The two-year-old, in a video shared on the Twitter page of their parents the Duke and Duchess of Cambridge, asks Sir David: "What animal do you like?"
Sir David explains why monkeys are his favourite animal, but because they can't be kept at home, the conservationist says his favourite pets are puppies.
He says: “I think I like monkeys the best because they’re such fun. They can jump all over the place and they don’t bite at least… some do, but if you’re a bit careful they don’t bite.
“And they’re so funny and I like them a lot. Mind you, you can’t have monkeys sitting around at home because that’s not where they live, they live out in the rain forest.
“So what can you have at home that you like? Well, which would you choose? A puppy or a kitten. It’s a very difficult question but I think I would go for a puppy.”
The video is opened by Prince George, who asks: “Hello David Attenborough, what animal do you think will be extinct next?”
He gets an optimistic response, with Sir David telling him he hopes people around the world work to ensure there are no more extinct animals.
Princess Charlotte, the next to ask a question, reveals she likes spiders and asks Sir David if he does too.
The 94-year-old replies: “I love spiders I’m so glad you like them! I think they’re wonderful things. "Why is it that people are so frightened of them?”
The three curious young royals, who are "massive fans" of Sir David, will have been excited to meet him after missing out when their parents got together with him for the filming of a new documentary.
It was revealed in the trailer for ITV documentary 'Prince William: A Planet For Us All' that the siblings were "upset" when William and Kate met with Sir David to film the programme and they did not.
In the trailer, the duchess tells Sir David: "The children were very upset that we were coming to see you and they weren't coming. They're massive fans of yours."