This week saw some sad news about the death of the sole survivor of a species.

I'm not naive; I know that species of animals and plants disappear virtually every day. But Lonesome George the giant tortoise was different: because he was the rarest known animal in the world, and because I met him when I was in the Galapagos two years ago.

George was 150 when he died. He had been living at the the Charles Darwin Research Station on the island of Santa Cruz, which is where I saw him. He seemed like a bit of a loner, ambling off in the distance, seeming content just to potter around his enclosure. The research station had been trying to get him to mate with females from similar species but he just wasn't interested. The closest the species came to continuation was when eggs were laid in 2008 and 2009 after mating with a similar species, but none hatched.

His species was Geochelone nigra abingdoni, or the Pinta island tortoise, discovered in 1877.

George was found dead by the man who'd looked after him for 40 years. The cause of death is being investigated, but is believed to be heart failure consistent with the natural end of a giant tortoise's life.

See more of the amazing wildlife in the Galapagos