When Good Intentions Meet Cold-Blooded Reality: Rethinking Habitat Management for Melbourne’s Threatened Reptiles and Frogs
By Steve Llewellyn – Based on a presentation by David De Angelis, Senior Consultant Zoologist/Ecologist, ABZECO
AABR Field Day- S Llewellyn
On a sunny September morning in 2025, around 30 bush regenerators gathered to hear ecologist David DeAngelis challenge some of our most fundamental assumptions about habitat restoration. His presentation on threatened reptiles and frogs in Greater Melbourne delivered an uncomfortable truth: sometimes, our best restoration efforts may be inadvertently destroying the very species we’re trying to save.
Cold-Blooded Indifference
The situation for Victoria’s reptiles and frogs is dire. Despite 30 years of formal evaluation and listing under conservation legislation, threatened herpetofauna continue their steady decline. In his 2015 paper “Cold-blooded indifference,” Nick Clemann documented this worsening trend, identifying a threat that’s rarely discussed but may be more pervasive than currently recognised: poor advice and planning.
According to the Action Plan for Australian Lizards and Snakes 2017, habitat loss remains the primary threat to these species, followed closely by livestock grazing, fire, and introduced predators. But it’s the intersection of these threats with misguided management that David’s presentation brought into sharp focus.
The Weed Paradox
Perhaps the most challenging message for bush regenerators was this: threatened reptiles and frogs are often persisting in heavily degraded, weed-dominated habitats. And they’re doing so precisely because those habitats provide the structural features they need.
AABR field day- photo S Llewellyn
David presented striking examples:
- Growling Grass Frogs using an Agapanthus (an exotic pest plant) for shelter in New Zealand (fyi GGF also non-native in NZ)
- Swamp Skinks thriving in the weed Sweet Vernal Grass (Anthoxanthum odoratum) but absent from nearby native sedge-dominated areas. (however this is not always the case – in other areas this result was reversed)
- Glossy Grass Skinks colonising vacant blocks dominated by Kikuyu, complete with discarded rubble and poor drainage.
- Striped Legless Lizards persisting in grasslands invaded by Serrated Tussock and Chilean Needle Grass
Research shows that when introduced Grader Grass was artificially clumped to mimic native tussock structure, Rainbow Skinks used it just as readily as indigenous grasses. The lesson? Habitat structure often matters more than plant species identity.
The Overshading Problem
Well-meaning revegetation projects, particularly around wetlands and waterways, frequently prioritise trees and shrubs. These are excellent for birds and mammals, but potentially catastrophic for reptiles and frogs. David showed images of dense riparian plantings that, while ecologically ’correct’, create deep shade that eliminates habitat for sun-loving, ground-dwelling species.
Growling Grass Frog habitat,Merri Creek- David de Angleis
The Growling Grass Frog provides a perfect case study. Research by Geoffrey Heard and colleagues demonstrated that these frogs prefer microhabitats with bare soil and bare rock in riparian zones and wetlands, with less preference for dense ground vegetation.
They need:
- At least one-third to half of water surfaces clear of vegetation for sunlight penetration
- High cover of submergent (underwater) aquatic plants
- Sparse overhanging vegetation
- Open banks for thermoregulation
Warmer, more saline water also reduces the risk of chytrid fungus infection. Chytrid is the deadly amphibian disease that threatens frog populations worldwide. By creating heavily shaded, densely vegetated ’ideal‘ wetlands, we may be inadvertently creating disease incubators.
The Southern Toadlet’s Secret
The Southern Toadlet (Pseudophryne semimarmorata) offers another sobering lesson. Bradley Jenner’s 2012 research revealed that this species breeds across an extraordinarily diverse range of Ecological Vegetation Classes – from Creekline Herb-rich Woodland to Swamp Scrub to Heathy Woodland. The common thread? Note the plant species composition, extent of overhanging canopy cover with open ground, and availability of adult shelter (ground shelter). These aspects of the landscape interplay with each other, but can be variable from site to site, with trend to overhanging woody canopy cover.
Rainfall data spanning over a century shows why habitat permanence matters more than perfection. Breeding occurs from April to May, with tadpoles taking approx. 6 months to metamorphose. In drought years, even suitable habitats can become death traps, although being a long-lived species (~10years in the wild,) short duration droughts aren’t catastrophic to population but longer duration poses a significant threat. An isolated population at Mullum Mullum Park (Melbourne) experienced complete tadpole desiccation in 2009’s dry spring, but successful emergence in 2010’s wetter conditions.
