Niche overlap between marsupial and eutherian carnivores: does competition threaten the endangered spotted-tailed quoll?

Effect of uneven tolerance to human disturbance on dominance interactions of top predators

Anthropogenic activities may alter felid assemblage structure, facilitating the persistence of tolerant species (commonly mesopredators), excluding ecologically demanding ones (top predators) and, consequently, changing coexistence rules. We aimed to determine how human activities influence intraguild relationships among top predators and their cascading effects on mesopredators, which remain poorly understood despite evidence of top carnivore decline. We used structural equation modeling at a continental scale to investigate how habitat quality and quantity, livestock density, and other human pressures modified the intraguild relations of the 3 species that are at the top of the food chain in the Neotropics: jaguars (Panthera onca), pumas (Puma concolor), and ocelots (Leopardus pardalis). We included presence-absence data derived from systematic studies compiled in Neocarnivores data set for these felid species at 0.0833° resolution. Human disturbance reduced the probability of jaguar occurrence by -0.35 standard deviations. Unexpectedly, the presence of sheep (Ovis aries) or goats (Capra aegagrus hircus) and jaguars was positively related to the presence of pumas, whereas puma presence was negatively related to the presence of ocelots. Extent of forest cover had more of an effect on jaguar (β = 0.23) and ocelot (β = 0.12) occurrences than the extent of protected area, which did not have a significant effect. The lack of effect of human activities on puma presence and the positive effect of small livestock supports the notion that pumas are more adaptable to habitat disturbance than jaguars. Our findings suggest that human disturbance has the potential to reverse the hierarchical competition dominance among large felids, leading to an unbalanced community structure. This shift disadvantages jaguars and elevates the position of pumas in the assemblage hierarchy, resulting in the exclusion of ocelots, despite their relatively lower susceptibility to anthropogenic disturbance. Our results suggest that conservation efforts should extend beyond protected areas to encompass the surrounding landscape, where complexities and potential conflicts are more pronounced.

The Zone Overlap Index: A new measure of shared resource use in the zoo

It is important that the environment provided in the zoo is relevant to the species being housed and its suitability be easily assessed by personnel. As shared space and resources can overlap in a zoo's enclosure a tool is required to measure the effects of such overlap between individual animals in a shared enclosure. This paper outlines the Pianka Index (PI), a tool used in ecology to quantify niche overlap, that has value in quantifying the amount of time that animals spend in shared enclosure zones. One limitation to this method, however, is that the established method of determining the PI requires division of the enclosure into equally sized zones, something that is not always relevant to a zoo enclosure. To combat this, we created a modified index, entitled the Zone Overlap Index (ZOI). This modified index is the exact mathematical equivalent of the original index when zone sizes are equal. When zone sizes are unequal, the ZOI generates higher values when animals share smaller, as opposed to larger, zones. This is because animals are more likely to share larger enclosure zones simply by chance, and shared use of smaller zones brings individuals into closer proximity with the potential for competition. To illustrate the application of the ZOI, a series of hypothetical situations were generated to reflect real-world scenarios, demonstrating how this index could be used to better understand zone occupancy overlap in the zoo.

A review of caracal and jungle cat diets across their geographical ranges during 1842-2021

Co-occurring carnivore species that are phylogenetically related or of similar size, morphology, and ecological needs often reduce competition by partitioning shared resources through temporal, spatial, and dietary niche segregation via behavioral adaptations. Caracals (Caracal caracal) and jungle cats (Felis chaus) co-occur in portions of their geographical ranges and are expected to display resource segregation in these ranges. We compiled scat, stomach content, and prey remains found data from published and unpublished sources to summarize information on the diets of caracals and jungle cats across their geographical ranges during 1842-2021. We obtained 63 sources from 26 countries in Europe, Asia, and Africa, in which caracal diet included 151 species while jungle cat diet included 61 species. We found that caracals and jungle cats did not exhibit dietary niche partitioning and had greater dietary similarities in areas of range overlap. We also found that caracals consumed more diverse prey species including prey with greater average body mass compared to jungle cats. Our results suggest that greater prey diversity in areas of range overlap, caracal predation on wide range of prey, and opportunistic feeding behavior that facilitates consumption of more diverse prey species compared to jungle cats, may facilitate co-occurrence between these two felid species.

