Suchergebnisse

Context Accurately estimating wildlife roadkill is necessary to compare different roads, periods, and species, and to plan and assess mitigation effectiveness. We must account for the two main sources of errors associated with carcass sampling – carcass detection and persistence. Open-population models are used to estimate abundance, survival probabilities, and recruitment in living animal populations, accounting for imperfect detection, and they can be used in the context of animal fatalities. Aims The aim of this study was to explore an open-population approach to estimate comparable roadkill rates from carcass capture–recapture data, accounting for carcass detection and persistence. Methods We surveyed carcasses of the white-eared opossum (Didelphis albiventris) and black-and-white tegu lizard (Salvator merianae) on four road stretches using two sampling designs with different number of visits and sampling sessions. Carcasses were marked to be recaptured over visits within the same sampling session, resulting in a capture history for each carcass. Encounter history data were modelled using the superpopulation formulation of the open-population capture–recapture model under Bayesian inference for different datasets. A daily roadkill rate per kilometre was derived from the model entry probability estimate. Key results We estimated a daily roadkill rate with 1501 captures from 447 opossum carcasses and 511 captures from 218 tegu carcasses. For full data, mean carcass detection over the sessions ranged from 0.49 to 0.85 for the opossum and from 0.27 to 0.80 for the tegu, and mean carcass persistence ranged from 0.60 to 0.94 for the opossum and from 0.64 to 0.91 for the tegu. Scenarios with more occasions and captures increased precision of roadkill rates. Conclusions We were able to explicitly estimate roadkill rates using an open-population capture–recapture model under a Bayesian framework. It provides accurate roadkill numbers for a known time frame and road extension, accounting for imperfect detection and its associated uncertainty. Under scenarios of few carcasses, users should consider a higher number of occasions. Implications Not addressing carcass sampling errors or simplistically addressing them (e.g. only once during the study period) could mislead mitigation efforts. The approach used here can be used to estimate fatalities in other locations, such as windfarms and powerlines, for which repeated observations of marked carcasses are an option.

Context The introduced red fox has driven the decline or extinction of numerous wildlife species in Australia, yet little information exists on the population densities of foxes in most ecosystems. Fox monitoring programs will differ widely depending on the goals of management, which, in turn, will determine whether the appropriate metric is a density estimate, or some proxy thereof, and the time and resources required. Aims This study aims to assist wildlife managers to design fit-for-purpose monitoring programs for foxes by providing a better understanding of the utility and precision of various monitoring methods. Methods We surveyed foxes monthly over four consecutive years in a semi-arid region of Australia by using sand plots, camera traps and GPS telemetry. The resultant data were used to produce population estimates from one count-based method, two spatially explicit methods, and two activity indices. Key results The incorporation of GPS-collar data into the spatial capture–recapture approaches greatly reduced uncertainty in estimates of abundance. Activity indices from sand plots were generally higher and more variable than were indices derived from camera traps, whereas estimates from N-mixture models appeared to be biased high. Conclusions Our study indicated that the Allen–Engeman index derived from camera-trap data provided an accurate reflection of change in the underlying fox density, even as density declined towards zero following introduction of lethal control. This method provides an efficient means to detect large shifts in abundance, whether up or down, which may trigger a change to more laborious, but precise, population monitoring methods. If accuracy is paramount (e.g. for reintroduction programs) spatially explicit methods augmented with GPS data provide robust estimates, albeit at a greater cost in resources and expertise than does an index. Implications Our study demonstrated that the shorter the survey period is, the greater is the likelihood that foxes are present but not detected. As such, if limited resources are available, longer monitoring periods conducted less frequently will provide a more accurate reflection of the underlying fox population than do shorter monitoring periods conducted more often.

