First-time mum Isobella gave birth to the healthy youngster on Saturday, watched on by keepers in a complication-free delivery.

"It's always exciting to have baby spider monkeys at the zoo, but an endangered primate is extra special," primate manager Harna Burton said.

Keepers are still none the wiser on the baby's gender.

"We're not sure yet if it's a boy or a girl," she said as the media caught its first glimpses of the tiny creature.

"Mum's holding it very closely, so we can't quite see. Once we do, we'll pick out a name."

Staff hailed the swift and natural birth a "hard-won achievement". It comes after the French-born Isobella, who arrived via Dubbo Zoo three years ago, experienced problems throughout her pregnancy.

She is already warming to parenthood, Ms Burton said, along with 20-year-old dad Oren who has turned protector.

"We do see mum holding (the baby) here and there and grooming (it) - doing all the right things," she said.

Isobella will provide round-the-clock care to the baby for the next 10 weeks and is unlikely to leave its side for at least a year.

It's the Victorian zoo's first spider monkey birth since now seven-year-old Estela swung into the hearts of visitors in January 2011.

Wild spider monkeys are found in the tropical rainforests of Central and South America, with females only giving birth once every two to five years.

The long-limbed and tailed species are 'threatened', according to an international conservation list, due to deforestation and indigenous peoples often hunting them for food.

"It's really exciting to have a baby that's contributing to a breeding program," Ms Burton said.

Australian Associated Press