Habitat use by the endangered spotted-tailed quoll in a fragmented landscape

The spotted-tailed quoll (Dasyurus maculatus) is an endangered mesopredator endemic to Australia. It is generally considered a forest-dependent species associated with large, intact forested habitats. In Australia’s mainland, quoll research has typically been conducted in contiguous forest, and consequently, the species’ presumed forest-dependency might reflect sampling bias rather than preferred habitat niche. Recent studies have revealed that quolls also persist in fragmented agricultural landscapes, raising questions about their true habitat requirements and preferences. In this study, we investigated quoll habitat use within a fragmented agricultural landscape in mainland Australia. We deployed 42 lured camera traps to determine quoll habitat preferences across four broad vegetation types (open grassland, grassy woodland, dry sclerophyll forest, and wet sclerophyll forest) based on quoll activity and occupancy. Quolls were detected in all vegetation types, and quoll activity indicated a preference for dry sclerophyll forest and grassy woodlands, although this preference varied depending on the time of year. Our results suggest that quoll habitat use in mainland Australia is more flexible than previously assumed, and we recommend further research on factors that may influence habitat preference such as prey availability and seasonal behavior. Understanding the factors that drive habitat use by quolls outside of contiguous forested landscapes will inform and improve conservation and management strategies to ensure critical habitat for the species is protected and retained in an increasingly fragmented landscape.

Is resource partitioning between two sympatric species of Gracilinanus (Didelphimorphia: Didelphidae) related to trophic and spatial niches?

Small mammal species may occur in sympatry, and it is relevant to investigate the mechanisms that lead to coexistence of the closely related species. Despite this, studies evaluating the coexistence of closely related Neotropical marsupials are insipient. The aim of this study was to analyse the mechanisms of resource partitioning between the sympatric species of mouse opossums Gracilinanus agilis and G. microtarsus (Didelphidae), evaluating their trophic and spatial niche. We hypothesized that G. agilis and G. microtarsus differ in at least one niche dimension (space use or food preferences) as a mechanism of coexistence. In the study we analysed trophic niche by evaluating the frequency of occurrence of food items present in Gracilinanus faeces. Also, we analysed spatial niche by comparing the vegetal stratum where the individuals were captured and its relationship with the environmental complexity. Both species presented a high trophic niche overlap, with differences in the frequencies of occurrence of the consumed items. Although the most frequent items in the faeces were Hymenoptera, Isoptera and Coleoptera, their proportion differed significantly between the two species. The variety of food items also differed, with flowers being more frequent in G. agilis diet, whereas fruits were more recorded for G. microtarsus. The spatial niche was very similar, with both species being more captured in the forest understory. However, habitat complexity influenced the abundance of both species, especially litter depth and its biomass of leaves. The results indicated that the coexistence of the two species is associated with the trophic and spatial niche, and that this niche segregation could be allowing closely related species of Gracilinanus to coexist.

Population Genetics of the Invasive Red Fox, Vulpes vulpes, in South-Eastern Australia

The use of genetic information in conservation biology has become more widespread with genetic information more readily available for non-model organisms. It has also been recognized that genetic information from invasive species can inform their management and control. The red fox poses a significant threat to Australian native fauna and the agricultural industry. Despite this, there are few recently published studies investigating the population genetics of foxes in Australia. This study investigated the population genetics of 94 foxes across the Illawarra and Shoalhaven regions of New South Wales, Australia. Diversity Array sequencing technology was used to genotype a large number of single nucleotide polymorphisms (N = 33,375). Moderate genetic diversity and relatedness were observed across the foxes sampled. Low to moderate levels of inbreeding, high-levels of identity-by-state values, as well as high identity-by-descent values were also found. There was limited evidence for population genetic structure among the foxes across the landscape sampled, supporting the presence of a single population across the study area. This indicates that there may be no barriers hindering fox dispersal across the landscape.

Does aerial baiting for controlling feral cats in a heterogeneous landscape confer benefits to a threatened native meso-predator?

Introduced mammalian predators can have devastating impacts on recipient ecosystems and disrupt native predator–prey relationships. Feral cats (Felis catus) have been implicated in the decline and extinction of many Australian native species and developing effective and affordable methods to control them is a national priority. While there has been considerable progress in the lethal control of feral cats, effective management at landscape scales has proved challenging. Justification of the allocation of resources to feral cat control programs requires demonstration of the conservation benefit baiting provides to native species susceptible to cat predation. Here, we examined the effectiveness of a landscape-scale Eradicat® baiting program to protect threatened northern quolls (Dasyurus hallucatus) from feral cat predation in a heterogeneous rocky landscape in the Pilbara region of Western Australia. We used camera traps and GPS collars fitted to feral cats to monitor changes in activity patterns of feral cats and northern quolls at a baited treatment site and unbaited reference site over four years. Feral cat populations appeared to be naturally sparse in our study area, and camera trap monitoring showed no significant effect of baiting on cat detections. However, mortality rates of collared feral cats ranged from 18–33% after baiting, indicating that the program was reducing cat numbers. Our study demonstrated that feral cat baiting had a positive effect on northern quoll populations, with evidence of range expansion at the treatment site. We suggest that the rugged rocky habitat preferred by northern quolls in the Pilbara buffered them to some extent from feral cat predation, and baiting was sufficient to demonstrate a positive effect in this relatively short-term project. A more strategic approach to feral cat management is likely to be required in the longer-term to maximise the efficacy of control programs and thereby improve the conservation outlook for susceptible threatened fauna.

