Fire regimes drive population trends of a threatened lizard in the central and western deserts of Australia

Context

Animal and plant populations in arid regions fluctuate in size and extent in response to rainfall, fire and predation. Understanding the influence of these drivers on the status and trends of populations is crucial to implementing effective conservation actions.

Aims

In this study, we quantified the long-term drivers and trends in populations of a threatened lizard, the great desert skink (Liopholis kintorei; Tjakura), in the central and western deserts of Australia.

Methods

We collated 23 years (2002–2023) of active Tjakuṟa burrow count data from 31 sites clustered in the following four regions: Yulara, Newhaven Wildlife Sanctuary, Uluṟu–Kata Tjuṯa National Park and Kiwirrkurra Indigenous Protected Area. We fitted a negative binomial regression model in a Bayesian framework to estimate trends in active burrow counts over time and quantified the effect of rainfall, mean annual normalised difference vegetation index (NDVI), time since fire and fire extent on active burrow counts.

Key results

Our results showed contrasting trends in Tjakuṟa active burrow counts across the four regions. At Kiwirrkurra, Newhaven Wildlife Sanctuary and Yulara, active burrow counts increased consistently at rates of 35% (0.298; 95% CI 0.099–0.471), 18% (0.168; 95% CI 0.029, 0.314) and 5% per year (0.045; 95% CI 0.017, 0.073) respectively. In contrast, active burrow counts in Uluṟu–Kata Tjuṯa National Park increased from 2002 to 2012 before steadily decreasing. Across all sites, fire was the most important predictor of active Tjakuṟa burrow counts, with a significant positive effect of time since fire (0.108; 95% CI 0.014–0.204) and a strong negative effect of fire extent in the previous year (−0.111; 95% CI −0.243 to −0.026).

Conclusions

Our results have highlighted the importance of delivering ongoing planned fire management programs that avoid burning vegetation directly at and around Tjakura burrow systems, while providing a patch mosaic across the surrounding landscape.

Implications

We recommend that monitoring of Tjakura burrows be standardised across regions and that site covariates, especially measures of predation pressure, be monitored to further understand drivers of population trends.