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In Australia many critical weight range (CWR) species are threatened by predation from the introduced Red Fox Vulpes vulpes. Understanding how these prey species respond to native predators such as the Tiger Quoll Dasyurus maculatus, and comparing their responses to foxes is important in understanding why fox predation is such a problem. Many northern hemisphere mammalian species have developed responses to the odours of the main species which prey upon them. The situation in Australia remains unclear. We looked at the effect of scenting traps with the faeces of the Tiger Quoll and the Red Fox on the capture rates of four species of CWR marsupials, the Long-nosed Bandicoot Perameles nasuta, the Southern Brown Bandicoot Isoodon obesulus, the Northern Brown Bandicoot I. macrourus and the Common Brushtail Possum Trichosurus vulpecula. None of these species responded to fox odour. However despite low capture rates, Northern Brown Bandicoots and Common Brushtail Possums were captured significantly more often i...

Summary 1. Graham & Lambin (2002) have reported on a weasel-reduction experiment, concluding that the impact of weasel predation on field vole survival was neither sufficient nor necessary to initiate and drive the cyclic decline of field vole populations in Kielder Forest, northern England. They also stated that their findings contradict conclusively the specialist predator hypothesis put forward to explain population cycles of voles in North Europe. 2. Straightforward inferences from Kielder Forest to the northern boreal zone are misleading, because the population cycles of voles in Kielder Forest differ essentially from North European vole cycles. The low amplitude of the vole cycles in Kielder Forest, their restricted spatial synchrony in comparison to northern Europe and the virtual lack of interspecific synchrony in Kielder Forest suggest that there are essential differences between the mechanisms responsible for the two types of cyclic fluctuations of voles. 3. The weasel-reduction experiment may provide a misleading picture on the role of predators, even in the Kielder Forest cycle. The experimental reduction of weasels alone may not stop the population decline of voles, because competing larger predators are expected to increase their hunting in the weasel-reduction areas. The small spatial scale of the experiment, which produced only slight, short-term differences in weasel densities between reduction and control areas, also suggests that other predators could have compensated easily for the weasels that were removed. 4. We propose a new version of the predation hypothesis to explain low-amplitude population cycles of voles in temperate Europe, including the Kielder Forest. The interaction between generalist predators and vole populations might account for these cycles because generalists can have a functional response that is destabilizing in the neighbourhood of the equilibrium point. As most generalists are orders of magnitude larger than weasels, and thus need much more food for survival, generalist-driven cycles should be characterized by high prey minima, as observed in Kielder Forest.

Habitat use of quokka (Setonix brachyurus) in the northern jarrah forest of Western Australia was determined by monitoring movements of 58 quokkas over 2 years in 5 local populations. Quokkas were largely restricted to Agonis swamps that occur patchily throughout the jarrah forest. Within swamps, they are habitat specialists, preferring early seral stages that have been burned within the previous 10 years. This preference derives from a combination of dietary requirements and refuge from predation. As swamps mature they become suboptimal, forcing quokkas to colonize new patches. Since the collapse of the metapopulation following the introduction of the European red fox (Vulpes vulpes) in the 1930s, quokkas have been forced to remain at a site because predation inhibits dispersal.

The management of wild canids (wild dogs/dingoes and foxes) presents a conservation dilemma for land managers across Australia. These canids are predators of wildlife and domestic stock but dingoes are considered native and anecdotal reports suggest that they may suppress foxes such that dingo/dog conservation may have a net benefit to wildlife. This study examines dietary and spatial interactions between wild dogs and foxes in the Greater Blue Mountains region of NSW to address the possibility of suppression through competitive exclusion by dogs on foxes. Predator diets were compared using faecal analysis as well as an analysis of 19 dietary studies from similar forest habitats in eastern Australia. Spatial relationships were examined using data from an extensive canid control programme. Diets of wild dogs and foxes showed a high degree of overlap in species taken, indicating potential for competition. But there was also evidence of resource partitioning with the size and arboreality of mammalian prey differing between the two predators. Wild dogs and foxes responded to different landscape-scale variation in the physical environment, but there was no clear evidence of large-scale differences in their distribution. At the fine scale there was a negative association between these predators that indicated possible temporal avoidance or localized habitat shifts. Therefore, there is evidence for dietary competition and fine-scale exclusion, but no support for landscape-scale exclusion of foxes by wild dogs in the Blue Mountains.

The home range and movements of the quokka Setonix brachyurus, a medium-sized macropodid marsupial, were investigated using radio telemetry. Fifty-eight quokkas from five remnant mainland populations in the northern jarrah (Eucalyptus marginata) forest of Western Australia were radio-collared and monitored for up to 2 years between 1998 and 2000. Mean (± SE) home-range sizes were 6.39 ± 0.77 ha and core ranges averaged 1.21 ± 0.12 ha. Male core home ranges were larger than those of females although not when corrected for body mass. Nocturnal ranges were larger than diurnal owing to nocturnal departures from the swamp. Ranges shifted to the edge of swamps in winter, as the swamps became inundated following rain, and toward the centre in autumn as the swamps dried. Quokka populations are thought to exist below carrying capacity at all sites and this probably caused the lack of dispersal observed in this study. We hypothesize that predation is suppressing population booms which would otherwise drive dispersal and thereby maintain metapopulation dynamics. Without dispersal to rescue unpopulated patches, we conclude that the original quokka metapopulation has collapsed and ameliatory measures are required.

There is strong debate over whether the intrinsic traits of individuals or the extrinsic environment exert the greater influence on small mammal population dynamics. We test the roles of maternal effects (an intrinsic factor) and predation risk (an extrinsic factor) in the population dynamics of wild strain house mice using a 2-factor enclosure experiment. Pre-release supplemental feeding with a high-fat diet created female treatment founders that were 6-10% heavier than controls, a condition that we predicted would be passed on as a maternal effect. Predation risk was enhanced using regular application of predator (red fox Vulpes vulpes) scats. Founder populations of six females and six males released into eight, 15 × 15 m enclosures showed near exponential population growth over 17 weeks (maximum 3 generations). But there were no responses to either treatment in terms of survival, inherited body weights, fecundity or population size. We suggest that elevated maternal condition may have only minor and transient intergenerational effects with little long-term consequence. We also suggest that the general significance of predator scats as a cue to predation risk to alter prey behaviour may have been overestimated. Hence our results question the role of either factor in causing long-term responses that influence condition to affect population processes.

