Suchergebnisse

Artificial food patches were used to examine whether red bellied-pademelons (Thylogale billiardierii) and Bennett's wallabies (Macropus rufogriseus rufogriseus) altered their foraging behaviour in an open habitat (a young plantation) in response to distance from cover, used as a surrogate for predation risk. Analyses using the full dataset showed no significant relationship between the amount of food eaten at a station and any of the cover variables. In contrast, regression analyses of the upper bounds dataset indicated that both increased distance from windrow (2.5-m-high stacks of burnt wood) and from nearest cover (windrow or forest at plantation edge) significantly reduced the amount of food consumed at a station. This indicates that distance from cover acts as a constraint on the amount of food eaten. When the feeding-station data were overlayed onto a map of scat densities across the study site, the amount of food eaten was positively related to the density of scats of both red-bellied pademelons and Bennett's wallabies. Our results demonstrate that these macropods trade-off increased foraging benefits in order to forage closer to protective cover. Furthermore, they represent the first time that artificial food patches, with progressively decreasing reward per search effort, have been used to assess foraging behaviour in macropods. This opens up a wide range of research opportunities aimed at examining macropod foraging, with both ecological and practical applications.

Agricultural riparian zones are often vulnerable to weed invasion and degradation of the physical streambank character through the trampling of livestock. Riparian zone restoration seeks to improve habitat biodiversity, minimise streambank erosion and improve water quality. In order for this to be effective land managers need to broadly understand the connections between riparian systems and adjoining agricultural ecosystems and to understand the habitat requirements of wildlife species adapted to the evolving riparian landscape. Common wombats (Vombatus ursinus) are abundant in the riparian agricultural landscapes of south-eastern Australia, but there is concern about their persistence in other landscapes. To understand the importance of riparian characteristics for wombats, we examined five physical and five vegetative characteristics associated with abundance of wombat burrows in the riparian zone of an agricultural landscape in south-eastern New South Wales, using two independent datasets. The abundance of wombat burrows increased substantially with increasing shrub cover in both datasets. There was weaker but consistent support for an association between wombat burrows and stream order and vegetation width. There were more burrows per metre by high than low order streams and burrows were most abundant at an intermediate vegetation width. In one of the two datasets, burrow abundance declined as the proportion of native shrubs in the shrub layer increased. As wombats are generally limited to riparian buffers in agricultural landscapes, these results are important as a first step toward managing and restoring the riparian zone. Restoration strategies, for example, may need to consider retaining patches of shrubs, even if they are weeds, whereas native shrubs are established in interspersed patches along larger rivers, in order to maintain suitable wombat habitat.

Abstract Context Wildlife surveys often rely on a single live-capture technique to sample animal populations. Yet, animal personality (e.g. bold vs shy) can drive heterogeneity in capture probability, leading to biased sampling during live-capture trapping surveys. Aims We tested whether a personality-related capture bias is similar between two live-capture techniques, or whether techniques with different capture mechanisms are biased towards certain spectrums of personality. Methods We compared two live-capture techniques commonly used for surveying lizards, namely, noosing and pitfall traps. Techniques were deployed several days apart to survey populations of a desert-dwelling agamid, the military dragon, and we used outdoor open-field arenas to test for personality traits relating to boldness, activity and exploration. Key results We found that noosing and pitfall traps sampled distinctly different spectrums of personality, with no individuals being captured by both techniques. Unexpectedly, noosing, which involved people approaching dragons to capture them, was biased towards shyer individuals that stayed close to shelter. In contrast, pitfall traps, which were generally set in open areas, were biased towards capturing individuals that moved further from shelter. Conclusions We demonstrated that different live-capture techniques can be biased towards different spectrums of personality. We attribute the relationship between personality and technique to an interaction between the capture mechanisms of each technique and individual perceptions of risk and microhabitat use. Implications To overcome biased and selective sampling and target individuals along a broad spectrum of personality, surveys should use complementary techniques that vary in their capture mechanisms.

Context
Fire and grazing have complex and interacting impacts on food resources available to endangered herbivores and can potentially be manipulated as part of conservation strategies.

Aims
We examined the interacting impacts of fire and grazing on the food resources available to a colony of endangered brush-tailed rock-wallabies (Petrogale penicillata) to test fire as a potential management tool.

