Oldest platypus found in the wild is ‘beyond all our expectations’, say researchers | Australia news

The biologist who first tagged a one-year-old platypus back in 2000 was astonished when it was recaptured last year, aged about 24, making it the oldest platypus found in the wild.

The director of the Australian Platypus Conservancy, Geoff Williams, has been researching the egg-laying mammals for decades, but said long-term research into the species can be expensive and rare.

The discovery of the 24-year-old male is thanks to a program which commenced in 1994 with Melbourne Water. Hundreds of platypus have been captured and tagged in the Melbourne area, so for them to reappear a few year’s later was not out of the ordinary.

“But this one is just beyond all our expectations in terms of how old it was,” Williams said. “It’s remarkable that this animal is still doing as well as he is after all these years.”

The 24-year-old male is the focus of a study published this week, co-authored by Williams, into platypus longevity. The male platypus was first captured and tagged in November 2000 at Monbulk Creek in Melbourne, and estimated to be one-year-old. He was recaptured along the same river system last September, at about 24 years of age.

The previous record holder was a 21-year-old female platypus captured in the upper Shoalhaven river in New South Wales.

Williams said that “not many” platypus are known to make it past 20 in the wild, but there is difficulty in developing a consensus on how long they live.

“It’s quite expensive and time-consuming to conduct [research] and consequently there have not been that many long-term studies,” Williams said. “Fortunately the [program with Melbourne Water] is probably the longest-running program of its type.

“The chances of picking up these [long] living animals is almost solely, at the moment, related to that program.”

While more research is needed, Williams said that population density and competition within a habitat played a large role in how long platypus survive.

During mating season, the males can become stressed if there is too much competition for the females. Williams said they can become “displaced, and pushed to the edge of the system” during any fighting.

“The more dense the population is, the more animals in the population, the [bigger] the struggle to be the dominant male and survive for a few years is,” he said.

Female platypus are also known to fight one another for food.

As the study notes, male platypus in the upper Shoalhaven River generally aren’t found beyond the age of seven due to the dense population and females making up 84% of the adult population.

In comparison there is a small, isolated and low-density population at Monbulk Creek, where the new record holder lives.

The co-author of the study, Gemma Snowball from Ecology Australia, was the one to recapture the 24-year-old platypus last year. She said there are six capturing sites at Monbulk Creek, across roughly 4km.

“The channel is also fairly narrow, so about one to four metres wide across the stretch of the channel, which [could make it] potentially easier to defend females,” she said.

At this stage the new record holder hasn’t been given a name, but Snowball joked “we probably should name this old boy because we’re quite familiar with him now”.

The oldest living platypus in Australia is a 30-year-old female who was born in the wild but lives in captivity. She feeds normally and is healthy, aside from arthritis in one wrist, cataracts in both eyes and signs she may be becoming deaf.

Her longer lifespan can be attributed to leading a “much, much less stressful life,” Williams said.

Platypus are listed as a near-threatened species on a national level. They are endangered in South Australia and vulnerable in Victoria.

Snowball said one of the most important things to do to protect platypus habitats was keeping waterways clean, and cutting circular rubbish – such as bracelets or hairbands – before disposing of it.