Habitat features and colony characteristics influencing ant personality and its fitness consequences

Several factors can influence individual and group behavioral variation that can have important fitness consequences. In this study, we tested how two habitat types (seminatural meadows and meadows invaded by Solidago plants) and factors like colony and worker size and nest density influence behavioral (activity, meanderness, exploration, aggression, and nest displacement) variation on different levels of the social organization of Myrmica rubra ants and how these might affect the colony productivity. We assumed that the factors within the two habitat types exert different selective pressures on individual and colony behavioral variation that affects colony productivity. Our results showed individual-/colony-specific expression of both mean and residual behavioral variation of the studied behavioral traits. Although habitat type did not have any direct effect, habitat-dependent factors, like colony size and nest density influenced the individual mean and residual variation of several traits. We also found personality at the individual-level and at the colony level. Exploration positively influenced the total- and worker production in both habitats. Worker aggression influenced all the productivity parameters in seminatural meadows, whereas activity had a positive effect on the worker and total production in invaded meadows. Our results suggest that habitat type, through its environmental characteristics, can affect different behavioral traits both at the individual and colony level and that those with the strongest effect on colony productivity primarily shape the personality of individuals. Our results highlight the need for complex environmental manipulations to fully understand the effects shaping behavior and reproduction in colony-living species.

High Trophic Niche Overlap between a Native and Invasive Mink Does Not Drive Trophic Displacement of the Native Mink during an Invasion Process

Simple Summary

Invasive species are widely recognized to negatively affect native species through both direct and indirect interactions. When diet overlap between the native and invasive species increases, their competitive interaction is expected to increase too. This in turn may lead to displacement of one of the species. However, the specific mechanisms of the diet displacement are still unclear. In this study, we analysed the diet and diet overlap between the critically endangered European mink and the invasive American mink during the invasion process of the latter species by means of stable isotope analyses. We found a significant diet overlap between the native and invasive mink when they co-occur, an important individual variation of diet, and no significant change of diet of the native species in response to the arrival of the invasive mink. These results suggest significant competitive pressure imposed on the native European mink by the invasive American mink. As such, urgent implementation of control measures of invasive species is needed to ensure the viability and conservation of endangered European mink populations.

Abstract

The pressure elicited by invasive species on native species significantly increases with the increase of the overlap of their ecological niches. Still, the specific mechanisms of the trophic displacement of native species during the invasion process are unclear. The effects of the invasive American mink (Neovison vison) on the critically endangered European mink (Mustela lutreola) was assessed by analyses of diet and niche overlap during the invasion process. To do this, the isotopic composition (δ¹³C and δ¹⁵N) of both species of mink and their four main types of prey was analysed. Significant trophic overlap between the native European mink and invasive American mink was found when they coexisted in sympatry. Furthermore, both mink species were characterised by significant individual variation in diet and no obvious change in diet of the native species in response to the arrival of the introduced species was observed. High niche overlap registered between both species in sympatry with no displacement in diet of the native mink in response to the arrival of the invasive mink is expected to have important consequences for the viability and conservation of the native mink populations, as it suggests high competitive pressure.

Human disturbance has contrasting effects on niche partitioning within carnivore communities

Among species, coexistence is driven partly by the partitioning of available resources. The mechanisms of coexistence and competition among species have been a central topic within community ecology, with particular focus on mammalian carnivore community research. However, despite growing concern regarding the impact of humans on the behaviour of species, very little is known about the effect of humans on species interactions. The aim of this review is to establish a comprehensive framework for the impacts of human disturbance on three dimensions (spatial, temporal and trophic) of niche partitioning within carnivore communities and subsequent effects on both intraguild competition and community structure. We conducted a systematic review of the literature on carnivore niche partitioning (246 studies) and extracted 46 reported effects of human disturbance. We found evidence that human disturbance impacts resource partitioning, either positively or negatively, in all three niche dimensions. The repercussions of such variations are highly heterogeneous and differ according to both the type of human disturbance and how the landscape and/or availability of resources are affected. We propose a theoretical framework of the three main outcomes for the impacts of human disturbance on intraguild competition and carnivore community structure: (i) human disturbance impedes niche partitioning, increasing intraguild competition and reducing the richness and diversity of the community; (ii) human disturbance unbalances niche partitioning and intraguild competition, affecting community stability; and (iii) human disturbance facilitates niche partitioning, decreasing intraguild competition and enriching the community. We call for better integration of the impact of humans on carnivore communities in future research on interspecific competition.

