Conservation ecology of Slater’s skink (Liopholis slateri) in central Australia

Author: Claire Elsa Treilibs

Treilibs, Claire Elsa, 2017 Conservation ecology of Slater’s skink (Liopholis slateri) in central Australia, Flinders University, School of Biological Sciences

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The varied habitats of arid Australia have a diverse and specialised fauna that have evolved a range of life history strategies to persist in this arid environment. Desert river floodplain habitats are geomorphologically distinctive from their non-mesic counterparts. For surface-dwelling animals in these floodplain habitats, persistence is a trade-off between the advantages of relatively abundant food resources and the costs of episodic surface disturbances from infrequent, but unpredictable, rainfall. Riverine environments, as a whole, are threatened by invasive C4 grasses and dramatic changes in fire regimes. How terrestrial species persist in these high-risk habitats is not well understood. Slater’s skink, Liopholis slateri, is a desert floodplain specialist, and it is endangered; the species has been recorded, relatively recently, at floodplain sites where it now no longer occurs. Land managers and ranger groups are investing in conserving L. slateri, but both ecological knowledge of, and survey protocols for the species are limited.

In this research, I sought to understand how L. slateri persists in disturbance-prone floodplain habitats. I focused my research on one population at Orange Creek. My aims were to (a) develop survey methods specific to L. slateri, and (b) use these methods to investigate the spatial dynamics, burrow occupancy, and fine-scale habitat use of a local population over four years.

I explored the use of photographic identification for L. slateri and compared the matching abilities of independent observers using a multi-choice key, with an automated computer algorithm, on a set of test photos. While neither independent observers nor computer matching had 100% accuracy, both systems sufficiently replicated my identifications, demonstrating the reliability of the technique for smaller populations. Future studies might consider using a combination of the two methods for individual identification of larger populations.

I investigated temporal activity patterns in L. slateri, with the aim of increasing detectability in observational surveys. Classification and regression tree (CART) models were used on repeated count data of individuals within a population, to correlate weather conditions with skink counts. Two weather variables, air temperature and humidity, influenced activity levels, but there was no consistent set of covariates that reliably explained surface activity. These data suggest that lizards respond to different weather conditions at different times of the day. I also found evidence of previously unreported nocturnal activity during the hottest months of the year.

In tracking the spatial dynamics of a population of over four years, I found evidence of a small and highly mobile, but site stable, population, with spatial clustering of burrows into local ‘neighbourhoods’. I observed both long-term residence of individuals and long-term use of burrows by multiple lizards at the site. Frequent movements within and among neighbourhoods, and regular new burrow construction, suggest a population capable of local dispersal in the event of high intensity disturbance. Dispersing individuals and some neighbourhoods may act as recolonization sources in the event of a flood extirpating the core population.

Using the spatial dynamics dataset, I characterised fine-scale habitat use of L. slateri within the broader floodplain. Eremophila sturtii and Hakea leucoptera were strong indicators of L. slateri occupancy. However, skink occupancy did not appear to be restricted to this vegetation assemblage, suggesting that L. slateri may be moderately flexible in its choice of habitat. Strong correspondence between buffel grass and lizard occupied areas, suggests that this invasive grass may be a considerable threat to L. slateri habitat.

The findings of this research have greatly increased our knowledge of the ecology of L. slateri, and our ability to effectively manage this endangered species. 

Keywords: conservation, non-invasive, lizard, photo-identification, desert

Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Biological Sciences
Supervisor: Mike Gardner