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A critical design component of studies measuring diversity is sampling effort. Allocation of sampling effort dictates how many sites can be sampled within a particular time-frame or budget, as well as sample duration, frequency and intensity, thereby determining the resolution and reliability of emergent inferences. Conventional survey techniques use fixed-effort methods that assume invariant detectabilities among sites and species. Several approaches have been developed in the past decade that account for variable detectability by using alternative sampling methods or by adjusting standard counts before analysis, but it is unclear how widely adopted these techniques have been or how current bird surveying norms compare with best-practice recommendations. I conducted a systematic search of the primary literature to ascertain how sampling effort is determined, how much effort is devoted to sampling each site and how variation in detectability is dealt with. Of 225 empirical studies of bird diversity published between 2004 and 2016, five used results-based stopping rules (each derived independently), 54 used proportional sampling, and 159 (71%) used implicit effort-based stopping rules (fixed effort). Effort varied widely, but 61% of studies used samples of 10 min or less and 62% of studies expended total effort per datum of 2 h or less, with 78% providing no justification for sampling efforts used and just 15% explicitly accounting for estimated detectability. Given known variation in detectability, relying on short-duration fixed-effort approaches without validation or post hoc correction means that most bird diversity studies necessarily under-sample some sites and/or species. Having identified current bird surveying norms and highlighted their shortcomings, I provide five practical solutions to improve sampling effort determination, urging contributors and consumers of empirical ecological literature to consider survey data in terms of sample completeness.
Context. Research has shown many negative effects of roads and traffic on wildlife and other biodiversity. The direct and indirect mechanisms through which roads and traffic harm animal populations vary across taxa, making mitigation of road effects a great challenge for conservation. As such, a large toolkit of species-specific management techniques may be needed to mitigate the negative effects of roads for wildlife and other biodiversity. The dunes sagebrush lizard, Sceloporus arenicolus, is a psammophilic (sand-loving) habitat specialist endemic to the Mescalero–Monahans Sandhills ecosystem of New Mexico and Texas. Within this ecosystem, roads fragment shinnery oak sand-dune landforms occupied by the species.
Aims. In the present study, we conducted behaviour trials in experimental enclosures to test whether the smallest roads restrict movements of the dunes sagebrush lizard. In addition, we also conducted trials to evaluate whether a sand-filled wildlife-crossing feature could facilitate road crossing.
Methods. We conducted behavioural trials on 24 dunes sagebrush lizards in our control enclosure and 22 lizards in our road and sand-filled wildlife-crossing enclosure. Movements were recorded for 15 min. The final locations at the end of each trial were analysed using circular statistics to determine whether movements in the road or the sand-filled wildlife-crossing enclosures were different from the control.
Key results. Our results supported the hypotheses that dunes sagebrush lizards avoid roads and do so according to a surface-avoidance mechanism. We also found that the wildlife crossing-feature design tested here had no effect on the movements or road-crossing frequency of dunes sagebrush lizard.
Conclusions. Surface-avoidance behaviour indicated that roads will persistently affect the movements of dunes sagebrush lizard, even when traffic is not present. Also, more research into an effective wildlife crossing is needed to increase connectivity of fragmented populations.
Implications. These findings help evaluate the impact of roads in creating isolated populations that experience increased demographic stochasticity and, in some instances, localised extirpation in this species. Our study can guide conservation plans for the dunes sagebrush lizard, and contribute to our understanding of road effects on biodiversity in general.
Context. Improving awareness to prevent exposure to rabies from bats is a public health priority. However, messages about bats and rabies often sensationalise this issue and represent bats in a negative way, which can negatively affect support for bat conservation.
Aims. The conflicts between public health goals and conservation needs seem unavoidable but are not irreconcilable. Natural resource managers and public health officials can work together to ensure that the importance of preventing exposure to rabies from bats is effectively communicated while at the same time promoting public appreciation of bat species. One efficacious way of achieving this communication goal may be through careful design of message content. This study aims to evaluate the efficacy of message design strategies in promoting rabies prevention and bat conservation.
