The gentle and much-loved bilby is one of Australia's most vulnerable species, but now researchers are seeking new ways to help it thrive — using peanut butter.

Key points: Research found bilbies may adopt seasonal breeding patterns in cooler climates

Research found bilbies may adopt seasonal breeding patterns in cooler climates Populations on South Australia's Eyre Peninsula appeared to stop breeding in autumn

Populations on South Australia's Eyre Peninsula appeared to stop breeding in autumn The results could help researchers release more captive-bred bilbies into the wild at the most effective time

The nationally vulnerable species breeds year-round in captivity and arid zones, but a study of populations at Venus Bay and Thistle Island on South Australia's Eyre Peninsula suggests that may not be the case in the southern parts of the country.

Research has found that bilbies may adopt seasonal breeding patterns in cooler climates.

If this is true, it will help researchers release captive-bred bilbies into the wild at the most effective time.

Data collected from the sites over three years shows the bilbies appeared to stop breeding during autumn.

"Not only were females not breeding in autumn, but the males' testes size relative to their body size actually decreased in late summer just before that cessation in breeding," lead researcher, Karleah Berris, said.

"[That] indicates it's not just driven by the females — it seems like there's something in the environment stopping them breeding during this autumn period."

Bilbies once covered 70 per cent of Australia but disappeared entirely from South Australia in the 1960s.

The bilby populations at both research sites are descended from animals bred in captivity at Monarto Zoo.

Ms Berris says the bilbies' "soft and meek" nature made them easy to handle. ( Supplied: Karleah Berris )

Sixteen were released at Thistle Island in 1997, and 19 at Venus Bay Conservation Park between 2001 and 2003.

Ms Berris, who completed the study as part of a PhD at the University of Adelaide, said her interest in bilbies stemmed from the fact research on the animals in southern Australia was limited.

"We do have some previous research that was done in the arid zone, which is where the last remnant populations occur," she said.

"Because they keep reasonably well in captivity, people study them in captivity also.

"But we just didn't really have any info from down south in South Australia because they became extinct so early on.

"I'd really love to see more introductions of this species around Australia. I thought if we had more information about what they do in different areas of Australia, we could actually plan our reintroductions better."

The research also found larger females were more likely to have twin litters. ( Supplied: Karleah Berris )

'Soft and meek animals' make job easy

The research involved trapping bilbies in cages every three months and counting and measuring the females' pouch young to determine when they had been born.

Working through the nights on the animals' nocturnal schedule posed the biggest challenge for Ms Berris — but the bilbies themselves were a pleasure to work with.

"They're just really soft and sort of meek animals," she said.

"They're not aggressive so I could just turn them over onto their back and check their pouches. They're obviously adorable."

Unlike their desert counterparts, the Eyre Peninsula bilbies were easy to catch.

"They're really hard to catch in arid areas where they're quite sparse," Ms Berris said.

"I'm not sure what it was about the bilbies down south but they really love peanut butter — so that was our bait.

"We had a few individuals that I think were becoming quite addicted to the peanut butter.

"I remember clearly one female at the Venus Bay Conservation Park who would be in one of two traps every night.

Nineteen captive-bred bilbies were released in the Venus Bay Conservation Park between 2001 and 2003. ( Supplied: Karleah Berris )

"I'm not sure why they were so trap-happy but it definitely made my project easier."

Ms Berris was assisted on her field trips by some special volunteers: her now-husband and eventually her young son and daughter, who were born during the study.

"Even though my son would have been about two-and-a-half the last time he saw one of these bilbies in the wild, he still just has bilbies on the brain," she said.

"I think he was indoctrinated so young that they're pretty much his favourite animal."

Research reveals most effective window for reintroduction

Ms Berris' research has implications for other researchers and conservationists deciding when to release captive-bred bilbies into the wild in areas that have a similarly temperate climate.

"If we want to reintroduce them, we're probably doing ourselves a favour by not reintroducing them in autumn," she said.

"It's probably better to introduce them at the start of the breeding season, possibly around winter, so that you get breeding straight away in that population."

Now a nationally vulnerable species, bilbies once covered 70 per cent of Australia. ( Supplied: Karleah Berris )

In addition, she found larger females tended to have more twin litters — a helpful way to boost population numbers.

"So for reintroductions that's important as well," Ms Berris said.

"If you can source some large females, you've probably got a better chance of increasing your population quickly, because they'll breed up and have twins out in the wild."

Low genetic diversity could still be a problem

Natural Resources Eyre Peninsula monitors the population at Venus Bay Conservation Park with infrared cameras that were originally intended to show feral cat activity.

Senior resources management officer, Liz McTaggart, said numbers were healthy despite the ongoing threat from a small number of cats that exist within the park's fenced-off predator exclusion zone.

The Thistle Island population was largely "self-managing", she said, as it did not have to contend with the introduced predators on the mainland.

Low genetic diversity could be one of the biggest future threats to small bilby colonies like the ones on Thistle Island (pictured) and at Venus Bay Conservation Park. ( Supplied: Liz McTaggart )

But she said the greatest threat to the small colonies' futures could be their low genetic diversity.

In 2017, the department started collecting genetic samples from the Venus Bay and Thistle Island bilbies for comparison with other populations around Australia.

"We have found from that work that there is a lower genetic health for both of those [populations]," Ms McTaggart said.

"A reduction in genetic health really can lower their ability to adapt.

"But overall it just really highlighted that we have certainly got a need for introducing genetics in the near future.

"We would certainly consider using those scientific findings for future genetic introduction."