The monkeys, 10 of which were gifted to Launceston in Tasmania by Japanese sister city Ikeda in 1981, will die out in about 25 years as a result of a council decision.
A unique attraction for the northern city, the monkeys' enclosure in a central park has been open to the public for viewing.
The troop has grown from 10 monkeys gifted to Launceston by its Japanese sister city Ikeda. (HANDOUT/LAUNCESTON CITY COUNCIL)
In 2000, it was revealed the herpes B virus had spread through the monkeys but discussions about euthanasing the troop were not well received.
Concerns about a lack of genetic diversity have increased in recent years.
National biosecurity laws prevent the importation of the species, with advice to council recommending their management be given urgent attention.
Veterinary advice said the best way forward was for surgical reproductive control of males, as opposed to culling or neutering some reproductive animals.
The council was also concerned continued breeding would leave the enclosure overcrowded and negatively affect health and wellbeing.
A council meeting on Thursday afternoon, which voted 10-1 in favour of sterilisation, was told there were signs of miscarriages and stillbirths in the troop.
"We know the Launceston community cares very much about the welfare of the City Park monkeys," Launceston Mayor Matthew Garwood said.
The macaque troop is a unique attraction for Launceston and residents care deeply about them. (HANDOUT/LAUNCESTON CITY COUNCIL)
"That's a sentiment that's also very much shared by both councillors and staff.
"The inability to introduce new genetic stock and the serious impacts on their health and wellbeing means we need to begin to consider the future of the troop.
"(The) decision was a difficult one, but it prioritises the welfare of the monkey troop so we can keep them as healthy and happy as possible for as long as possible.
"The ... monkeys will still be with us for decades to come and we'll continue to care for them to the highest possible standards."
Mr Garwood said he would write to the mayor of Ikeda to explain the decision.
Councillor Andrea Dawkins, who supported the motion, said community expectations had changed.
"Perhaps if we were offered this opportunity (to have monkeys) now, we wouldn't say yes," she said.
"Animals in captivity purely for the enjoyment of people is something that we've moved through."
Desexing of male monkeys is expected to take place across two years.
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