Skye Wassens

Movement patterns of southern bell frogs (Litoria raniformis) in response to flooding

Within the semiarid regions of New South Wales, Australia, the endangered southern bell frog (Litoria raniformis) occupies a landscape that is characterised by unpredictable rainfall and periodic flooding. Limited knowledge of the movement and habitat-occupancy patterns of this species in response to flood events has hampered conservation efforts. We used radio-tracking to assess changes in movement patterns and habitat occupancy of L. raniformis (n = 40) over three different periods (November, January and April/May) that coincided with the flooding, full capacity and subsequent drying of waterbodies within an irrigation landscape. We assessed (1) the use of permanent and ephemeral habitats in response to flooding and drying and (2) distances moved, turning angles and dispersion of frogs during wetland flooding, full capacity and drying. Individuals remained in permanent waterbodies in November but had abandoned these areas in favour of flooded ephemeral waterbodies by January. As the ephemeral waterbodies dried, radio-tracked individuals moved back into permanent waterbodies. The movement patterns of radio-tracked individuals were significantly different in the three radio-tracking periods, but did not differ significantly between sexes. Individuals moved significantly greater distances over 24 h, in straighter lines and movements were more dispersed while they occupied ephemeral waterbodies during January than when they occupied permanent waterbodies during November and April/May. Local weather conditions did not influence movement patterns when all three tracking periods were modelled together using a single linear stepwise regression. The dynamic distribution of habitat patches over space and time, combined with changing patterns of resource utilisation and movement of L. raniformis, highlights the importance of incorporating both permanent and ephemeral habitat patches into conservation plans. Reductions in flood frequency and extent of ephemeral wetlands due to modified flooding regimes have the capacity to limit dispersal of this species, even when permanent waterbodies remain unchanged.

Review of the past distribution and decline of the Southern Bell Frog Litoria raniformis in New South Wales

The Southern Bell Frog Litoria raniformis was formally widespread throughout south eastern Australia. Poor knowledge of the past and present distribution of populations and the pattern of decline currently limits our ability to plan conservation measures. The past and present distribution of L raniformis in New South Wales (NSW) is described through the use of museum records, wildlife databases, reports and surveys. Survey identified a further 10 populations, all in lower Murrumbidgee floodplain (Lowbidgee), and confirmed the absence of L raniformis in past habitats along the middle reaches of the Murrumbidgee River. Based on past records, L raniformis declines have been substantial. The eastern edge of the geographic range has shifted approximately 500 km west from the South Eastern Highlands, and the northern edge of its range has shifted 200 km south from the most northerly population in Willandra National Park. Litoria raniformis is currently restricted to the semi-arid zone of NSW with populations oc...

A commentary on 'Long-term ecological trends of flow-dependent ecosystems in a major regulated river basin', by Matthew J. Colloff, Peter Caley, Neil Saintilan, Carmel A. Pollino and Neville D. Crossman

Colloff et al. in Marine and Freshwater Research (http:dx.doi.org/10.1071/MF14067) examined time-series data for flow-dependent vegetation, invertebrates, fish, frogs, reptiles and waterbirds in the Murray–Darling Basin, 1905–2013. They concluded that temporal patterns fluctuated, declining during droughts and recovering after floods. They suggested that major changes in land use in the late 19th century permanently modified these freshwater ecosystems, irretrievably degrading them before major water diversions. Restoring water to the environment might then be interpreted as not addressing biotic declines. We argue that their conclusions are inadequately supported, although data quality remains patchy and they neglected the influence of hydrology and the timing and extent of water resource development. We are critical of the lack of adequate model specification and the omission of statistical power analyses. We show that declines of native flow-dependent flora and fauna have continued through the 20th and early 21st centuries, in response to multiple factors, including long-term changes in flow regimes. We argue that flow-regime changes have been critical, but not in isolation. So, returning water to the environment is a prerequisite for sustained recovery but governments need to improve monitoring and analyses to adequately determine effectiveness of management of the rivers and wetlands of the Murray–Darling Basin.

