Human activity in the urban environment impacts habitat choice and survival of Tiliqua rugosa rugosa within the Perth Metropolitan Area

Rebecca L Millsteed

Increasing urbanisation is resulting in habitat fragmentation and degradation bringing humans and wildlife closer together. This introduces threats to wildlife from altered resource availability in urban habitats and direct consequences resulting from encounters with humans and their activities. One species seemingly adapted to urban living within the Perth metropolitan area, Tiliqua rugosa rugosa, is an endemic lizard species, commonly known as the bobtail. Bobtails are habitat generalists who use human-made elements in the modified urban environment to meet their survival needs. Unfortunately, this exposes them to threats from human activity resulting in the need for rehabilitation. This study examines the human impact on this species by identifying what they are most at risk from in urban habitats and how successfully they are rehabilitated after suffering harm. Using 5 years of admission data from Kanyana Wildlife Rehabilitation Centre, the reasons for bobtail admissions were analysed to assess what put bobtails most at risk of harm. Rescue location data was then used to conduct habitat surveys to identify where and in what types of habitats bobtails were most at risk in the Perth metropolitan area. The success of rehabilitation was assessed by conducting GPS tracking of 13 bobtails released from Kanyana after rehabilitation as well as 10 wild caught bobtails from selected rescue locations to compare the behaviours of the two groups. This comparison included comparing the home range sizes, movement behaviour and conducting health assessments to determine if wild bobtails in rescue locations were healthy, and if the rehabilitated bobtails returned to normal pre-injury behaviour post release. Penetrating trauma, mostly from dog attacks was found to pose the most threat to bobtails accounting for 30-40% of all admissions, followed by 16-24% for blunt trauma caused by motor vehicle collisions and injury from garden equipment. Bobtails are most at risk from trauma on private property with 68% of bobtails rescued there. Less than 50% of all trauma admissions had successful outcomes from the injuries sustained, although those that survive are successfully rehabilitated and shown to return to normal behaviour post-release when compared to those in the wild. Mean home range sizes of 4.49ha were recorded which did not differ for admission reason or release type. The home ranges of rehabilitated bobtails were comparable to wild bobtails regardless of whether they were returned to the rescue location or relocated. Wild bobtail populations in the Perth metropolitan area were assessed as generally healthy as were rehabilitated bobtails for the duration of their post-release study with the only readmissions for injuries unrelated to their rehabilitation need. Rehabilitation was assessed as successful with rehabilitated bobtails showing normal movement and behaviour post-release indicating they had not been adversely impacted by their time in care. The modification of a personal GPS tracker was also included in this study to test for its suitability as a cheaper alternative for use in tracking bobtails.

Human activity in the urban environment impacts habitat choice and survival of Tiliqua rugosa rugosa within the Perth Metropolitan Area

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