Human-resource subsidies alter the dietary preferences of a mammalian top predator

Bottom-up rather than top-down mechanisms determine mesocarnivore interactions in Norway

Interactions among coexisting mesocarnivores can be influenced by different factors such as the presence of large carnivores, land-use, environmental productivity, or human disturbance. Disentangling the relative importance of bottom-up and top-down processes can be challenging, but it is important for biodiversity conservation and wildlife management. The aim of this study was to assess how the interactions among mesocarnivores (red fox Vulpes vulpes, badger Meles meles, and pine marten Martes martes) were affected by large carnivores (Eurasian lynx Lynx lynx and wolf Canis lupus), land cover variables (proportion of agricultural land and primary productivity), and human disturbance, as well as how these top-down and bottom-up mechanisms were influenced by season. We analyzed 3 years (2018-2020) of camera trapping observations from Norway and used structural equation models to assess hypothesized networks of causal relationships. Our results showed that land cover variables were more strongly associated with mesocarnivore detection rates than large carnivores in Norway. This might be caused by a combination of low density of large carnivores in an unproductive ecosystem with strong seasonality. Additionally, detection rates of all mesocarnivores showed positive associations among each other, which were stronger in winter. The prevalence of positive interactions among predators might indicate a tendency to use the same areas and resources combined with weak interference competition. Alternatively, it might indicate some kind of facilitative relationship among species. Human disturbance had contrasting effects for different species, benefiting the larger mesocarnivores (red fox and badger) probably through food subsidization, but negatively affecting apex predators (wolf and lynx) and smaller mesocarnivores (pine marten). In a human-dominated world, this highlights the importance of including anthropogenic influences in the study of species interactions.

‛Trophic switch' by catfish community from predation to scavenging modulated by human food discard in an estuarine bay

Benthic predatory catfishes are voracious and opportunistic predators and can easily shift their diet according to the availability of prey. In this study, feeding ecology of catfishes from two adjacent habitats of an estuarine bay is compared. The lower bay was relatively pristine as compared to the upper bay and was represented by two families of catfishes-Plotosidae and Ariidae, while the upper bay represented only ariid catfishes. Gut content analysis revealed that catfish predators from lower bay consumed conventional prey like teleosts and benthic invertebrates with a linear pattern of ontogenetic dietary shift. Plicofollis dussumieri and Plotosus canius occupied the position of top predators in the lower bay and were specialized feeders. Other predators like Plotosus lineatus, Arius arius, Arius jella, and Arius maculatus were generalist feeders occupying the position of mesopredators. However, in the upper bay, the catfish predators represented by Arius maculatus, Arius jella, and Arius arius predominantly fed on human discarded food. The easily available human food in the form of chicken, corn, and rice as noted from the investigated guts shows altered trophic guilds of ariid catfishes wherein only mid to large-sized catfish community was noted in this bay. A distinct "trophic switch" altered the trophic function from predation to scavenging which was observed in their feeding behavior. The anthropogenic impact in the form of unmanaged organic waste alters the role of predatory catfishes thereby restructuring the food web that may lead to unknown changes in the estuarine benthic ecosystems resulting in reduced ecosystem services.

