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Specimens of Dolichoperoides macalpini (Nicoll, 1914) (Digenea: Dolichoperoididae) were collected from Australian venomous snakes (Elapidae): Notechis scutatus Peters, 1861 and Austrelaps superbus (Günther, 1858) from Tasmania and surrounding islands and N. s. occidentalis Glauert, 1948 from wetlands near Perth, Western Australia. Despite variation in morphological measurements, genetic analysis showed that the one species of digeneans infected the snakes from all locations. This study presents the first DNA sequences for D. macalpini (internal transcribed spacer, 18S, 28S), confirming its placement in a family separate from the Reniferidae and Telorchiidae. Analysis of the infection dynamics of infection in Western Australian snakes showed significant differences in levels of infection between wetland locations, season and year of collection. Infection of D. macalpini was reported in the gastrointestinal tract, including the mouth, in freshly euthanised snakes in Western Australia, and in the lung in Tasmanian snakes, consistent with earlier reports. Differences in morphology and site of infection are suggested to be due to a combination of season and maturity of the digenean, with infection potentially occurring early in the season, as the snakes emerge from torpor. The need for research on the seasonal dynamics of infection with this parasite is discussed.

Wetlands are particularly vulnerable to degradation in urban environments, partially due to the introduction of non-native plants. Invasive weeds in wetlands can replace native plants leading to alterations in habitat composition and vegetation, in turn, animal movements and ultimately population dynamics might be affected. Here we investigate how home range size and movements of western tiger snakes (Notechis scutatus occidentalis) differ in wetlands dominated by invasive kikuyu grass (Cenchrus clandestinus) compared to wetlands dominated by native vegetation to understand if and how the movement ecology of this top-order predator is altered by vegetation homogenization. To do so, we used Autocorrelated Kernel Density Estimators (AKDE) to estimate home range size, dynamic Brownian Bridge Movement Models to document movement trajectory confidence areas, and compared movement distances using a Bayesian regression model. Home range sizes by tiger snakes were 14.59 ± 9.35 ha smaller in areas dominated by invasive versus native vegetation. Moreover, within-day movement distances tended to be smaller in areas dominated by invasive versus native vegetation (mean ± SD: 9 ± 3 m versus 18 ± 6 m), but there was considerable overlap between the 95% credible intervals between these two groups. Smaller home ranges by tiger snakes in areas dominated by invasive kikuyu grass were likely driven by thermoregulation, with snakes moving vertically between basking locations on top of kikuyu and shelter sites at the base, rather than travelling horizontally along the ground to open basking areas in sites dominated by native vegetation. Additionally, fragmentation of sites dominated by invasive vegetation might have contributed to the comparatively smaller home ranges of snakes there. These findings add to our understanding how changes in habitat composition driven by invasive vegetation can affect animal space use and emphasise the need for further studies to understand how these changes affect population dynamics.

Invasive plants are a threat to natural ecosystems worldwide with urban wetlands being some of the most susceptible and highly modified environments of all. The tiger snake (Notechis scutatus) is a top predator that persists in urban wetlands in south-western Australia, many of which have been degraded by introduced kikuyu grass (Cenchrus clandestinus). To evaluate the potential impact of kikuyu grass on habitat quality for western tiger snakes we quantified the structural features of habitats within wetlands degraded by kikuyu grass and compared them to wetlands with native vegetation, examined tiger snake prey availability, assessed predation risk for juvenile snakes using clay models, and measured the thermal quality of the vegetation. Proliferation of kikuyu grass reduced habitat structural heterogeneity by reducing available bare ground and increasing vegetation density. This homogenisation of habitat structure had little effect on the predation risk for juveniles or the thermal properties of tiger snake shelter sites; however, one key snake prey species, the motorbike frog, had significantly lower abundance in the most impacted habitat. Habitat types with more structural complexity also offered tiger snakes more stable thermal regimes and lower predation risk. These findings indicate that the current extent of kikuyu grass invasion offers overall similar habitat quality for tiger snakes and may contribute to their persistence in urban wetlands, but they, along with their anuran prey, may befit from some increased habitat structural complexity in open areas.

Urban ecosystems and remnant habitat 'islands' therein, provide important strongholds for many wildlife species including those of conservation significance. However, the persistence of these habitats can be undermined if their structure and function are too severely disrupted. Urban wetlands, specifically, are usually degraded by a monoculture of invasive vegetation, disrupted hydrology, and chronic-contamination from a suite of anthropogenic pollutants. Top predators-as bioindicators-can be used to assess and monitor the health of these ecosystems. We measured eight health parameters (e.g., parasites, wounds and scars, tail loss and body condition) in a wetland top predator, the western tiger snake, Notechis scutatus occidentalis. For three years, snakes were sampled across four wetlands along an urban gradient. For each site, we used GIS software to measure the area of different landscapes and calculate an urbanisation-landscape score. Previously published research on snake contamination informed our calculations of a metal-pollution index for each site. We used generalised linear mixed models to assess the relationship between all health parameters and site variables. We found the metal-pollution index to have the most significant association with poor body condition. Although parasitism, tail loss and wounds differed among sites, none of these parameters influenced body condition. Additionally, the suite of health parameters suggested differing health status among sites; however, our measure of contemporary landscape urbanisation was never a significant predictor variable. Our results suggest that the health of wetland predators surrounding a rapidly growing city may be offset by higher levels of environmental pollution.