Spatio-temporal partitioning facilitates mesocarnivore sympatry in the Stara Planina Mountains, Bulgaria

The top trophic level in many terrestrial food webs is typically occupied by mammalian carnivores (Order Carnivora) that broadly affect and shape ecosystems through trophic cascades. Their inter-specific interactions can further complicate effects on community dynamics as a consequence of intra-guild competition. The capacity for competitive mammalian carnivores to segregate their hunting and activity regimes is in major part a function of their similarity, in terms of body-size and dietary niche; termed the 'niche variation hypothesis'. In this study, we used camera-trapping to investigate intra-guild interactions and spatio-temporal partitioning among five mesocarnivores, the golden jackal (Canis aureus), European badger (Meles meles), red fox (Vulpes vulpes), European wildcat (Felis sylvestris) and stone marten (Martes foina), in the Stara Planina Mountains, Bulgaria. We collected a total of 444 images of golden jackals, 236 images of European badgers, 200 images of red foxes, 171 images of stone martens, and 145 images of European wildcats, from 6612 camera-days across fifteen camera-trapping stations. With respect to body size, the three smaller species (fox, wildcat and marten) were active in different time periods than the two larger competitors (jackal and badger) through both the warm and cold season. The more similar the trophic niche between species pairs (particularly relating to rodent consumption), the greater the spatio-temporal partitioning we observed within the pair; however, this adapted to seasonal dietary shifts. In conclusion, spatial and temporal (fine-scale and seasonal) niche partitioning appeared to reduce encounter probabilities and competition and may act to facilitate sympatric coexistence among this regional mesocarnivore guild.

Scent-sniffing dogs can discriminate between native Eurasian and invasive North American beavers

The invasion of a species can cause population reduction or extinction of a similar native species due to replacement competition. There is a potential risk that the native Eurasian beaver (Castor fiber) may eventually be competitively excluded by the invasive North American beaver (C. canadensis) from areas where they overlap in Eurasia. Yet currently available methods of census and population estimates are costly and time-consuming. In a laboratory environment, we investigated the potential of using dogs (Canis lupus familiaris) as a conservation tool to determine whether the Eurasian or the North American beaver is present in a specific beaver colony. We hypothesized that dogs can discriminate between the two beaver species, via the odorant signal of castoreum from males and females, in two floor platform experiments. We show that dogs detect scent differences between the two species, both from dead beaver samples and from scent marks collected in the field. Our results suggest that dogs can be used as an “animal biosensor” to discriminate olfactory signals of beaver species, however more tests are needed. Next step should be to test if dogs discern between beaver species in the field under a range of weather conditions and habitat types and use beaver samples collected from areas where the two species share the same habitat. So far, our results show that dogs can be used as a promising tool in the future to promote conservation of the native beaver species and eradication of the invasive one. We therefore conclude that dogs may be an efficient non-invasive tool to help conservationist to manage invasive species in Europe, and advocate for European wildlife agencies to invest in this new tool.

Living with roommates in a shared den: Spatial and temporal segregation among semifossorial mammals

Positive interspecific interactions in animal communities (i.e. den sharing) have long been overlooked in animal ecology. The assessment of spatiotemporal overlap among species living within the same burrow system is paramount to explain their strategies of interspecific coexistence. We studied spatiotemporal behavioural patterns of coexistence among four den-sharing mammal species (i.e. the crested porcupine Hystrix cristata, the Eurasian badger Meles meles, the red fox Vulpes vulpes and the European pine marten Martes martes), inhabiting a hilly area of central Italy. Intensive camera trapping (September 2015-September 2018) was used to estimate the interspecific overlap of both temporal and spatial activity patterns for all species combinations. An extensive nocturnal temporal overlap was recorded among all the species, except the diurnal pine marten. However, crested porcupines were mostly active in the darkest nights, whereas bright moonlight enhanced the hunting success of the red fox. Activity of badgers was limited in bright nights only during cold months, when predation pressure and poaching risk were the highest. Crested porcupines avoided spatial sharing outside the den with both nocturnal carnivores, particularly during the winter, when its cubs are in the den. Overlap in ranging areas and activity rhythms between the red fox and the Eurasian badger may be promoted by a remarkable food niche partitioning. Conversely, spatiotemporal overlap between red foxes and pine martens suggested a significant interspecific spatial partitioning, due to the overlap in feeding habits. Den-sharing represents a form of positive interspecific interaction which may limit energy waste and increase local species diversity and densities. Species using the same burrow system may show both spatial and temporal niche partitioning throughout the year, thus allowing a non-competitive coexistence.

