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European rabbit fleas were released among Australian wild rabbits in the late 1960s to supplement mosquitoes as vectors of myxoma virus. Data from study sites across southern Australia in the 1960s and 1970s are reviewed to discern common elements of flea-borne myxomatosis epizootics and a simple model is proposed to explain how virus virulence and food quality interact to determine rabbit abundance. Low, stable populations of rabbits implied that, despite virus attenuation and increased rabbit disease resistance, flea-borne myxomatosis was extremely important in controlling rabbit populations. Despite the enhancement of myxomatosis, livestock producers benefitted little from the additional pasture because marketing difficulties were not conducive to industry growth. Native wildlife likely benefitted, nonetheless.
Context: Management actions that suppress introduced predator densities can benefit the population recovery of native species. Nevertheless, ensuring that predator management produces measurable population-level benefits can be influenced by multiple factors affecting species detection. Monitoring designs using multiple survey methods may perform better than increasing sampling effort with single-method protocols.
Aims: This study aimed to estimate individual and cumulative detection probabilities and site occupancy estimates from the use of five different monitoring methods to survey a native mesopredator, the lace monitor (Varanus varius). Second, we assessed the effect of lethal red fox (Vulpes vulpes) baiting on lace monitor detection probabilities and site occupancy estimates collected from each monitoring method.
Methods: Multi-method sampling for Varanus varius occurred at 76 sites across lethal fox baited and non-baited habitats in East Gippsland, Victoria. Bayesian site occupancy models were used to estimate the effects of detection method and fox-baiting treatments on Varanus varius detection probability and site occupancy.
Key results: Method-specific detection probabilities (P = 0.00–0.12) and site occupancy estimates (Ψ = 0–0.53) varied considerably among methods, but combinations of multi-method monitoring improved lace monitor detection probability (P = 0.11–0.18) and site occupancy (Ψ = 0.87 ± [0.66–0.93]−0.91 ± [0.76–0.97] mean ± [95% credible intervals]) above any single method. However, there was extreme heterogeneity in the size and direction of the introduced predator baiting effect on method-specific lace monitor detection. Three methods (box traps and two different visual search surveys) all indicated lace monitor detection probabilities increased in fox-baited sites. However, sand pads reported a decrease in lace monitor detection at fox-baited sites, whereas pipe traps obtained no detections.
Conclusions: Combining detection data from all methods led to the inference of a positive fox-baiting effect, albeit with a smaller magnitude and better certainty than that estimated using a reduced method monitoring design, which had fewer detection data after excluding biased detection from sand pads.
Implications: Using a multi-method monitoring approach improved lace monitor detection and reduced sampling effort. However, depending on sampling methodology, the management effects on lace monitors can change.
Context. Anticoagulants have been used in New Zealand for decades, but few data are available on the sustainability of these toxins for rodent control. It is important to regularly monitor for resistance in long-term brodifacoum-use areas and establish a database for future references.
Aims. This study aimed to estimate the effective dose (ED50) of brodifacoum for ship rats from an area of New Zealand with no history of brodifacoum use, in order to establish a blood-clotting response test for assessing resistance in rodent populations from other areas.
Methods. A ranging study was conducted whereby successive groups of ship rats were administered brodifacoum doses that were increased or decreased progressively, until an International Normalised Ratio (INR) of 3.6 was reached. Linear regression was used to model the relationship between dose and INR, and ED50 dose was estimated using the resulting model.
Results. None of the rats appeared susceptible to brodifacoum at previously reported LD50 exposures for this species. The ED50 of brodifacoum was estimated to be 2.88 mg/kg for males and 3.81 mg/kg for females. These values are 6–8 times greater than the previously published lethal dose values for ship rats in New Zealand.
Conclusions. Blood-clotting inhibition was detected in the rats only following high doses of brodifacoum, which may indicate resistance within the sampled population.
