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Complete separation of endangered prey from introduced predators improves prey survival at the cost of reduced predator recognition and antipredator behaviours, termed 'prey naiveté'. Headstarting is a conservation strategy that has been used to improve the survival of juveniles for numerous species, whereby prey is separated from predators only in their vulnerable early life stage before release to the wild. However, by isolating prey from predators headstarting could compromise prey individuals' antipredator behaviour. Here, we evaluate the effects that headstarting has on the survival, dispersal, body condition and flight initiation distance (FID) of a terrestrial mammal, the bridled nailtail wallaby Onychogalea fraenata. Young bridled nailtail wallabies were isolated from predators in a 9.2 ha predator‐free fenced exclosure and were released into the wild once their body mass exceeded 3 kg. There was no difference in dispersal, body condition or survival of headstarted wallabies compared to wild‐raised wallabies. FID of headstarted wallabies assessed using night‐vision goggles was lower than wild‐raised wallabies in the week following release, but converged with that of wild‐raised wallabies within 4 weeks post‐release. Our results show that headstarting can be an effective conservation strategy for terrestrial mammals whose early life stages are vulnerable to introduced predators. [ABSTRACT FROM AUTHOR]

Predation is a key factor contributing to the failure of reintroductions of vertebrates but there is variation in predation risk between individuals. Understanding the traits that render some animals less susceptible to predation, and selecting for these traits, may help improve reintroduction success. Here, we test whether prior exposure to predators or specific morphological and/or behavioural attributes explained variation in post‐reintroduction survival in a moderate and low predator density environment. We exposed a population of the threatened burrowing bettong (Bettongia lesueur) to controlled densities of feral cats (Felis catus) for ≥3 years. We then conducted two translocations of cat‐exposed and control populations that had no exposure to predators to a new site where cats were present at moderate, then low density. Variation in survival of burrowing bettongs was not explained by prior predator exposure to predators or measured individual traits at moderate cat density. At lower cat densities, males died sooner and burrowing bettongs with larger hind feet survived longer. Although prior cat‐exposure did not confer a survival advantage at low cat densities, the cat‐exposed burrowing bettong population had larger hind feet (n = 44) compared to the control population (n = 45) suggesting that trait divergence between cat‐exposed and non‐cat‐exposed burrowing bettongs may not yet be sufficient for improved survival. Alternatively, prior predator exposure may not confer a survival advantage because they are "outgunned" by evolutionarily novel cats. Predation is a major problem thwarting successful reintroductions world‐wide. Exposing populations to predators over longer time periods and periodically testing survival will be required to determine whether pre‐release predator exposure prepares animals for life with novel predators. Our study highlights the importance of reducing predator activity at release sites prior to reintroduction to enable any benefits from intraspecific variation in survival traits to be realised. [ABSTRACT FROM AUTHOR]

How to manage hybridization and introgression in wild animals is controversial. Wildlife managers and researchers may often rely upon phenotypic variables such as coat colour to inform on ground management decisions. In Australia, dingoes are typically believed to be ginger in colour, and unusual coat colours such as brindle or sable are widely posited to be evidence of contemporary domestic dog hybridization. We carried out microsatellite‐based genotyping on 1325 wild canids from southeastern Australia of known coat colour to estimate the extent of domestic dog introgression. A key aim of our study was to examine the relationship between coat colour and ancestry in wild dingoes. We observed that 27.4% of our samples were dingoes with no evidence of domestic dog ancestry whilst 72.6% were dingoes with some domestic dog ancestry. Our data confirm that feral dogs, domestic dogs with no dingo ancestry, are rare in the wild, representing less than 1.5% of the population. There was no coat colour that could distinguish dingoes with or without dog ancestry from each other. Contrary to popular belief, colours such as brindle and patchy were positively associated with dingoes with no dog ancestry and were less common in dingoes of mixed ancestry. A key finding of this work is that coat colour should not be used to assess ancestry in dingoes. Further research is needed to uncover the antiquity, origin and potential adaptive value of these genomic regions. It is possible that this is a similar example of adaptive introgression as has been observed in North American wolves with black coat colour. These data add perspective to global debates about how to manage and conserve enigmatic animal populations in the presence of modern or historical introgression. [ABSTRACT FROM AUTHOR]