Effect of free-ranging dogs and cats on medium-sized wild mammal assemblages in urban protected areas of a Mexican city

Abstract ContextUrban protected areas (PAs) are the habitat of several Neotropical medium-sized wild mammal (MSWM) species. However, this richness is seriously threatened by the growing populations of free-ranging dogs and cats in these areas. AimsThe aim of the present study was to evaluate the effect of free-ranging dogs and cats on the assemblage structure of MSWM in PAs of Xalapa city, Veracruz, Mexico. MethodsCamera traps were used to assess the effect of abundance and activity of dogs and cats on richness, abundance, dominance and activity of MSWM across two urban and three peri-urban PAs. The effect of plant diversity, vegetation structure and PA on mammal richness, activity and abundance were also evaluated. Key resultsThe dominance of MSWM was higher in peri-urban areas than urban areas, and the activity of dogs and cats from peri-urban and urban PAs was similar with wildest MSWM. Only inside urban areas did the size of the area and the dogs’ activity have a negative effect on the richness, activity and abundance of MSWM. Moreover, the activity and abundance of cats also had a negative effect on the activity of MSWM in urban PAs. The presence of dogs affected the latency of appearance of MSWM. ConclusionsThe presence of free-ranging dogs and cats in urban PAs affects MSWM assemblages and their appearance latency. ImplicationsThe potential harm of free-ranging dogs and cats on the community of MSWM in urban areas is clear, as is the need for increased scientific research to aid in the control of these exotic species in urban landscapes.

From carrion to Christmas beetles: the broad dietary niche of the red fox in a hybrid coastal ecosystem in south-eastern Queensland

The diet of the European red fox (Vulpes vulpes) was investigated through analysis of 1185 scats collected between 2010 and 2014 from coastal south-east Queensland, Australia. By both frequency of occurrence and volume, its diet was dominated by terrestrial arthropods, marine arthropods, vegetation and birds, although the remains of the short-tailed shearwater (Ardenna tenuirostris) consumed as carrion dominated the latter. Terrestrial arthropods, primarily insects of the order Coleoptera, were eaten all year (61% frequency of occurrence, FO) but varied seasonally (35–67%FO), mostly due to the consumption of large numbers of Christmas beetles (Anoplognathus spp.) in the summer months. Marine arthropods consisted almost entirely of ghost crabs (Ocypode spp.) and seasonal variation in consumption was evident (33–72%FO) and likely correlated with ghost crab abundance. Fruit and berries were an important food item for foxes all year but also varied seasonally (30–65%FO). The opportunistic diet of this fox population is discussed in the context of dietary differences, but common opportunism, reported in other Australian and overseas studies.

Top carnivore decline has cascading effects on scavengers and carrion persistence

Top carnivores have suffered widespread global declines, with well-documented effects on mesopredators and herbivores. We know less about how carnivores affect ecosystems through scavenging. Tasmania's top carnivore, the Tasmanian devil (Sarcophilus harrisii), has suffered severe disease-induced population declines, providing a natural experiment on the role of scavenging in structuring communities. Using remote cameras and experimentally placed carcasses, we show that mesopredators consume more carrion in areas where devils have declined. Carcass consumption by the two native mesopredators was best predicted by competition for carrion, whereas consumption by the invasive mesopredator, the feral cat (Felis catus), was better predicted by the landscape-level abundance of devils, suggesting a relaxed landscape of fear where devils are suppressed. Reduced discovery of carcasses by devils was balanced by the increased discovery by mesopredators. Nonetheless, carcasses persisted approximately 2.6-fold longer where devils have declined, highlighting their importance for rapid carrion removal. The major beneficiary of increased carrion availability was the forest raven (Corvus tasmanicus). Population trends of ravens increased 2.2-fold from 1998 to 2017, the period of devil decline, but this increase occurred Tasmania-wide, making the cause unclear. This case study provides a little-studied potential mechanism for mesopredator release, with broad relevance to the vast areas of the world that have suffered carnivore declines.

Resource partitioning between kit foxes (Vulpes macrotis) and coyotes (Canis latrans): a comparison of historical and contemporary dietary overlap

Range expansions by generalists can alter communities and introduce competitive pressures on native species. In the Great Basin Desert, USA, coyotes (Canis latrans Say, 1823) have colonized and are now sympatric with native kit foxes (Vulpes macrotis Merriam, 1888). Since both species have similar diets, dietary partitioning may facilitate coexistence. We analyzed coyote and kit fox diets, then compared our results to an earlier study. Because populations are dynamic, we expected that decreases in prey or increases in predator abundance could alter dietary patterns. We found no significant changes in population-level prey diversity for kit foxes or coyotes, but found high levels of dietary overlap between species. We did detect a significant decrease in the relative importance of leporids (family Leporidae) in the diets of both canids, but they remained important for coyotes. The relative importance of small mammals was greater for kit foxes than coyotes, but their importance had not changed significantly over time. We detected significant declines in prey diversity per sample (scat-level dietary diversity) for both canids, suggesting that during a foraging event, individuals may encounter less diverse prey now than historically. These findings suggested that kit foxes and coyotes were not limited by prey, despite high dietary overlap.

