Rare twin baby siamangs born at Auckland Zoo

Australasia's first twin siamang gibbons have been born at Auckland Zoo.

This tiny twosome (a male, and most likely a female – yet to be positively identified) are doing great, thanks to very attentive and nurturing parents.

To date, just two per cent of recorded captive-bred births of siamangs world wide have resulted in twins. Normally this species of lesser ape (native to rainforests of the Malay Peninsular and Sumatra) produces just one offspring at a time – and that is usually only once every two to three years.

The twins, born in late March to 23 year old mum Iuri and 18 year old dad Itam, arrived less than two years after their last offspring - 22 month old Irian, who is proving to be extremely inquisitive about his new siblings.

Adult siamangs mate for life. Iuri (from Adelaide Zoo) and Itam (from Berlin Zoo) have been together at Auckland Zoo since early 1988, and have to date produced seven offspring. (Their eldest son Ipoh, now 10 years old, was sent to a zoo in Mexico in 2001 and has just become a father).

While wanting the pair to breed again, the Zoo was not expecting a result quite so soon.

"We actually did two pregnancy tests on Iuri and both came back negative, though such a false result is not uncommon for a lesser ape such as a siamang," says primate keeper Jodie Gosden.

"After a physical examination we were fairly sure she was pregnant, but were absolutely amazed when she produced twins," says Jodie.

Siamang gibbon, the largest of the nine species of gibbon, are known for their parenting skills, and both Iuri and Itam are well and truly living up to that reputation.

The yet unnamed twins (who weighed just 150 grams when born) cling tightly to their mum where it's safe and warm and they can suckle and get all the sustenance they need. They will stay like this for their first two months of life before even being able to crawl on mum.

“Their crys and screams are uncannily human-like, just like a newborn baby,” says Jodie.

Dad's job is grooming mum, and sometimes the babies, staying close when he senses any trouble, and for a lot of the time keeping his irrepressible 22 month old son Irian occupied.

The twins will be fully mobile at four to six months old, climbing in their enclosure in the McDonald’s Rainforest, though their legs will still be a little weak. Like the adults, they will also be able to rotate their shoulder joints 360 degrees – a movement that enables siamang gibbon to swing so adeptly through the trees.

While they will be weaned by around six months, it will be a year before they have fully developed the muscles in their throat to vocalise the distinctive siamang gibbon boom and bark, which distinguishes this species as the loudest of all the primates. Both sexes have a naked vocal sac beneath the chin which inflates to produce distinct notes. This twice daily vocalisation helps them form and maintain a pair bond as well as advertising and defending territory.

Siamang gibbon reach sexual maturity at about eight years of age. Auckland Zoo is likely to retain the twins until they are around four years of age.

Siamang gibbon are classified as ‘near threatened’ (approaching vulnerable). They are still taken for the pet trade and their natural habitat is being destroyed for the timber industry and for cattle. Other species of the gibbon family, such as the silvery gibbon, are highly endangered.

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