A critically endangered Sumatran orangutan in New Orleans, in the US has given birth to a healthy male baby, but his twin brother died in the womb, officials at the Audubon Zoo said.

Twelve-year-old Menari gave birth to the first baby without trouble on Christmas Eve and was mothering it appropriately, but she was having problems after that, according to a news release.

A team of on-call medical professionals was brought in, including neonatology specialists who usually treat humans.

Menari was anesthetised and ultrasound showed that the second baby was dead and badly positioned. The team was able to remove it without a caesarean section, the zoo said.

The great apes named for their long red hair are considered critically endangered by the International Union for Conservation of Nature.

Threats include hunting and the destruction of the forests and peat swamps where they spend nearly all their time up in trees.

Fewer than 14,000 live in the wild and their numbers are declining as palm oil plantations spread into their forest habitat, according to the Audubon Nature Institute, which runs the zoo.

When Menari’s pregnancy was announced in October, the zoo said there was about a 1% chance of orangutan twins. Twin births are inherently high risk.

“This is a bittersweet time for our team, but, given the very serious complications with the second infant, we are extremely happy that Menari and the surviving infant are together and doing well,” said Audubon’s senior vet, Bob MacLean.

He said the veterinary team and specialists were very pleased with Menari’s recovery and her natural mothering instincts so far.

The baby was bottle-fed overnight, while Menari recovered, Mr MacLean told The Associated Press.

“Menari immediately took the infant back Christmas morning, when offered to her, and she successfully began nursing,” he said.

Mother and baby are behind the scenes to give them time to bond and to let keepers and vets care for them, the zoo said. It said the baby was nursing very well.

Vets do not know what caused the death of the other baby, which was also full-term, Mr MacLean said.

“The medical team on hand did indicate that the placenta appeared abnormal. We will be sending tissues for histopathology to glean more information, but those results will be many weeks to come,” he said.

Menari was hand-reared and is a first-time mother.

However, she was able to observe her mother, Feliz, and foster-sister Reese giving birth and raising babies – Feliz in 2019 and Reese in February.

Menari and half-sister Bulan often eat, sleep or forage together, the zoo said.

“This recent experience with infants has helped to prepare Menari for motherhood,” the news release said.

The infant is the third for father Jambi, who also sired the babies born in 2019 and this year. He went to New Orleans in 2018 from Hannover Zoo in Germany.

It may be six years or more before his next babies.

Sumatran orangutans are not weaned until they are about seven years old, and females have the longest period between births of any mammals, 8.2 to 9.3 years, according to the International Union for Conservation of Nature.