Context Understanding habitat suitability for feral animals across a landscape is important for conservation planning because the spatial and temporal availability of water provides critical limits to native biodiversity and the processes that threaten it. Previous attempts to support management actions on feral pig populations through predictions of population abundance, distribution and seasonal resource constraints have been confounded by a lack of knowledge, classification and mapping of waterholes – which are critical to their survival. Aims In this paper, we aimed to apply a waterhole classification scheme for feral pig management to address gaps in our understanding of water and food availability through space and time, at scales relevant to feral animal movement and resource use. Methods We utilise an attribute-based waterhole classification scheme for ecosystem-based management by defining a waterhole typology of feral pig habitat suitability and applying it spatially. Key results Five attributes (water permanence, predictability of inundation, oceanic influence, dominant vegetation and shading) reflect many of the critical requirements for feral pig habitat in northern Australia. The attributes directly relate to the environmental constraints that exert population and behavioural pressure on feral pigs. These attributes were applied spatially in a specific hierarchy to group waterholes into 21 types. Conclusions A waterhole typology that characterises within the context of their suitability for feral pig populations is foundational for systematic adaptive management and monitoring programs that aim to reduce the impact of threatening processes on freshwater ecosystems. Implications Refining the mapping of important feral pig habitat variables (water and food) will greatly improve modelling approaches that aim to support data-driven management approaches, such as connectivity analysis and estimating population dynamics to inform culling programs. Here we demonstrate a significant increase in overlap with known feral pig distributions using a much smaller mapped effective management area when compared with previous best available spatial products.

Context Translocation is a common management strategy for wildlife populations, yet hard-release of reptiles, including box turtles (Terrapene spp.), has often proven ineffective due to homing attempts and wandering. Soft-release translocation has been presented as a possible method for mitigation of the negative effects of hard-release translocation, but studies incorporating standard soft-release strategies have produced mixed results and often see persistent homing attempts by soft-released study animals. Aims The aim of this study was to examine long-term holding (>1 year) of box turtles at an off-site location prior to translocation as a means to reduce homing attempts and wandering commonly observed in immediate-release box turtles. Methods We radiotracked translocated Terrapene carolina triunguis to compare movements of nine immediate-release box turtles and nine box turtles that had been maintained for >1 year at a nearby off-site holding facility (long-term holding) prior to a 750–1000 m translocation. Key results Box turtles held long-term before a short-distance translocation moved significantly shorter distances each day post-release than immediate-release turtles. Turtles held long-term moved in non-directional, random orientations, whereas immediate-release turtles exhibited consistent directionality in movements back towards their initial capture (home) locations. Conclusions Our results demonstrated that turtles held off-site remained within the translocation site more reliably than the immediate-release turtles, which had a higher tendency to home. Implications Long-term holding of turtles prior to translocation could significantly reduce homing responses and wandering, thus increasing translocation efficacy while reducing intensity of post-translocation management.

Context Recent declines in small game hunting participation are concerning because of the resulting decline in conservation funding generated from hunting. Combatting hunting participation declines requires understanding what impacts hunters' satisfaction. Literature on hunter satisfaction has primarily focused on big game hunters, elements of which may not apply to small game hunters. Aims The objective of this study was to assess the impact of various harvest and non-harvest factors on Tennessee small game hunters' satisfaction. Methods After the 2019–2020 small game hunting season ended, a sample of 15 115 Tennessee hunters and trappers was asked to participate in a mix-mode questionnaire related to their expectations, harvest, motivations, constraints, and satisfaction. Key results In total, 3994 individuals responded to the questionnaire and 1440 reported they participated in the 2019–2020 hunting and trapping season, 634 of which hunted small game. A path analysis showed that small game hunters' seasonal satisfaction was influenced by expectations, appreciative motivations, structural and interpersonal constraints, satisfaction with the number of game animals seen and harvested, use of public land, and harvest success. Conclusion Various activity-related factors significantly impact small game hunters' seasonal satisfaction. Implications These findings shed light on the various factors that influence small game hunters' seasonal satisfaction and could help wildlife agencies develop programming to help retain current small game hunters. To improve small game hunters' seasonal satisfaction, we suggest agencies focus on addressing structural constraints, fostering realistic expectations, and providing opportunities to fulfil appreciative motivations.

Context Carrion is a high-energy and nutrient-rich resource that attracts a diverse group of vertebrate scavengers. However, despite the carrion pool being highly seasonal in its availability, there is little understanding of how scavengers utilise carcasses across all four seasons. Aim To assess how season influences carcass-detection times by vertebrate scavengers and their rates of scavenging. Methods We used remote cameras to monitor vertebrate scavenging at 15 eastern grey kangaroo (Macropus giganteus) carcasses in four consecutive seasons (summer, autumn, winter, and spring; total 58 carcasses) in the Australian Alps. Key results In total, 745 599 remote-camera images were captured, within which 34 vertebrate species were identified, nine of which were recorded to actively scavenge. Time to first detection of carcasses by vertebrate scavengers was 5.3 and 9.6 times longer during summer (average 144 h) than during spring (average 34 h) and winter (average 24 h) respectively. Rates of vertebrate scavenging were highest in winter and spring, with brushtail possums (Trichosurus vulpecula) accounting for 78% of all scavenging events during winter, and ravens (Corvus spp.) accounting for 73% during spring. High rates of carcass use by these mesoscavengers may reflect a scarcity of other food sources, the demands of their breeding season, or a relative absence of scavenging by larger dominant species such as dingoes (Canis dingo) and wedge-tailed eagles (Aquila audax). Conclusions These findings demonstrate the highly seasonal nature of vertebrate scavenging dynamics in an alpine ecosystem, and that mesoscavengers, not apex scavengers, can dominate the use of carcasses. Implications Accounting for the effects of season is integral to understanding the way animals utilise carcasses in alpine and other strongly seasonal environments; and for developing further our knowledge of ecosystem processes linked to decomposition.

