Sometimes threatened species turn up on your doorstep. Kath Tuft describes how Plains Mice reintroduced themselves to Arid Recovery.
As anyone who has ever assisted a species reintroduction program will know, it’s a heckload of effort. Detailed translocation proposals and ethics applications need to be prepared. Animals have to be captured and transported from source populations, often on remote islands. Animals must be fitted with radiocollars and then intensely monitored for many months following reintroduction. All of this can take years, thousands of staff and volunteer hours, and big bucks (Moseby et al. 2011).
Nicki Munro and John Read release one of the first bilbies into Arid Recovery.
We had an incredible instance where a threatened species turned up of its own accord without anyone lifting a finger. This was the Plains Mouse, Pseudomys australis, a beautiful little native mouse from arid Australia.
Plains Mice were once widespread across large parts of inland Australia. Now their distribution is greatly shrunken and their occurrence almost entirely confined to a specific cracking clay habitat with characteristic depressions known as gilgais (Brandle et al. 1999). Plains Mice persist in parts of far northern South Australia, but had never been recorded near Roxby Downs and the Arid Recovery Reserve until 2006.
A young Plains Mouse. Photo: Helen Crisp
That was the year I first came to Arid Recovery as a volunteer on the annual vertebrate trapping survey. To everyone’s surprise, a unique rodent with a Roman nose and short tail turned up at a trapping site within the Northern Expansion. It turned out to be one of the first Plains Mice recorded in the area for many decades.
When the main trapping survey had ended I was tasked with finding out more about these new arrivals. Were there more? What habitats were they occurring in? What burrows were they using? I had a great time trapping about the place and surveying for burrows. To find their burrows we lightly glued tiny glow sticks to fur on their backs and followed them as they bounced off with their little beacon. At that time, the Plains Mice were confined to a fairly small area of the cracking clay and gilgai habitat they are known for.
Me trapping Plains Mice 11 years ago. Photo: Hugh McGregor
Coming back to Arid Recovery 10 years later the situation is entirely different. There are Plains Mice absolutely everywhere. You can’t drive anywhere without seeing them scampering across the track. Where once they were confined to the classic cracking clay areas, they now occupy all habitats within the reserve: dunes, stony swales and canegrass swamps. The first Plains Mice to colonise the reserve very quickly found they were onto a good thing with no feral cats and foxes to prey on them. With that predation pressure relieved, they happily occupied the whole place in abundance.
Map of Plains Mice records in 2006 (left) and in 2016 (right). From one corner of the reserve, they have spread across the entire place in all habitats.
How did they find Arid Recovery in the first place? Plains Mice were known from areas several hundred kilometres further north near Lake Eyre, but not as far south as Roxby Downs. The likely answer is that Plains Mice were given a lucky break by the release of calicivirus, Australia’s first rabbit biocontrol. Calici swept through the rabbit population in the late 1990’s. The huge drop in rabbit numbers seemed to lead to a substantial reduction in the numbers of feral cats and foxes. Plains Mice, and other small native mammals, expanded in range as a result (Pedler et al. 2016).
What’s particularly neat about the Plains Mice at Arid Recovery, is that they might now be re-seeding the surrounding landscape. Trapping over the last few years has found them in good numbers outside the Reserve.
Abundance of Plains Mice at trapping sites inside and outside the reserve over time.
The resourceful Plains Mouse did all the hard work of reintroducing itself into the haven that is Arid Recovery. Hopefully in time we will see them disperse and re-establish well beyond the Reserve itself. These little rodents have shown that predator-proof fenced reserves can have value well beyond their core purpose of protecting reintroduced critical weight range species.
We eagerly await the next endangered species to show up on our doorstep and find sanctuary.