Abstract
With the growth in urban developments, there is increasing interest in behavioural plasticity and how it changes under different levels of urbanisation. Researchers are especially interested in how different species would behaviourally respond to new environments, using species responses as a key conservation discussion point in developing and establishing urban areas. Previously, it had been stated that species belonging to the Reptilian class have tolerated human interaction and are adjusting their behaviours. However, it remains unclear precisely how lizards would behaviourally respond to urban areas, limiting our guidance on conservation policies, especially in developing cities. There is also a taxonomic bias for the class Reptilia, especially on smaller squamates, when investigating behavioural changes under urban contexts. As such, I wanted to expand upon this knowledge gap and have selected the New Zealand Tussock skink (Oligosoma chionochloescens) in my study to analyse behavioural plasticity under varying levels of urbanisation. Tussock skinks were known to tolerate humans as they occupy urban settlements, but it is unclear if their behaviours differ from those in areas with less urban development. This study aimed to build upon behavioural plasticity in urban-living lizards and microhabitat preferences in urban areas. Thus, I asked whether Tussock skinks in urban environments exhibit greater risk aversion and lower emergence rates than those in non-urban environments. For the microhabitat question: Would urbanisation influence the composition and structure of microhabitat use by Tussock skinks in habitats with limited natural substrates? I aim todetermine the microhabitat differences between two distinct sites with differing availablemicrohabitat compositions.
The study involved 31 behavioural recordings, comprising 14 sessions at the Dunedin Botanical Gardens and 17 at Orokonui Ecosanctuary, resulting in 293 recorded emergence instances. Instances is when a skink emerges under varying amounts of cover for a set duration. I also recorded the associated microhabitat for each recording day when skinks were present. Behavioural observations were conducted between August and December 2024. Although overall emergence counts were comparable between sites, the use of cover differed significantly, indicating that urban skinks were more risk-averse and spent more time under refuge.
I also investigated behavioural responses to a novel object and human disturbances. Neither factor had a significant effect, as skinks displayed consistent behaviour regardless of the presence of a novel object or varying levels of disturbance. These results suggest that Tussock skinks may already tolerate human interaction and novel stimuli. Microhabitat analyses revealed that skinks preferred certain substrate types depending on availability. For example, Botanical Gardens skinks frequently utilised gravel and vegetation, while Orokonui skinks favoured boulders and anthropogenic substrates. Overall, these findings demonstrate that Tussock skinks adjust their behaviour and substrate use depending on the surrounding microhabitat structure, with urban skinks showing signs of increased risk aversion likely linked to the altered habitat composition of urban environments.
This thesis lays the groundwork for understanding the behaviour of lizards living in urban areas and adds knowledge to previous discoveries around behavioural plasticity under different urbanisation levels.