Sir David Attenborough has revealed that the most distressing moment of his career was watching chimpanzees attack and kill monkeys.

On a live Q&A on Reddit, the naturalist and broadcaster was asked about the worst memory of his long career as a television naturalist.

He said: "Seeing chimpanzees kill monkeys - they do this to eat them. They chase them, set an ambush, catch them, and tear them apart."

In a wide-ranging series of questions, Atrenborough said that his favourite amphibian was the poison tree frog, "because it has very interesting mating behaviour".

"There are a whole group of them, perhaps 30 species."

The most human thing he has seen animals do is act deceitfully, in particular, hungry chimpanzees, he said.

"When [a] colobus monkey finds a very precious piece of food, it [makes] the alarm call it would make if a snake were to arrive. All the other monkeys run away and it gets the food."

His scariest moment came while he was working with birds and was "chased by a cassowary".

Chimpanzees display a common human trait: deceit Wikimedia Commons

Attenborough, who is globally renowned and synonymous with BBC nature documentaries, offered a wise word to his fans on the site. When asked what change he would like concerning nature and the environment, he replied: "People should realise that waste of anything is something that we cannot afford in this overcrowded world.

"Cherish the natural world because you're a part of it and you depend on it."

Attenborough also commented on the issue of mass extinction and confirmed that the planet has entered a new era. It was "not possible to reverse the damage we've done", he said.

"We are undoubtedly exterminating species at a speed which has never been known before."

He added that the book reponsible for changing the scientific world - after Darwin's Origin of Species - was Rachel Carson's Silent Spring.

He even answered a few personal questions, much to the delight of his fans. If invited for afternoon tea - we can wish - he is partial to a chocolate biscuit, he said.

As for his free time, Sir David Attenborough likes to "spend a lot of it sleeping".