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Context An understanding of large herbivore habitat choices in heterogeneous African protected areas is important for the better management of these key ecosystems.
Aims To determine habitat use of African buffalo (Syncerus caffer) and plains zebra (Equus quagga) in a heterogeneous protected area.
Methods Zambezi National Park (ZNP), Zimbabwe, was divided into five vegetation types using an unsupervised classification on a Landsat satellite image that was classified into five land cover classes, using the K-means classification algorithm. African buffalo and plains zebra densities were then determined in each vegetation type using road transect surveys monthly between January 2013 and December 2015. Normalised difference vegetation index (NDVI), grass biomass, grass height and grass quality (nitrogen, calcium, phosphorus and acid detergent fibre content) were determined in each vegetation type during the wet (November to April) and dry (August to October) seasons to establish their quality as habitats for African buffalo and plains zebra.
Key results Both African buffalo and plains zebra mostly foraged in mixed and grassland areas, and avoided Zambezi teak vegetation type. Zambezi teak vegetation type had high NDVI due to the dense tree cover. Both African buffalo and plains zebra preferred vegetation types with intermediate grass biomass (approximately 300 g m−2) and grass height (approximately 16 cm). Grass nutritive value (in terms of nitrogen, phosphorus and acid detergent fibre) declined from wet to dry season in all vegetation types.
Conclusions African buffalo and plains zebra in the ZNP confined their habitat use mostly to two vegetation types (mixed and grassland), which together covered 25% of the protected area.
Implications Teak (Baikiaea plurijuga) vegetation, which accounted for about 60% of the ZNP, was avoided by both African buffalo and plains zebra, suggesting that a significant part of the protected area was not used by the two herbivores.
Context. Anthropogenic landscape modification and fragmentation result in loss of species and can alter ecosystem function. Assessment of the ecological value of urban reserve networks requires baseline and continued monitoring. However, depending on the desired indicators and parameters, effective monitoring can involve extensive sampling that is often financially or logistically infeasible.
Aims. We employed a low-intensity, mixed-detector survey design to monitor the small-mammal community across a network of 53 fragmented forest preserves (225 sites) in a highly urbanised landscape in the Chicago metropolitan area from August to October, 2009–2012.
Methods. We used a sequential process to fit single-season occupancy and pairwise co-occurrence models for six common small mammal species to evaluate habitat associations and interspecific interactions.
Key results. Shrew species and meadow voles occurred more often in open canopy-associated habitats, whereas occupancy was greater for eastern chipmunks, grey squirrels and white-footed mice in closed-canopy habitats. Habitat associations were complicated by negative pairwise interactions, resulting in reduced occurrence of meadow voles when predatory short-tailed shrews were present and lower occupancy rates of white-footed mouse when chipmunk competitors where present. White-footed mice co-occurred with short-tailed shrews, but detection of white-footed mice was lower when either eastern chipmunks or short-tailed shrews were present, suggesting that densities of these species could be inversely related.
Conclusions. We found evidence for both habitat segregation and interspecific interactions among small mammal species, by using low-intensity sampling across the reserve network. Thus, our sampling and analysis approach allowed for adequate assessment of the habitat associations and species interactions within a small-mammal community.
Implications. Our findings demonstrated the utility of this monitoring strategy and community as bioindicators for urban-reserve networks. The approach described holds promise for efficient monitoring of reserve networks in fragmented landscapes, critical as human population densities and urbanisation increase, and we discuss how adaptive sampling methods could be incorporated to further benefit conservation efforts.
Context. Eradication of invasive species is necessary to protect and assist the recovery of native species and ecosystems. Knowing when to declare an eradication has been successful after ongoing non-detections is a challenge.
Aims. The rapid eradication assessment (REA) model is a powerful simulation framework to determine, given model parameters and a fixed level of monitoring effort, the level of confidence in declaring the success of pest eradication. The aim of the present study was to extend the current functionality of the REA model for broader applicability.
Methods. The REA model was advanced so that it was able to account for (1) usage of multiple static device types with different probabilities of detection, (2) incursion detection at a known location and (3) usage of mobile detection devices, which are increasingly being used in conservation.