Methods. This study tested messages in two USA National Park Service sites. Participants (n = 480) were randomly assigned to one of four message conditions as part of a 2 (risk–benefit vs risk-only of bats) × 2 (human blame vs bat blame for disease) between-subjects factorial design, or to a control (no message) condition.
Key results. The results show that all four messages were persuasive in promoting the rabies exposure prevention behaviour compared with the control condition. In addition, when participants were exposed to the bat-blame messages, more positive beliefs about bats were elicited if the messages included risk–benefit information rather than risk-only information.
Conclusions. Our study suggests that public health and wildlife conservation goals can be obtained simultaneously through careful message design.
ImplicationsFor messages that focus on just the risk information about bats, we suggest at least mentioning anthropogenic factors contributing to the spread of diseases to avoid unintended negative consequences for bat conservation. If messages emphasise bats as the source for spreading diseases, mentioning the benefits of bats may generate more positive beliefs about bats. Both strategies require some modification of the mainstream messages about bats and rabies to meet both public health and conservation goals.
Context. Research on species’ habitat associations is strengthened if it combines coarse-grained landscape data with finer-scale parameters. However, due to the effort required to measure fine-scale parameters, studies on threatened species that unite these two scales remain relatively rare.
Aim. This study aimed to undertake a multi-scale analysis of the habitat association of the threatened Petrogale lateralis (MacDonnell Ranges race) in the Anangu Pitjantjatjara Yankunytjatjara (APY) Lands, South Australia.
Method. Analyses were conducted at four spatial scales: (1) across the Central Ranges IBRA Region (regional scale); (2) on hills in the APY Lands at which P. lateralis is extant and extinct (site scale); (3) at ‘core’ and ‘non-core’ areas within those hills (hillside scale); and (4) at rocky refuges. The maximum entropy approach through the software MaxEnt was used for the analysis at the regional scale. At the remaining scales, fieldwork was used to collect, and regression modelling to analyse, data.
Key results. At the regional scale, presence was associated with slope and geology. At the site scale, aspect, rock abundance and habitat type are likely to have facilitated animal persistence at extant sites. At the hillside scale, the aspect, vegetation type and rock complexity of core areas are likely to have contributed to their higher use. Size, exposure and accessibility were significant predictors of the use of rocky refuges.
Conclusions. All four spatial scales yielded novel information on the habitat associations of P. lateralis, supporting previous researchers’ suggestions that habitat modelling should be conducted at multiple spatial scales.
Implications. The study exemplifies the utility of combining MaxEnt modelling with fieldwork-derived data. The results may have conservation implications for this threatened race, and may also provide a model for other studies of faunal habitat associations.
Context. Resource partitioning of diet and microhabitat was examined for five sympatric species of freshwater turtles in the Daly River in the northern end of Northern Territory (Top End) in Australia. The Daly River supports a high diversity of freshwater turtles, making it the ideal place to study a freshwater turtle community.
Aims. To determine the dry-season diet and microhabitat use of Carettochelys insculpta, Elseya dentata, Chelodina oblonga, Emydura victoriae and Emydura subglobosa worrelli and examine intraspecific and interspecific niche overlap and ontogenetic dietary shift.
Methods. Gut contents were collected by stomach flushing, and microhabitat use was determined by recording where each turtle was first seen before capture. Diet and microhabitat use were compared using an index of relative importance. Niche overlap was measured with Horn’s overlap index.
Key results.Carettochelys insculpta is an opportunistic omnivore that feeds mostly on ribbonweed (Vallisneria spiralis) and aquatic snails. Elseya dentata is herbivorous, feeding primarily on aquatic algae. The diets of C. insculpta and E. dentata overlapped moderately, but the overall niche overlap was low because they occupied different microhabitats within the river. Chelodina oblonga fed very little, and may use the Daly River as a dry-season refuge. Emydura victoriae is molluscivorous, consuming more molluscs as it grows. This ontogenetic dietary shift was associated with megacephaly (extreme broadly expanded head that is too large to fit into the carapace) and expanded triturating surfaces. This specialisation allows adult E. victoriae to feed exclusively on molluscs and so their diet overlapped little with other species. Emydura subglobosa worrelli was omnivorous, consuming mostly freshwater sponge and apparently preferring more lentic water.