Trophic downgrading of an adaptable carnivore in an urbanising landscape

Urbanisation critically alters wildlife habitat and resource distribution, leading to shifts in trophic dynamics. The loss of apex predators in human-transformed landscapes can result in changes in the ecological roles of the remaining mesocarnivores. Decreased top-down control together with increased bottom-up forcing through greater availability of anthropogenic foods can result in a predation paradox. Understanding these changes is important for conserving ecological function and biodiversity in rapidly urbanising systems. Here, we use stable isotope analysis to provide insight into longer term changes in trophic position, niche width and overlap of an elusive, medium-sized urban adapter, the caracal (Caracal caracal) in and around the city of Cape Town, South Africa. Using fur samples (n = 168) from individuals along a gradient of urbanisation we find that overall caracals have a broad isotopic dietary niche that reflects their large variation in resource use. When accounting for underlying environmental differences, the intensity of anthropogenic pressure, measured using the Human Footprint Index (HFI), explained variation in both food subsidy use (δ13C values) and trophic status (δ15N values). The significantly higher δ13C values (P < 0.01) and lower δ15N values (P < 0.001) of caracals in more urbanised areas suggest that predator subsidy consumption occurs via predictable, anthropogenic resource subsidies to synanthropic prey. These prey species are predominantly primary consumers, resulting in shifts in diet composition towards lower trophic levels. Further, caracals using areas with higher HFI had narrower isotope niches than those in less impacted areas, likely due to their hyperfocus on a few lower trophic level prey species. This pattern of niche contraction in urban areas is retained when accounting for caracal demographics, including sex and age. The removal of apex predators in human-transformed landscapes together with reliable resource availability, including abundant prey, may paradoxically limit the ecological influence of the remaining predators, and bring about a degree of predator trophic downgrading. The dampening of top-down control, and thus ecosystem regulation, likely points to widespread disruption of trophic dynamics in rapidly developing areas globally.

Diet of the Dingo in Subtropical Australian Forests: Are Small, Threatened Macropods at Risk?

Carnivores fulfil important ecological roles in natural systems yet can also jeopardise the persistence of threatened species. Understanding their diet is, therefore, essential for managing populations of carnivores, as well as those of their prey. This study was designed to better understand the diet of an Australian apex predator, the dingo, and determine whether it poses a threat to at-risk small macropods in two floristically different yet geographically close reserves in subtropical Australia. Based on an analysis of 512 scats, dingo diets comprised 34 different prey taxa, of which 50% were common between reserves. Our findings add support to the paradigm that dingoes are opportunistic and generalist predators that prey primarily on abundant mammalian fauna. Their diets in the Border Ranges were dominated by possum species (frequency of occurrence (FOC) = 92.5%), while their diets in Richmond Range were characterised by a high prevalence of pademelon species (FOC = 46.9%). Medium-sized mammals were the most important dietary items in both reserves and across all seasons. The dietary frequency of medium-sized mammals was generally related to their availability (indexed by camera trapping); however, the avoidance of some species with high availability indicates that prey accessibility may also be important in dictating their dietary choices. Other prey categories were supplementary to diets and varied in importance according to seasonal changes in their availability. The diets included two threatened macropods, the red-legged pademelon and black-striped wallaby. Our availability estimates, together with earlier dietary studies spanning 30 years, suggest that the red-legged pademelon is resilient to the observed predation. The black-striped wallaby occurred in only two dingo scats collected from Richmond Range and was not detected by cameras so the threat to this species could not be determined. Two locally abundant but highly threatened species (the koala and long-nosed potoroo) were not detected in the dingoes' diets, suggesting dingoes do not at present pose a threat to these populations. Our study highlights the importance of site-based assessments, population monitoring and including data on prey availability in dietary investigations.

Efficacy of Management Efforts to Reduce Food-Related Dingo-Human Interactions and Conflict on K'gari (Fraser Island), Australia

Humans and dingoes (Canis familiaris (dingo)) share the environment of K'gari, and conflict inevitably occurs between the two species, particularly over food. Dingo attacks on humans have occurred, and some have been serious and even fatal in outcome. Wildlife feeding may cause animals to develop unnatural and potentially dangerous behaviours towards conspecifics and humans on a relatively frequent basis. Food-based attraction has been implicated in the development of human-directed aggression in the dingo population of K'gari. Supplemental feeding, whether intentional or accidental, alters wildlife foraging behaviours and may have consequences at the population and ecosystem levels. Management strategies such as education programs, prohibition of inappropriate human behaviours (compliance) and fencing of garbage dumps have each been implemented to stop the intentional or inadvertent feeding of dingoes by people. However, there has been no formal assessment of the effectiveness of these interventions at reducing food-related dingo-human incidents over time. We collated and analysed 7791 unique reports of dingo-human interactions on K'gari between 1990 and 2020, inclusive of 1307 food-related reports, including the severity of these interactions. These data showed clear seasonal peaks in the percentage of food-related dingo-human interactions, corresponding with biologically significant breeding periods in autumn and weaning and dispersing in spring. Trends in serious food-related incidents remained stable overtime. Less serious food-related incidents declined, suggesting that management efforts were successful. However, these efforts appear to have reached the limits of their effectiveness. Further innovations are required to reduce serious incidents involving the relatively few dingoes and people still experiencing conflict, and thereby provide protection to both species on K'gari.

