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Context. Some prey species can shift their daily activity patterns to reduce the risk of encountering predators, and, in turn, predators develop strategies to increase their chances of meeting prey. European rabbit (Oryctolagus cuniculus) is a key species in Iberian Mediterranean ecosystems. It is the main prey for many vertebrate predators. It is also a game species and is often the target of management measures such as translocations.
Aims. To test whether rabbits adjust their activity patterns in response to differing predation regimes in a management context.
Methods. Rabbits were translocated from a donor area, with a high rabbit density, to a release area in central Spain, with a semi-permeable fenced plot and an unfenced plot, which had no rabbits before the translocation. We estimated daily activity patterns and relative abundance index (RAI) for mesocarnivores and rabbits by using camera-traps, and calculated Jacobs selection index (JSI) to classify each species in a diel period. Additionally, we calculated the activity overlap between prey and mesocarnivores in the different areas.
Key results. Rabbits were nocturnal in the donor area, where only two mesocarnivore species were detected, red fox (Vulpes vulpes, with a high RAI) and Egyptian mongoose (Herpestes ichneumon, with a low RAI). However, in the unfenced area, where five mesocarnivore species were present, rabbits showed a crepuscular trend with two activity peaks, around sunrise and around sunset. In contrast, rabbits showed a nocturnal activity in the fenced plot, where four mesocarnivore species were detected but where only the Egyptian mongoose (strictly diurnal) had a high RAI value.
Conclusions and implications. The results suggest that rabbits in the fenced plot adapted their activity to avoid the diurnal mongooses. Conversely, rabbits in unfenced areas showed a trend towards day/twilight activity patterns as an adaptation to a diverse community of mesocarnivores. Rabbits can adapt their daily activity patterns to reduce predation risk depending on the pressure exerted by different predator species, with conservation and management implications. These adaptations would allow higher success of rabbit translocations despite the risk of predation by carnivores and could help in the management design of future translocations of this key species.
Context. Determining the most efficient detection method for a target species is key for successful wildlife monitoring and management. Driven transects and sign surveys are commonly used to monitor populations of the endangered numbat (Myrmecobius fasciatus). Camera trapping is being explored as a new method. These methods were unevaluated for efficacy and cost for numbat detection.
Aims. To compare efficacy and costing of driven transects, sign surveys and camera trapping for detecting numbats in the Upper Warren region, Western Australia.
Methods. Seven repeat sign surveys and driven transects, as well as 4 months of camera trapping, were conducted concurrently at 50 sites along three transects. Numbat detection rates and costing of the three techniques were compared, and detection probabilities were compared between sign surveys and camera trapping.
Key results. Numbat signs were detected during 88 surveys at 39 sites, exceeding camera trapping (26 detections at 13 sites) and driven transects (seven detections near five sites). The estimated probability for detecting a numbat or a sign thereof (at a site where numbats were present) ranged from 0.21 to 0.35 for a sign survey, and 0.02 to 0.06 for 7 days of camera trapping. Total survey costs were lowest for driven transects, followed by camera trapping and sign surveys. When expressed as cost per numbat detection, sign surveys were cheapest.
Conclusions. Comparative studies of survey methods are essential for optimal, cost-effective wildlife monitoring. Sign surveys were more successful and cost effective than camera trapping or driven transects for detecting numbats in the Upper Warren region. Together with occupancy modelling, sign surveys are appropriate to investigate changes in occupancy rates over time, which could serve as a metric for long-term numbat monitoring.
Implications. There is no ‘best’ method for wildlife surveys. Case-specific comparison of animal detection methods is recommended to ensure optimal methods. For the numbat population in the Upper Warren region, further studies are needed to improve numbat detection rates from camera trapping, and to test sign surveys in autumn (March to May), when surviving juvenile numbats have established their own territory and assumptions regarding population closure are less likely to be violated.
Context. Road mitigation to reduce animal–vehicle collisions (AVCs) is usually based on analysis of road survey animal carcass data. This is used to identify road sections with high AVC clusters. Large mammals that are struck and die away from a road are not recorded nor considered in these analyses, reducing our understanding of the number of AVCs and the cost–benefit of road mitigation measures.
Aims. Our aim was to develop a method to calculate a correction factor for large mammal carcass data reported through road survey. This will improve our understanding of the magnitude and cost of AVCs.
Method. Citizen scientists reported animal carcasses on walking surveys along transects parallel to the highway and reported observations using a smartphone application at three sites over a 5-year period. These data were compared with traditional road survey data.
Key result. We found that many large mammals involved in AVCs die away from the road and are, therefore, not reported in traditional road surveys. A correction factor of 2.8 for our region can be applied to road survey data to account for injury bias error in road survey carcass data.
Conclusions. For large mammals, AVCs based on road survey carcass data are underestimates. To improve information about AVCs where little is known, we recommend conducting similar research to identify a correction factor to conventionally collected road survey carcass data.