Pollution and pesticide use have been linked to evolution of chemical resistance and phenotypic shifts in invertebrates, but less so in vertebrates. Here we provide evidence that poisoning directed towards a mammalian carnivore, the dingo (Canis dingo), is linked to an increase in dingo body mass. We compared the skull length of dingoes, a proxy for size, from three regions where dingo populations were controlled by distributing poisoned meat baits and an unbaited region, before and after the introduction of the toxin sodium fluoroacetate (Compound 1080). Following 1080 introduction, dingo skull length increased in baited regions but not in the unbaited region. We estimate that after 1080 introduction, the skull length of female and male dingoes in baited regions increased by 4.49 and 3.6 mm, respectively. This equates to a 1.02- and 0.86-kg increase in mean body masses of female and male dingoes, respectively. We hypothesize that dingo body size has increased in baited regions due to 1080 selecting for animals with larger body size or because a reduction in dingo abundance in baited areas may have removed constraints on growth imposed by intraspecific competition and prey availability. Our study provides evidence that pesticide use can prompt phenotypic change in comparatively large and long-lived large vertebrates. [ABSTRACT FROM AUTHOR]

The conservation benefits of maintaining social groupings during and after animal translocations are unclear. Although some studies report improved post-release survival, others found no discernible influence on reintroduction success. Understanding the effects of social groupings is difficult because release methods can influence the animals' ability to maintain social groups. We explored this relationship by first studying whether release protocols influenced post-release cohesion in the communal burrowing bettong Bettongia lesueur , and then investigating whether maintenance of social cohesion conferred any post-release advantage. We released bettongs into a small (8 ha) and large (2,600 ha) area and compared the proportion that maintained social groupings in the different settings. The proportion of bettongs sharing with previous warren co-occupants was higher than expected by chance in both areas, however, a significantly higher proportion of bettongs maintained social groupings in the small (75%) compared to the large release area (13%). This suggests bettongs prefer to maintain social groupings but are unable to locate members of their group in large release areas. Bettongs that did maintain social groupings showed no difference in reproductive or health outcomes compared to those that formed new social groupings, suggesting no benefit to reintroduction success. We conclude that release protocols can influence post-release cohesion, but that greater cohesion does not necessarily confer advantages to group-living animals. To test the importance of social cohesion, further research on reintroductions should compare post-release parameters for animals released using protocols that do and do not facilitate maintenance of social groupings. [ABSTRACT FROM AUTHOR]

Recent studies suggest that apex predators play a pivotal role in maintaining healthy, balanced ecosystems. However, a criticism of studies investigating the ecological role of apex predators is that understanding does not come from manipulative experiments. Here, we use a before-after-control-impact-paired design to test predictions generated from trophic cascade theory (TCT) and mesopredator release hypothesis (MRH) by experimentally introducing dingoes into a 37-km2 paddock and measuring the resultant effects on mammal assemblages. To increase precision of parameter estimates generated by our experiment, we used a Bayesian framework which included prior information recorded from a mensurative study located in a comparable ecosystem that contrasted indices of mammal abundance where dingoes were common and rare. Results of the mensurative study were consistent with TCT and MRH. When using an uninformative prior, results of the experiment showed that dingo addition only had a negative effect on kangaroo activity. Use of an informative prior reduced uncertainty of the posterior mean parameter estimates from the experiment and suggested that red foxes were affected negatively and small mammals and rabbits were affected positively by dingo introduction. However, the prior had a strong influence on the posterior mean effect sizes for small mammals, rabbits and foxes. Opposite polarity of uninformed and prior parameter estimates for rabbits suggests that the prior was incompatible with the uninformed estimates from the manipulative experiment. Our study shows how use of logical informative priors can help to overcome statistical issues associated with low-replication in large-scale experiments, but the strong influence of the prior means that our findings were driven largely by the mensurative study. [ABSTRACT FROM AUTHOR]

