Chester Zoo celebrates birth of world's rarest chimpanzee- PublishedA critically endangered Western chimpanzee, which conservationists say is the "world's rarest chimpanzee", has been born at a zoo.Chester Zoo said the birth was a "small but vital boost" to the global population of the species which was "under huge threat" in the wild.The chimpanzee's arrival was a "small but vital boost to the global population of Western chimpanzees, at a time when it's most needed for this critically endangered species", he added.The zoo said just 18,000 Western chimpanzees remain across Africa and it is the first subspecies of chimpanzee to ever be declared critically endangered by the International Union for the Conservation of Nature (IUCN).Mike Jordan, animal and plant director at the zoo, said: "In the last 25 years alone the world has lost 80% of its Western chimpanzee population, so the arrival of a healthy baby here at Chester offers us real hope that we can help turn things around for this species.""