with a kick that can kill. Why do they fight and what skills must a winner have?

David discovers the curiosities that have led to accusations of forgery but have ultimately helped us rethink evolution. When early explorers brought the first specimen of a duck-billed platypus back to England in 1799, it was thought so bizarre it was deemed a hoax, while the midwife toad became the centre of a raging scientific storm in the 1920s that led to accusations of fakery.

Some animals appear to have taken Nature’s gifts and stretched them to extreme limits. With these two natural curiosities one creature, the giraffe, has ended up with a super-stretched neck, the other, the chameleon, a super stretchy tongue. In both cases nature has found a way to turn the ordinary into the extraordinary.

David encounters two examples where Nature has tinkered with the aging process to alarmingly different effect – the first grows old while trapped in a young body while the second looks old from birth but might hold the key to a long life.

The single spiral tusk of the narwhal inspiration for tales of unicorns and the myriad variations on the twist of the snail shell have delighted and fascinated naturalists and artists since the dawn of civilization.

Zebra stripes vary subtly between the different species but there is one group of animals that has evolved colourful patterns of seemingly infinite variety, the butterflies. In this episode David looks at two examples of animal patterns that have bedazzled and baffled science for a long time, and uses modern tools to unlock their secrets.

Sir David Attenborough continues to shine the spotlight on nature's most amazing animals this time looking at the vision in squid and owls. Perhaps not a classic pairing, both owls and squid have incredible adaptations for being able to navigate at night.

Here we discover that some animals are able to trick others into believing they are something that they are not. The art of deception is a powerful attribute for some.

We'll find out how nature is incredibly inventive and has produced two unique mechanisms of natural construction that have fascinated scientists for centuries; weaving in birds and silk.

"Strange Parents" asks how we usually recognise animals as either male or female and how each sex normally plays a particular role in their own life cycle. However both hyenas and seahorses completely break the gender rules.

"Magical Appearances" explores how swallows magically appear each spring and asks how did complex and beautiful insects like butterflies suddenly arrive in the summer. The discovery of the swallow’s epic migration and the revelation that butterflies could metamorphose into totally different looking adults were scientific stories both cloaked in mystery and controversy.

The blue whale and the flamingo both have bodies determined by their diet. Blue whales grow enormous by feeding on tiny shrimp-like creatures, while flamingos spend their lives eating with their heads upside down. Both are oddities in their own groups and yet both are curiously similar.

David Attenborough investigates two shells that have proved to be winners in evolution: the bird’s shell and the hard shell of the tortoise. The ostrich egg is so strong it’s possible for a person to stand on it without it breaking – how does the chick break out of this fortress? The evolution of the tortoise shell was for a long time a mystery and this bony box offers a lot more than just protection.

Sir David Attenborough uses this episode to investigate two animals who are capable of true virgin birth - the production of offspring without the need for sex.

This episode explores the story of two animals that hide behind seemingly impregnable coat of arms. Can Sir David Attenborough get in behind their armour and reveal their mysteries?

After initially gaining frightening reputations, it's now known that gorillas and bats are a lot gentler and considerate than their early reputations suggest.

Plants and animals have some curious super senses that enable them to see, hear and feel things that are quite invisible to us.

In this episode we explore the remarkable adaptations of two creatures that have evolved to survive the most challenging of conditions and seem to defy the laws of nature.

Fleas are supposed to be able to jump the equivalent of a human leaping over St. Paul’s Cathedral and cheetahs purportedly can clock speeds of 70 miles per hour. But are these claims really true? The discovery of the world's most elastic natural protein in insects and the development of a hi-tech tracking collar have helped reveal the truth. So can these creatures really achieve what should be physically impossible?

Orangutans can use tools but such skills remained undiscovered for centuries. They were considered as just clever mimics until discovery in remote Sumatran swamps revealed their true potential. Clever crows also make surprisingly sophisticated tools. How have the curious minds of these two animals helped them become so inventive?

The bodies of some animals stretch and shrink in extraordinary ways. The anaconda can swallow prey twice its own body size - and then wait for over a year until their next meal. The camel’s curious hump can almost double in weight giving it the energy to travel huge distances across deserts. What is the secret behind these expandable bodies?

Humans are not alone in using medicines against injuries and infection. Some animals protect themselves with natural remedies in the most extraordinary ways. Hippos produce a blood-red “sweat” that acts as a sunblock and helps fight infections, while capuchin monkeys rub themselves with insect-repellent leaves to protect against insect bites.

Salamanders can regenerate entire legs and tails to replace ones they have lost, while deer shed their massive antlers and re-grow them from a few remaining cells each year. How do these creatures regenerate entire body parts and why is it not possible for all animals to do the same?