Conclusions. The freshwater turtles of the wet–dry tropics are usually reported as being heavily reliant on the seeds, fruits and leaves of riparian vegetation; however, the present study showed that the dry-season diet in perennial rivers is primarily of aquatic origin.
Implications. The study suggested that populations of C. insculpta, E. dentata and E. victoriae could be threatened by broad-scale development in northern Australia if there were substantive impacts on aquatic macrophytes and molluscs in the Daly River system.
Context. Monitoring is a key component in managing wildlife populations and is critical for revealing long-term population trends of endangered species. Cryptic or highly mobile species that occur in low densities and in remote terrain require the development of specific monitoring methods. The southern cassowary is an Australian endangered species that poses many challenges for conducting population surveys.
Aims. The aims of the present study were to determine the effectiveness of camera traps in detecting cassowaries at a site, to determine whether visual lures increased detection rates, and to explore the potential of camera traps in population surveys.
Methods. Coloured lures (mimicking large blue and red fruit) were placed in front of a set of camera traps and compared with controls (no lures) at 29 survey sites on the Daintree coast, northern Queensland, Australia.
Key results. Camera traps with lures (1) detected more birds, (2) had a shorter detection latency, (3) had a marginally greater number of captures, (4) experienced a longer capture duration, (5) were more likely to have the cassowary stop in front of the camera, and (6) achieved a 95% probability of detecting cassowaries in 12 trap days, compared with 28 trap days without lures.
Conclusions. An increase in the number of cassowaries detected, the reduction in camera latency times and the ability to identify the birds enables a more efficient approach to estimating population sizes over existing methods. This is the first published study to use visual lures to conduct camera trapping of birds.
Implications. The use of camera traps with lures is a practical and cost-efficient technique for the rapid detection of cassowaries at a site and lends itself to studies of population structure, size and trends.
Context. Translocation is widely used to help avoid extinction of species from threatening processes. A fundamental objective of translocation is to establish self-sustaining populations; estimating demographic parameters is critical to assessing success of these programs and can also be used to support future management actions.
Aims. We estimated demographic parameters to evaluate the success of translocating the northern quoll Dasyurus hallucatus to two islands (Astell and Pobassoo), in response to the threat posed by the introduced cane toad Rhinella marina on the Australian mainland.
Methods. We used capture–mark–recapture methods to monitor both populations at regular intervals from initial release in 2003 until 2009 and a one-off survey in 2014.
Key results. Relative abundance (trap success) increased exponentially in the first 4 years, declined, and then stabilised in subsequent years. The population of female northern quolls on Astell Island peaked in 2006 with an estimate of 3640 (95% CI 3022–4257), and on Pobassoo Island the peak was 2007 with 617 (95% CI 531–703) females. In 2014 the population had decreased to 2193 (95% CI 1920–2467) on Astell and 451 (95% CI 359–543) on Pobassoo. Apparent survival and body condition decreased significantly following the population peak, possibly related to density dependence.
Conclusion. Both populations of northern quolls reached their regulation phase after going through establishment and growth phases, which included exceeding carrying capacity. The pattern was similar between the populations.
Implications. Increased survival and recruitment at threat-free translocation sites contributes to successful establishment of self-sustaining populations.
Context. Achieving successful conservation outcomes in habitat creation and reintroductions requires an understanding of how species use their habitat and respond to these interventions. However, few initiatives directly compare microhabitat selection between remnant and managed habitats to measure effectiveness and evaluate outcomes. Probability of detection is also rarely included in studies on microhabitat use, which may lead to erroneous conclusions if detectability varies between variables.
Methods. In this study, we used the endangered green and golden bell frog (Litoria aurea) to compare differences in microhabitat-use patterns in both a remnant and a constructed habitat. A detectability study was also conducted to determine detection probabilities among microhabitats.