Distinctive diets of eutherian predators in Australia

Introduction of the domestic cat and red fox has devastated Australian native fauna. We synthesized Australian diet analyses to identify traits of prey species in cat, fox and dingo diets, which prey were more frequent or distinctive to the diet of each predator, and quantified dietary overlap. Nearly half (45%) of all Australian terrestrial mammal, bird and reptile species occurred in the diets of one or more predators. Cat and dingo diets overlapped least (0.64 ± 0.27, n = 24 location/time points) and cat diet changed little over 55 years of study. Cats were more likely to have eaten birds, reptiles and small mammals than foxes or dingoes. Dingo diet remained constant over 53 years and constituted the largest mammal, bird and reptile prey species, including more macropods/potoroids, wombats, monotremes and bandicoots/bilbies than cats or foxes. Fox diet had greater overlap with both cats (0.79 ± 0.20, n = 37) and dingoes (0.73 ± 0.21, n = 42), fewer distinctive items (plant material, possums/gliders) and significant spatial and temporal heterogeneity over 69 years, suggesting the opportunity for prey switching (especially of mammal prey) to mitigate competition. Our study reinforced concerns about mesopredator impacts upon scarce/threatened species and the need to control foxes and cats for fauna conservation. However, extensive dietary overlap and opportunism, as well as low incidence of mesopredators in dingo diets, precluded resolution of the debate about possible dingo suppression of foxes and cats.

Hybridisation between dingoes and domestic dogs in proximity to Indigenous communities in northern Australia

In northern Australia, wild dog populations potentially interact with domestic dogs from remote communities, which would create opportunities for disease transmission at the wild-domestic interface. An example is rabies, in the event of an incursion into northern Australia. However, the likelihood of such wild-domestic interactions is ambiguous. Hybridisation analyses based on 23 microsatellite DNA markers were performed on canine-origin scats collected in bushland areas around remote Indigenous communities in the Northern Peninsula Area, Queensland. Sufficient DNA was extracted from 6 of 41 scats to assess the percentage of dingo purity. These scats most likely originated from two 'pure' domestic dogs (0% dingo purity), one hybrid (20% dingo purity) and three 'pure' dingoes (92%-98% dingo purity). The two domestic dog samples were collected in the vicinity of communities. The location of two of the dingo-origin samples provides genetic evidence that dingoes are present in areas close to the communities. The availability of anthropogenic food resources likely creates opportunities for interactions with domestic dogs in the region. The hybrid sample demonstrates the occurrence of antecedent contacts between both populations by means of mating and supports the likelihood of a spatio-temporal overlap at the wild-domestic interface. This represents the first genetic survey involving a wild dog population of equatorial northern Queensland, with evidence of dingo purity. Our results have implications for potential disease transmission within a priority area for biosecurity in northern Australia.

Fear and stressing in predator-prey ecology: considering the twin stressors of predators and people on mammals