Individuals often respond to threatening situations in consistently different ways and these differences may predict later translocation success. Thus, the ability to easily identify these differences prior to translocation may assist in improving conservation outcomes. We asked whether burrowing bettongs (Bettongia lesueur), a marsupial species that has undergone significant decline since the introduction of exotic predators to Australia, responded in consistently different ways to capture in traps, and if so, whether this was related to anti-predator behaviour, ranging behaviour and survival following translocation. Behavioural responses of 40 bettongs were measured and included response to removal from traps (trap docility), latency to leave a trap or bag and escape behaviour upon release. We used flight initiation distance to measure escape behaviour, and distance moved from diurnal refuges during nocturnal foraging to measure ranging behaviour. Survival was measured through radiotracking after release. Behaviours scored during removal from a trap were consistent and repeatable, and formed a behavioural syndrome with anti-predator and ranging behaviour. Less docile bettongs foraged closer to refuges and had longer flight initiation distances. Less docile bettongs were also more likely to survive after release, although the sample size of mortalities was small. Our results suggest that behaviours scored during trapping could be a useful metric for pre-release screening in translocation programs to enhance the chances of individual survival post-release. [ABSTRACT FROM AUTHOR]

Many predators are also scavengers that feed on carrion and human refuse. Therefore, the availability of carrion can elevate the abundance or activity of facultative scavengers, amplifying predation pressure on prey. On Australian beaches, fishermen often discard fish carcasses that could attract facultative scavengers, both native, such as Australian ravens C orvus coronoides, and invasive, such as European red foxes V ulpes vulpes, and result in elevated rates of predation on wildlife. We tested whether the presence of fish carcasses increased the risk of depredation for nearby nests of beach-nesting birds by deploying artificial nests in 12 subsidized and 12 control patches, spaced 1 km apart, on a beach. We placed a fish carcass in each subsidized patch, but not at control patches. In each patch, we placed two artificial nests, which resembled red-capped plover C haradrius ruficapillus nests, 80 m apart and 40 m from carcasses at subsidized patches. Nest predators were identified from tracks and predator activity near subsidized and control nests was measured by counting tracks crossing a straight transect (220 m). The activity of a native predator, the Australian raven, was 17 times higher near (<80 m) nests with fish carcasses than nests without carcasses. After 72 h, 96% of nests near carcasses were depredated compared with 30% of nests without carcasses. Ravens were identified as the culprit for 80% of depredated nests. Although other predators were present in the study area, they did not depredate artificial nests in this experiment. Previous studies have highlighted the effects of permanent and/or large-scale food resources on scavenger abundance and impact. A key management implication of our study is that even small, sparsely distributed, temporally irregular food subsidies, provided by humans, can elevate the activity and predatory impacts of facultative scavengers. [ABSTRACT FROM AUTHOR]

A sound understanding of the taxonomy of threatened species is essential for setting conservation priorities and the development of management strategies. Hybridization is a threat to species conservation because it compromises the integrity of unique evolutionary lineages and can impair the ability of conservation managers to identify threatened taxa and achieve conservation targets. Australia's largest land predator, the dingo C anis dingo, is a controversial taxon that is threatened by hybridization. Since their arrival <5000 yBP (years Before Present) dingoes have been subject to isolation, leading to them becoming a unique canid. However, the dingo's taxonomic status is clouded by hybridization with modern domesticated dogs and confusion about how to distinguish 'pure' dingoes from dingo-dog hybrids. Confusion exists because there is no description or series of original specimens against which the identities of putative hybrid and 'pure' dingoes can be assessed. Current methods to classify dingoes have poor discriminatory abilities because natural variation within dingoes is poorly understood, and it is unknown if hybridization may have altered the genome of post-19th century reference specimens. Here we provide a description of the dingo based on pre-20th century specimens that are unlikely to have been influenced by hybridization. The dingo differs from the domestic dog by relatively larger palatal width, relatively longer rostrum, relatively shorter skull height and relatively wider top ridge of skull. A sample of 19th century dingo skins we examined suggests that there was considerable variability in the colour of dingoes and included various combinations of yellow, white, ginger and darker variations from tan to black. Although it remains difficult to provide consistent and clear diagnostic features, our study places morphological limits on what can be considered a dingo. [ABSTRACT FROM AUTHOR]