Key results. An invasive rat incursion response on Great Mercury Island in New Zealand is used as a comprehensive example to demonstrate the distribution of estimated probability of pest absence among the cases using the current REA model and the extensions presented here.
Conclusions. Although Great Mercury Island already had a sparse but extensive island-wide network of static biosecurity surveillance devices, and deployed additional static devices around the area of incursion, the greatest improvement in the estimated probability of pest absence following a rat incursion was from additionally using a trained rodent-detection dog.
Implications. The added functionality in the REA model and demonstration of its use on a real-world scenario will allow more realistic application by wildlife managers.
Context. Organisms living in small, isolated populations with very restricted ranges are at high risk of extirpation due to various direct and indirect forces than mainland populations. Roatán spiny-tailed iguanas (Ctenosaura oedirhina) are endemic to the 146-km2 island of Roatán, Honduras. Harvesting for consumption, fragmentation of habitat and predation by domestic animals threaten the existence of this lizard. This species is federally protected in Honduras; however, enforcement is rare. These iguanas are also listed as Endangered by the International Union for Conservation of Nature (IUCN) and are on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This species is geographically and genetically isolated into small subpopulations that are declining in density.
Aims. To estimate the population size of Roatán spiny-tailed iguanas (Ctenosaura oedirhina) on the island of Roatán, Honduras.
Methods. Distance sampling surveys have been used to monitor this species since 2012, and have been used to determine population density at five study sites. Estimates of density at those sites and across the island were used to calculate the population size of this species.
Key results. The present study elucidates that the high-density populations remaining are declining. The current population size is estimated to be 3759 (95% CI = 1406–12 616) individuals within the study sites, with 730 additional iguanas potentially outside of the study sites.
Conclusions. If the current level of decline continues, this species may become extirpated from some locations on Roatán, and go extinct in the wild. Although Honduras does have laws protecting this species and other wildlife, enforcement must be enhanced.
Implications. Lack of enforced protection for this species allows poaching for consumption to continue, which has been shown to alter its distribution and cause increased adult mortality. Local customs value the consumption of this species, creating a delicate management situation. Recommendations include strategies that mitigate the threat posed by consumption and increase enforcement of the current laws, while acknowledging cultural traditions.
Context. Species conservation assessments require information on distribution, habitat requirements and population demography and trends. Uncertain conservation assessments limit effective planning and may lead to poor management decisions. Top-order predators generally receive considerable attention from ecologists and conservation biologists, with the notable exception of large pythons and boas. They are typically elusive and have low population densities, posing challenges for ecological research and monitoring. Ecological and demographic data are lacking for most large snake species and are generally inadequate to properly assess conservation status or to evaluate their broader ecological roles. The Oenpelli python (Simalia oenpelliensis) is Australia’s second-longest snake species, but remains one of the least-known of the world’s pythons.
Aims. We sought to use non-systematically collected data from multiple sources to evaluate Oenpelli python population trends and habitat associations, and to assess its conservation status.
Methods. We identified apriori biases in data and evaluated their influences on environmental models and temporal variability in reporting patterns. We then used these findings to assess the conservation status of this species, identify knowledge gaps, and refine future survey and monitoring methods.
Key results. Oenpelli python records were strongly associated with monsoon rainforest, sandstone outcrops and perennial streams, irrespective of detection biases. Total area of occupancy was estimated to be 19 252 km2. Detection patterns were strongly seasonal and associated with periods of low rainfall and low moonlight, informing better-targeted survey and monitoring methods with improved sensitivity.
Conclusions. Oenpelli pythons have a highly fragmented distribution owing to their strong association with monsoon rainforest. This habitat is likely to provide more food resources and refuge from high temperatures than are the surrounding savanna woodlands. Detection probability should improve by surveying Oenpelli pythons in September on moonless nights and following periods of high rainfall. Taking a precautionary approach, the Oenpelli python qualifies as Vulnerable under IUCN criteria, supporting its current Red List and Northern Territory Government status.
Implications. Non-systematically collected data on poorly known species can be used to improve conservation assessments where there may otherwise be high uncertainty. The present study also highlighted the paucity of ecological knowledge of large iconic snake species globally.