Context Coxiella burnetii is suspected as a novel pathogen contributing to decreased pup production in Australian fur seals (Arctocephalus pusillus doriferus). It has recently been described from a single breeding colony in Bass Strait, has previously been associated with two decreasing populations of northern hemisphere pinnipeds and is a known reproductive pathogen. Data around its disease ecology in marine mammals are sparse. Aims To determine whether environmental DNA (eDNA) can be used to survey for C. burnetii in Australian fur seal breeding colonies. To determine whether C. burnetii in Australian fur seals is the same genotype as terrestrial Australian C. burnetii. Methods Soil samples were collected from Kanowna Island and Seal Rocks. Placental samples were collected from Kanowna Island. Soil was evaluated for eDNA using a quantitative polymerase chain reaction (qPCR) for com1 gene. Placental samples were evaluated with com1, htpAB and IS1111 markers. Multiple-locus variable number of tandem repeats analysis for three microsatellite loci (ms-24, ms-28 and ms-33) was used to determine relatedness to Australian C. burnetii genotypes. Key results eDNA results varied between pre-and post-pupping at Seal Rocks. When targeting the com1 gene, the post-pupping prevalence at Kanowna Island and Seal Rocks was 59.6% and 90%, respectively. eDNA PCR inhibition of samples was low at 1.9%. There was very poor, sporadic to absent IS1111 amplification in placental samples. The com1 and htpAB qPCRs had an overall prevalence across placental samples of 39.2% and 56.7% respectively. In 90.1% of placental samples (n = 11), the ms-28 locus amplified. Neither ms-24 nor ms-33 amplified. Conclusions eDNA is an effective tool to survey Australian fur seal breeding colonies in the post-pupping period for C. burnetii. The prevalence appears to be much higher in the Seal Rocks colony than in the Kanowna Island colony. It appears that this is not a terrestrial Australian genotype but rather closely related to genotypes detected in marine mammals in the northern hemisphere. Implications This research significantly expands our ability to survey for C. burnetii in Australian fur seals and other marine mammals. It highlights knowledge gaps in our understanding of the disease ecology and phylogeny of C. burnetii in marine mammals.

Context The spatio-temporal partitioning of large carnivores is influenced by interspecific competition and coexistence within small, enclosed reserves. Lions (Panthera leo), spotted hyaenas (Crocuta crocuta) and leopards (Panthera pardus) are the three largest African carnivores and have the greatest potential for intra-guild competition, particularly where space is limited. Aim To investigate the spatio-temporal partitioning between lions, spotted hyaenas and leopards in a small (~75 000 ha), enclosed nature reserve, Madikwe Game Reserve (Madikwe), South Africa. Methods We deployed 110 camera traps (baited n = 55 and unbaited n = 55) across Madikwe from 26 August 2019 until 6 May 2020. Von Mises kernel density plots were used to investigate daily temporal partitioning among the three species. A multiple-species, single-season occupancy model was used to investigate daily space use patterns. Key results We found both temporal and spatial exclusion between lions and spotted hyaenas on Madikwe. However, no evidence was found of spatio-temporal partitioning between lions and leopards, and spotted hyaenas and leopards. Conclusions Exploitative and interference competition on Madikwe might be high enough to warrant spatio-temporal partitioning between lions and spotted hyaenas to avoid the negative effects of intra-guild competition. Contrastingly, patterns observed between leopards and both lions and spotted hyaenas preclude the possibility of top-down control by superior carnivores. Implication These findings call for an adaptive management approach, where both carnivore and prey species compositions are constantly monitored. Management strategies such as these will allow for the conservation of valuable resources (i.e. prey species) to ensure the persistence of large carnivore populations across African ecosystems.