The deserts of Arid Recovery are teeming with an incredible diversity of small mammal and reptile species.
The Australian deserts have an incredibly rich diversity of small mammals and reptiles. As many as seven species of small mammals and 42 reptiles species have been caught in our region. By building the predator-proof fence and removing cats, foxes and rabbits, we have altered these communities dramatically.
Some species have benefited enormously, including some threatened species. Other species have not.
When the first cat-proof fence at Arid Recovery went up, there was originally almost no difference in the abundance of small mammals inside and outside the reserve. Three years later, the rodent populations within the reserve exploded. This is particularly the case for the Spinifex Hopping Mouse (Notomys alexis) and Bolam’s Mouse (Pseudomys bolami) which are now over 15 times higher inside the reserve compared to outside the reserve where foxes, cats and rabbits are still present.
Spinifex Hopping Mice (Notomys alexis) are now 15 times more abundant within the reserve compared to outside. Photo by Ryan Francis.
The abundance of little carnivourous mammals, like the Fat-tailed Dunnart (Sminthopsis crassicaudata) and the Stripe-faced Dunnart (Sminthopsis macroura), have not increased since feral animals were removed. This could be due to competition for invertebrate prey from Greater Bilbies and Western Barred Bandicoots, as the highest capture rates of these Dasyurids were recorded where both reintroduced natives and ferals are absent.
Populations of little carnivorous marsupials like the Fat-tailed Dunnart are more common outside the reserve. Photo by Ryan Francis.
In 2006, the nationally threatened Plains Mouse (Pseudomys australis) was first caught inside the reserve. Since then, numbers of Plains Mice inside the reserve have increased and it is frequently seen during spotlighting surveys.
The dramatic increase in rodents inside the reserve is due to freedom from predation, and more food due to the absence of rabbits. There was little difference between the abundance of native rodents inside the reserve and the control (where reintroduced species were absent). This suggests that competition between native rodents and reintroduced species is minimal.
Numbers of the introduced house mouse (Mus domesticus) have not increased inside the reserve. This suggests that within the reserve native rodents may be out-competing the non-native house mice.
Abundance of small mammals at monitoring sites. Graph adapted from Moseby et al. 2009.
Reptiles like this (Lucasium stenodactylum) Photo by Ryan Francis.
In complete contrast to the mammals, reptile abundance and diversity has actually decreased in the reserve. This was particularly the case for small gecko species such as the Beaked Gecko (Rhynchoedura ornata) and the Crowned Gecko (Diplodactylus stenodactylus), and for some smaller skinks such as the Southern Sand Slider (Lerista labialis).
Small lizards like this Sand Slider (Lerista labialis) have declined inside the predator-proof fence. Photo by Ryan Francis.
The drop in reptile numbers is thought to be influenced by an increase in Sand Goannas (Varanus gouldii). They have increased significantly inside the reserve following the removal of feral cats and foxes. Sand goannas are important predators of small reptiles and may suppress numbers of small reptiles within the reserve (see here).
Arid Recovery continues to monitor small vertebrates every year. More complexities are emerging as the reserve matures. Keep an eye on this page and our blog to watch it unfold. If you can make it to Roxby Downs, come and volunteer for our annual trapping.
Every year we monitor our small mammal and reptiles over a week of intensive trapping with the help of volunteers.
Written by Rachael Loneragan (March 2017)