Predators induce stress in prey and can have beneficial effects in ecosystems, but can also have negative effects on biodiversity if they are overabundant or have been introduced. The growth of human populations is, at the same time, causing degradation of natural habitats and increasing interaction rates of humans with wildlife, such that conservation management routinely considers the effects of human disturbance as tantamount to or surpassing those of predators. The need to simultaneously manage both of these threats is particularly acute in urban areas that are, increasingly, being recognized as global hotspots of wildlife activity. Pressures from altered predator-prey interactions and human activity may each initiate fear responses in prey species above those that are triggered by natural stressors in ecosystems. If fear responses are experienced by prey at elevated levels, on top of responses to multiple environmental stressors, chronic stress impacts may occur. Despite common knowledge of the negative effects of stress, however, it is rare that stress management is considered in conservation, except in intensive ex situ situations such as in captive breeding facilities or zoos. We propose that mitigation of stress impacts on wildlife is crucial for preserving biodiversity, especially as the value of habitats within urban areas increases. As such, we highlight the need for future studies to consider fear and stress in predator-prey ecology to preserve both biodiversity and ecosystem functioning, especially in areas where human disturbance occurs. We suggest, in particular, that non-invasive in situ investigations of endocrinology and ethology be partnered in conservation planning with surveys of habitat resources to incorporate and reduce the effects of fear and stress on wildlife.

High rates of cannibalism and food waste consumption by dingoes living at a remote mining operation in the Great Sandy Desert, Western Australia

Mining operations in remote Australia represent a unique opportunity to examine the impact of supplementary food and water provision on local wildlife. Here, we present a dietary analysis of dingoes living at a mine site in the Great Sandy Desert, Western Australia. A total of 270 faeces (scats) were collected from across the mine footprint on two occasions three months apart. The most frequently consumed food resource was anthropogenic (rubbish), which was found in 218 of 270 faeces (80.7% of scats and 65.3% of scat volume). Also of note was a high proportion of dingo remains, which was found in 51 of 270 faeces (18.9% of scats and 10.4% of scat volume), suggesting the occurrence of cannibalism. These findings highlight the potential influence of human-modified areas and associated resource availability on the diet of dingoes, and have implications for the environmental management of areas surrounding mining operations.

Subsidies from anthropogenic resources alter diet, activity, and ranging behavior of an apex predator (Canis lupus)

Acquisition of resources can be costly and individuals are predicted to optimize foraging strategies to maximize net energy gain. Wolves (Canis lupus) would be expected to scavenge on subsidies from anthropogenic resources when these resources provide an energetic benefit over the capture of wild prey. We examined the effects of subsidies from anthropogenic resources in the form of livestock carcass dumps (LCDs) on wolf space use, activity, tortuosity, and diet in portions of North America’s northern hardwood/boreal ecosystem. We fitted 19 wolves with global positioning system collars during May–August of 2009–2011 and 2013–2015. Wolves with LCDs within their home ranges used areas adjacent to LCDs greater than non-LCD sites and had decreased home ranges and activity as compared to wolves without LCDs in their home ranges. Additionally, cattle comprised at least 22% of wolf diet from scavenging in areas with LCDs present as compared to no cattle in the diet of wolves without access to LCDs. Subsidies from anthropogenic resources in the form of LCDs can serve as attractants for wolves and alter wolf diet, activity, and ranging behavior. Apex predators may alter their behavior where subsidies from anthropogenic resources occur and management of these subsidies should be considered when attempting to reduce the impacts of humans on wolf behavior.

Restriction of anthropogenic foods alters a top predator’s diet and intraspecific interactions

Anthropogenic foods are utilized by many animals around the world, and these resources could impact dietary preferences and intra- and interspecific interactions. Under a quasi-Before-After-Control-Impact experimental design, we assessed how dingoes (Canis dingo) responded to a decline in anthropogenic foods in the Tanami Desert, central Australia. We did so by assessing dingo diets close to and away from human influence during a period when food waste was available at two rubbish tips, and then during a period when food waste was restricted at one of the tips. Our results demonstrate that access to anthropogenic foods can alter a top predator’s diet. Namely, dingoes showed a preference for eating the desert mouse (Pseudomys desertor) in areas where food waste was restricted, whereas dingo diets did not reflect ambient prey availability at areas where food waste was constantly available. Reduced availability of food waste also affected interactions between dingoes, with cannibalism decreasing where food waste was removed, and it may have increased consumption of a subordinate mesopredator, the feral cat (Felis catus). By implication, efforts to manage food waste could reestablish or strengthen interactions between predators and their wild prey with possible cascading consequences for ecosystems.