Context. Camera traps are one of the most popular tools used to study wildlife worldwide. Numerous recent studies have evaluated the efficiency and effectiveness of camera traps as a research tool. Nonetheless, important aspects of camera-trap methodology remain in need of critical investigation. One such issue relates to camera-trap viewshed visibility, which is often compromised in the field by physical obstructions (e.g. trees) or topography (e.g. steep slopes). The loss of visibility due to these obstructions could affect wildlife detection rates, with associated implications for study inference and management application.
Aims. We aimed to determine the effect of camera-trap viewshed obstruction on wildlife detection rates for a suite of eight North American species that vary in terms of ecology, commonness and body size.
Methods We deployed camera traps at 204 sites throughout an extensive semi-urban park system in Cleveland, Ohio, USA, from June to September 2016. At each site, we quantified camera-trap viewshed obstruction by using a cover-board design. We then modelled the effects of obstruction on wildlife detection rates for the eight focal species.
Key results. We found that detection rates significantly decreased with an increasing viewshed obstruction for five of the eight species, including both larger and smaller mammal species (white-tailed deer, Odocoileus virginianus, and squirrels, Sciurus sp., respectively). The number of detections per week per camera decreased two- to three-fold as visibility at a camera site decreased from completely free of obstruction to mostly obstructed.
Conclusions. These results imply that wildlife detection rates are influenced by site-level viewshed obstruction for a variety of species, and sometimes considerably so.
Implications. Researchers using camera traps should address the potential for this effect to ensure robust inference from wildlife image data. Accounting for viewshed obstruction is critical when interpreting detection rates as indices of abundance or habitat use because variation in detection rate could be an artefact of site-level viewshed obstruction rather than due to underlying ecological processes.
Context. Pest species are a widespread environmental and biodiversity threat and understanding people’s attitudes towards managing pests is critical for nature conservation. Attitudes towards pest species and their management are often contextually dependent on the species and location, and no domain-free measure is currently available. This prevents straightforward comparisons of studies and generalisation of attitudes towards pest species globally.
Aim. Undertake initial psychometric tests of a unidimensional pest-management attitude (PMA) scale in three community samples from the two largest cities of New Zealand. The PMA scale comprises statements intentionally absent of specific reference to pest species or pest-management methods, and avoids terminology that has the potential to become outdated, as a result of evolving management methods and technology or the emergence of new pests. This broad focus aims to enable the ongoing use of the scale, within differing geographical contexts.
Method. Two studies tested the psychometric properties of the PMA scale. Tests comprise assessing the scales dimensionality through exploratory and confirmatory factor analysis, and measurement equivalence across samples. Internal consistency was tested through Cronbach’s α, and demographic and context-specific measures were used to validate the scale using correlation measures.
Results. Exploratory and confirmatory factor analyses confirmed the nine-item, one-factor model of the PMA scale in Study 1 (n = 1190). Measurement and structural invariance of the one-factor model was confirmed across two distinct samples in Study 2 (n = 739 and 705). Internal consistency (Cronbach’s alphas = 0.73 to 0.81) and criterion-related validity of the PMA scale was supported in both studies, with greater PMA scores being associated with membership of a conservation or environmental organisation, active participation in conservation over the past 12 months, active actions for pest control, and not owning a pet.
Conclusions. Results demonstrated high construct and criterion validity of the PMA scale, which might have powerful global utility as a context-independent measure of attitudes to pest species and their management.
Implications. Through generalising the social components of pest management, regardless of target species or method, there is potential to unify global studies in pest management.
Context. Data obtained from camera traps are increasingly used to inform various population-level models. Although acknowledged, imperfect detection probabilities within camera-trap detection zones are rarely taken into account when modelling animal densities.
Aims. We aimed to identify parameters influencing camera-trap detection probabilities, and quantify their relative impacts, as well as explore the downstream implications of imperfect detection probabilities on population-density modelling.
Methods. We modelled the relationships between the detection probabilities of a standard camera-trap model (n = 35) on a remotely operated animal-shaped soft toy and a series of parameters likely to influence it. These included the distance of animals from camera traps, animal speed, camera-trap deployment height, ambient temperature (as a proxy for background surface temperatures) and animal surface temperature. We then used this detection-probability model to quantify the likely influence of imperfect detection rates on subsequent population-level models, being, in this case, estimates from random encounter density models on a known density simulation.
