A RARE Asian elephant calf has "astonished" experts after being born at Chester Zoo.

The newborn arrived overnight last Thursday to 35-year-old mum Thi Hi Way after an assumed gestation of 25 months.

Keepers and scientists at the zoo believed that Thi had started a natural resorption process after hormone tracking showed that the mum of six previous calves was due to give birth three months prior, and she was slowly returning to her normal weight.

Chester and District Standard:

Despite the unusual circumstances, Thi gave birth to a healthy baby boy and keepers at the zoo say both mum and calf, who is yet to be named, are doing very well.

Mike Jordan, Chester Zoo's collections director, said: "Thi is a wonderful matriarch to our family herd and a really experienced mum. She has successfully given birth to seven calves before, but this time around circumstances were really quite astonishing.

"We believed Thi had exceeded her normal gestation period, which we were monitoring closely.

"Her hormone levels, behaviour and drop in weight gave us every indication that she may have been resorbing the calf – a natural process that some elephants experience.

"However, nature always has that incredible ability to surprise you and that was certainly the case when we came in yesterday morning.

"The new youngster was up on his feet, suckling from mum and bonding closely with the rest of the family herd, including one-year-old calves, Indali and Aayu. It's truly magnificent to witness."

Chester and District Standard:

Chester Zoo is part of a breeding programme co-ordinated by the European Association of Zoos and Aquariums (EAZA) that is focused on sustaining the elephant population in Europe. The new calf is another huge boost to these efforts.

Asian elephants are listed as endangered on the International Union for the Conservation of Nature's (IUCN's) Red List, threatened by habitat loss, poaching, disease and direct conflict with humans.

Tim Rowlands, curator of mammals at the zoo, added: "It's absolutely magical to see Thi bring another new arrival into the world.

"These momentous events always bring the entire elephant family together and we expect to see the other young calves in the group showing a lot of interest in the little one over the coming days, weeks and months.

"Crucially, this is important news for Asian elephants more widely. The species is endangered in the wild. If we don't act now then the unthinkable could happen.

"By combining our breeding programme successes with field projects in the wild, we are really making a difference for these magnificent animals."

Zoo conservationists have been operating in India for more than 12 years, preventing extinction in the wild by utilising the skills and knowledge developed working with the herd in Chester.

A major Chester Zoo project in Assam, northern India, has successfully eliminated conflict between local communities and the nearby Asian elephant population, offering a blueprint for the future conservation of the species.

Meanwhile, scientists at the zoo are leading the global fight to find a cure for a deadly disease which is threatening Asian elephants globally, in zoos and the wild.

There is currently no cure for elephant endotheliotropic herpesvirus, also known as EEHV, but Chester Zoo researchers are leading the fight to produce a vaccine, thanks in part to more than £150,000 in donations from the public as part of a major Never Forget fundraising campaign.

Chester Zoo's elephant house is open to visitors as normal.