The ecological impact of an invasive species can be heterogeneous through space and time. One such case in Australia involves native freshwater crocodiles Crocodylus johnstoni, which are highly sensitive to invasive cane toads Rhinella marina in some areas, whereas other populations experience little or no mortality from ingestion of the toxic toads. We studied the impact of toad invasion on three crocodile populations: one crashed, one showed a minor decrease and one appeared unaffected. We tested three hypotheses for the cause of this spatial variation in impact: differences among populations in toad-crocodile encounter rates (proximity of toads to crocodiles during spotlight surveys), differences in crocodile feeding responses (trials of prey preference in the laboratory) and differences in crocodile physiology (reduction of swim speed after receiving a dose of toad toxin). We found little divergence among populations in any of these traits: crocodiles from the three populations all encountered cane toads in the wild, and exhibited similar feeding responses and toxin tolerances. Thus, we cannot confidently identify causation for the impact heterogeneity. Reliance on alternative food resources and an ability to rapidly learn taste aversion may have allowed crocodiles to deal with toad arrival in Lake Argyle and the Daly River. Future work could usefully evaluate potential explanations for the failure of these adaptive mechanisms in the severely affected ( Victoria River) population. We suggest that spatial variation in the availability of alternative prey (and thus the willingness of crocodiles to attack a novel toxic prey item) may have contributed to that variation in impact. [ABSTRACT FROM AUTHOR]

Resources are produced in pulses in many terrestrial environments, and have important effects on the population dynamics and assemblage structure of animals that consume them. Resource-pulsing is particularly dramatic in Australian desert environments owing to marked spatial and temporal variability in rainfall, and thus primary productivity. Here, we first review how Australia's desert mammals respond to fluctuations in resource production, and evaluate the merits of three currently accepted models (the ecological refuge, predator refuge and fire-mosaic models) as explanations of the observed dynamics. We then integrate elements of these models into a novel state-and-transition model and apply it to well-studied small mammal assemblages that inhabit the vast hummock grassland, or spinifex, landscapes of the continental inland. The model has four states that are defined by differences in species composition and abundance, and eight transitions or processes that prompt shifts from one state to another. Using this model as a template, we construct three further models to explain mammalian dynamics in cracking soil habitats of the Lake Eyre Basin, gibber plains of the Channel Country, and the chenopod shrublands of arid southern Australia. As non-equilibrium concepts that recognise the strongly intermittent nature of resource pulsing in arid Australia, state-and-transition models provide useful descriptors of both spatial and temporal patterns in mammal assemblages. The models should help managers to identify when and where to implement interventions to conserve native mammals, such as control burns, reduced grazing or predator management. The models also should improve understanding of the potential effects of future climate change on mammal assemblages in arid environments in general. We conclude by proposing several tests that could be used to refine the models and guide further research. [ABSTRACT FROM AUTHOR]

In arid environments, ecological refuges are often conceptualised as places where animal species can persist through drought owing to the localised persistence of moisture and nutrients. The mesopredator release hypothesis (MRH) predicts that reduced abundance of top-order predators results in an increase in the abundance of smaller predators (mesopredators) and consequently has detrimental impacts on the prey of the smaller predators. Thus according to the MRH, the existence of larger predators may provide prey with refuge from predation. In this study, we investigated how the abundance of an endangered rodent Notomys fuscus is affected by Australia's largest predator, the dingo Canis lupus dingo, introduced mesopredators, introduced herbivores, kangaroos and rainfall. Our surveys showed that N. fuscus was more abundant where dingoes occurred. Generalised linear modelling showed that N. fuscus abundance was associated positively with dingo activity and long-term annual rainfall and negatively with red fox Vulpes vulpes activity. Our results were consistent with the hypothesis that areas with higher rainfall and dingoes provide N. fuscus with refuge from drought and predation by invasive red foxes, respectively. Top-order predators, such as dingoes, could have an important functional role in broad-scale biodiversity conservation programmes by reducing the impacts of mesopredators. [ABSTRACT FROM AUTHOR]