Key results. Detection probabilities mostly varied predictably in relation to measured parameters, and decreased with an increasing distance from the camera traps and speeds of movement, as well as heights of camera-trap deployments. Increased differences between ambient temperature and animal surface temperature were associated with increased detection probabilities. Importantly, our results showed substantial inter-camera (of the same model) variability in detection probabilities. Resulting model outputs suggested consistent and systematic underestimation of true population densities when not taking imperfect detection probabilities into account.
Conclusions. Imperfect, and individually variable, detection probabilities inside the detection zones of camera traps can compromise resulting population-density estimates.
Implications. We propose a simple calibration approach for individual camera traps before field deployment and encourage researchers to actively estimate individual camera-trap detection performance for inclusion in subsequent modelling approaches.
Context. The common brushtail possum (Trichosurus vulpecula) is a protected native species in Australia that can access buildings in urban areas and cause considerable damage or disruption to building occupants. Although several strategies to discourage this species from entering buildings have been recommended, few have been evaluated empirically.
Aims Our study aims to analyse how landscaping and building construction influence occupancy of buildings by the common brushtail possum.
Methods. We collated reports of possums occupying 134 buildings over 12 years on the campus of The Australian National University (ANU), in the Australian Capital Territory (ACT). We used generalised linear modelling (GLM) to identify associations between the total number of reported possum-related incidents for buildings and a range of landscape and building characteristics.
Key results. Controlling for the effect of building size, we found that the number of reported possum-related incidents in buildings was positively associated with the percentage of tree and shrub canopy cover within the calculated home-range buffer distance of 49 m from buildings, length of canopy overhanging roofs and building age, and negatively associated with tree species richness and number of trees with natural hollows and nest boxes within 49 m of buildings. There were likely to be more possum-related reports from buildings in areas where the dominant tree genus was native, buildings with parapets (walls extending above the roof), buildings with structures penetrating from the roof, buildings with tile roofs and gable roofs.
Conclusions. A combination of suitable habitat surrounding buildings, suitable access to the roofs of buildings and weak points in building roofs (e.g. parapets, roof penetrations), makes them more vulnerable to occupancy by the common brushtail possum.
Implications. Our results provided clues for managing existing buildings, or designing new buildings, in a way that may reduce the likelihood of occupancy by the common brushtail possum. Our study also demonstrated how building-maintenance records can be used to address human–wildlife conflict over time.
Context. Wild dogs, including dingoes and dingo cross-breeds, are vertebrate pests when they cause financial losses and emotional costs by harming livestock or pets, threaten human safety or endanger native fauna. Tools for lethal management of these animals currently include aerial baiting with poisoned baits. In New South Wales (NSW), Australia, aerial baiting was previously permitted at a rate of 40 baits km−1 but a maximum rate of 10 baits km−1 was subsequently prescribed by the Australian Pesticides and Veterinary Medicines Authority. The efficacy of these baiting rates has not been quantified in eastern Australia, undermining the value of the policy and rendering adaptive management efforts difficult, at best.
Aim. To quantify the mortality rate of wild dogs exposed to aerial baiting at historic and currently approved rates, i.e. 40 baits per kilometre and 10 baits per kilometre, respectively.
Methods. Wild dog mortality rates were measured at sites in mesic north-eastern NSW, where aerial baiting was applied to control wild dogs and contrasted with sites and individuals where no baiting was undertaken. In total, 132 wild dogs were trapped and fitted with GPS-VHF telemetry collars before annual aerial baiting programs. Collars were used to locate animals after aerial baiting and to determine the fates of individuals.
Key results. 90.6% of collared wild dogs exposed to aerial baiting at 40 baits km−1 died, whereas only 55.3% of those exposed to 10 baits km−1 died (Welsh’s t = 4.478, P = 0.004, v = 6.95). All wild dogs that were not exposed to toxic baits survived during the same periods.
Conclusion. Managers using aerial baiting to maximise wild dog mortality in mesic south-eastern Australia should use 40 baits km−1 rather than 10 baits km−1.
Implications. Wild dog population reduction for mitigation of livestock and faunal predation requires the application of efficacious control. The currently prescribed maximum aerial baiting rate of 10 baits km−1 is inadequate for controlling wild dog populations in mesic forest environments in NSW.
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