Don’t you love it when native wildlife use places we least expect, whether it’s Peregrine Falcons breeding on sky scrapers, migratory waders feeding at sewerage treatment ponds, or pythons sleeping under verandas. These species are making the most out of situations beyond their control. Similar good news stories exist in our farming landscapes. Some native animals have clearly benefitted from agriculture (e.g. galahs, corellas and butcherbirds). Many other species, reptiles in particular, don’t mind a certain amount of grazing pressure. Some lizards are actually more common in native pastures than in fragments of bush, and many small native mammals and lizards readily use alternative shelters such as scrap iron and old farm buildings.
For over a decade now, we have been researching wildlife on farms in south-eastern Australia. During this time, we have seen reptiles in places that have undergone big changes in vegetation cover. Open paddocks, tree plantings, rocky outcrops and stands of regrowth; places which now support very few native mammals, still support many reptiles. In saying that, more could be done to safeguard common species against unpredictable changes in land use.
Two strategies often used to improve wildlife on farms include increasing native vegetation cover in the landscape and improving the condition of small fragments of native vegetation. These two strategies benefit animals in different ways. For example, birds will quickly colonise and breed in replanted vegetation (if conditions are right), but it may take decades before possums and gliders use tree plantings. For less mobile species, such as small lizards and snakes, we don’t yet have a clear understanding of how effective these two strategies are for improving their numbers.
We decided to address this knowledge gap by studying reptiles across a range of modified environments, including grazed remnant vegetation, grazing paddocks and restored vegetation (native tree plantings and pine plantations). Over a 12 year period, we counted reptiles in three regions of southern NSW: (1) Riverina bioregion, (2) South West Slopes bioregion and (3) Nanangroe property. We also collected a number of variables we considered to be important for explaining the presence of different species. These included aspect and elevation, local-scale habitat attributes (such as the amount of logs, rocks, native grass and large trees), and the amount of native vegetation in the landscape. Using data from 443 sites, we examined habitat-relationships for three geckos, one legless lizard, nine lizards and one snake. We obtained 1193 individual reptile records from a total of 2435 surveys. That’s still a lot of survey effort just to obtain over 1000 observations!
We asked the question - is the presence of different species on a 1 ha site best explained by topographic variables, local-scale habitat variables or landscape-scale variables such as native vegetation cover? Overall, we found local-scale habitat variables explained the presence of a large number of species (12/19 possible cases to be precise). This was evident in the Riverina bioregion, where Ragged Snake-eyed Skink, Tessellated Gecko and Common Dwarf Skink all preferred sites with complex vegetation structure. The Ragged Snake-eyed Skink was also found in places with a high number of large trees, whereas Tessellated Gecko and Common Dwarf Skink preferred areas with few trees.
In some cases, aspect influenced the presence of some species. In Nanangroe, Large Striped Skink and Copper-tailed Skink occupied sites with a northern aspect, whereas Southern Rainbow Skink preferred sites with a southern aspect. Native vegetation cover in the surrounding landscape was important for explaining the presence of the tree-dwelling Marbled Gecko and Ragged Snake-eyed Skink in the South West Slopes. In the Riverina, the soil-swimming Timid Slider was also more likely to occur in areas with high amounts of native vegetation cover.
These findings suggest that conservation efforts to improve reptile numbers should focus on improving the condition of the ground layer (i.e. local-scale management). This can be achieved by modifying the way native vegetation is managed. Restricting the removal of fallen timber, managing weeds and reducing grazing pressure will improve ground cover habitat. Many reptile species depend on fallen timber and tussock grass for shelter, so actions that increase logs and tussock grass cover are beneficial. These actions will have further benefit if they are carried out across the farm.
Although we suggest that local-scale management will benefit a wide variety of reptiles on farms, increasing the total amount of native vegetation in the landscape will benefit tree-dwelling lizards and other species that live on the ground by providing resources such as fallen timber and leaf litter. Ultimately, both conservation strategies will be important in the long run. So, by making a few adjustments to the way grazing land is managed, we should continue to see reptiles living in some parts of our farming landscapes well into the future.
If you would like to know more about this study, click on the link here.
Article based on publication:
Michael, D.R., Ikin, K., Crane, M., Okada, S. and Lindenmayer, D.B. (2016) Scale-dependent occupancy patterns in reptiles across topographically different landscapes. Ecography 39. doi:10.1111/ecog.02199