Fundamentally, El Niño Southern Oscillation (ENSO) is a climatic and oceanographic phenomenon, but it has profound effects on terrestrial ecosystems. Although the ecological effects of ENSO are becoming increasingly known from a wide range of terrestrial ecosystems (Holmgren et al., 2001), their impacts have been more intensively studied in arid and semiarid systems. In this brief communication, we summarize the main conclusions of a recent symposium on the effects of ENSO in these ecosystems, which was convened as part of the First Alexander von Humboldt International Conference on the El Niño Phenomenon and its Global Impact, in Guayaquil, Ecuador, from 16-20 May 2005. Participants in the symposium shared results and perspectives from research conducted in North and South America and Australia, regions where the ecological effects of ENSO have been studied in depth. Although the reports covered a wide array of organisms and ecological systems (Fig. 1), a recurring theme was the strong increase in rainfall associated with ENSO events in dry ecosystems (during the El Niño phase of the oscillation in the Americas and the La Niña phase in Australia). Because inter-annual variability in precipitation is such a strong determinant of productivity in arid and semiarid ecosystems, increased ENSO rainfall is crucial for plant recruitment, productivity and diversity in these ecosystems. Several long-term studies show that this pulse in primary productivity causes a subsequent increase in herbivores, followed by an increase in carnivores, with consequences for changes in ecosystem structure and functioning that can be quite complex. Much of the work presented at the symposium represents research that was or will be published elsewhere. However, we take this opportunity to summarize some of the main points that emerged from our presentations and the resulting discussion on the general effects of ENSO on arid and semiarid ecosystems. [ABSTRACT FROM AUTHOR]

Patch-burning is frequently advocated as a management tool to enhance the biodiversity and pasture values of spinifex (Triodia) grasslands. In this study we compare the capture rates of small mammals in habitats regenerating shortly after fire (aged 1–5 years) and in long-unburnt habitats (aged>25 years). To unravel the effects of temporally and spatially variable rainfall on capture rates, the study was replicated at three locations spaced over 50 km apart that experience different rainfall regimes. Ten species of small mammals were captured over the course of the study, between October 1999 and June 2001.Pseudomys desertorshowed a strong preference for long-unburnt habitats.Notomys alexis,Sminthopsis youngsoniandSminthopsis hirtipesshowed some preferences for regenerating habitats, but these were not consistent throughout the study. Factors indicative of temporal and spatial variation in rainfall, time and site had important effects on capture rates. High rainfalls associated with the La Niña phase of the El Niño/Southern Oscillation in 2000 increased seed production and prompted eruptions of rodent species and the carnivorousDasycercus cristicauda. The greatest numbers of captures were made at the sites that received the highest rainfalls. We conclude that patch-burning regimes do not benefit small mammals directly, but are likely to increase the resilience of‘fire-sensitive’ species that are dependent on dense spinifex by reducing the extent of wildfires. [ABSTRACT FROM AUTHOR]

Disruption to species-interaction networks caused by irruptions of herbivores and mesopredators following extirpation of apex predators is a global driver of ecosystem reorganization and biodiversity loss. Most studies of apex predators' ecological roles focus on effects arising from their interactions with herbivores or mesopredators in isolation, but rarely consider how the effects of herbivores and mesopredators interact. Here, we provide evidence that multiple cascade pathways induced by lethal control of an apex predator, the dingo, drive unintended shifts in forest ecosystem structure. We compared mammal assemblages and understorey structure at seven sites in southern Australia. Each site comprised an area where dingoes were poisoned and an area without control. The effects of dingo control on mammals scaled with body size. Activity of herbivorous macropods, arboreal mammals and a mesopredator, the red fox, were greater, but understorey vegetation sparser and abundances of small mammals lower, where dingoes were controlled. Structural equation modelling suggested that both predation by foxes and depletion of understorey vegetation by macropods were related to small mammal decline at poisoned sites. Our study suggests that apex predators' suppressive effects on herbivores and mesopredators occur simultaneously and should be considered in tandem in order to appreciate the extent of apex predators' indirect effects. [ABSTRACT FROM AUTHOR]