The exploitation of predator signals by potential prey is well researched, but relatively little is known about how predators exploit chemical cues (either deliberate signals or waste by-products) produced by their prey. In Finland, the urine of some small rodents ( Microtus spp. and Clethrionomys spp.) is reflective in the ultraviolet range of wavelengths, and diurnal raptors with ultraviolet vision use these urine marks to track their rodent prey. This study examines the potential for such a phenomenon in Australian systems by studying the ultraviolet properties of urine from 13 native and introduced mammal species that are variously preyed upon by raptors. Urine from all 13 species displayed various levels of ultraviolet absorbance in their urine and fluorescence in the ultraviolet range. However, no signs of ultraviolet hyper-reflectance were detected, suggesting that the urine of European voles have unique ultraviolet properties. Ultraviolet-sensitive predators in Australia may be able to distinguish between species based on variation in the ultraviolet absorbance of their urine, but ultraviolet properties did not differ between prey and non-prey species, nor marsupial and placental groups. Moreover, because many natural surfaces are ultraviolet absorbing, it is unlikely that raptors could rely upon the ultraviolet properties of urine to target key prey species.

We examined the foraging behaviour and habitat use of two species of small Australian mammal (Antechinus flavipes and Sminthopsis murina) in response to predation risk in remnant eucalypt woodland. Predation risk was manipulated by providing refuge in the form of ground level wire netting to reduce risks from avian and mammalian predators. Giving-up-densities (GUD) using artificial food trays (20 mealworms in 1.5 l vermiculite) quantified the foraging behaviour in response to predation risk, by measuring the quitting harvest rate. Both A. flavipes and S. murina had lower GUDs (number of mealworms remaining) under the netting than in the open, most likely because these areas have lower predation risk. Animals also made greater visits to tracking tunnels under the netting compared to in the open. Tracking animal movements using fluorescent pigments also revealed preference for natural microhabitats that were structurally complex with animals moving most where logs and rock crevices were present. These results suggest that small mammals may use habitat structure to reduce their risks of predation. If future studies are able to demonstrate commensurate population-level responses, manipulation of habitat may be a useful management option to complement the direct control of exotic predators such as foxes and feral cats.

Predator odours and habitat structure are thought to influence the behaviour of small mammalian prey, which use them as cues to reduce risks of predation. We tested this general hypothesis for house mice, Mus domesticus, by manipulating fox odour density via addition of fox scats and habitat via patchy mowing of vegetation, for populations in 15 × 15-m field enclosures. Using giving-up densities (GUDs), the density of food remaining when an animal quits harvesting a patch, we measured foraging behaviours in response to these treatments. Mice consistently avoided open areas, leaving GUDs two to four times greater in these areas than in densely vegetated patches. However, mouse GUDs did not change in response to the addition of fox scats, even immediately after fresh scats were added. There was no interaction between fox odour and habitat use. We then tested whether habituation to fox odours had occurred, by comparing the individual responses to scats of eight mice born into enclosures with fox scats to those of eight mice born into scat-free enclosures and five wild mice. In smaller enclosures, GUDs of trays with scats did not differ from GUDs of trays without scats for any treatment. We conclude that exposure to high levels of fox odours did not alter the foraging behaviour of mice, but that mice did reduce foraging in areas where habitat was removed, perceiving predation risk to be greater in these areas than controls. We suggest further that studies using the ‘scat-at-trap’ technique, which have shown avoidance of predator odours by mice and other small mammals, may overestimate the general avoidance of predator odours by free-living prey, which must forage with a constant background of predator odours.

Predation impacts by introduced predators are predicted to be most intense in island ecosystems, and also variable depending on environmental conditions, but large-scale experimental field testing is rare. In this study we examine the factors that determine the distribution and abundance of vole metapopulations preyed upon by feral American mink Mustela vison in the outer Finnish archipelago of the Baltic Sea. Specifically, we follow the dynamics of field voles Microtus agrestis and bank voles Clethrionomys glareolus on 40 small islands under variable rainfall as part of a large-scale mink removal experiment. For both vole species occupancy rates were negatively influenced by island isolation, as were extinction events for field voles. High summer rainfall in 1998 corresponded to large vole populations where mink were absent, populations that then crashed in 1999 and 2000 when below average rains fell during the summer breeding season. Where mink were present however, vole abundance remained more constant between years with no boom-bust apparent. We conclude that weather and predation may drive vole abundance whereas habitat patchiness and metapopulation processes more strongly drive vole distributions. There may also be potential for interaction between these factors: because feral mink prevent rapid vole population growth after good summer rains, and vole dispersal is influenced by population size, feral mink may be changing vole dispersal patterns to disrupt the natural metapopulation dynamic. Hence this indirect impact of mink could lead to gradual erosion of vole populations in the outer archipelago by reducing recolonisation processes.

Domestic dogs are typically prohibited from National Parks and other wildlife reserves partly because managers fear that dog faeces will deter native small mammals from their normal behaviours. We tested this notion for two native small mammals in Ku-ring-gai Chase National Park, near Sydney Australia by comparing the first-night trap success of traps with experimental addition of domestic dog faeces placed near the trap entrance to control traps. Bush Rats Rattus fuscipes, the most abundant species captured, showed no aversion to dog faecal odours across 20 sampled sites and entered control and dog-scented traps equally (n=73 captures). Also, the presence of dog faeces had no association with the body size or sex of captured animals. This lack of response may be because rats do not identify dog scats as a cue to predation risk or because dog scats are an unreliable cue to predation hazards. Either way, faeces from domestic dogs dropped in native habitats appear unlikely to deter small native fauna due to...

Predation is a common problem limiting the success of efforts to reintroduce vertebrates. Naive animals typically suffer high predation rates soon after release despite strong site fidelity in the first few days that would normally reduce predator encounter rates. However, recent theory predicts that low mobility can be associated with high concentrations of odour wastes that are attractive to predators, leading to low survival for individuals that move little. In this paper we test this model for captive-raised Microtus voles reintroduced into suitable habitat in western Finland where they are mainly hunted by chemo-sensing predators. Patterns in vole movement behaviour showed a humped relationship with time: animals moved little soon after release, then made exploratory movements from 3 to 6 days, which then subsided. Predation rates were highest in the first 3 days, with no vole mortalities occurring after voles began substantially moving beyond their release sites. Moreover, voles that survived the 3-week study period were more mobile than voles that were killed by scent-hunting predators, during the initial 3 days and during the final 3 days when voles also had lower mobility. These results suggest that the innate fear response of naive animals, which limit their movements in an unfamiliar environment, may be counterproductive when reduced mobility leads to waste accumulation that is attractive to potential predators. Consequently, pre-release conditioning of captive-raised individuals may need to consider methods to overcome initial release-site fidelity in order to enhance long-term survival prospects after reintroduction.