Degrees of population-level susceptibility of Australian terrestrial non-volant mammal species to predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus)

Context Over the last 230 years, the Australian terrestrial mammal fauna has suffered a very high rate of decline and extinction relative to other continents. Predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus) is implicated in many of these extinctions, and in the ongoing decline of many extant species. Aims To assess the degree to which Australian terrestrial non-volant mammal species are susceptible at the population level to predation by the red fox and feral cat, and to allocate each species to a category of predator susceptibility. Methods We collated the available evidence and complemented this with expert opinion to categorise each Australian terrestrial non-volant mammal species (extinct and extant) into one of four classes of population-level susceptibility to introduced predators (i.e. ‘extreme’, ‘high’, ‘low’ or ‘not susceptible’). We then compared predator susceptibility with conservation status, body size and extent of arboreality; and assessed changes in the occurrence of species in different predator-susceptibility categories between 1788 and 2017. Key results Of 246 Australian terrestrial non-volant mammal species (including extinct species), we conclude that 37 species are (or were) extremely predator-susceptible; 52 species are highly predator-susceptible; 112 species are of low susceptibility; and 42 species are not susceptible to predators. Confidence in assigning species to predator-susceptibility categories was strongest for extant threatened mammal species and for extremely predator-susceptible species. Extinct and threatened mammal species are more likely to be predator-susceptible than Least Concern species; arboreal species are less predator-susceptible than ground-dwelling species; and medium-sized species (35 g–3.5kg) are more predator-susceptible than smaller or larger species. Conclusions The effective control of foxes and cats over large areas is likely to assist the population-level recovery of ~63 species – the number of extant species with extreme or high predator susceptibility – which represents ~29% of the extant Australian terrestrial non-volant mammal fauna. Implications Categorisation of predator susceptibility is an important tool for conservation management, because the persistence of species with extreme susceptibility will require intensive management (e.g. predator-proof exclosures or predator-free islands), whereas species of lower predator susceptibility can be managed through effective landscape-level suppression of introduced predators.

Dietary partitioning of Australia's two marsupial hypercarnivores, the Tasmanian devil and the spotted-tailed quoll, across their shared distributional range

Australia's native marsupial fauna has just two primarily flesh-eating 'hypercarnivores', the Tasmanian devil (Sarcophilus harrisii) and the spotted-tailed quoll (Dasyurus maculatus) which coexist only on the island of Tasmania. Devil populations are currently declining due to a fatal transmissible cancer. Our aim was to analyse the diet of both species across their range in Tasmania, as a basis for understanding how devil decline might affect the abundance and distribution of quolls through release from competition. We used faecal analysis to describe diets of one or both species at 13 sites across Tasmania. We compared diet composition and breadth between the two species, and tested for geographic patterns in diets related to rainfall and devil population decline. Dietary items were classified into 6 broad categories: large mammals (≥ 7.0kg), medium-sized mammals (0.5-6.9kg), small mammals (< 0.5kg), birds, reptiles and invertebrates. Diet overlap based on prey-size category was high. Quoll diets were broader than devils at all but one site. Devils consumed more large and medium-sized mammals and quolls more small mammals, reptiles and invertebrates. Medium-sized mammals (mainly Tasmanian pademelon Thylogale billardierii), followed by large mammals (mainly Bennett's wallaby Macropus rufogriseus) and birds, were the most important prey groups for both species. Diet composition varied across sites, suggesting that both species are flexible and opportunistic foragers, but was not related to rainfall for devils. Quolls included more large mammals but fewer small mammals and invertebrates in their diet in the eastern drier parts of Tasmania where devils have declined. This suggests that a competitive release of quolls may have occurred and the substantial decline of devils has provided more food in the large-mammal category for quolls, perhaps as increased scavenging opportunities. The high diet overlap suggests that if resources become limited in areas of high devil density, interspecific competition could occur.

Multidimensional differentiation in foraging resource use during breeding of two sympatric top predators

Ecologically-similar species were found to develop specific strategies to partition their resources, leading to niche differentiation and divergence, in order to avoid interspecific competition. Our study determines multi-dimensional differentiation of two sympatric top-predators, long-legged buzzards (LLB) and short-toed eagles (STE), which recently became sympatric during their breeding season in the Judean Foothills, Israel. By combining information from comprehensive diet and movement analyses we found four dimensions of differentiation: (1) Geographic foraging area: LLB tended to forage relatively close to their nests (2.35 ± 0.62 km), while STE forage far from their nest (13.03 ± 2.20 km); (2) Foraging-habitat type: LLBs forage at low natural vegetation, avoiding cultivated fields, whereas STEs forage in cultivated fields, avoiding low natural vegetation; (3) Diurnal dynamics of foraging: LLBs are uniformly active during daytime, whereas STEs activity peaks in the early afternoon; and (4) Food-niche: while both species largely rely on reptiles (47.8% and 76.3% for LLB and STE, respectively), LLB had a more diverse diet and consumed significantly higher percentages of lizards, while STE consumed significantly higher percentages of snakes. Our results suggest that this multidimensional differentiation allows the spatial coexistence of these two dense populations in the study area.