Contribution of mussel fall-off from aquaculture to wild lobster Homarus americanus diets

Anthropogenic subsidies to natural systems can influence the diet of mobile omnivore species and co-occurring species. This study assessed if fall-off from mussel aquaculture subsidized wild populations of mobile scavengers and predators, such as the commercially important lobster Homarus americanus. A Bayesian stable isotope-mixing model with parameters determined from the literature and from a 105 days laboratory feeding experiment was applied to wild lobsters to determine how important the various food sources were in these lobsters, especially mussel fall-off. Isotopic values were mainly affected by lobster size with model outputs indicating that large lobsters (>80 mm cephalothorax) fed mainly on mussels from the mussel farm (46% of the diet) while small ones fed mostly on the rock crab Cancer irroratus (99%). The contribution of mussel subsidies to the lobster's diet was thus size-specific and direct (i.e. through mussel fall-off and not through co-occurring species such as rock crab). The absence of a link between food sources and lipid energy content in lobsters suggested that the reduction of rock crab consumption would have to be more drastic to affect the general health of large lobsters in the short term.

Feeding responses of the golden jackal after reduction of anthropogenic food subsidies

Little is known of the resources that limit or promote the rapidly expanding golden jackal (Canis aureus) population in Europe. We hypothesised that in an area of intensive big game hunting, a reduction of the main food resource (human subsidised big game viscera) would result in dietary switching. We used multivariate analyses to test whether the dietary composition of 200 jackal stomachs varied between two 2-yearly survey occasions, the first without big game viscera removal (availability of 68 kg viscera/year/km²) followed by a period with viscera removal (minimum of 50 kg of viscera/year/km² removed). The proportion of empty stomachs and the stomach wet content weight did not differ between the two periods. Even after the reduction of food subsidies, the primary food of jackals was viscera and carrion from wild ungulates (frequency of occurrence: 45% vs. 30%; wet weight: 55% vs. 29%, respectively), and scavenging was not affected by season or sex. Log-linear analysis of frequency data revealed no significant differences between survey occasions in consumption of either food type. MANCOVA of wet weight data revealed that in the first period with food subsidies jackals consumed a higher proportion of adult wild boar (11.6% vs. 1.3%; from predation or scavenging), while juvenile wild boar (0 vs. 11.8%; from predation or scavenging), domestic animals (0.8% vs. 6.2%; mostly from scavenging) and invertebrates (2.6% vs. 4.1%) increased in the second period. The stomachs in the second survey occasion contained more varied food items, but the trophic niche was not significantly wider. The feeding responses of this mesopredator to the reduction of food subsidies were less pronounced than expected. Because in high big game density areas, wild ungulate carrion from different mortality causes are available in high quantities throughout the year, predator populations can be maintained despite the high amount of viscera removal.

Moving in the Anthropocene: Global reductions in terrestrial mammalian movements

Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission.

Utilisation of stranded marine fauna washed ashore on K’gari (Fraser Island), Australia, by dingoes

Stranded marine fauna have been identified as a potentially significant food resource for terrestrial carnivores, but how such subsidisation influences terrestrial species ecology is not well understood. We describe the dietary and behavioural responses of dingoes (Canis familiaris) to the occurrence of large-animal marine strandings (e.g. dead cetaceans, marine turtles and pinnipeds) between 2006 and 2016 on K’gari (Fraser Island), Australia, to better understand the trophic links between marine and terrestrial systems. A total of 309 strandings were recorded during this period (~3.1 strandings per month), yielding an annual average of 30.3 tons of available carrion to the 100–200 dingoes present on the island. Carcass monitoring with camera traps showed that dingoes used carcasses almost daily after a short period of decomposition. Whole packs of up to seven dingoes of all age classes at a time were observed visiting carcasses for multiple successive days. These data demonstrate that large-animal marine subsidies can be a common, substantial and important food source for dingoes, and that the estimated daily dietary needs of roughly 5–10% of the island’s dingo population were supported by this food source. Our data suggest that marine subsidisation can influence terrestrial carnivore diet, behaviour and abundance, which may produce cascading indirect effects for terrestrial ecosystems in contexts where subsidised carnivores interact strongly with other species.