Grassland Specialists in a Changing Landscape
The presentation highlighted the precarious situation of grassland specialists like the Tussock Skink and Striped Legless Lizard. These species face a double threat: habitat loss from development and habitat degradation from inappropriate management.
Modified Grassland-Tussock Skink Habitat-Keilor
In one case, River Red Gums and Fragrant Saltbush were planted to ’restore‘ a grassy slope, only for later surveys to discover Striped Legless Lizards present. The local council was forced to remove the trees and a number of saltbush to prevent shading out the critically important grassland habitat. Michael Scroggie’s research found that strategic use of fire and grazing can benefit Striped Legless Lizard populations, but intense and concurrent application of both disturbances may trigger population collapse.
For frogs and reptiles in riparian or wetland areas that like dense, low-lying groundcover (e.g. Growling Grass Frog, Glossy Grass Skink and Swamp Skink), planting their preferred dense cover of short tussock and/or spreading grasses would help with reducing the risk or erosion as well. Dense tree and/or shrub cover seems to be more the issue for those critters (disease/chytrid fungus risk for GGF and thermal/basking issue for the mostly terrestrial skinks).
Examples of indigenous plants providing suitable habitat for the Glossy Grass Skink and Swamp Skink along inland waterways and wetlands in Victoria:
- Mat Grass (Hemarthria uncinata var. uncinata)
- Australian Sweet-grass (Glyceria australis)
- Swamp wallaby-grasses (Amphibromus spp.)
- Spiny-headed Mat-rush (Lomandra longifolia)
- Large Tussock-grass (Poa labillardierei)
Examples of indigenous plants providing suitable habitat for the Striped Legless Lizard and Tussock Skink in the grasslands of southern Victoria:
- Kangaroo Grass (Themeda triandra)
- Spear-grasses (Austrostipa spp.)
- Wallby-grasses (Rytidosperma spp.)
What This Means for Bush Regenerators
Bush regen example- Field day- S Llewellyn
David’s presentation challenges us to think beyond simple native/exotic dichotomies.
Key takeaways include:
- Survey before you act: Engage herpetofauna experts to assess sites before implementing major vegetation changes. That weedy paddock might be a refuge population’s last stand.
- Prioritise structure over species (initially): When threatened species are present in weedy habitat, replace that habitat gradually with structurally similar indigenous plants rather than removing weeds en masse.
- Maintain open areas: Not every square metre needs dense vegetation. Sun-loving reptiles need basking sites, open ground, and sparse overstorey.
- Use appropriate grasses: Plant low, tussock-forming indigenous grasses like Kangaroo Grass, Poa species, Mat-grass, and spear-grasses that provide the structural complexity reptiles need.
- Think about microhabitat features: Rocks, logs (preferably hardwood), and termite mounds are critical. As an example, in the southern parts of Australia, the Lace Monitor is understood to use active mounds of Nasutitermes exitiosus termites for egg-laying – yet this species is often targeted by pest controllers.
- Avoid overshading wetlands: When revegetating riparian zones in areas with threatened frogs, maintain sparse tree/shrub cover and prioritise aquatic vegetation diversity.
The Path Forward
David’s presentation wasn’t a counsel of despair, but a call for more sophisticated, evidence-based management. The pilot project by First Friends of Dandenong Creek, working with Maroondah City Council, shows what’s possible: they scalped a small low-lying area and planted it with indigenous grasses and moisture-loving groundcovers specifically for the Glossy Grass Skink. This targeted, species-specific approach represents the future of threatened species management.
The uncomfortable reality is that some of our threatened reptiles and frogs are now ecological refugees, clinging to survival in degraded habitats because those are the only places left with the right structure. Before we “improve” these sites with conventional restoration techniques, we need to ask: improve for whom?
As bush regenerators, we pride ourselves on restoring ecosystems. But perhaps it’s time to acknowledge that for some threatened species, survival trumps purity. The challenge ahead is to transition these populations from weedy refuges to indigenous habitat without losing them in the process – a task requiring patience, expertise, and a willingness to question our assumptions.
Growling Grass Frog, Merri Creek – David De Angelis
References
Why do lizards avoid weeds? – Jessica Hacking, Richard Abom, Lin Schwarzkopf
Heard, G. et al._2014_Wetland characteristics influence disease risk for a threatened amphibian
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