Tracking neighbours promotes the coexistence of large carnivores

The study of competition and coexistence among similar interacting species has long been considered a cornerstone in evolutionary and community ecology. However, understanding coexistence remains a challenge. Using two similar and sympatric competing large carnivores, Eurasian lynx and wolverines, we tested the hypotheses that tracking among heterospecifics and reactive responses to potential risk decreases the probability of an agonistic encounter when predators access shared food resources, thus facilitating coexistence. Lynx and wolverines actively avoided each other, with the degree of avoidance being greater for simultaneous than time-delayed predator locations. Wolverines reacted to the presence of lynx at relatively short distances (mean: 383 m). In general, lynx stayed longer, and were more stationary, around reindeer carcasses than wolverines. However, when both predators were present at the same time around a carcass, lynx shortened their visits, while wolverine behavior did not change. Our results support the idea that risk avoidance is a reactive, rather than a predictive, process. Since wolverines have adapted to coexist with lynx, exploiting lynx-killed reindeer carcasses while avoiding potential encounters, the combined presence of both predators may reduce wolverine kill rate and thus the total impact of these predators on semi-domestic reindeer in Scandinavia. Consequently, population management directed at lynx may affect wolverine populations and human-wolverine conflicts.

Diet of dingoes and other wild dogs in peri-urban areas of north-eastern Australia

Knowledge of the resource requirements of urban predators can improve our understanding of their ecology and assist town planners and wildlife management agencies in developing management approaches that alleviate human-wildlife conflicts. Here we examine food and dietary items identified in scats of dingoes in peri-urban areas of north-eastern Australia to better understand their resource requirements and the potential for dingoes to threaten locally fragmented populations of native fauna. Our primary aim was to determine what peri-urban dingoes eat, and whether or not this differs between regions. We identified over 40 different food items in dingo scats, almost all of which were mammals. Individual species commonly observed in dingo scats included agile wallabies, northern brown bandicoots and swamp wallabies. Birds were relatively common in some areas but not others, as were invertebrates. Dingoes were identified as a significant potential threat to fragmented populations of koalas. Dietary overlap was typically very high or near-identical between regions, indicating that peri-urban dingoes ate the same types or sizes of prey in different areas. Future studies should seek to quantify actual and perceived impacts of, and human attitudes towards, peri-urban dingoes, and to develop management strategies with a greater chance of reducing human-wildlife conflicts.

Research priorities for the northern quoll (Dasyurus hallucatus) in the Pilbara region of Western Australia

The Pilbara population of the northern quoll (Dasyurus hallucatus) has been seldom studied, and the impacts of threats such as altered fire regimes, total grazing pressure, predation and mining and infrastructure development are not well understood. While the Pilbara was once thought likely to provide refuge for northern quolls from the poisonous cane toad (Rhinella marina), recent modelling suggests that cane toads will invade the region. The environmental approvals process for mining development in the Pilbara has generated considerable offset funds that are to be directed towards research on the northern quoll. In an effort to identify future research priorities for this species in the Pilbara through a collaborative process, the Western Australian Department of Parks and Wildlife hosted a workshop attended by scientists, environmental consultants, mining proponents and state and federal regulators. Participants at the workshop identified five key areas for future research effort: (1) develop appropriate and standardised survey and monitoring methods; (2) define areas of critical habitat and better understand how disturbance affects habitat quality; (3) improve our understanding of population dynamics; (4) better understand the key threats to the northern quoll and the interactions between these threats in the Pilbara; and (5) determine whether the northern quoll will colonise restored areas or artificial habitat. We provide the expected timelines and current allocation of resources to these research priorities over the next 10 years. We reflect on the lessons learnt from the workshop process and consider ways to improve the outcomes of such collaborative exercises.

Recent decline of an endangered, endemic rodent: does exclusion of disturbance play a role for Hastings River mouse (Pseudomys oralis)?

Context The role of disturbance and its exclusion is fundamental to the conservation of threatened species. Aims We used the habitat accommodation model as a framework to investigate the importance of forest disturbance for the endangered Hastings River mouse, Pseudomys oralis, focusing on timber harvesting. Methods Our study comprised two separate surveys. We resurveyed old survey sites (n = 24) where the species was originally recorded as either present (logging excluded) or absent (subsequently logged). A second survey targeted trapping in high-quality habitat stratified by different times since logging. Finally, we analysed a 15-year trapping dataset targeting P. oralis to assess associations with co-occurring species. Key results The resurvey of old sites resulted in 12 P. oralis individuals being trapped, compared with 46 individuals in original surveys. Substantial declines were observed over time in transects where logging was excluded (60–82% decline), whereas there was little change at transects where P. oralis was not previously trapped and that were subsequently logged. The second survey yielded 27 P. oralis captures at post-logging sites assessed as high quality. Occupancy was very high (ψ = 0.93 ± 0.21) in transects logged 7–15 years ago and was 60% less in transects where logging was excluded for 35–45 years (ψ = 0.37 ± 0.22), whereas occupancy in transects logged 2–6 years ago was intermediate. This pattern of higher occupancy in logged areas was mirrored for the mean number of P. oralis trapped per transect. Ordination of habitat data showed an association of P. oralis with heath, mat-rushes and logs, whereas rats (Rattus and Melomys) were associated with ferns and shrubs. Camera traps revealed low background levels of predator presence. A negative exponential relationship was found between probability of occupancy of P. oralis and rat abundance from a 15-year trapping dataset (44 275 trap-nights), suggesting that rats may compete with P. oralis. Conclusions Our results supported the habitat accommodation model and suggested that disturbance is likely to influence the persistence of P. oralis. However, an interaction between predation and loss of cover from high-frequency disturbance (fire or intense grazing) cannot be excluded as a key threat. Implications Disturbance should be incorporated into the management of some species. Adaptive monitoring is recommended to assess alternative management regimes.

