REINTRODUCED populations of the endangered numbat appear to be increasing in wildlife sanctuaries in the lower Murray Darling Basin, five years after a drought triggered a decline in populations.
Ecologists at Australian Wildlife Conservancy are hopeful that increased sightings of the species indicate that the populations are rebounding and returning to pre-drought levels.
The numbat was absent in the Murray-Darling Basin for more than 100 years until 1993, when 15 individuals were released inside an 1100-hectare feral predator-free fenced area at Yookamurra Wildlife Sanctuary in south east Australia.
The numbat reintroduction at Yookamurra was initiated by Earth Sanctuaries, before AWC took over management in 2002 and finished work on the feral predator-free area.
In 1999, another numbat population was established at Scotia Wildlife Sanctuary, on Barkandji country in far western NSW.
It consisted of 43 founders released in a 4000ha feral predator-free fenced area.
The fenced area was expanded to 8000ha and a further 30 numbats were released in 2011-2012.
By December 2020, a third population was established within the largest fenced cat and fox-free area on mainland Australia, in Mallee Cliffs National Park.
In partnership with NSW National Parks and Wildlife Service, 15 numbats were released in 2020, and joined by another 31 individuals in 2021 and 2022.
The fenced areas (known as safe havens) play a vitally important role in providing refuge to populations of reintroduced species, including the numbat, from introduced predators such as feral cats and foxes.
During standardised surveys of the reintroduced numbats, ecologists recorded frequent sightings within the fenced areas until 2018-19, when the Murray Darling region experienced its severest drought conditions in more than 120 years.
Numbat sightings were few and far between with the Yookamurra population dropping from an estimated 52 in 2017 to just 25 in 2018, while Scotia’s population fell from an estimated 629 in 2017 to 133 in 2018 and 83 in 2019.
AWC’s acting regional ecologist for South Australia, Dr Alexandra Ross, said the drop in numbat sightings during the drought was reflective of wider trends in the environment at that time.
“Populations of native animals undergo natural cycles of boom and bust in response to prevailing conditions,” Dr Ross said.
“Australia’s variable climate leads to big fluctuations in numbers of small mammals from one year to the next. This holds true within AWC’s network of fenced safe havens.”
Wetter weather conditions and regrowth of vegetation over the past 12 months appear to have improved the small insectivore’s status at both Yookamurra and Scotia sanctuaries.
Ecologists encountered 14 numbats during an eight-day survey at Yookamurra in January this year, which produced a population estimate of 42 individuals, the highest estimate since before the drought.
Meanwhile, Scotia’s population was estimated at 287 by a survey in November 2023, more than double the 2019 low point.
The AWC said that while it was too soon to calculate a population for numbats in Mallee Cliffs, where they are still becoming established, ecologists have had more incidental sightings in the past five months, with detections on camera traps also increasing, indicating their numbers are growing.
The method of surveying numbats involves driving along transect areas within the predator-proof fence.
The transect areas are inspected twice a day – 30 minutes after sunrise when the temperature reaches at least 11 degrees, and again in the afternoon.
Dr Rachel Ladd, AWC senior wildlife ecologist at Scotia, said that although surveying the diurnal species can be arduous, biodiversity monitoring is a key part of effective conservation at the sanctuaries.
“It’s pretty gratifying to think that across these three populations, there are now hundreds of numbats in this part of the country, where 25 years ago there were none,” Dr Ladd said.
“It’s a thrill to get a glimpse of their little stripy backs as they trot through the mallee searching for termites.”
Species profile: Numbat
The numbat is a small, diurnal Australian mammal recognisable by its distinctive rusty orange and grey-black fur.
Once found across much of arid and semi-arid southern Australia, the species fell victim to habitat loss and introduced predators (cats and foxes), and now only two naturally occurring populations remain, both in south-west WA.
The species has an extremely specialised diet comprised almost exclusively of termites.
As the sun rises and the day heats up, the temperature of the upper layers of soil increases, and termites move into a network of shallow tunnels and chambers just below the ground surface.
Numbats detect the termites with their acute sense of smell, and use their front paws to scrape away the soil and expose them, before licking them up with their long tongue.
