Suchergebnisse

Context River regulation, coupled with climate change, has caused significant declines in global freshwater biodiversity. In Australia, water extraction within the Murray–Darling Basin (MDB) has reduced the frequency, extent and duration with which floodplains are inundated, resulting in widespread declines in wetland-dependent biodiversity, including reptiles. The endangered Ngabi (Hemiaspis damelii) is associated with floodplain systems in the MDB, yet its distribution and ecological requirements are poorly understood, hampering conservation actions. Aims We sought to validate an assumption that Ngabi is associated with wetland vegetation communities before investigating factors affecting its probability of detection in the lower Murrumbidgee catchment in southern New South Wales. We predicted Ngabi occurrence patterns would relate to frog abundance, wetland hydrology, microhabitat attributes and meteorological variables. Methods We compared Ngabi observations from 16 paired wetland and dryland vegetation transects to evaluate associations with vegetation type. We then used generalised linear mixed models to relate snake presence and absence to prey (frog abundance), microhabitat (logs and ground cover), wetland hydrology (water depth and inundation frequency) and meteorological conditions, using 12 repeat surveys between September 2018 and March 2021. Key results Fifty-eight snakes were observed at five of eight wetlands during the study. Ngabi was exclusively recorded in river red gum/spike rush or lignum vegetation communities, and was absent from sandhill woodland or chenopod communities. The probability of detecting Ngabi increased with ambient temperature and weakly with wetland inundation frequency, but not frog abundance, microhabitat attributes or year. Conclusions Ngabi is strongly associated with floodplain vegetation communities and, to some extent, frequently inundated wetlands in southern NSW, suggesting water management agencies should incorporate threatened floodplain snake species into future wetland management plans. The use of environmental water to restore aspects of flow regimes, improve wetland health and aquatic diversity is likely to benefit other wetland-dependent snake populations across the MDB. Implications The positive relationship between Ngabi detections and ambient temperature will be important for designing an effective monitoring program for the species across the MDB. Furthermore, our findings provide insight into the benefits of using environmental water to create wetland refuges to maintain floodplain snake populations during droughts.

Context Habitat loss and fragmentation are leading causes of biodiversity decline worldwide. In Australia, woodland habitat has been extensively cleared and fragmented yet there has been limited research on the effects of habitat loss and fragmentation on semi-arid reptiles, impeding conservation planning and recovery efforts. Aims We aimed to investigate factors influencing the distribution and occurrence of habitat specialist and generalist reptile species on a large agricultural holding in south-eastern Australia that has experienced habitat loss and fragmentation. Methods Reptiles were surveyed using pitfall and funnel traps and active searches across 20 sites stratified by land use and vegetation type. Twelve sites were established in remnant woodland patches embedded within an agricultural matrix and eight sites were established in a private conservation reserve on the same property. Generalised linear models were used to explore relationships between the occurrence of eight reptile species and predictor variables describing site, landscape and vegetation variables. Key results Of the 31 reptile species that were detected, eight were modelled. The results revealed that four specialist species, the eastern mallee dragon (Ctenophorus spinodomus), nobbi dragon (Diporiphora nobbi), barred wedge-snouted ctenotus (Ctenotus schomburgkii) and shrubland pale-flecked morethia (Morethia obscura), were closely associated with the conservation reserve, and that the southern spinifex ctenotus (Ctenotus atlas) had a strong association with spinifex (Triodia scariosa) dominated vegetation community. Conclusions Reptile habitat specialists are particularly sensitive to habitat loss and fragmentation and are at a higher risk of local extinction compared with habitat generalists. Reptile occurrence was reduced in remnant woodland patches, but remnant patches also supported a suite of habitat generalists. Implications A suite of semi-arid reptile species are sensitive to the effects of habitat loss and fragmentation and are susceptible to localised extinction. However, the presence of habitat generalists within woodland remnants highlights the value of retaining representative habitat patches in agricultural landscapes. Conservation of semi-arid woodland reptiles will depend on the retention of large tracts of protected vegetation across a broad range of soil types to maintain habitat heterogeneity and reptile diversity.