Interspecific and geographic variation in the diets of sympatric carnivores: dingoes/wild dogs and red foxes in south-eastern Australia

Dingoes/wild dogs (Canis dingo/familiaris) and red foxes (Vulpes vulpes) are widespread carnivores in southern Australia and are controlled to reduce predation on domestic livestock and native fauna. We used the occurrence of food items in 5875 dingo/wild dog scats and 11,569 fox scats to evaluate interspecific and geographic differences in the diets of these species within nine regions of Victoria, south-eastern Australia. The nine regions encompass a wide variety of ecosystems. Diet overlap between dingoes/wild dogs and foxes varied among regions, from low to near complete overlap. The diet of foxes was broader than dingoes/wild dogs in all but three regions, with the former usually containing more insects, reptiles and plant material. By contrast, dingoes/wild dogs more regularly consumed larger mammals, supporting the hypothesis that niche partitioning occurs on the basis of mammalian prey size. The key mammalian food items for dingoes/wild dogs across all regions were black wallaby (Wallabia bicolor), brushtail possum species (Trichosurus spp.), common wombat (Vombatus ursinus), sambar deer (Rusa unicolor), cattle (Bos taurus) and European rabbit (Oryctolagus cuniculus). The key mammalian food items for foxes across all regions were European rabbit, sheep (Ovis aries) and house mouse (Mus musculus). Foxes consumed 6.1 times the number of individuals of threatened Critical Weight Range native mammal species than did dingoes/wild dogs. The occurrence of intraguild predation was asymmetrical; dingoes/wild dogs consumed greater biomass of the smaller fox. The substantial geographic variation in diet indicates that dingoes/wild dogs and foxes alter their diet in accordance with changing food availability. We provide checklists of taxa recorded in the diets of dingoes/wild dogs and foxes as a resource for managers and researchers wishing to understand the potential impacts of policy and management decisions on dingoes/wild dogs, foxes and the food resources they interact with.

Home range and activity patterns measured with GPS collars in spotted-tailed quolls

The spotted-tailed quoll (Dasyurus maculatus) is the largest marsupial carnivore on mainland Australia. It usually occurs at relatively low population densities and its cryptic nature makes it exceedingly difficult to observe in its natural habitat. On the mainland the species is also listed as nationally endangered and more information is needed to direct any meaningful conservation effort. In this study we aimed to elucidate quolls’ spatial requirements and activity patterns using GPS collars on 10 males and 4 females. Quolls were predominantly nocturnal but some individuals showed pronounced daytime activity. There was no apparent seasonal shift in the timing of activity. The movement of quolls appeared to be confined to home ranges that were relatively large for predators of their size. Furthermore, males used home ranges about three times as large as that of the smaller females. There appeared to be some spatial segregation between not only females, which have been considered territorial, but also males. Overall, it is likely that the larger areas used by males is partly caused by the sexual dimorphism in body mass that entails differences in prey requirements and spectrum, but probably is also a function of a promiscuous mating system. All of these could explain the observed more unidirectional movement and larger distances travelled per day by males.

The (non)effects of lethal population control on the diet of Australian dingoes

Top-predators contribute to ecosystem resilience, yet individuals or populations are often subject to lethal control to protect livestock, managed game or humans from predation. Such management actions sometimes attract concern that lethal control might affect top-predator function in ways ultimately detrimental to biodiversity conservation. The primary function of a predator is predation, which is often investigated by assessing their diet. We therefore use data on prey remains found in 4,298 Australian dingo scats systematically collected from three arid sites over a four year period to experimentally assess the effects of repeated broad-scale poison-baiting programs on dingo diet. Indices of dingo dietary diversity and similarity were either identical or near-identical in baited and adjacent unbaited treatment areas in each case, demonstrating no control-induced change to dingo diets. Associated studies on dingoes' movement behaviour and interactions with sympatric mesopredators were similarly unaffected by poison-baiting. These results indicate that mid-sized top-predators with flexible and generalist diets (such as dingoes) may be resilient to ongoing and moderate levels of population control without substantial alteration of their diets and other related aspects of their ecological function.