How animals locate nutritious but camouflaged prey items with increasing accuracy is not well understood. Olfactory foraging is common in vertebrates and the nutritional desirability of food should influence the salience of odour cues. We used signal detection analysis to test the effect of nutritional value relative to the conspicuousness of food patches on rates of foraging improvement of wild house mice Mus musculus searching for buried food (preferred peanuts or non-preferred barley). Olfactory cues were arranged to make food patches conspicuous or difficult to distinguish using a novel form of olfactory camouflage. Regardless of food type or abundance, mice searching for conspicuous food patches performed significantly better than mice searching for camouflaged patches. However, food type influenced how mice responded to different levels of conspicuousness. Mice searching for peanuts improved by similar rates regardless of whether food was easy or hard to find, but mice searching for barley showed significant differences, improving rapidly when food was conspicuous but declining in accuracy when food was camouflaged. Our results demonstrate a fundamental tenet of olfactory foraging that nutritional desirability influences rates of improvement in odour discrimination, enabling nutritious but camouflaged prey to be located with increasing efficiency.

Olfaction is a common sensory mode of communication in much of the Vertebrata, although its use by adult frogs remains poorly studied. Being part of an open signalling system, odour cues can be exploited by ‘eavesdropping’ predators that hunt by smell, making association with odour a high-risk behaviour for prey. Here, we show that adult great barred frogs ( Mixophes fasciolatus ) are highly attracted to odour cues of conspecifics and those of sympatric striped marsh frogs ( Limnodynastes peronii ). This attraction decreased significantly with the addition of odours of a scent-hunting predator, the red-bellied black snake ( Pseudechis porphyriacus ), indicating that frogs perceived predation risks from associating with frog odours. Male frogs, however, maintained some attraction to unfamiliar conspecific scents even with predator odours present, suggesting that they perceived benefits of odour communication despite the risk. Our results indicate that adult frogs can identify species and individuals from their odours and assess the associated predation risk, revealing a complexity in olfactory communication previously unknown in adult anurans.

For foraging herbivores, both food quality and predation risk vary across the landscape. Animals should avoid low-quality food patches in favour of high-quality ones, and seek safe patches while avoiding risky ones. Herbivores often face the foraging dilemma, however, of choosing between high-quality food in risky places or low-quality food in safe places. Here, we explore how and why the interaction between food quality and predation risk affects foraging decisions of mammalian herbivores, focusing on browsers confronting plant toxins in a landscape of fear. We draw together themes of plant–herbivore and predator–prey interactions, and the roles of animal ecophysiology, behaviour and personality. The response of herbivores to the dual costs of food and fear depends on the interplay of physiology and behaviour. We discuss detoxification physiology in dealing with plant toxins, and stress physiology associated with perceived predation risk. We argue that behaviour is the interface enabling herbivores to stay or quit food patches in response to their physiological tolerance to these risks. We hypothesise that generalist and specialist herbivores perceive the relative costs of plant defence and predation risk differently and intra-specifically, individuals with different personalities and physiologies should do so too, creating individualised landscapes of food and fear. We explore the ecological significance and emergent impacts of these individual-based foraging outcomes on populations and communities, and offer predictions that can be clearly tested. In doing so, we provide an integrated platform advancing herbivore foraging theory with food quality and predation risk at its core.

Camera trapping in wildlife management and research is a growing global phenomenon. The technology is advancing very quickly, providing unique opportunities for collecting new biological knowledge. In order for fellow camera trap researchers and managers to share their knowledge and experience, the First International Camera Trapping Colloquium in Wildlife Management and Research was held in Sydney, Australia. Camera Trapping brings together papers from a selection of the presentations at the colloquium and provides a benchmark of the international developments and uses of camera traps for monitoring wildlife for research and management. Four major themes are presented: case studies demonstrating camera trapping for monitoring; the constraints and pitfalls of camera technologies; design standards and protocols for camera trapping surveys; and the identification, management and analyses of the myriad images that derive from camera trapping studies. The final chapter provides future directions for research using camera traps. Remarkable photographs are included, showing interesting, enlightening and entertaining images of animals 'doing their thing', making it an ideal reference for wildlife managers, conservation organisations, students and academics, pest animal researchers, private and public land managers, wildlife photographers and recreational hunters.

Animals often form groups to reduce the risk of predation through the per capita dilution of their individual predation risk. The advantages of grouping also influence the timing of reproduction in many species. In particular, synchrony in the timing of births may have evolved as a predator-avoidance strategy as it dilutes the risk of predation upon vulnerable newborn and naive young. Eggs of an Australian freshwater turtle, Emydura macquarii, can hatch synchronously despite developmental asynchrony among eggs of a clutch and hatchlings have a reduced predation risk by emerging from the nest as a group. Developmental asynchrony within clutches was induced to reflect natural nests by dividing clutches and incubating them at either 25°C or 30°C. Some eggs were then reunited with their clutch-mates and hatching occurred synchronously in some of these groups. In groups where synchronous hatching did not occur, less advanced eggs still hatched earlier than the normal incubation period. Synchrony occurred because the less advanced eggs hatched up to five days earlier than the control embryos. We conclude that the less advanced embryos within a clutch either accelerate their development or hatch prematurely to ensure synchrony of hatching and hatchling group formation may facilitate emergence from the nest and dilute predation risk.

Eastern grey kangaroos, Macropus giganteus , are thought to respond to high risks of predation by foraging closer to refuge and by forming larger groups, but females with newly emergent offspring mostly forage alone, a response thought to reduce predation risk on the latter. I tested these hypotheses for wild kangaroo populations in southeastern Australia, using a field-based experimental reduction of a potential predator, the red fox, Vulpes vulpes . I monitored kangaroo foraging behaviour in two fox removal and two control sites by counting scats at 30 and 150 m from refuge during September 1994 and 1995 (after 5 and 16 months of fox control). I also monitored kangaroo group sizes in all sites, using monthly or bimonthly direct observations over 22 months of fox reduction. In both years, fox removal caused kangaroos to deposit relatively more scats further from refuge than in control sites where fox numbers were more than 85% higher. This suggests strongly that kangaroos spend more time foraging close to refuge when predation risk is high. Group sizes were also smaller in fox removal sites although only during June–October when the majority of females had large pouch young. In November–March, group size decreased in all sites owing to the solitary behaviour of many females with young at foot. However, where foxes were removed, the mean group size of such females was smaller than in control sites and females were also more often alone where foxes were removed. These results suggest that solitary behaviour increases rather than decreases predation risk. This experiment highlights that grouping behaviour is risk sensitive and that some individuals accept higher risks of predation to mitigate other costs of group foraging.