Key results. Aquatic vegetation was used more than expected in both the remnant and constructed habitats, and rock piles were utilised less than expected in the constructed habitat, despite their recommendation in most habitat templates. We found that detection probabilities altered the outcomes of abundance estimates for nearly all the measured microhabitat variables.
Conclusions. Future management for this species should focus on providing high proportions of aquatic vegetation. Furthermore, although rock piles have been utilised greatly in past L. aurea habitat creation, placing large rocks on a managed site is expensive and time consuming. Future management initiatives may need to focus on providing smaller proportion of rocks, which would be a more appropriate use of resources.
Implications. With conservation management projects increasing over the next few decades, understanding habitat use before implementing strategies should be a priority as it will provide important insights and inform decision-making for optimum habitat creation and restoration. Furthermore, accounting for detectability in microhabitat use studies is essential to avoid wrong conclusions that may negatively affect the success of ecological management strategies.
Context. Infrastructure development in ski-resort areas has led to the modification of slopes and, often, the replacement of native plant species with exotic grasses. Modified ski slopes are effectively linear areas of disturbance that separate natural habitat and provide barriers to the movement of native animal species. To overcome these barriers, boulder-filled and culvert-style wildlife crossings have been constructed across disturbed ski slopes and under roadways to facilitate the movement of small native mammal species among areas of remnant habitat, but generally they differ in size and locality. The use of boulder-filled and under-road culvert crossings of different length has not been evaluated.
Aims. We determine whether fauna utilise wildlife crossings in ski resorts and whether variations in crossing length influence the species using the crossings.
Methods. We monitored boulder-filled crossings of two size classes (long or short) biannually from March 2009 to April 2013, using hair tubes. We monitored an additional two under-road culvert crossings with remote infrared cameras.
Key results. The results indicated that all crossings, regardless of size, are utilised by small mammals. However, we detected threatened species, such as Mastacomys fuscus (broad-toothed rat), more frequently in crossings of greater length.
Conclusions. To maintain linkages for small-mammal populations within ski resorts, we recommend the continued use of boulder-filled crossings on ski slopes. These crossings may be particularly important in facilitating the movement of small mammals across wide areas of ski-slope disturbance.
Implications. The context and maintenance of crossings is likely to be important for their long-term use by small mammals, as are complementary strategies to restore structural habitat connectivity on ski slopes, such as strategically implemented native vegetation plantings.
Context. Supplementary resource provision is increasingly used by conservation managers to manipulate habitat conditions that limit population growth of threatened species. These methods are popular in reintroduction programs because they can assist released individuals to adapt to novel environments. In situ management and reintroductions are being used to recover warru (black-footed rock-wallaby, Petrogale lateralis MacDonnell Ranges race) on the arid Anangu Pitjantjatjara Yankunytjatjara (APY) Lands of South Australia. Direct predation by introduced predators is thought to be the main cause of population decline, but indirect predation effects reducing access to water resources has also been proposed as a limiting factor.
Aims. To determine whether warru would use supplementary water and so provide a tool to alleviate resource pressure for in situ (wild) and reintroduced warru populations.
Methods. We provided supplementary water to a wild and reintroduced warru population across 12 months. Drinking rates were calculated by monitoring water points with camera traps and modelled against plant moisture content and total rainfall. We also examined whether number of visits to water points by warru predators and competitors was significantly different to control points (no water present).
Key results. Wild and reintroduced warru used water points within 0–10 days of installation. No significant increase in visits by predators or competitors was observed at water points. Drinking rates were significantly higher during dry winter months (March–October) for both wild and re-introduced populations.
Conclusions. Supplementary water is readily utilised by warru. Water could be provided in this manner to warru populations where predators are present, particularly during drier months (generally March–October on the APY Lands), periods of drought or after fire, when food resources will have a lower water content and/or be less abundant. This may increase breeding rates and recruitment of young, and improve the probability of persistence for populations of this threatened species, and should be further investigated.
Implications. Supplementary water provision may be a useful tool to increase population growth rates for threatened mammalian herbivores in arid habitats. Experimental trials of the uptake of supplementary water and effects on population dynamics will provide important data for implementing adaptive management frameworks for conservation.
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