Implications. Identifying road mitigation sites by transportation agencies tends to focus on road sections with above-threshold AVC numbers and where cost–benefit analyses deem mitigation necessary. A correction factor improves AVC estimate accuracy, improving the identification of sites appropriate for mitigation, and, ultimately, benefitting people and wildlife by reducing risks of AVCs.
Context. Tree hollows are a key habitat resource for hollow-nesting species, including the northern Australian Gouldian finch (Erythrura gouldiae). Certain fire and disturbance regimes limit tree hollow availability in the northern Australian savannas.
Aims. This study investigated the influence of fire regime and vegetation structure on the density of tree hollows at Gouldian finch breeding sites.
Methods. Fire scars were mapped across breeding sites by using LANDSAT images. Vegetation plots within sites were spatially stratified according to three fire-regime attributes, namely, fire frequency, late dry-season wildfire frequency and time since the last fire. Tree hollow and vegetation structural attributes were measured at each vegetation plot. We modelled the relationship among hollow density, fire and vegetation attributes by using general linear mixed models with site as the random factor.
Key results. We found that the highest tree-hollow density was found at plots with high eucalypt tree density and cover and with the lowest frequency of late dry-season wildfires (<1 wildfire over 5 years). Tree-hollow density declined after >2 years without fire. Hollow density was not directly related to total fire frequency.
Conclusions. This study adds to previous work on grass seed resources in highlighting the importance of fire in Gouldian finch ecology. This study particularly highlighted the importance of reducing the impacts of high-intensity late dry-season wildfires because of their negative impacts on tree-hollow density, which is a key resource for breeding Gouldian finches.
Implications. We recommend the use of a network of interconnected annual patchy early dry-season prescribed burns for protecting Gouldian breeding habitat from threat of high-intensity wildfires. We do NOT recommend fire exclusion from Gouldian finch breeding habitats. This is because fire risks to hollow-bearing trees, and grass seed resources, increase with the long-term accumulation of savanna litter fuels in the absence of fire.
Context. Forest harvest practices have the potential to alter habitat available to forest fauna. One aspect of harvesting practice that has received little research attention is the effect of multiple rotations on available habitat, and its use by fauna.
Aims. We examined one component of habitat that is critical to many taxa, coarse woody debris (CWD). In forests of north-eastern New South Wales, Australia, we aimed to assess whether harvest (moderate intensity for saw-logs) frequency influences CWD levels, and whether fauna activity on CWD varies with harvest frequency and with CWD attributes.
Methods. Using habitat surveys and camera trapping, we compared CWD quantity and quality in unharvested sites with those that had been harvested once, twice and three times, and assessed fauna use of CWD.
Key results. We found significantly greater volume of non-hollow CWD, and of medium-sized pieces (15–30 cm diameter), in sites harvested three times versus unharvested sites. Camera trapping showed that the activity and composition of fauna were similar across these harvest treatments. Our results also found that a broad range of fauna used a variety of logs, including large and small logs in various states of decay.
Conclusions. Consistent with other Australian studies, our results suggested that there are no detectable impacts of harvesting on hollow or large CWD. Further studies using radio-tracking or similar methods are needed to more comprehensively assess how CWD is used by fauna.
Implications. CWD was used broadly by a range of species and should be targeted for retention under ecologically sustainable forest management practices to ensure that it continues to be present in harvested landscapes. This is particularly important in places where an intensification of practices is being considered.
Context. Lethal control through the application of 1080 baits is widely used in Australia to manage the negative impacts of wild dogs (dingoes, wild domestic dogs and their hybrids) on cattle production, but its effectiveness in this regard is not well understood.
Aims. To evaluate the efficacy of once yearly 1080 baiting on dingoes and its effects in mitigating predation and sublethal impacts on beef cattle.
Methods. A replicated experiment with two paired treatments (1080 poisoned and non-poisoned) was conducted on each of four cattle stations of 3782–10 850 km2, over 2.5 years (2000–02) in the southern Northern Territory. The study was undertaken in relatively good rainfall years.
Key results. Track-based surveys indicated that dingo abundance declined on poisoned relative to non-poisoned areas immediately following a single baiting episode. However, there was no detectable difference about 8 months after baiting. No difference was detected in observed levels of calf damage or calf loss between poisoned and non-poisoned areas.
Conclusions. The results add to the growing body of consistent evidence that contemporary dingo control practices yield little benefit to rangeland beef producers most of the time.
Implications. Routine dingo baiting (as currently undertaken) may be largely unnecessary for beef cattle producers in arid and semiarid areas. Alternative strategies and practices to reduce dingo mauling and predation impacts should be investigated using replicated and controlled field studies.
Context. Human–elephant conflict (HEC) is a major threat to Asian elephants as humans and elephants are forced to share common resources. In Sri Lanka, human-dominated landscapes adjacent to protected areas promote high rates of HEC, especially in the form of crop-foraging by elephants. Crop-foraging can be dangerous to both elephants and humans involved in the conflict. Gunfire is a common way for human communities to deter crop-foraging elephants, and gunshot wounds are commonly described in this elephant population on necropsy.