Ecology of Stimson's python (Antaresia stimsoni) in the MacDonnell Ranges of central Australia

Stimson’s python (Antaresia stimsoni) is a small nocturnal python (Pythonidae) that occurs throughout Australia’s arid zone. Despite its wide distribution and localised abundance, no field-based studies have been undertaken on this species. We investigated activity patterns, habitat use, diet, and body sizes of A. stimsoni in the MacDonnell Ranges bioregion of the Northern Territory. Data were collected at night by road-cruising along a sealed road transect over 12 consecutive months. We found that the species copes with the extreme weather variability of arid Australia by remaining active over a broad range of air temperatures and maximising activity following rainfall when relative humidity is high and ground-dwelling frogs, a significant prey source, are likely to be abundant. A. stimsoni ceased activity only during the coldest months of the year. The species occurs in a range of vegetation types, with an apparent preference for riparian woodland, and its ability to thrive in the MacDonnell Ranges may be related to the abundance of rock-outcrops for refuge. Our results for diet and body size support previous research based on museum specimens, confirming that A. stimsoni feeds on a range of terrestrial vertebrates and is not sexually dimorphic.

Identifying Critical Habitat for Australian Freshwater Turtles in a Large Regulated Floodplain: Implications for Environmental Water Management

Freshwater turtles face many threats, including habitat loss and river regulation reducing occupancy and contributing to population decline. Limited knowledge of hydrological conditions required to maintain viable turtle populations in large floodplain wetlands hinders effective adaptive management of environmental water in regulated rivers. We surveyed three turtle species over 4 years across the Lower Murrumbidgee River floodplain, a large wetland complex with a long history of water resource development. Using site and floodplain metrics and generalized linear models, within a Bayesian Model Averaging framework, we quantified the main drivers affecting turtle abundance. We also used a hierarchical modeling approach, requiring large sample sizes, quantifying possible environmental effects while accounting for detection probabilities of the eastern long-necked turtle (Chelodina longicollis). The three species varied in their responses to hydrological conditions and connectivity to the main river channel. Broad-shelled turtles (Chelodina expansa) and Macquarie River turtles (Emydura macquarii macquarii) had restricted distributions, centered on frequently inundated wetlands close to the river, whereas the eastern long-necked turtles were more widely distributed, indicating an ability to exploit variable habitats. We conclude that turtle communities would benefit from long-term management strategies that maintain a spatiotemporal mosaic of hydrological conditions. More specifically, we identified characteristics of refuge habitats and stress the importance of maintaining their integrity during dry periods. Neighboring habitats can be targeted during increased water availability years to enhance feeding and dispersal opportunities for freshwater turtles.

Description and genetic characterization of a new Contracaecum larval type (Nematoda: Anisakidae) from Australia

Nematode parasites belonging to the genus Contracaecum are economically important parasites with zoonotic significance. Adult Contracaecum spp. are found in the stomach of marine mammals or piscivorous birds, and larval stages infect a wide range of invertebrates and fish species. Human infection with Contracaecum larvae has been reported in Australia and other countries after the consumption of infected fish. Although the genus Contracaecum comprises numerous species, thus far only four Contracaecum larval types have been specifically identified, therefore their life cycle and biology are not yet fully understood. In this study, a new Contracaecum larva (type IV), found in the intestinal tissue of carp caught from Coonancoocabil Lagoon, New South Wales, Australia, is described and characterized genetically. It was identified as Contracaecum bancrofti, a unique Australian species reported previously from the Australian pelican in Northern Territory, New South Wales, Victoria and South Australia. This study highlights the role of migratory birds and introduced fish species, such as carp, in distributing zoonotic pathogens not only across the continent but also from marine to freshwater systems. Coonancoocabil Lagoon is located in the Murrumbidgee Valley National Park, a highly managed conservation area with native fish in wetlands located in close proximity to several fish farms and hatcheries. Infection of a highly resilient invasive fish species, such as carp, with a zoonotic parasite of low host specificity, such as Contracaecum larvae, should be alarming for aquaculture and environmental authorities.