Implications. Relatively low susceptibility, or resistance, to brodifacoum in New Zealand ship rats may be mediated by spatial connections between areas with different histories and patterns of anticoagulant rodenticide use.
Context: Understanding the factors determining the impacts of roads and how they fragment landscapes limiting the movement of animals, is key to implement efficient mitigation measures.
Aims: Here we investigate if road orientation in relation to limiting resources, a largely overlooked factor on road impact assessments, can influence the movement of animals within a landscape where water resources are spatially clustered.
Methods: We evaluated movement by monitoring animal tracks on unpaved roads: two with a North–South orientation and two with an East–West orientation.
Key results: Animals were more likely to follow roads leading to limiting resources (i.e. East–West orientation), confirming human linear structures can facilitate wildlife movements. Carnivores were more likely to follow roads with any orientation and for longer compared to ungulates, whereas ungulates followed roads mainly in the orientation of limiting resources.
Conclusions: Road orientation affects how roads influence the movement of animals in landscapes where resources are distributed along a spatial gradient with different effects for ungulates and carnivores.
Implications: The key implications of this work affect the planning and implementation of mitigation strategies and safety measures. Our results suggest road-crossing infrastructure and fences will be most important in roads traversing a gradient to allow wildlife movement while preventing collisions. For roads along a gradient, crossing structures may be less important, but fences or appropriate signage could be useful to prevent or warn drivers of animals travelling on the road.
Context: Leiopelma archeyi is a threatened New Zealand amphibian species translocated for conservation purposes. A disease outbreak triggered the translocation of 70 frogs to Pureora Forest in 2006 to establish a new wild population of L. archeyi. Ten years after, 60 more frogs were translocated to this site to enhance the genetic and demographic profile of L. archeyi in Pureora Forest. Here, we analysed 14 years of capture–recapture monitoring data collected for this translocated population.
Aims: Our aim was to estimate population demographic parameters that allow us to assess the demographic performance of this translocated population.
Methods: We used spatially explicit capture–recapture (SECR; also called spatial capture–recapture) multi strata/session models to estimate population density and derive its rate of change over time.
Key results: Here we show that the density of translocated Leiopelma archeyi in Pureora (central North Island, New Zealand) remains stable for most of the study period. After the release of 70 frogs in 2006, density varied from 0.02 frogs/m2 in April 2007 to 0.06 frogs/m2 in December 2014. After the second release of 60 frogs in 2016, density in Pureora of L. archeyi varied from 0.21 frogs/m2 in November 2016 to 0.63 frogs/m2 in November 2018.
Conclusions: The study species is a long-lived k-selected species, therefore long-term monitoring (>20 years) is required to corroborate demographic indicators. Nevertheless, as the current density estimates are higher than the density estimated for this population after each release (April 2007 and November 2016), we suggest progress towards the establishment of a new wild population of L. archeyi in Pureora Forest.
Implications: Translocations are a useful conservation tool for many threatened species and post-release monitoring data are the main source of information needed to empirically prove their success.
Context: Records collected when sick, injured or dead animals arrive at wildlife care facilities have potential to offer insights into population declines and identify key threatening processes for conservation and management intervention.
Aims: Records compiled from a centralised Queensland Government database of koala (Phascolarctus cinereus) arrivals to care facilities across South East Queensland were analysed to explore long- and short-term trends in arrivals in terms of seasonality, causes, outcomes and spatial distribution, with a particular focus on insights hospital records could provide into the potential role of disease in koala population declines.
Methods: Analysis was conducted on over 22 years of records of koalas arriving at care facilities collated by the Queensland Government. We summarised causes of hospital arrivals and outcomes. We utilised time-series methods to explore short-term cyclic dynamics in the data, and spatial tools to document changes in the distribution of koala arrivals.