Aims. We sought to quantify and describe unique scar patterns among Asian elephants in a protected area, Wasgamuwa National Park, attributed to HEC.
Methods. We identified 38 adult female and 64 adult male elephants and recorded the age class and body condition of each with established standards. Using photographs, we counted the number, position, and relative size of all scars on each animal.
Key results. Male elephants had significantly more scars than did females, and for males, the number of scars increased progressively with age. Additionally, male elephants with higher body conditions had more scars. Finally, males tended to have more scars towards the head, especially at older ages.
Conclusions. Differences in total scar counts between the sexes in this population imply that male elephants in this area more frequently engage in HEC than do females, following observations previously described in the literature. Furthermore, the fact that male elephants acquired progressively more scars as they aged, and that fatter elephants had more scars, indicates that previous exposure to HEC may not have been a deterrent for future events among these males, and potentially, crops served as valuable food sources for these animals. Finally, the changing body locations of these scars with age in males possibly shows plastic behavioural responses during crop-foraging or lower tolerance by farmers towards habitual crop foragers.
Implications. These results emphasise the need for animal-based approaches to HEC mitigation. Similarly, conservation managers in Sri Lanka and other elephant range countries should investigate similar methods that estimate patterns of HEC to develop effective management strategies directly targeting animals most likely to engage in conflict.
KEYWORDS: bait availability monitoring, Europa Island, Population biology, rat eradication, Spatially explicit capture–recapture, tidally inundated habitats
Context. Mangroves and intertidal habitats have been identified as particularly challenging environments for bait application within both tropical and temperate environments, because bait applied to areas that are tidally inundated could degrade rapidly or become inaccessible to rats.
Aims. To determine rat density, ranging behaviour and probability of detection using different monitoring devices; additionally, to determine the availability (persistence, durability and uptake) of rodenticide baits within tidally inundated mangrove habitats.
Methods. The population biology of black rats (Rattus rattus) was studied in two contrasting mangrove habitats on Europa Island, and spatially explicit mark–recapture studies were performed to estimate densities and activity of rats. A series of bait availability trials was conducted to determine the durability of rodenticide baits on the ground and uptake in the canopy (‘bait bolas’).
Key results. Black rats were found to be abundant in mangrove, and despite daily tidal inundation, still maintained ranging behaviour consistent with rats in adjacent terrestrial habitats. Larger rodenticide bait blocks remained within tidally inundated habitat throughout tidal cycles and were available and remained palatable to rats for at least three consecutive nights, although strong bait competition occurred with crabs. Bait bolas were available in mangrove canopy exclusively to rats and consumption commenced on the first night.
Conclusions. The results provide evidence that mangrove habitats are an important habitat for rats, but the biology of rats in these habitats does not meaningfully differ from adjacent terrestrial habitats. With the use of larger rodenticide blocks, tidal inundation does not affect bait availability, but crabs remain a major competitor for these baits. Alternatively, the present study revealed that bait bolas limit bait access to rats alone. Development as an aerial eradication technology should be also recommended.
Implications. These results provide a proof of concept that eradication of rats from tidally inundated habitats such as mangrove should be possible with only small modifications to current best practice.
Context. Fire management advice for fauna conservation in protected areas must often be based on expert opinion and extrapolation from very few scientific studies. More monitoring and research are needed to better inform land managers tasked with both managing for biodiversity and managing the threat of bushfires.
Aims. To document changes in the activity of native and introduced mammal species in response to planned burns in a small, isolated woodland reserve in Tasmania.
Methods. Over a 10-year period, mammal activity was monitored before and after two separate moderate-intensity planned burns in 20-ha management blocks and in unburnt blocks of similar size by using live-trapping and camera-trapping. Vegetation density was monitored concurrently, and we also searched burnt areas for animals killed by fire.
Key results. The activity of most mammal populations was largely unaffected by the two planned burns. However, during one of the burns, over 20 rufous-bellied pademelons were directly killed as a result of a need to conduct a backburn. The population recovered after 3 years. The activity of red-necked wallabies, common brushtail possums and short-beaked echidnas generally increased across the whole study area during the 10-year monitoring period. Limited evidence suggests that eastern barred bandicoot and European rabbit activity increased after fire. No swamp rat activity was recorded in burnt areas following the planned burns. Unexpectedly they did not recolonise burnt areas and also ceased to be active in control areas for the last 3 years of the study; we hypothesise that this may be due to the increased dryness and thinning of vegetation.
Conclusions. We found that most of the mammal populations within this small, isolated reserve were resilient to the planned burning program, with no or limited short-term effect for all but one species. The absence of swamp rats from burnt or unburnt areas for the last 3 years of our study suggests that factors other than fire are also affecting this species.
Implications. Planned burning is an important tool for biodiversity conservation, but its use needs to be underpinned by empirical data because mammal fire responses are likely to be site-, time- and context-specific.
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