Methods
We conducted two manipulative experiments using a repeated-measures split-block design. We measured the effects of grazing and strategic burning on total vegetation biomass and on particular plants selected by rock-wallabies. In the first experiment we measured the impact of rock-wallaby grazing alone. In the second experiment we measured grazing impacts by both rock-wallabies and potentially competitive sympatric macropods. Grazing was manipulated with three treatments: grazed (open), ungrazed (fenced) and procedural control (half fence).

Key results
In both experiments, burning resulted in greater above-ground biomass of plants selected by rock-wallabies. The response of different plant functional groups to fire was staggered, with forb biomass peaking early and browse biomass increasing above unburnt levels a year after burning.

Conclusions
Despite the limited grazing pressure exerted by the small colony of rock-wallabies in Experiment 1 we detected a negative grazing effect on forbs growing after fire in burnt plots. In Experiment 2, grazing pressure was much more marked due to the high densities of sympatric macropods. In this case, while burning resulted in greater biomass of plants selected by rock-wallabies, grazing (predominantly by sympatric macropods) negated this effect.

Implications
Small patchwork burning can be a useful tool to improve food resources for brush-tailed rock-wallabies, with effects sustained over more than two years. However, when rock-wallabies are sympatric with possible competitor species, the grazing impacts of sympatric macropods may cancel out any benefits to rock-wallabies.

Context Monitoring programs provide valuable information on wildlife populations, thereby underpinning strategies for conservation and control. For threatened species, where every animal represents a substantial portion of the population, representative sampling is vital. One fundamental challenge during sampling is understanding drivers of survey bias; for instance, behavioural heterogeneity in trap response. Methods such as capture–mark–recapture have long been used to estimate capture and recapture heterogeneity; yet, this method, like many others, is able to gather data only from the trappable and re-trappable portion of the population; a problem that presents a particular challenge for small or vulnerable populations. A greater understanding of why biases arise can result in improved survey methods, more reliable survey data and increased modelling accuracy. Aims We focus on an endangered species with unusually high recapture probabilities (0.78–0.92), namely, the mountain pygmy-possum (Burramys parvus). Specifically, we examine whether, within a single trapping session, a recapture bias exists either as a function of past trapping experience or personality. Methods We tested whether recapture probability differs among cohorts with different capture histories ('known' animals captured during trapping sessions in previous years vs 'new' animals trapped for the first time in this study). We also tested for individual personality, general risk-taking behaviour during foraging, and subsequent links to recapture probability. Key results Recapture probability was significantly affected by cohort. New animals had lower probabilities of recapture and took fewer risks during foraging than did known animals. Although personality did not significantly influence recapture probability, it did influence risk-taking during foraging. Conclusions Despite high recapture probability within the populations, captures were significantly skewed towards a subset of the population, likely being due to different perceptions of risk among individuals. Implications Understanding potential sources of bias during live-capture surveys is the initial step towards modifying and improving surveys to reduce sampling biases and to ensure representative population sampling.

Context Wildlife is ubiquitous in urban environments, resulting in frequent interactions with humans and human infrastructure. The result of these interactions is often negative, in the form of road injury, orphaning of dependent young or eviction from natural home ranges. Wildlife rehabilitation programmes are devised to counter these negative interactions. However, the success of current management strategies is rarely assessed. Aims We aimed to determine whether short-term survival of juvenile hand-reared common brushtail possums (Trichosurus vulpecula) released in the wild was a function of (1) intrinsic factors such as sex, individual personality and level of human habituation, and (2) extrinsic factors such as release practice (soft vs hard-release) or location (urban vs rural). We also evaluated the relationship between habituation to humans and time spent in care by possums, if presence of conspecifics during the rehabilitation process influenced the development of individual personality, and if this differed in hand-raised animals compared with wild individuals. Methods We radio-tracked and monitored 20 hand-reared juvenile possums (10 females and 10 males) for up to 40 days after release in the wild. Key results Eight possums (40%) survived until the end of the study, nine possums (45%) were killed by foxes or had to be returned into care and three possums (15%) had unknown fates (i.e. lost VHF signal). We found that more exploratory individuals and those less human-habituated were more likely to be successful in the wild in both rural and urban areas, whether or not they were hard or soft released. Conclusions Our results suggest that personality is a key criterion to consider when evaluating the success of rehabilitation programmes. Behavioural traits of hand-reared brushtail possums differed significantly from those of wild individuals, showing that captive conditions can affect the development of personality. Hand-reared possums that spent more time in care were also more likely to display highly human-habituated behaviours. Implications By demonstrating which factors influence success of hand-reared wildlife after release in the wild, our results help in evaluating current rearing and release practices, and improve the evidence base for developing best practice wildlife rehabilitation guidelines.

