Bilby populations inside Australian Wildlife Conservancy’s (AWC) feral predator-free safe havens have experienced a year of growth, according to the results of the conservation organisation’s annual Bilby census.
Recent AWC surveys confirmed that populations of Bilbies, Australia’s home-grown alternative to the Easter Bunny, are experiencing a boom within five protected sites – Mt Gibson (WA), Scotia (NSW) and Yookamurra (SA) Wildlife Sanctuaries as well as two NSW government partnership project areas in the Pilliga and Mallee Cliffs National Park.
From 2021 to 2022, Bilby populations increased across AWC sanctuaries from an estimated 1,230 individuals to 1,480. AWC protects at least 10% of Australia’s remaining Bilby population which is estimated at around 10,000 individuals.
The increase in Bilby populations within AWC sanctuaries can be attributed to the increased rainfall in parts of the country during Australia’s second year of La Niña, which replenished the landscape and provided good conditions for breeding. It is also evidence of the effectiveness of AWC’s safe havens in protecting some of Australia’s most vulnerable species.
Bilbies made a historic return to a 9,570-hectare feral predator-free area within Mallee Cliffs National Park in southwestern NSW in October 2019. Prior to the translocation, the iconic species had been absent from the area for over a century.
Thriving in their former range, the population doubled within the first six months to reach an estimated 108 individuals by July 2020. Over the next two years, the population would undergo a ‘boom and bust cycle’ to thrive when environmental conditions are good and bust during drought and food scarcity.
As of March 2022, the population is estimated to be at 116 individuals. During a recent health survey using 100 cage traps over four nights, the Mallee Cliffs team recorded 57 individuals on site made up of 23 females and 34 males. Of the females captured, 48% showed signs of recent breeding activity.
Mallee Cliffs National Park population estimates:
October 2019 – 50 individuals reintroduced to Mallee Cliffs
July 2020 – 108 individuals
November 2020 – 63 individuals, a decline likely caused by reduced seasonal activity and trap success
March 2021 – 118 individuals
November 2021 – 58 individuals
March 2022 – 116 individuals
Mt Gibson in the WA Wheatbelt joined the fight to conserve the iconic Australian mammal in 2016. Between 2016-2018, 56 individuals were released inside the 7,800 hectares feral-predator free area.
This nocturnal species is currently monitored via remote camera traps. The annual survey provides information on the species’ occupancy within the sanctuary’s safe haven. The results have shown that there has been substantial increase in Bilby occupancy since the translocations.
Mt Gibson ecologists are now trialling spotlighting to obtain a population estimate. The results are currently being analysed, but they saw more than 50 Bilbies every night during a recent spotlighting survey which is encouraging evidence that this survey will be able to provide an estimate. Staff also observed a large number of sub-adult Bilbies during the survey, which is evidence that the population is successfully breeding.
Bilbies returned to the Pilliga State Conservation Area in northern NSW in late 2018, where they had been absent from the landscape for more than 100 years. Sixty individuals were released into the conservation area’s 680-hectare feral predator-free breeding area.
The population remained steady for the first two years but more than doubled to an estimated 155 individuals by the end of 2021.
Thanks to higher-than-average rainfall over the last year (685mm of rain in 2021 vs the average annual 616m), conditions in the Pilliga are good for the Bilbies. All captures during the December 2021 survey were healthy and all adult females were carrying pouch young – giving a positive outlook on the future of the species in the Pilliga.
“This was the most successful trapping session thus far,” said Vicki Stokes, AWC Wildlife Ecologist for the Pilliga. “Our next survey will be in June 2022 and we’re expecting the population to continue to grow because conditions in the Pilliga are so good with all the recent rain. It is such a delight to see all the Bilby diggings and burrows as you walk through the forest, something that has been missing from the landscape for a long time.”
Pilliga State Conservation Area population estimates:
November 2018 – 60 individuals reintroduced to the Pilliga
October 2019 – 30 individuals
May 2020 – 54 individuals
December 2020 – 60 individuals
May 2021 – 50 individuals
December 2021 – 155 individuals
Scotia Wildlife Sanctuary in western NSW is home to the largest population of Bilbies within Australian Wildlife Conservancy’s feral predator-free sanctuaries. The population within the 8,000 hectares safe haven regularly sits above 1,000 individuals during boom periods when conditions are optimal.
The species was reintroduced to Scotia in June 2010, with 334 individuals. It didn’t take long for the population to start breeding and their numbers grew to 1,217 individuals within the first five years.
Following a health survey in March 2022, the population was estimated at 1,126 individuals. This was a slight overall growth from the estimate in September 2021 of 1,037 individuals and a substantial increase from the sanctuary’s drought periods in May 2019 and 2020 when population size was estimated at 148 and 275 individuals, respectively.
Scotia Wildlife Sanctuary population estimates:
June 2010 – 334 individuals reintroduced to Scotia
March 2015 – 1,217 individuals
March 2018 – 1,031 individuals
May 2019 – 148 individuals
May 2020 – 275 individuals
September 2021 – 1,037 individuals
March 2022 – 1,126 individuals
Bilby numbers remain steady at Yookamurra Wildlife Sanctuary over the last 12 months, with a population estimate of 80 individuals for March 2022 compared to 83 individuals in April 2021. This consistent result was largely driven by welcome rainfall in late spring which increased food resources for the species and created good breeding conditions.
AWC ecologists were pleased with the consistent estimate, saying it’s a sign that the population remains stable and slowly recovering after record-breaking low rainfall in 2018–19 contributed to a decline in individuals to 49 (March 2020) and 19 (September 2020).
Bilbies were first reintroduced to Yookamurra in 1996 by Earth Sanctuary Ltd. as part of a breeding program. AWC acquired the property in 2002 and upgraded the predator-proof fence to establish a 1,100 hectares feral predator-free area. Bilbies were released into this wider area in 2007 and again in 2011 when the captive breeding program was discontinued.
Spotlight surveys were introduced at Yookamurra in 2015 to monitor the population which can fluctuate greatly between seasons.
Yookamurra Wildlife Sanctuary population estimates:
2002 – AWC acquired Yookamurra where Bilbies were part of a breeding program
2007 – Bilbies released from breeding program into a 1,100 hectares feral free area
2015 – Spotlight surveys introduced to the sanctuary
March 2015 – 81 individuals
September 2015 – 54
March 2017 – 133 individuals
September 2017 – 61 individuals
March 2018 – 91 individuals
September 2018 – 8 individuals
March 2019 – 125 individuals
September 2019 – 34 individuals
March 2020 – 49 individuals
September 2020 – 19 individuals
March 2021 – 83 individuals
March 2022 – 80 individuals
Bilbies are heading back to the bush in 2022, with AWC planning a reintroduction of the species inside a 9,450-hectare safe haven at Newhaven Wildlife Sanctuary. The reintroduction is part of an ambitious plan to restore up to 10 locally extinct species to Central Australia.
More information will be available soon about the Bilby’s return to this part of the Northern Territory.
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