By Katherine Tuft
It is now a year since the crippling drought ended, and the reserve has re-emerged as a very much altered ecosystem. With the latest data on our animals and plants collected, an interesting picture is emerging of new winners and losers.
Prior to the drought of 2017-2019, the fauna of the reserve was dominated by one species in the kangaroo family; the burrowing bettong. A series of good rainfall periods from 2010 onwards supported the bettong population to grow to huge numbers, with estimates of over 8,000 animals. They had no predators, were contained within the fence, and are generalist herbivores able to eat anything from leaves and seeds through to roots and bark. When we did track counts to monitor reintroduced species, bettongs made up more than 90% of the tracks counted, while bandicoots and bilbies were far less common. Similarly, the native rodent community was dominated by two species (hopping mice and plains mice) during most annual trapping surveys, and other smaller rodents like Bolam’s mice became increasingly rare. The flora in the reserve was more dominated by unpalatable shrubs compared to outside the fence, whilst some more palatable plants like ruby saltbush had become very rare.
The drought began in 2017 and things changed rapidly (you can read more about it in our “Desperately dry” blog). Over one year, bettong numbers fell dramatically to the point that we were worried they could become locally extinct. Small mammals dropped to almost undetectable levels. Many ancient chenopod plants died, as did tough desert trees like mulga. It was a hard time for staff and volunteers, and we didn’t know how long the drought would drag on for or whether some of the species might be lost for good.
A good summer storm in early 2020 functionally marked the end of the drought. Throughout the rest of the year we had average annual rainfall. The trees and shrubs that had survived drought started to show signs of recovery. Due to the summer rain, grass became plentiful. Yet the first of the reintroduced animal species to recover were a surprise to us. It was not the seed- or shrub-eaters, but the bilbies and Shark Bay bandicoots. And not only have they recovered fast, both are already at the highest levels we have ever recorded in some parts of the reserve. Both species eat a lot of insects, and we are interested to understand why these species have done so much better.
Based on the latest trapping in March, small mammals and reptiles have also boomed (read about in our latest blog) Hopping mice have come back with a vengeance, their tracks covering every square cm in some parts of the sand dunes. Excitingly, some species that have been undetectable for several years have reappeared. This year we caught a desert mouse for the first time in 10 years, and were also pleased to see sandy inland mice and short-tailed mice again after absences of 10 years.
Droughts are not inherently bad. In fact, they can be an important ‘reset’ for arid ecosystems. That’s certainly been the case for Arid Recovery. Whilst many of the impacts have been severe, there’s been some unexpected winners. With bettongs no longer overabundant, other species are having a chance to shine. The bandicoots are now at the highest activity levels ever recorded in the reserve. With the bilbies recovering so fast, we are now able to supply other reintroduction projects.
Not all ecosystem components can recover so rapidly however. We have serious concerns for chenopod shrubs. If severe droughts become more frequent, the replacement rate of these slow-growing plants may not be able to keep up with the rate of die-off and there will be serious flow-on implications for other species that rely on them.
It can be grim working in arid ecosystems as droughts become increasing severe. But no matter how bad the drought, we must move forward and continue understanding how to protect our wildlife from the ever-increasing threats they face.