Bad news for bobtails: understanding predatory behaviour of a resource-subsidised corvid towards an island endemic reptile

Context Resource subsidisation as a result of urbanisation and other human activity can have positive impacts for some opportunistic predators. Many species of corvid have benefitted from the expansion of human-dominated habitats; however, their impacts on co-occurring prey fauna are generally poorly understood. Aims We aimed to test the hypothesis that urbanisation associated with tourism impacts the predator–prey relationship between Australian ravens, or wardongs (Corvus coronoides), a ubiquitous corvid of southern Australia, and Rottnest Island bobtails (Tiliqua rugosa konowi), a subspecies of bobtail lizard isolated to a small (19km2) island off the coast of Western Australia. Methods Using clay model lizards and camera traps, we assessed the wardongs’ attack rates by distance from the settlement and by whether the model was in closed or open habitat. Key Results We found that while wardongs preyed upon Rottnest Island bobtails, predation was not affected by proximity to human settlement despite the highest number of wardongs being found there. Models in closed vegetation were attacked by wardong significantly more than were those in open vegetation. Implications Increased predation rates in closed vegetation suggests that current revegetation efforts on the island may be increasing the availability of preferred hunting habitat for the wardong. This finding may influence decisions by management on whether to control the large population of wardongs on the island.

Paws without claws? Ecological effects of large carnivores in anthropogenic landscapes

Large carnivores are frequently presented as saviours of biodiversity and ecosystem functioning through their creation of trophic cascades, an idea largely based on studies coming primarily out of relatively natural landscapes. However, in large parts of the world, particularly in Europe, large carnivores live in and are returning to strongly human-modified ecosystems. At present, we lack a coherent framework to predict the effects of large carnivores in these anthropogenic landscapes. We review how human actions influence the ecological roles of large carnivores by affecting their density or behaviour or those of mesopredators or prey species. We argue that the potential for density-mediated trophic cascades in anthropogenic landscapes is limited to unproductive areas where even low carnivore numbers may impact prey densities or to the limited parts of the landscape where carnivores are allowed to reach ecologically functional densities. The potential for behaviourally mediated trophic cascades may be larger and more widespread, because even low carnivore densities affect prey behaviour. We conclude that predator-prey interactions in anthropogenic landscapes will be highly context-dependent and human actions will often attenuate the ecological effects of large carnivores. We highlight the knowledge gaps and outline a new research avenue to study the role of carnivores in anthropogenic landscapes.

Home range of a male jaguar spatially associated with the landfill of the city of Playa del Carmen, Mexico

Understanding how jaguars (Panthera onca) adapt to disturbed landscapes, especially urbanized areas, can help us prevent adverse situations, thus reducing conflict, and perhaps even achieve coexistence with these predators. Playa del Carmen, a city located in the middle of a natural corridor linking two jaguar conservation units (JCUs; Sian Ka’an and Yum Balam), is facing intense pressure from tourism-related city growth. From January 2013 to March 2014, we tracked an adult male jaguar using a satellite collar and found that the presence of the Playa del Carmen landfill had a clear influence on a male jaguar’s home range and movements. We observed that this particular jaguar had the smallest seasonal home range and core areas reported in the literature (particularly during the dry season in 2013, where the home range was only 16.22 km2 and the core area was 2.5 km2) and also that the seasonal core areas overlapped with the area covered by the landfill (with a number of important locations within the landfill). Our results showed that male jaguars are surviving in areas previously not considered as jaguar habitat and are taking advantage of the human resources within. We hope that these results encourage more jaguar studies to be carried out in areas disturbed by human activities.

