Sir David Attenborough has said the death of the last male northern white rhino is "another catastrophe and another warning signal".
The 91-year-old television naturalist was speaking following the death of the 45-year-old rhino in Kenya earlier this week.
Sir David said: "It's another extinction which is our doing."
He made the comments at the opening of a new dinosaur exhibition at the Yorkshire Museum in York.
Hope for preserving the northern white rhino now lies in developing in vitro fertilisation (IVF) techniques.
Sir David added that the problems facing those protecting other endangered animals were "huge, simply because the world is so crowded there's not the space for things".
The new exhibition called Yorkshire's Jurassic World features virtual reality recreations of the time of the dinosaurs as well as collections of fossils and other displays.
The veteran broadcaster said he grew up loving fossils and still found them exciting.
"Going up to a rock and hitting it with a hammer and it falls open and you see the most beautiful, perfect shell that nobody's seen for for 150 million years, if that isn't romantic I don't know what is," he said.
"Certainly, as a boy I was absolutely fixated with fossils. I collected them and I suppose I learned the rudiments of biology out of viewing fossils."