Signs of post-drought recovery on Bon Bon

Graeme Finlayson (Ecologist)
Published 24 Nov 2020 
about  Bon Bon Station Reserve  

Ooldea Dunnart (Sminthopsis ooldea) <br/> Ooldea Dunnart (Sminthopsis ooldea)
Dunnart 'jellybean' joeys.<br/> Dunnart 'jellybean' joeys.
A first for the Bon Bon trapping records – A Pygmy Mulga Monitor (Varanus gilleni).<br/> A first for the Bon Bon trapping records – A Pygmy Mulga Monitor (Varanus gilleni).
Blind snakes (Anilios endoterus) are one of the most unusual critters encountered.<br/> Blind snakes (Anilios endoterus) are one of the most unusual critters encountered.
Volunteer Meredith Geyer releasing a Dunnart.<br/> Volunteer Meredith Geyer releasing a Dunnart.
The colourful Jan's Banded Snake (Simoselaps bertholdi).<br/> The colourful Jan's Banded Snake (Simoselaps bertholdi).
Broad-banded Sand-swimmer (Eremiascincus richardsonii).<br/> Broad-banded Sand-swimmer (Eremiascincus richardsonii).
Volunteers Tony Geyer and Tamara Potter help with animal processing (Photo: Meredith Geyer).<br/> Volunteers Tony Geyer and Tamara Potter help with animal processing (Photo: Meredith Geyer).
Central Netted Dragon (Ctenophorus nuchalis).<br/> Central Netted Dragon (Ctenophorus nuchalis).
An adorable Smooth Knob-tail Gecko (Nephurus levis).<br/> An adorable Smooth Knob-tail Gecko (Nephurus levis).

One of the most anticipated events on the calendar for our South Australian reserves is small vertebrate trapping. These surveys provide the opportunity to eyeball some of the lesser encountered critters that roam through our landscapes.

This year on Bon Bon, after two years of drought right across the region, the reserve has finally experienced some decent rainfall – with the resulting country looking stunning.

The vegetation has responded and the birdlife is prolific, including even a few irregular avian visitors turning up on the rarely filled lake system. Given the conditions, we were all excited about the possibility of peering into a pitfall trap and gazing upon the adorable eyes of a Dunnart, or even something we hadn’t seen in previous surveys.

Trapping is conducted on our reserves to monitor changes in the abundance and species composition of the small vertebrates, including mammals, reptiles and if we’re lucky, frogs!

In arid ecosystems these changes are driven by climatic variables such as rainfall, but can also be influenced by our management, such as the control of introduced species, removal of introduced herbivores and associated recovery of vegetation.

The surveys can also be used to detect rare or threatened species and are a fantastic opportunity to engage with our community and volunteer network who are so critical to the work we conduct on our reserves.

This year we were joined by seven dedicated volunteers, four of whom had come all the way from Kangaroo Island!

One of the goals of trapping at Bon Bon this year was to investigate whether small vertebrates can be used as an indicator of the success of our adaptive predator management, that is, whether more small vertebrates will be trapped in areas where there are very few foxes, compared to areas on the reserve where foxes are still detected.

This year we added smaller pit traps to our existing trapping sites (different sized pit traps catch different critters) and added some new sites. In addition, we only conducted trapping in the Mulga on Sandplain vegetation community. Invertebrates were collected from both the vertebrate pitfall traps and from small vials, specifically installed to sample this taxonomic group at each of the monitoring sites. 

The survey resulted in the capture of more than 300 individuals and 30 species (22 reptiles, 7 mammals and 1 amphibian), with Southern Sandsliders (Lerista labialis), Eyre Basin Beaked Geckoes (Rhynchoedura eyrensis), and Royal Ctenotus (Ctenotus regius), the most encountered species.

Beaded Geckoes (Lucasium damaeum) and Sand-plain Geckoes (Lucasium stenodatylum) were also trapped in greater numbers than the surveys conducted in 2018 and 2019.

Mammal numbers were still relatively low, although seven species were detected. 

Ooldea Dunnarts were trapped 11 times throughout the week. To our delight this included one female who was carrying five tiny joeys.

Hopefully over the next 12 months, if conditions continue to improve, we would anticipate that mammal numbers might increase across the reserve. Preliminary analysis suggests that more individuals and more species were captured in the ‘core area’, where fox detections have remained very low for the past 18 months.

Further analysis will reveal whether the results of this survey can be used to monitor the effectiveness of our local predator abatement program. 

We're grateful to the team of volunteers, with whom we could share these amazing critters and without whom this survey would not have been possible. 

Dunnart 'jellybean' joeys.<br/> Dunnart 'jellybean' joeys.
A first for the Bon Bon trapping records – A Pygmy Mulga Monitor (Varanus gilleni).<br/> A first for the Bon Bon trapping records – A Pygmy Mulga Monitor (Varanus gilleni).
Blind snakes (Anilios endoterus) are one of the most unusual critters encountered.<br/> Blind snakes (Anilios endoterus) are one of the most unusual critters encountered.
Volunteer Meredith Geyer releasing a Dunnart.<br/> Volunteer Meredith Geyer releasing a Dunnart.
The colourful Jan's Banded Snake (Simoselaps bertholdi).<br/> The colourful Jan's Banded Snake (Simoselaps bertholdi).
Broad-banded Sand-swimmer (Eremiascincus richardsonii).<br/> Broad-banded Sand-swimmer (Eremiascincus richardsonii).
Volunteers Tony Geyer and Tamara Potter help with animal processing (Photo: Meredith Geyer).<br/> Volunteers Tony Geyer and Tamara Potter help with animal processing (Photo: Meredith Geyer).
Central Netted Dragon (Ctenophorus nuchalis).<br/> Central Netted Dragon (Ctenophorus nuchalis).
An adorable Smooth Knob-tail Gecko (Nephurus levis).<br/> An adorable Smooth Knob-tail Gecko (Nephurus levis).