Abstract Context Providing wildlife with supplementary water is a conservation technique that offers an immediate positive impact to animals. However, the potential negative impacts should be assessed. Aims We aimed to assess the potential negative effects of water stations on visiting wildlife due to the risk of predation and disease transmission. Methods We assessed potential benefits and costs of water supplementation in rural Australia by investigating the behavioural response of animals, at koala (Phascolarctos cinereus) water stations, to weather and to previous visitor species. To determine the risk of disease transmission, water and swab samples were taken from the water stations. Faecal contamination was quantified, and real-time PCR was used to identify various pathogens, including Chlamydia. Key results We found that koalas, brushtail possums (Trichosurus vulpecula) and foxes (Vulpes vulpes) responded to hot, dry weather with longer visits to water stations, indicating a benefit of water supplementation to native wildlife, but also to invasive species. Native animals did not alter their behaviour when their visits were preceded by another species, even when this was a potential predator. The presence of pathogens (i.e. Chlamydia and C. perfringens) at the stations did not depend on the number of species that visited but was higher in summer (December to February), representing a potential risk of disease transmission. Conclusions Water stations are an effective conservation tool because they can benefit threatened species during hot, dry weather, but there are risks associated with using supplemental water. Implications Although potential risks are low, they should still be considered. Efforts should be taken to exclude invasive species and water stations should be cleaned regularly while appropriate personal protective equipment is worn.

Abstract Context Precise and accurate estimates of animal numbers are often essential for population and epidemiological models, as well as for guidance for population management and conservation. This is particularly true for threatened species in landscapes facing multiple threats. Estimates can be derived by different methods, but the question remains as to whether these estimates are comparable. Aims We compared three methods to estimate population numbers, namely, distance sampling, mark–recapture analysis, and home-range overlap analysis, for a population of the iconic threatened species, the koala (Phascolarctos cinereus). This population occupies a heavily fragmented forest and woodland habitat on the Liverpool Plains, north-western New South Wales, Australia, on a mosaic of agricultural and mining lands. Key resultsAll three methods produced similar estimates, with overlapping confidence intervals. Distance sampling required less expertise and time and had less impact on animals, but also had less precision; however, future estimates using the method could be improved by increasing both the number and expertise of the observers. ConclusionsWhen less intrusive methods are preferred, or fewer specialised practitioners are available, we recommend distance sampling to obtain reliable estimates of koala numbers. Although its precision is lower with a low number of sightings, it does produce estimates of numbers similar to those from the other methods. However, combining multiple methods can be useful when other material (genetic, health and demographic) is also needed, or when decisions based on estimates are for high-profile threatened species requiring greater confidence. We recommend that all estimates of population numbers, and their precision or variation, be recorded and reported so that future studies can use them as prior information, increasing the precision of future surveys through Bayesian analyses.

Context
There is growing recognition of the importance of animal personality in wildlife ecology and management. Individuals that differ consistently in their behaviours from others of the same population are considered to exhibit different personalities. Personality can be easily quantified with repeat tests on animals held in captivity. However, captive-based tests may not always be possible for logistical reasons and tests conducted in captivity can alter naturally occurring behaviours. Development of methods to assess personality in the field over short-term capture is an important alternative to long-term captive tests.

Aims
To develop and refine field-based tests that can be used to easily define personality traits of wild common brushtail possum (Trichosurus vulpecula), eliminating the need to bring individuals into captivity for an extended period of time.

Methods
We developed a series of short-term capture protocols to quantify personality traits of the common brushtail possum in the field, using handling-bag tests, modified open-field tests, trap-behaviour tests and release tests.

Key results
Personality traits of brushtail possums could be measured in several different ways, but refining methods was crucial to reveal traits efficiently. Behaviours related to several personality traits (boldness, docility and activity/exploration) could be measured rapidly in the field with our methods, and were repeatable over time.

Conclusions
Rapid, reliable and easy-to-perform quantification of personality of brushtail possums in the field is possible. This may sometimes be the only available option, and has advantages over long captive trials in terms of animal welfare and cost.

Implications
The present study provides a baseline for future research on the personality of common brushtail possums and its application to management and control strategies for the species.