It’s a dog eat dog world: observations of dingo (Canis familiaris) cannibalism

Cannibalism in predators has been reported for a range of species throughout the world, including observations of dingoes (Canis familiaris) eating dingoes in Australia. Here, we report on camera trap observations of dingoes feeding on the carcasses of dingoes and showing aggressive behaviours towards live-trapped conspecifics. At this site, cannibalism and conspecific aggression by dingoes was not caused by food shortages, but was more likely a result of high dingo density in a focal area. We present the first camera trap image observations of dingoes eating dingoes and describe aggressive encounters between live animals.

Human expansion precipitates niche expansion for an opportunistic apex predator (Puma concolor)

There is growing recognition that developed landscapes are important systems in which to promote ecological complexity and conservation. Yet, little is known about processes regulating these novel ecosystems, or behaviours employed by species adapting to them. We evaluated the isotopic niche of an apex carnivore, the cougar (Puma concolor), over broad spatiotemporal scales and in a region characterized by rapid landscape change. We detected a shift in resource use, from near complete specialization on native herbivores in wildlands to greater use of exotic and invasive species by cougars in contemporary urban interfaces. We show that 25 years ago, cougars inhabiting these same urban interfaces possessed diets that were intermediate. Thus, niche expansion followed human expansion over both time and space, indicating that an important top predator is interacting with prey in novel ways. Thus, though human-dominated landscapes can provide sufficient resources for apex carnivores, they do not necessarily preserve their ecological relationships.

Spotted hyaena space use in relation to human infrastructure inside a protected area

Increasing human population growth has led to elevated levels of human-carnivore conflict. However, some carnivore populations have adapted to urban environments and the resources they supply. Such associations may influence carnivore ecology, behaviour and life-history. Pockets of urbanisation sometimes occur within protected areas, so that anthropogenic influences on carnivore biology are not necessarily confined to unprotected areas. In this study we evaluated associations between human infrastructure and related activity and space use of spotted hyaenas within one of the largest protected areas in South Africa, the Kruger National Park. Home range size was smaller for the dominant female of a clan living in close proximity to humans than that of the dominant female of a clan without direct access to human infrastructure. The home range including human infrastructure was also used less evenly during the night, presumably when the animals were active. Within this home range, a village area was preferred during the night, when the least modified areas within the village were preferred and administration and highly modified areas were avoided. During the day, however, there were no preference or avoidance of the village area, but all habitats except unmodified habitats within the village area were avoided. We suggest that human infrastructure and associated activity influenced hyaena space use, primarily through alterations in the spatial distribution of food. However, these effects may have been indirectly caused by habitat modification that generated favourable hunting habitat rather than a direct effect caused by access to human food such as garbage. Because of the often pivotal effects of apex predators in terrestrial ecosystems, we encourage further work aimed to quantify how human presence influences large carnivores and associated ecosystem processes within protected areas.

Insects for breakfast and whales for dinner: the diet and body condition of dingoes on Fraser Island (K'gari)

Top-predators play stabilising roles in island food webs, including Fraser Island, Australia. Subsidising generalist predators with human-sourced food could disrupt this balance, but has been proposed to improve the overall health of the island’s dingo (Canis lupus dingo) population, which is allegedly ‘starving’ or in ‘poor condition’. We assess this hypothesis by describing the diet and health of dingoes on Fraser Island from datasets collected between 2001 and 2015. Medium-sized mammals (such as bandicoots) and fish were the most common food items detected in dingo scat records. Stomach contents records revealed additional information on diet, such as the occurrence of human-sourced foods. Trail camera records highlighted dingo utilisation of stranded marine fauna, particularly turtles and whales. Mean adult body weights were higher than the national average, body condition scores and abundant-excessive fat reserves indicated a generally ideal-heavy physical condition, and parasite loads were low and comparable to other dingo populations. These data do not support hypotheses that Fraser Island dingoes have restricted diets or are in poor physical condition. Rather, they indicate that dingoes on Fraser Island are capable of exploiting a diverse array of food sources which contributes to the vast majority of dingoes being of good-excellent physical condition.

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.