We used a food-supplementation experiment to test the hypothesis that small-mammal populations are food-limited during winter in southeastern Australia. We trapped small mammals along 120- to 150-m transects at 12 creek and 12 ridgetop sites (representing high- and low-quality habitats) for 2 months prior to winter and 2 months during winter. High-quality food (peanut butter, honey, oats, and dried cat food) was provided ad libitum for 7 weeks during winter at four sites in each habitat. Eight sites were provided with empty feeding tubes and eight were untreated. Seven weeks of food supplementation caused numerical increases of 4.0- and 5.0-fold for the rodents Rattus fuscipes and Rattus lutreolus, respectively. Increases were due largely to immigration, and were only observed in the high-quality creek habitats (R. lutreolus were exclusively captured at creek sites). Food supplementation also led to an increase in body mass and reversed the hiatus in winter breeding for rodents. These results suggest that populations of both species are limited by winter food availability. However, survival rates (indexed from recapture rates) were not affected by food supplementation. Mean body mass of the marsupial Antechinus stuartii also increased with food supplementation, but other demographic parameters showed no response; numbers declined at creek sites after additional food was provided. Trapping-revealed measures of interspecific association showed that A. stuartii avoided areas of high rat numbers after additional food was provided. It is thus likely that interference competition from the much larger and more abundant rodents forced A. stuartii out of the food-supplemented creek sites, hence mediating the direct effects of food supplementation on this species.

We investigated the impact of red fox (Vulpes vulpes Linnaeus 1758) predation on juvenile eastern grey kangaroos (Macropus giganteus Shaw 1790) using a replicated predator removal experiment. In two sites in Namadgi National Park, south-eastern Australia, a persistent 1080 poisoning campaign over 18 months reduced fox density by more than 85%, and to less than 10% of the fox density in two other sites with no fox baiting. Changes in the mother : young ratios and densities of kangaroo populations were monitored twice monthly along 2-km transects in each site from July 1993 to February 1995. Compared to nonremoval sites, where foxes were controlled, 25-40% more females retained juveniles over the period when these young became emergent from the pouch. This higher survival of emergent pouch young resulted in a significantly higher proportion of juveniles in kangaroo populations at fox control sites, which resulted in a significantly higher annual growth rate. We conclude that predation upon juveniles is an important limiting factor for kangaroo populations in Namadgi NP.

Summary 1. Introduced vertebrate predators are one of the most important threats to endemic mammal species. Prey naivety can lead to heavy losses to alien predators, which may be additive to ‘natural’ sources of mortality that limit prey populations. Alternatively, predators may take only individuals that are surplus to the population, and hence predator control may have little benefit for susceptible native prey populations. 2. A field-based predator removal experiment was used to test the predator limitation and doomed surplus hypotheses on the impact of introduced red foxes Vulpes vulpes on populations of native bush rats Rattus fuscipes in south-eastern Australia. 3. Poison baiting was used in July 1993 to reduce fox numbers in two fox-removal sites from 2·8–3·4 km–1 (spotlight counts) to less than 0·5 km–1 within 6 months. Fox density in two non-removal sites remained typically five times higher than that in removal sites. 4. Bush rat numbers on replicated trapping plots showed no response to fox removal, and rodent numbers fluctuated seasonally in all sites over 22 months of fox control, which represented two breeding seasons for rats. 5. Fox removal also had no effect on rat persistence time, adult body weight, captures of juveniles or immature animals during the breeding season, nor captures of immigrant or transient animals. 6. The general lack of response by rat populations to fox removal supported the doomed surplus hypothesis, that fox predation operated as a compensatory source of mortality rather than an additive one. Consequently, there was no measured benefit to native rat populations of intensive short-term fox control. 7. The results suggest that where predation pressure is low, not all predation mortality will be additive to prey populations even if it results from a predator introduced to the ecosystem. Hence, indiscriminate control of introduced predators is unlikely to produce uniform benefits for all the species they prey upon. Feral predator control should therefore be targeted for native species known to be predation limited or for species where any mortality threatens persistence.

Predator-avoidance behavior of native bush rats ( Rattus fuscipes ) to an introduced predator ( Vulpes vulpes ) was investigated by measuring their responses to predator odor. Trapping success of wild bush rats was compared between clean traps and traps scented with fox odor, set along creeks in Namadgi National Park in southeastern Australia. Two experimental designs were used; the first measured trapping success of clean and scented traps alternating along a trapline through bush rat habitat in winter, spring and summer. The second design offered a choice of clean and scented traps at each trap station and was repeated in spring and summer. Relative trapping successes were analyzed to determine if rats avoided fox odor. Multiple t- tests showed no avoidance responses with similar numbers of captures in clean and fox-scented traps. Consequences of the apparent naivete of bush rats to the odor of an introduced predator are discussed.

Dog walking is among the world's most popular recreational activities, attracting millions of people to natural areas each year with diverse benefits to human and canine health. But conservation managers often ban dog walking from natural areas fearing that wildlife will see dogs as potential predators and abandon their natural habitats, resulting in outcry at the restricted access to public land. Arguments are passionate on both sides and debate has remained subjective and unresolved because experimental evidence of the ecological impacts of dog walking has been lacking. Here we show that dog walking in woodland leads to a 35% reduction in bird diversity and 41% reduction in abundance, both in areas where dog walking is common and where dogs are prohibited. These results argue against access by dog walkers to sensitive conservation areas.

Naivete can occur within any novel antagonistic interaction, and competitive forces play a fundamental role in shaping community structure, yet competitive naivete has received very little attention in the literature to date. Naivete towards a novel competitor is unlikely to result in immediate mortality, but could potentially affect access to resources and hence population growth and survival. In cases where only one species (either native or alien) remains naive to the other, the species that recognizes the other will gain advantage, with implications for both the persistence of the native species and the establishment and spread of the invasive. The invasive black rat (Rattus rattus) has spread throughout many coastal areas of Australia, and competes with the native bush rat (Rattus fuscipes) wherever they coexist. As these rats have now been interacting for approximately 200 years, and multi-species rodent communities generally maintain their structure through olfactory communication, our aim was to determine whether these two very closely related species recognize one another’s odors and use them to mediate their interactions. We used remote-sensing cameras deployed in single- and mixed-species sites to record the behavioral responses of each species to conspecific, heterospecific and control odors. Black rats investigated bush rat odors but not vice versa, suggesting that bush rats may remain naive towards their new competitor. Highly successful invaders such as black rats may possess traits such as broad recognition templates and rapid learning capabilities that contribute to their ongoing success in invading new environments.

