Platypuses are back at Australia’s oldest national park after disappearing from it roughly 50 years ago. On Friday, wildlife officials released four females inside Royal National Park, located south of Sydney in the state of New South Wales, with plans to introduce two additional females and four males in the near future, according to a statement from the University of New South Wales.
The duck-billed, egg-laying mammals haven’t been recorded within the park’s bounds since the 1970s. Experts suspect a nearby chemical spill during that decade wiped out platypuses within the park, however, the elusive creatures may have already been struggling, reports the Isobel Roe for the Australian Broadcasting Corporation.
But after years of careful planning, wildlife experts hope the creatures will re-establish a foothold in the park’s waterways, including the Hacking River, where they were released. Conservationists have been preparing the local ecosystem for the platypuses’ return by reducing the number of predators in the area, such as cats and foxes. They’ve also been studying the park’s water quality and food availability, per the ABC.
Established in 1879, Royal National Park is the oldest national park in Australia and the second oldest in the world, reports Reuters’ James Redmayne. It should provide the founding group of ten platypuses with plenty to eat—researchers found a healthy population of caddis fly larvae, shrimp, dragonfly nymphs and other macroinvertebrates.
Biologists collected the platypuses from various populations in southeastern New South Wales to help ensure genetic diversity. Before their re-release into the wild, the mammals spent time at the Taronga Zoo in Sydney, which opened a new platypus rescue and rehabilitation center to care for them. Then, the platypuses were outfitted with transmitters that will track their movements as they adjust to their new home.
Conservationists translocated the females first to give them a chance to get acclimated before the more rambunctious males arrive, which will happen a week to ten days later. Then, ideally, the park’s newest residents will mate, multiply and thrive.
“We’re just looking to see if these platypus survive,” says Rob Brewster, the rewilding program manager for WWF-Australia, to the ABC. “If they do, then obviously breeding, the establishing of burrows and a next generation is a midterm success indicator. And beyond that, we want to see these platypus spreading out.”
Once found throughout Tasmania and eastern Australia, platypuses have been facing a “silent extinction” because of a variety of threats, including predators, pollution, bushfires, deforestation and drought, according to WWF-Australia. Their populations have declined by as much as 31 to 65 percent in some areas, and the International Union for Conservation of Nature lists them as “near threatened.”
The platypus translocation is a collaborative project involving the University of New South Wales, the Taronga Conservation Society Australia, WWF-Australia and the New South Wales National Parks and Wildlife Service.
In the long run, researchers hope that platypuses can become the “new sentinels” of the country’s rivers, says Richard Kingsford, an ecologist and the director of the Center for Ecosystem Science at the University of New South Wales, in the university statement.
“If your platypuses are doing well, the river is probably in pretty good shape,” he adds.