Banning Fisheries Discards Abruptly Has a Negative Impact on the Population Dynamics of Charismatic Marine Megafauna

Food subsidies have the potential to modify ecosystems and affect the provision of goods and services. Predictable Anthropogenic Food Subsidies (PAFS) modify ecosystems by altering ecological processes and food webs. The global concern over the effects of PAFS in ecosystems has led to development of environmental policies aimed at curbing the production or ultimately banning of PAFS. However, the effects of reducing or banning PAFS are not known. We explore the consequences of PAFS removal in a marine ecosystem under two scenarios: 1) gradual reduction, or 2) an abrupt ban, using a mass balance model to test these hypotheses–The reduction or loss of PAFS will: i) modify trophic levels and food webs through effects on foraging by opportunistic species, ii) increase the resilience of opportunistic species to food shortages, and iii) modify predator–prey interactions through shifts in prey consumption. We found that PAFS lower the trophic levels of opportunistic scavengers and increase their food pathways. Scavengers are able to switch prey when PAFS are reduced gradually but they decline when PAFS are abruptly banned. PAFS reduction to a certain minimal level causes a drop in the ecosystem’s stability. We recommend gradual reduction of PAFS to a minimal level that would maintain the ecosystem’s stability and allow species exploiting PAFS to habituate to the food subsidy reduction.

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.

Cryptic function loss in animal populations

The essential functional roles performed by animal species are lost when they become locally extinct, and ecosystems are critically threatened by this decline in functional diversity. Theory that links function, diversity, and ecosystem stability exists but fails to assess function loss that occurs in species with persistent populations. The entire functional role of a species, or a critical component of it, can be lost following large population declines (functional extinction), following population increase, or after behavioural adaptations to changes in the population, community, habitat, or climate. Here, we provide a framework that identifies the scenarios under which 'cryptic' function loss can occur in persistent populations. Cryptic function loss is potentially widespread and critically threatens ecosystem stability across the globe.

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.

Roaming behaviour and home range estimation of domestic dogs in Aboriginal and Torres Strait Islander communities in northern Australia using four different methods

Disease transmission parameters are the core of epidemic models, but are difficult to estimate, especially in the absence of outbreak data. Investigation of the roaming behaviour, home range (HR) and utilization distribution (UD) can provide the foundation for such parameter estimation in free-ranging animals. The objectives of this study were to estimate HR and UD of 69 domestic dogs in six Aboriginal and Torres Strait Islander communities in northern Australia and to compare four different methods (the minimum convex polygon, MCP; the location-based kernel density estimation, LKDE; the biased random bridge, BRB; and Time Local Convex Hull, T-LoCoH) for investigation of UD and estimating HR sizes. Global positioning system (GPS) collars were attached to community dogs for a period of 1-3 days and positions (fixes) were recorded every minute. Median core HRs (50% isopleth) of the 69 dogs were estimated to range from 0.2 to 0.4 ha and the more extended HR (95% isopleth) to range from 2.5 to 5.3 ha, depending on the method used. The HR and UD shapes were found to be generally circular around the dog owner's house. However, some individuals were found to roam much more with a HR size of 40-104 ha and cover large areas of their community or occasionally beyond. These far roaming dogs are of particular interest for infectious disease transmission. Occasionally, dogs were taken between communities and out of communities for hunting, which enables the contact of dogs between communities and with wildlife (such as dingoes). The BRB and T-LoCoH are the only two methods applied here which integrate the consecutiveness of GPS locations into the analysis, a substantial advantage. The recently developed BRB method produced significantly larger HR estimates than the other two methods; however, the variability of HR sizes was lower compared to the other methods. Advantages of the BRB method include a more realistic analytical approach (kernel density estimation based on movements rather than on locations), possibilities to deal with irregular time periods between consecutive GPS fixes and parameter specification which respects the characteristics of the GPS unit used to collect the data. The BRB method was therefore the most suitable method for UD estimation in this dataset. The results of this study can further be used to contact rates between the dogs within and between communities, a foundation for estimating transmission parameters for canine infectious disease models, such as a rabies spread model in Australia.