The invasion of alien species into areas beyond their native ranges is having profound effects on ecosystems around the world. In particular, novel alien predators are causing rapid extinctions or declines in many native prey species, and these impacts are generally attributed to ecological naïveté or the failure to recognise a novel enemy and respond appropriately due to a lack of experience. Despite a large body of research concerning the recognition of alien predation risk by native prey, the literature lacks an extensive review of naïveté theory that specifically asks how naïveté between novel pairings of alien predators and native prey disrupts our classical understanding of predator-prey ecological theory. Here we critically review both classic and current theory relating to predator-prey interactions between both predators and prey with shared evolutionary histories, and those that are ecologically 'mismatched' through the outcomes of biological invasions. The review is structured around the multiple levels of naïveté framework of BanksDickman (2007), and concepts and examples are discussed as they relate to each stage in the process from failure to recognise a novel predator (Level 1 naïveté), through to appropriate (Level 2) and effective (Level 3) antipredator responses. We discuss the relative contributions of recognition, cue types and the implied risk of cues used by novel alien and familiar native predators, to the probability that prey will recognise a novel predator. We then cover the antipredator response types available to prey and the factors that predict whether these responses will be appropriate or effective against novel alien and familiar native predators. In general, the level of naïveté of native prey can be predicted by the degree of novelty (in terms of appearance, behaviour or habitat use) of the alien predator compared to native predators with which prey are experienced. Appearance in this sense includes cue types, spatial distribution and implied risk of cues, whilst behaviour and habitat use include hunting modes and the habitat domain of the predator. Finally, we discuss whether the antipredator response can occur without recognition per se, for example in the case of morphological defences, and then consider a potential extension of the multiple levels of naïveté framework. The review concludes with recommendations for the design and execution of naïveté experiments incorporating the key concepts and issues covered here. This review aims to critique and combine classic ideas about predator-prey interactions with current naïveté theory, to further develop the multiple levels of naïveté framework, and to suggest the most fruitful avenues for future research.

Olfaction is an important sense for many animals, yet its role in foraging by herbivores is poorly known. Many plants contain volatile compounds, such as terpenes, that are not only volatile but can be toxic if ingested. Volatile terpenes can be used by herbivores to assess leaf quality, but there is little evidence for whether they are also used as a searching cue. We applied the giving-up density (GUD) framework to examine fine-scale foraging by two free-ranging mammalian herbivores, the brush-tail possum (Trichosurus vulpecula) and the swamp wallaby (Wallabia bicolor), using patches with food and an inedible matrix that varied in content of a volatile terpene, 1,8-cineole. We tested the effect of (1) increasing dietary cineole concentration, and (2) masking the food odor by adding cineole to the inedible matrix, thus overriding the smell released by the diet. In both species GUD was affected by dietary cineole; a high cineole concentration raised GUD, consistent with its role as a toxin. There was a significant effect of masking on GUD for wallabies but not for possums, suggesting that odor was an important foraging cue at the feeding patch only for the former. Differences in ecological niche and diet may explain this pattern. We suggest that herbivores, such as the swamp wallaby, opportunistically eavesdrop on plant volatiles, i.e., take advantage of the signal proffered for a different function. The cost of this eavesdropping for plants, however, is presumably counteracted by other ecological benefits of these volatiles, including a reduction in leaf consumption as a function of toxicity.

With progressively increasing anthropogenic habitat disturbances, restoration of impacted landscapes is becoming a critical element of biodiversity conservation. Evaluation of success in restoration ecology rarely includes faunal components, usually only encompassing abiotic and floral components of the ecosystems. Even when fauna is explicitly included, it is usually only species presence/absence criteria that are considered. If restoration is to have a positive outcome, however, populations in restored habitats should exhibit comparable survival and reproductive rates to populations found in undisturbed surroundings. If a species recolonises restored areas but later experiences decreased fitness, restored areas could become ecological sinks or traps. We investigated this possibility in a case study of koalas Phascolarctos cinereus occupying rehabilitated mining areas on North Stradbroke Island, Australia. Our holistic approach compared rehabilitated and undisturbed areas on the basis of their vegetation characteristics, of koalas' body condition, roosting trees, diet, as well as predator index. Koalas using rehabilitated areas appeared to be able to access an adequate supply of roosting and fodder trees, were in good condition and had high reproductive output. We did not find any significant differences in predator density between rehabilitated areas and undisturbed surroundings. The results presented in this study showed there was no evidence that the post-mining rehabilitated areas constitute ecological sinks or traps. However, to reach a definitive conclusion as to whether areas rehabilitated post-mining provide at least equivalent habitat to undisturbed locations, additional research could be undertaken to assess foliar nutrient/water/toxin differences and predation risk in rehabilitated areas compared with undisturbed areas. More generally, the evaluation of whether restoration successfully produces a functional ecological community should include criteria on the fitness of faunal populations reoccupying such sites, so as to ensure functioning ecosystems, rather than ecological sinks or traps, are the outcome.

Many studies have reported the aversive reactions of prey towards a predator's odour signals (e.g. urine marks), a behaviour widely thought to reduce the risk of predation by the predator. However, because odour signals persist in the environment, they are vulnerable to exploitation and eavesdropping by predators, prey and conspecifics. As such, scent patches created by one species might attract other species interested in information about their enemies. We studied this phenomenon by examining red fox investigation of odours from conspecifics and competing species in order to understand what prey are responding to when avoiding the odours of a predator. Surprisingly, foxes showed limited interest in conspecific odours but were highly interested in the odours of their competitors (wild dogs and feral cats), suggesting that odours are likely to play an important role in mediating competitive interactions. Importantly, our results identify that simple, dyadic interpretations of prey responses to a predator odour (i.e. cat odour = risk of cat encounter = fear of cats) can no longer be assumed in ecological or psychology research. Instead, interactions mediated by olfactory cues are more complex than previously thought and are likely to form a complicated olfactory web of interactions.

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.