Body sizes, activity patterns and habitat relationships of the orange-naped snake (Furina ornata) (Serpentes : Elapidae) in the MacDonnell Ranges, Northern Territory

Abstract. Orange-naped snakes (Furina ornata) are small elapids that occur in tropical to arid regions throughout northern and central Australia. We report on the first field-based study of this species, investigating body sizes, activity patterns, and habitat use in the semiarid MacDonnell Ranges bioregion of central Australia. Using systematic road-cruising, we encountered 69 live F. ornata along a 77-km sealed road-transect over a 12-month period from August 2009 to July 2010. Based on measures of snout-to-vent length (SVL), we found that female F. ornata (mean SVL = 459 ± 6.3 (s.e.) mm; n = 16) were larger than males (SVL = 372 ± 25.2 (s.e.) mm; n = 44) (t = 4.7358, P < 0.0001), and that both sexes were larger than previously reported from museum specimens. Despite the extreme weather variability experienced in arid Australia, we found that activity patterns were not significantly related to temperature, rainfall or humidity, and F. ornata was active in all but the single coldest month of the year. The habitat-use analysis found that F. ornata was more likely to be recorded in areas with greater cover of hummock grass (Triodia spp.) and less cover of rocky outcrops or boulders. Hummock grasslands in arid Australia have an abundant and diverse skink fauna, which may attract F. ornata, whose diet consists primarily of diurnal skinks.

Adaptive Management of Return Flows: Lessons from a Case Study in Environmental Water Delivery to a Floodplain River

For many floodplain rivers, reinstating wetland connectivity is necessary for ecosystems to recover from decades of regulation. Environmental return flows (the managed delivery of wetland water to an adjacent river) can be used strategically to facilitate natural ecosystem connectivity, enabling the transfer of nutrients, energy, and biota from wetland habitats to the river. Using an informal adaptive management framework, we delivered return flows from a forested wetland complex into a large lowland river in south-eastern Australia. We hypothesized that return flows would (a) increase river nutrient concentrations; (b) reduce wetland nutrient concentrations; (c) increase rates of ecosystem metabolism through the addition of potentially limiting nutrients, causing related increases in the concentration of water column chlorophyll-a; and (d) increase the density and species richness of microinvertebrates in riverine benthic habitats. Our monitoring results demonstrated a small increase in the concentrations of several key nutrients but no evidence for significant ecological responses was found. Although return flows can be delivered from forested floodplain areas without risking hypoxic blackwater events, returning nutrient and carbon-rich water to increase riverine productivity is limited by the achievable scale of return flows. Nevertheless, using return flows to flush carbon from floodplains may be a useful management tool to reduce carbon loads, preparing floodplains for subsequent releases (e.g., mitigating the risk of hypoxic blackwater events). In this example, adaptive management benefited from a semi-formal collaboration between science and management that allowed for prompt decision-making.

The effect of survey method on the detection probabilities of frogs and tadpoles in large wetland complexes

Knowledge of the probability of detecting a species with a given survey effort is important when planning monitoring programs. The present paper compares detection probabilities for six survey methods: audio-visual transect surveys targeting adult frogs, and sweep netting, bait traps, small fyke nets, large fyke nets and seine netting targeting tadpoles. Data were drawn from repeat surveys of 16 wetlands over a 3-year period (2008–2011). Detection probabilities of each method and species combination were determined by maximum likelihood estimation. Audio-visual surveys targeting adults had a higher probability of detecting individual species than did methods targeting their tadpoles. However, the presence of adults was a reasonably poor indicator of the presence of their tadpoles on any given survey occasion. Of the methods employed to target tadpoles, large and small fyke nets had a significantly higher probability of detecting tadpoles of all species than did bait traps, seining or sweep nets. Differences in the detection probability of different methods demonstrated that the choice of survey method can bias towards particular groups of species and, in some cases, underestimate breeding activity by frog species in large waterbodies.