Three orangutans from Auckland Zoo will head to the United States in a bid to help breed more of their kind.

Bornean orangutans Indra and Horst have been at the zoo for 25 years - during which time 20-year-old Intan was born.

They will leave on July 27, to be relocated to the Busch Gardens Zoo in Tampa Bay, Florida, as part of a captive breeding programme.

Auckland Zoo primate team leader Amy Dixon says the dramatic drop in orangutan numbers in parts of the world is a sad reality.

"What is incredibly sad to comprehend is that in the 25 years that Indra and Horst have lived at Auckland Zoo and had Intan, orangutan numbers in Sumatra have plummeted to around 7000 and in Borneo to less than 50,000."

The significant drop in the species is due to the growth of palm oil plantations taking over the apes' rainforest habitat, Ms Dixon said.

"And if it continues, orang-utans will be extinct in the wild within the next 12 years."

Auckland Zoo will hold a special public farewell for the family trio next weekend, with unique encounters with the orangutans, a farewell album for signing and conservation displays about orangutans.

Paintings made by Horst and Indra will also be up for sale on the day.

Last week a pair of siamang apes - who had been living at the Auckland Zoo for over 20 years - retired from breeding and were taken to Hamilton Zoo.

Iuri and Itam produced six offspring during their time at the Auckland Zoo.

The public is invited to farewell Indra, Horst and Intan on Sunday July 19, at the Auckland Zoo, from 10.30am to 3pm.