Urban landscapes are often located in biologically diverse, productive regions. As such, urbanization may have dramatic consequences for this diversity, largely due to changes in the structure and function of urban communities. We examined the influence of landscape productivity (indexed by geology), housing density and vegetation clearing on the spatial distribution of nocturnal insect biomass and the foraging activity of insectivorous bats in the urban landscape of Sydney, Australia. Nocturnal insect biomass (g) and bat foraging activity were sampled from 113 sites representing backyard, open space, bushland and riparian landscape elements, across urban, suburban and vegetated landscapes within 60 km of Sydney's Central Business District. We found that insect biomass was at least an order of magnitude greater within suburban landscapes in bushland and backyard elements located on the most fertile shale influenced geologies (both p

Many primate species are threatened with extinction and are the focus of extensive conservation efforts including re-introduction, captive breeding and habitat conservation. Welfare-based rehabilitation (hereafter also ‘rehabilitation’) is a management strategy commonly used for primates, particularly those species targeted by the pet and bush meat trades. Rehabilitation of rescued primates typically has the dual motivation of welfare and conservation, but has not been assessed as a conservation strategy. As the species involved in rehabilitation are often endangered (e.g. chimpanzees, gorillas, orang-utans), it is important for rehabilitation projects to follow a ‘best practice’ model in order to increase positive outcomes. In this study, we compared the approaches of 28 welfare-based primate rehabilitation projects to the ‘IUCN guidelines for nonhuman primate re-introductions’, in addition to components of the ‘Best practice guidelines for the re-introduction of great apes’ in order to assess where additional work might be needed for released animals to contribute to conservation outcomes. Few projects examined complied with the guidelines for re-introduction, failing to incorporate important factors such as quarantine, long term post-release monitoring and training for predator awareness. Further development of species-specific rehabilitation guidelines may improve the outcomes of future rehabilitation projects. To support this, we recommend that detailed methods and results be published for all rehabilitation efforts, regardless of the outcome.

Individuals are at risk when communicating because conspicuous signals attract both conspecifics and eavesdropping predators. This predation cost of communicating has typically been attributed to signalling individuals because of their conspicuous role, and is a core concept within sexual selection and communication ecology. But, if predators are attracted to signals, then receivers, both intended or otherwise, may also find themselves at risk of predation. Here, we review the theoretical basis and empirical evidence that receiving also carries a risk of predation. We distinguish between the risks of receiving and responding to signals, and we argue that receivers of signals that are long lived, are highly predictable in time or place and/or cannot be received quickly are likely to be at greater risk of predation compared to receivers of signals without these properties. We review recent empirical evidence from a variety of taxa that supports the hypothesis that receivers (including heterospecific prey) are aware of these risks and that they modify their behaviour to balance the risks against the benefits of receiving under predation threat. We also discuss the wider implications of risky receiving for receiving and signalling behaviour in prey, as well as for the prey's predators.

Establishing species distribution and population trends are basic requirements in conservation biology, yet acquiring this fundamental information is often difficult. Indirect survey methods that rely on fecal pellets (scats) can overcome some difficulties but present their own challenges. In particular, variation in scat detectability and decay rate can introduce biases. We studied how vegetation communities affect the detectability and decay rate of scats as exemplified by koalasPhascolarctos cinereus: scat detectability was highly and consistently dependent on ground layer complexity (introducing up to 16% non-detection bias); scat decay rates were highly heterogeneous within vegetation communities; exposure of scats to surface water and rain strongly accelerated scat decay rate and finally, invertebrates were found to accelerate scat decay rate markedly, but unpredictably. This last phenomenon may explain the high variability of scat decay rate within a single vegetation community. Methods to decrease biases should be evaluated when planning scat surveys, as the most appropriate method(s) will vary depending on species, scale of survey and landscape characteristics. Detectability and decay biases are both stronger in certain vegetation communities, thus their combined effect is likely to introduce substantial errors in scat surveys and this could result in inappropriate and counterproductive management decisions.

The most striking feature that links all the contributions to the theme of Science under siege: zoology under threat, is the rejection of the notion that science is optional in our society, i.e. that science can be ignored, even derided. In the main, these anti-science worldviews derive from religious groups that are hostile to science, a political or commercial stance that sees short-term gains in rejecting or undermining science, or a non-zoological understanding of animals that arrives at a philosophical position opposed to the study and management of wild animals. The extreme ‘animal rights’ position is also inimical to conservation of our native fauna, although an ethical approach to animals and the environment is a critical component to their long-term management and we both encourage, and participate in, this debate. Brian Martin, in his engaging paper on Breaking the siege: guidelines for struggle in science, observed that when scientists come under attack, it is predictable that the attackers will use methods to minimise public outrage over the attack, including covering up the action, devaluing the target, reinterpreting what is happening, using official processes to give an appearance of justice, and intimidating people involved. Zoology is under attack, so are working zoologists, and the distressing consequence for our fauna will be its continuing decline. With increasing rates of extinction that reflect threats, such as invasive species and climate change compounding the impact of simplified landscapes, Australia is being progressively robbed of its rich zoological legacy.

The impact of alien predators on native prey populations is often attributed to prey naiveté towards a novel threat. Yet evolutionary theory predicts that alien predators cannot remain eternally novel; prey species must either become extinct or learn and adapt to the new threat. As local enemies lose their naiveté and coexistence becomes possible, an introduced species must eventually become 'native'. But when exactly does an alien become a native species? The dingo (Canis lupus dingo) was introduced to Australia about 4000 years ago, yet its native status remains disputed. To determine whether a vulnerable native mammal (Perameles nasuta) recognizes the close relative of the dingo, the domestic dog (Canis lupus familiaris), we surveyed local residents to determine levels of bandicoot visitation to yards with and without resident dogs. Bandicoots in this area regularly emerge from bushland to forage in residential yards at night, leaving behind tell-tale deep, conical diggings in lawns and garden beds. These diggings were less likely to appear at all, and appeared less frequently and in smaller quantities in yards with dogs than in yards with either resident cats (Felis catus) or no pets. Most dogs were kept indoors at night, meaning that bandicoots were not simply chased out of the yards or killed before they could leave diggings, but rather they recognized the threat posed by dogs and avoided those yards. Native Australian mammals have had thousands of years experience with wild dingoes, which are very closely related to domestic dogs. Our study suggests that these bandicoots may no longer be naïve towards dogs. We argue that the logical criterion for determining native status of a long-term alien species must be once its native enemies are no longer naïve.