Key results: In the long term, koala hospital arrivals increased modestly from 1997 to 2014, before falling into decline by 2018. Long-term changes are dwarfed by short-term fluctuations, including clear annual cyclic dynamics associated with car strike and dog attack, which peak from August to October each year, likely coinciding with the onset of the koala breeding season. Seasonality is also detected in disease-associated arrivals. Known severe declines in wild koala populations in South East Queensland, an area of intensive urbanisation and associated loss of koala habitat, are not reflected in the overall koala hospital arrival numbers. Our analysis suggests that severe local declines in wild koala abundance have been obscured by increases in the catchment areas from which koalas are entering the hospital network.
Conclusions: Koala hospital records provide an extensive dataset that can be mined for insights into koala population dynamics and threatening processes. However, interpretation of our findings must consider limitations and biases inherent in data collection.
Implications: Despite acknowledged shortcomings in terms of bias and data quality, retrospective analysis of records from care facilities can provide important insights for guiding conservation efforts. For example, our findings with respect to seasonality in koala hospital arrivals mirror results reported for other locales, suggesting that cyclic dynamics are not a local phenomenon, but occur more broadly across the species range, with implications for seasonal delivery of conservation actions.
Context. Many threatened species persist in modified landscapes. Species in these landscapes often inhabit vegetation strips adjacent to linear structures such as roads, railways and artificial waterways. These vegetation strips may act as refugia or provide resources, but the associated structures (e.g. roads) may also act as barriers to movement. The southern brown bandicoot (eastern subspecies) is listed as Endangered in Australia and is known to inhabit modified landscapes.
Aim. We aim to determine the extent of occupancy of southern brown bandicoots and the relative importance of different habitat types. Our data are intended to provide a baseline for future monitoring of changes to bandicoot populations, and to further our understanding of the relative importance of different habitat types for management and conservation.
Methods. We conducted a remote-camera survey of southern brown bandicoots, at 98 locations across a 60 000 ha region south-east of Melbourne. Bandicoots in this area inhabit patches of remnant habitat in reserves and remnant, modified or non-native vegetation strips along roadsides and artificial waterways created in the 19th century to drain swampland. These habitat fragments sit within a matrix of agricultural, residential and commercial land.
Key results. Our results suggest that bandicoot occupancy is higher along artificial waterways (0.76) than along roadsides (0.35) or within reserves (0.39).
Implications. Habitat along waterways is often different from remnants, with a mix of weedy and native vegetation. The implication of this is a potential conflict between habitat and vegetation management for bandicoots, weed control and maintenance of drains and associated levees.
Ambika P. Khatiwada, Wendy Wright, Kyran Kunkel, Monsoon P. Khatiwada, Carly Waterman, Santosh Bhattarai, Hem S. Baral, Chiranjibi P. Pokheral, Fredrik Dalerum
Context. People and wildlife are coming into greater contact worldwide because of the increasing human footprint. Although some species tolerate certain levels of human activities, others are vulnerable to human disturbance, potentially altering their spatial or temporal patterns of activity in response to disturbance by humans.
Aims. We evaluated the influence of human activity on burrow activity of the Chinese pangolin, a Critically Endangered species that is heavily persecuted for subsistence and illegal trade.
Methods. We deployed remotely triggered camera traps at pangolin burrows located at four sites with contrasting levels of human density and infrastructure in Nepal, and estimated burrow-activity patterns of pangolins by using a kernel-density estimator based on the time stamp of camera trap observations.
Key results. Our findings did not suggest that anthropogenic disturbance affected pangolin burrow activity, but we acknowledge that these findings were based on a limited number of observations. Peak pangolin burrow activity was observed after midnight in three of the study sites, including those with highest and lowest levels of human activity. The fourth area, which had intermediate levels of human activity, had an earlier peak in burrow activity, possibly caused by prey deficiency owing to intense agriculture.
Conclusions. We suggest that pangolins may tolerate human activity because of their strictly nocturnal temporal niche, but that this tolerance has made them vulnerable to poaching because it allows them to co-exist spatially with humans.
Implications. Nocturnal species may be particularly prone to non-conflict-related persecution, because they may be easily accessible targets for illegal hunting activities.
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