London - A British zoo was celebrating after the birth of a rare Rothschild's giraffe, the numbers of which have dwindled to fewer than 1 600 in its native Kenya and Uganda."First-time mum, Tula, delivered the most precious Christmas gift on Boxing Day," said Chester Zoo in a message posted on its Facebook page, along with a picture of the mother and her 180cm calf standing between her legs.Rothschild's giraffes are one of the world's most at-risk species and fewer than 1,600 exist in the wild, according to Sarah Roffe, head of giraffes at the zoo in northwest England."The new arrival is an important boost to numbers," added Roffe. "It really is the best Christmas gift we could have ever have wished for."When it gets a little more used to its long legs, it will be introduced to the rest of the herd but, for now, it's important that mum and calf spend a few days together striking up those early bonds," explained the keeper.The creatures are named after Walter Rothschild, the British zoologist and creator of the Tring Natural History Museum in central England and are identified by their colouring and lack of markings on the lower leg.They are sometimes known as the Baringo giraffe, in reference to their prevalence around Lake Baringo in Kenya, and also the Ugandan giraffe, where their population has dwindled by 90% in the last 45 years, according to the zoo.Roffe warned the species was "often overlooked", and was experiencing "a silent extinction" due to loss of habitat and hunting for their meat.'Silent extinction' Chester Zoo has 20 000 animals and welcomes 1.6 million visitors each year.The zoo's giraffe experts travelled to Uganda earlier in the year to carry out their first ever census on the Rothschild's giraffe, part of efforts to understand why their population is not increasing."Initiatives like this really show the role that modern zoos play in animal conservation and it will give us a better understanding of how we can help protect the species and its future," said Tim Rowlands, the zoo's curator of mammals.Wild giraffe numbers have plummeted by 40% in the last three decades, and the species is now "vulnerable" to extinction, a top conservation body warned earlier this month.The population of the world's tallest land mammal dropped to below 100 000 in 2015, mainly due to shrinking habitats and illegal hunting, the International Union for the Conservation of Nature (IUCN) reported."These majestic land animals are undergoing a silent extinction," Julian Fennessy, co-chair of the IUCN's specialist group on giraffes, said in a statement.Previously, giraffes held the status of "least concern" on the IUCN's Red List, which tracks the conservation status of fauna and flora and ends with the category "extinct".Giraffes are spread out across southern and eastern Africa, with smaller pockets in west and central Africa.