1. Olfactory predator search processes differ fundamentally to those based on vision, particularly when odour cues are deposited rather than airborne or emanating from a point source. When searching for visually cryptic prey that may have moved some distance from a deposited odour cue, cue context and spatial variability are the most likely sources of information about prey location available to an olfactory predator. 2. We tested whether the house mouse (Mus domesticus), a model olfactory predator, would use cue context and spatial variability when searching for buried food items; specifically, we tested the effect of varying cue patchiness, odour strength, and cue-prey association on mouse foraging success. 3. Within mouse- and predator-proof enclosures, we created grids of 100 sand-filled Petri dishes and buried peanut pieces in a set number of these patches to represent visually cryptic 'prey'. By adding peanut oil to selected dishes, we varied the spatial distribution of prey odour relative to the distribution of prey patches in each grid, to reflect different levels of cue patchiness (Experiment 1), odour strength (Experiment 2) and cue-prey association (Experiment 3). We measured the overnight foraging success of individual mice (percentage of searched patches containing prey), as well as their foraging activity (percentage of patches searched), and prey survival (percentage of unsearched prey patches). 4. Mouse foraging success was highest where odour cues were patchy rather than uniform (Experiment 1), and where cues were tightly associated with prey location, rather than randomly or uniformly distributed (Experiment 3). However, when cues at prey patches were ten times stronger than a uniformly distributed weak background odour, mice did not improve their foraging success over that experienced when cues were of uniform strength and distribution (Experiment 2). 5. These results suggest that spatial variability and cue context are important means by which olfactory predators can use deposited odour cues to locate visually cryptic prey. They also indicate that chemical crypsis can disrupt these search processes as effectively as background matching in visually based predator-prey systems.

1. Foraging herbivores must deal with plant characteristics that inhibit feeding and they must avoid being eaten. Principally, toxins limit food intake, while predation risk alters how long animals are prepared to harvest resources. Each of these factors strongly affects how herbivores use food patches, and both constraints can pose immediate proximate costs and long-term consequences to fitness. 2. Using a generalist mammalian herbivore, the common brushtail possum (Trichosurus vulpecula), our aim was to quantitatively compare the influence of plant toxin and predation risk on foraging decisions. 3. We performed a titration experiment by offering animals a choice between non-toxic food at a risky patch paired with food with one of five toxin concentrations at a safe patch. This allowed us to identify the tipping point, where the cost of toxin in the safe food patch was equivalent to the perceived predation risk in the alternative patch. 4. At low toxin concentration, animals ate more from the safe than the risky patch. As toxin concentration increased at the safe patch, intake shifted until animals ate mainly from the risky patch. This shift was associated with behavioural changes: animals spent more time and fed longer at the risky patch, while vigilance increased at both risky and safe patches. 5. Our results demonstrate that the variation in toxin concentration, which occurs intraspecifically among plants, can critically influence the relative cost of predation risk on foraging. We show that herbivores quantify, compare and balance these two different but proximate costs, altering their foraging patterns in the process. This has potential ecological and evolutionary implications for the production of plant defence compounds in relation to spatial variation in predation risk to herbivores.

Urbanization is an extreme form of habitat modification, but retention of native vegetation in bushland reserves may improve the ecological sustainability of cities. We focused on bats (Microchiroptera) and investigated the use of the urban matrix and surrounding bushland in a region of Sydney, Australia, where remnant bushland persists and gardens often support large trees. Ultrasonic surveys were conducted at 40 sites over one summer season in the backyard matrix, bushland remnants and surrounding National Parks to determine which species were present, and the influence of landscape elements and habitat characteristics on activity, species richness and presence of individual species. In total, 15 of the 17 microbat species known from the Sydney region were recorded in the study area. Yet only three of these species, Chalinolobus gouldii, Mormopterus species 2 and Miniopterus schreibersii were present in more than 40% of sites. Bat activity was significantly higher in remnant bushland on shale soils and in backyards, compared with sandstone gully and ridge remnants, or reference sites in nearby National Parks. Furthermore, species assemblages in urban areas were different from assemblages in reference sites. Of all the habitat characteristics examined, the amount of bushland within 0.5–3 km surrounding a site and tree density were the most common predictors of individual species presence, particularly rare species. Area of bushland, hollow abundance and average tree diameter were positively correlated with species richness, while tree diameter was the strongest predictor of total microbat activity. The proximity of large areas of bushland and the many trees remaining in residential areas of the northern ‘leafy’ suburbs of Sydney allowed the persistence of a range of bat species. The higher bat activity on fertile shale soils indicated that bushland remnants embedded within cities can have high conservation value for bats. Surveys in more urbanized areas of Sydney are needed to test predictions of the models derived in this study.

Background Predator attraction to prey social signals can force prey to trade-off the social imperatives to communicate against the profound effect of predation on their future fitness. These tradeoffs underlie theories on the design and evolution of conspecific signalling systems and have received much attention in visual and acoustic signalling modes. Yet while most territorial mammals communicate using olfactory signals and olfactory hunting is widespread in predators, evidence for the attraction of predators to prey olfactory signals under field conditions is lacking. Methodology/Principal Findings To redress this fundamental issue, we examined the attraction of free-roaming predators to discrete patches of scents collected from groups of two and six adult, male house mice, Mus domesticus, which primarily communicate through olfaction. Olfactorily-hunting predators were rapidly attracted to mouse scent signals, visiting mouse scented locations sooner, and in greater number, than control locations. There were no effects of signal concentration on predator attraction to their prey's signals. Conclusions/Significance This implies that communication will be costly if conspecific receivers and eavesdropping predators are simultaneously attracted to a signal. Significantly, our results also suggest that receivers may be at greater risk of predation when communicating than signallers, as receivers must visit risky patches of scent to perform their half of the communication equation, while signallers need not.

6 páginas, 1 figura.-- Parte de este trabajo fue presentado a la Conferencia de la Sociedad de Mamíferos (2010) y fue galardonado con el Premio Acorn a la mejor presentación estudiantil., Early detection of predators by their prey is an essential element of antipredator tactics, and for many mammalian predator prey interactions, detection comes mainly via a predators olfactory cues. The avoidance of predator odors can reduce the likelihood of encountering predators and increases the chances of prey survival. However, the role of coevolutionary history in the exploitation of odors in mammalian predator–prey interactions is not so well understood. The prey naiveté hypothesis predicts the lack of effective antipredator behaviors given the lack of a coevolution between predator and prey but has so far been only tested on native prey. In this study, we describe the short-time responsiveness of an introduced prey species, the European rabbit (Oryctolagus cuniculus), to scents from coevolved and novel predators in Australia. We quantified rabbit activity rates by means of pellet counting and activity indices based on footprints, in a series of experimental plots treated with predator odors, and both methods yielded consistent results. Rabbits responded to coevolved predators by reducing their activity rates to scented experimental plots, whereas no avoidance was found for novel allopatric predators. These results suggest a shared evolutionary history between the antipredatory responses of rabbits and their natural predators., Predoctoral fellowship to I.C.B. from the Spanish Ministry of Science and Innovation that covered a short stay abroad, during which this project was conducted; Australian Research Council Discovery Grants (University of New South Wales) DP0881455 and DP0877585 to P.B.B.

Colonisation, an important part of meta-population dynamics of fragmented populations, depends on both the dispersal ability and the ability to establish in the new habitat. Predation can hinder successful establishment of prey, and where the predation pressure comes from an alien predator, the effects on colonisation might be devastating. We studied the establishment of field voles (Microtus agrestis) inhabiting small islands of the archipelago of the Baltic Sea, SW Finland, under presence and absence of the alien American mink (Mustela vison). We translocated “experienced” voles from islands with mink, and “inexperienced” voles from islands from which mink had been removed, to other islands where mink was present or absent. By radio-tracking we studied survival, space and microhabitat use of voles within four weeks after translocation. Survival of voles on mink islands was significantly lower than on mink-free islands, but “experienced” voles did not survive better than “inexperienced” voles. “Experienced” voles were more often located in juniper habitats than “inexperienced” voles, but they appeared not to gain any survival benefit from altered microhabitat use. This study provides novel evidence, that alien mink predation inhibits establishment of colonising field voles and may thus ultimately induce extinction of voles from the outer archipelago.

The black rat, Rattus rattus, is an alien rodent in Australian ecosystems where niche overlap with native small mammals may lead to competition for resources and displacement of native species. In coastal habitats surrounding Jervis Bay in south-eastern Australia, R. rattus co-occurs with the native bush rat, Rattus fuscipes, and brown antechinus, Antechinus stuartii. Relative distributions and abundances, and fine-scale space use suggest invasive and native rodents compete for use of space and habitat. Such competitive interactions were not evident between R. rattus and native A. stuartii, which was negatively influenced more by disturbance to habitat. Differences in rodent communities between spatially separate forests forming the northern and southern peninsulas of Jervis Bay potentially reflect symmetrical competition and differences in competitive outcomes. In southern forests, R. rattus was largely restricted to patches of disturbed forest associated with campgrounds. Competitive interference by native rodent populations inhabiting surrounding intact forests may have so far limited R. rattus colonization of these areas. In northern forests, R. rattus was the predominant rodent irrespective of disturbance, while populations of R. fuscipes were unusually low seemingly due to poor juvenile recruitment. Native individuals avoided areas frequented by adult R. rattus and given that species did not partition use of microhabitats, R. rattus most likely precluded R. fuscipes from suitable habitat and in doing so limited native populations. We discuss how natural disturbance of habitat and human activity have potentially facilitated successful invasion by R. rattus of the northern forests. Studies that manipulate rodent populations are required to support these interpretations of observed patterns.

Conspicuous signals may attract both intended receivers as well as unintended receivers such as predators. However, signalling individuals are not the only ones at risk when communicating, as the intended receiver may encounter eavesdropping predators that are attracted to the same signals. Here, we show that the house mouse (Mus domesticus) behaviourally responds to social signals (scents) as though receiving carries a risk of predation. We presented mice with their own scents (low social benefit to receiving) and those from an unknown "intruder" (high social benefit to receiving) under high (cat urine added) and low (water added) perceived predation risk. Mice traded-off the potential social benefits of receiving a signal against the costs of potential predator encounter. Receiving rates of both social signals (own and intruder) were high under low predation risk. Mice reduced receiving of both social signals when predation risk was increased; however, the effect was greater for their own low value scent than for the high social value intruder scent. Notably, rates of signalling did not vary with the level of perceived predation risk. Our findings suggest that mice traded-off the potential social benefits of receiving a signal (scent mark) against the costs of potential predator encounter. We suggest that, for some species, the costs of communication are borne more by the receivers than the signallers, and that the influence of risks to receivers on the design of communication systems may have been underestimated.

This paper investigates the impacts of a population of introduced black rats Rattus rattus (Rodentia: Muridae) in native bushland at North Head at the entrance to Sydney Harbour, Australia. The black rat is an invasive pest species known the world over for its economic impacts on agriculture and its environmental impacts on native wildlife (Long 2003). The presence of black rats at North Head is of particular concern because of the conservation value of the area. North Head supports endangered populations of long-nosed bandicoots Perameles nasuta, little penguins Eudyptula minor, and sunshine wattle Acacia terminalis, along with an additional 119 species of native fauna (Skelton et al. 2003a). North Head also supports 159 species of exotic flora, 428 species of native flora and an endangered ecological community of Eastern Suburbs Banksia Scrub (Skelton et al. 2003b). Plans are currently under consideration to further protect the native flora and fauna in a sanctuary that would incorporate an existing National Park and part of an ex-military site. Black rats are probably the most abundant pest mammal species on the headland and, for the sanctuary to succeed, identification and management of the potential threats to the native flora and fauna are necessary. The aim of this study is to explore the potential impacts that black rats may have on species of conservation concern at North Head. Around the world, black rats are responsible for the consumption of food stores and agricultural crops. They also forage on native vegetation. On average, black rats consume 10% of their body weight each day (Long 2003), making them potentially important in terms of their grazing pressure on endemic plants. Although they are omnivorous (Watts and Braithwaite 1978; Clark 1981, 1982; Watts 1995; Long 2003), a large portion of black rat diet may include leaves, stems, seeds and/or fruit (Norman 1970; Cox 1997). Importantly, the grazing of seedlings by black rats can negatively impact the population recruitment in some plants (Crawley 1983; Wilson et al. 2003; Brown 2005), and rodent grazing can substantially increase plant mortality (e.g. Hulme 1996). Moreover, when feeding on plants, rodents generally show preferences for younger seedlings over older plants (Ostfield et al. 1997). At North Head, there is concern over the potential impact of black rats on the recruitment of endangered plants (Skelton et al. 2003a), particularly sunshine wattle. Sunshine wattle is an acacia that occurs patchily within heathland. The major threat to this species is habitat reduction (NSW National Parks and Wildlife Service 2004a), but its seeds and seedlings may be vulnerable to rat predation, particularly in remnant heathland near urban areas. Black rats are known predators of sunshine wattle seedlings in commercial nurseries (C. Miller, pers. comm.). The first aim of this study is to determine the level of black rat foraging on sunshine wattle seedlings relative to other vertebrate grazers. Impacts of black rats Rattus rattus across an urban/ bushland interface at Sydney’s North Head Tania A. Rose1,2 and Peter B. Banks1 1School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia