Anthropogenic Resource Subsidies Research Articles

Assessing the impacts of recreation on the spatial and temporal activity of mammals in an isolated alpine protected area.

The management objectives of many protected areas must meet the dual mandates of protecting biodiversity while providing recreational opportunities. It is difficult to balance these mandates because it takes considerable effort to monitor both the status of biodiversity and impacts of recreation. Using detections from 45 camera traps deployed between July 2019 and September 2021, we assessed the potential impacts of recreation on spatial and temporal activity for 8 medium- and large-bodied terrestrial mammals in an isolated alpine protected area: Cathedral Provincial Park, British Columbia, Canada. We hypothesised that some wildlife perceive a level of threat from people, such that they avoid 'risky times' or 'risky places' associated with human activity. Other species may benefit from associating with people, be it through access to anthropogenic resource subsidies or filtering of competitors/predators that are more human-averse (i.e., human shield hypothesis). Specifically, we predicted that large carnivores would show the greatest segregation from people while mesocarnivores and ungulates would associate spatially with people. We found spatial co-occurrence between ungulates and recreation, consistent with the human shield hypothesis, but did not see the predicted negative relationship between larger carnivores and humans, except for coyotes (Canis latrans). Temporally, all species other than cougars (Puma concolor) had diel activity patterns significantly different from that of recreationists, suggesting potential displacement in the temporal niche. Wolves (Canis lupus) and mountain goats (Oreamnos americanus) showed shifts in temporal activity away from people on recreation trails relative to off-trail areas, providing further evidence of potential displacement. Our results highlight the importance of monitoring spatial and temporal interactions between recreation activities and wildlife communities, in order to ensure the effectiveness of protected areas in an era of increasing human impacts.

Abundance, demography, and harvesting of water snakes from agricultural landscapes in West Java, Indonesia

Context Across much of its geographic range, the masked water snake, Homalopsis buccata, is harvested each year in large numbers, questioning the sustainability of that offtake. Aims To quantify abundance and demography of water snakes in anthropogenically disturbed habitats in an area of West Java, where these snakes are subject to intensive harvest. Methods We accompanied professional snake-collectors, and conducted our own surveys of ponds and irrigation canals, to record the numbers and attributes (species, sex, size, etc.) of snakes that were captured using a variety of methods. Key results Snakes of several species were abundant, with mean capture rates of 32 666 snakes km−1 of irrigation canals, and 57 501 snakes km−2 of fishponds (9500 and 43 788 for H. buccata alone). Sex ratios of H. buccata were female-biased in ponds but not irrigation channels. Ponds underlain by deeper mud contained more snakes. Collecting methods varied among habitat types, in a way that reduced collateral risk to commercially farmed fish in ponds. Conclusions These water snakes are extremely abundant in Java, despite high levels of historical and continuing harvest. The inference of low population sizes for H. buccata in Indonesia, as presented in the IUCN Red List, is erroneous. Implications An ability to utilise anthropogenic resource subsidies (in this case, fish farmed in village ponds) allows some native predator species to attain remarkably high abundances, and to withstand intense efforts at harvesting.

Broad‐scale occurrence of a subsidized avian predator: Reducing impacts of ravens on sage‐grouse and other sensitive prey

Abstract Expanding human enterprise across remote environments impacts numerous wildlife species. Anthropogenic resources provide subsidies for generalist predators that can lead to cascading effects on prey species at lower trophic levels. A fundamental challenge for applied ecologists is to disentangle natural and anthropogenic influences on species occurrence, and subsequently develop spatially explicit models to help inform management and conservation decisions. Using Bayesian hierarchical occupancy models, we mapped the broad‐scale occurrence of common ravens Corvus corax as a function of natural and anthropogenic landscape covariates using >15,000 point count surveys performed during 2007–2016 within the Great Basin region, USA. Raven abundance and distribution is substantially increasing across the American west due to unintended anthropogenic resource subsidies. Importantly, ravens prey on eggs and chicks of numerous species including greater sage‐grouse Centrocercus urophasianus, an indicator species whose decline is at the centre of national conservation strategies and land‐use policies. Anthropogenic factors that contributed to greater raven occurrence were: increased road density, presence of transmission lines, agricultural activity, and presence of roadside rest areas. Natural landscape characteristics included lower elevations with greener vegetation (Normalized Difference Vegetation Index), greater stream and habitat edge densities, and lower percentages of big sagebrush Artemisia tridentata spp. Interactions between anthropogenic sources of nesting substrate and food subsidies suggested that raven occurrence increased multiplicatively when these resource subsidies co‐occurred. Overall, the average probability of raven occurrence estimated within sagebrush ecosystems of the study area was c. 0.83. Synthesis and applications. We demonstrate how anthropogenic factors can be disentangled from natural effects when making spatially explicit predictions of subsidized predators occurring across expansive landscapes. This approach can guide management decisions where subsidized predators overlap sensitive prey habitats. For example, we identify areas where elevated raven occurrence coincides with breeding sage‐grouse concentration areas and appears to be largely driven by anthropogenic factors. Management applications could focus on reducing raven access to anthropogenic subsidies in these areas, while prioritizing habitat improvements for sage‐grouse elsewhere. Our approach is applicable to other species where widespread survey data are available.

Asymmetric assimilation of an anthropogenic resource subsidy in a freshwater food web

Anthropogenic subsidies occur readily, especially with growing human development neighboring natural systems. Determining how these subsidies permeate into native food webs is important, but currently not well understood. Here, we used a combination of stable isotopes and fatty acids as bio-tracers to explore the pathway(s) of assimilation of an anthropogenic resource (aquaculture feed) provided by freshwater cage aquaculture. Our results point to an asymmetric assimilation of aquaculture feed by native organisms into and through the food web. Specifically, two pelagic fish species (an intermediate consumer and a top predator) show elevated trophic positions (based on δ15N signatures driven by aquaculture feed) and higher proportions of essential fatty acids (18:2n-6 and 18:3n-3) in waters surrounding the aquaculture facility compared to control sites lacking aquaculture cages, suggesting feed consumption. Fish that appeared to assimilate feed also had higher n-3 long chain poly unsaturated fatty acids (LC PUFA) proportions, indicating a possible role of the feed subsidy for fish health. Alternatively, there was no evidence of feed assimilation through the littoral energy channel. Our findings provide new insight into an emerging research area that asks how anthropogenic resource subsidies affect species health and properties of food webs. Since many habitats experience both natural and anthropogenic subsidy inputs, the multiple tracer approach employed here shows promise for studying how subsidies may affect species health and behavior, as well as food web structure and ultimately stability.

Optimal foraging in seasonal environments: implications for residency of Australian flying foxes in food-subsidized urban landscapes.

Bats provide important ecosystem services such as pollination of native forests; they are also a source of zoonotic pathogens for humans and domestic animals. Human-induced changes to native habitats may have created more opportunities for bats to reside in urban settings, thus decreasing pollination services to native forests and increasing opportunities for zoonotic transmission. In Australia, fruit bats (Pteropus spp. flying foxes) are increasingly inhabiting urban areas where they feed on anthropogenic food sources with nutritional characteristics and phenology that differ from native habitats. We use optimal foraging theory to investigate the relationship between bat residence time in a patch, the time it takes to search for a new patch (simulating loss of native habitat) and seasonal resource production. We show that it can be beneficial to reside in a patch, even when food productivity is low, as long as foraging intensity is low and the expected searching time is high. A small increase in the expected patch searching time greatly increases the residence time, suggesting nonlinear associations between patch residence and loss of seasonal native resources. We also found that sudden increases in resource consumption due to an influx of new bats has complex effects on patch departure times that again depend on expected searching times and seasonality. Our results suggest that the increased use of urban landscapes by bats may be a response to new spatial and temporal configurations of foraging opportunities. Given that bats are reservoir hosts of zoonotic diseases, our results provide a framework to study the effects of foraging ecology on disease dynamics.One contribution of 14 to a theme isssue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

Responses of migratory species and their pathogens to supplemental feeding.

Migratory animals undergo seasonal and often spectacular movements and perform crucial ecosystem services. In response to anthropogenic changes, including food subsidies, some migratory animals are now migrating shorter distances or halting migration altogether and forming resident populations. Recent studies suggest that shifts in migratory behaviour can alter the risk of infection for wildlife. Although migration is commonly assumed to enhance pathogen spread, for many species, migration has the opposite effect of lowering infection risk, if animals escape from habitats where pathogen stages have accumulated or if strenuous journeys cull infected hosts. Here, we summarize responses of migratory species to supplemental feeding and review modelling and empirical work that provides support for mechanisms through which resource-induced changes in migration can alter pathogen transmission. In particular, we focus on the well-studied example of monarch butterflies and their protozoan parasites in North America. We also identify areas for future research, including combining new technologies for tracking animal movements with pathogen surveillance and exploring potential evolutionary responses of hosts and pathogens to changing movement patterns. Given that many migratory animals harbour pathogens of conservation concern and zoonotic potential, studies that document ongoing shifts in migratory behaviour and infection risk are vitally needed.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

From wetland specialist to hand-fed generalist: shifts in diet and condition with provisioning for a recently urbanized wading bird.

Many wildlife species shift their diets to use novel resources in urban areas. The consequences of these shifts are not well known, and consumption of reliable-but low quality-anthropogenic food may present important trade-offs for wildlife health. This may be especially true for carnivorous species such as the American white ibis (Eudocimus albus), a nomadic wading bird which has been increasingly observed in urban parks in South Florida, USA. We tested the effects of anthropogenic provisioning on consumer nutrition (i.e. dietary protein), body condition and ectoparasite burdens along an urban gradient using stable isotope analysis, scaled mass index values and GPS transmitter data. Ibises that assimilated more provisioned food were captured at more urban sites, used more urban habitat, had lower mass-length residuals, lower ectoparasite scores, assimilated less δ15N and had smaller dietary isotopic ellipses. Our results suggest that ibises in urban areas are heavily provisioned with anthropogenic food, which appears to offer a trade-off by providing low-quality, but easily accessible, calories that may not support high mass but may increase time available for anti-parasite behaviours such as preening. Understanding such trade-offs is important for investigating the effects of provisioning on infection risk and the conservation of wildlife in human-modified habitats.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

Consequences of resource supplementation for disease risk in a partially migratory population.

Anthropogenic landscape features such as urban parks and gardens, landfills and farmlands can provide novel, seasonally reliable food sources that impact wildlife ecology and distributions. In historically migratory species, food subsidies can cause individuals to forgo migration and form partially migratory or entirely sedentary populations, eroding a crucial benefit of migration: pathogen avoidance through seasonal abandonment of transmission sites and mortality of infected individuals during migration. Since many migratory taxa are declining, and wildlife populations in urban areas can harbour zoonotic pathogens, understanding the mechanisms by which anthropogenic resource subsidies influence infection dynamics and the persistence of migration is important for wildlife conservation and public health. We developed a mathematical model for a partially migratory population and a vector-borne pathogen transmitted at a shared breeding ground, where food subsidies increase the nonbreeding survival of residents. We found that higher resident nonbreeding survival increased infection prevalence in residents and migrants, and lowered the fraction of the population that migrated. The persistence of migration may be especially threatened if residency permits emergence of more virulent pathogens, if resource subsidies reduce costs of infection for residents, and if infection reduces individual migratory propensity.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

Reviewing the effects of food provisioning on wildlife immunity.

While urban expansion increasingly encroaches on natural habitats, many wildlife species capitalize on anthropogenic food resources, which have the potential to both positively and negatively influence their responses to infection. Here we examine how food availability and key nutrients have been reported to shape innate and adaptive immunity in wildlife by drawing from field-based studies, as well as captive and food restriction studies with wildlife species. Examples of food provisioning and key nutrients enhancing immune function were seen across the three study type distinctions, as were cases of trace metals and pharmaceuticals impairing the immunity of wildlife species. More generally, food provisioning in field studies tended to increase innate and adaptive responses to certain immune challenges, whereas patterns were less clear in captive studies. Mild food restriction often enhanced, whereas severe food restriction frequently impaired immunity. However, to enable stronger conclusions we stress a need for further research, especially field studies, and highlight the importance of integrating nutritional manipulation, immune challenge, and functional outcomes. Despite current gaps in research on this topic, modern high throughput molecular approaches are increasingly feasible for wildlife studies and offer great opportunities to better understand human influences on wildlife health.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

Health hazards to wild birds and risk factors associated with anthropogenic food provisioning.

Provision of supplementary food for wild birds at garden feeding stations is a common, large-scale and year-round practice in multiple countries including Great Britain (GB). While these additional dietary resources can benefit wildlife, there is a concomitant risk of disease transmission, particularly when birds repeatedly congregate in the same place at high densities and through interactions of species that would not normally associate in close proximity. Citizen science schemes recording garden birds are popular and can integrate disease surveillance with population monitoring, offering a unique opportunity to explore inter-relationships between supplementary feeding, disease epidemiology and population dynamics. Here, we present findings from a national surveillance programme in GB and note the dynamism of endemic and emerging diseases over a 25-year period, focusing on protozoal (finch trichomonosis), viral (Paridae pox) and bacterial (passerine salmonellosis) diseases with contrasting modes of transmission. We also examine the occurrence of mycotoxin contamination of food residues in bird feeders, which present both a direct and indirect (though immunosuppression) risk to wild bird health. Our results inform evidence-based mitigation strategies to minimize anthropogenically mediated health hazards, while maintaining the benefits of providing supplementary food for wild birds.This article is part of the theme issue ‘Anthropogenic resource subsidies and host–parasite dynamics in wildlife’.

Assessing the direct and indirect effects of food provisioning and nutrient enrichment on wildlife infectious disease dynamics.

Anthropogenic resource supplementation can shape wildlife disease directly by altering the traits and densities of hosts and parasites or indirectly by stimulating prey, competitor or predator species. We first assess the direct epidemiological consequences of supplementation, highlighting the similarities and differences between food provisioning and two widespread forms of nutrient input: agricultural fertilization and aquatic nutrient enrichment. We then review an aquatic disease system and a general model to assess whether predator and competitor species can enhance or overturn the direct effects of enrichment. All forms of supplementation can directly affect epidemics by increasing host population size or altering parasite production within hosts, but food provisioning is most likely to aggregate hosts and increase parasite transmission. However, if predators or competitors increase in response to supplementation, they could alter resource-fuelled outbreaks in focal hosts. We recommend identifying the traits of hosts, parasites or interacting species that best predict epidemiological responses to supplementation and evaluating the relative importance of these direct and indirect mechanisms. Theory and experiments should examine the timing of behavioural, physiological and demographic changes for realistic, variable scenarios of supplementation. A more integrative view of resource supplementation and wildlife disease could yield broadly applicable disease management strategies.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

Human-nature interactions and the consequences and drivers of provisioning wildlife.

Many human populations are undergoing an extinction of experience, with a progressive decline in interactions with nature. This is a consequence both of a loss of opportunity for, and orientation towards, such experiences. The trend is of concern in part because interactions with nature can be good for human health and wellbeing. One potential means of redressing these losses is through the intentional provision of resources to increase wildlife populations in close proximity to people, thereby increasing the potential for positive human–nature experiences, and thence the array of benefits that can result. In this paper, we review the evidence that these resource subsidies have such a cascade of effects. In some Westernized countries, the scale of provision is extraordinarily high, and doubtless leads to both positive and negative impacts for wildlife. In turn, these impacts often lead to more frequent, reliable and closer human–nature interactions, with a greater variety of species. The consequences for human wellbeing remain poorly understood, although benefits documented in the context of human–nature interactions more broadly seem likely to apply. There are also some important feedback loops that need to be better characterized if resource provisioning is to contribute effectively towards averting the extinction of experience.This article is part of the theme issue ‘Anthropogenic resource subsidies and host–parasite dynamics in wildlife’.

Anthropogenic resource subsidies and host-parasite dynamics in wildlife.

For a wide range of wildlife, anthropogenic change and human activities modify the abundance, distribution and timing of food resources [1,2]. Although activities such as deforestation and overfishing deplete resources for many wildlife species, in other cases, urbanization, agriculture and supplemental feeding can provide wildlife with abundant and predictable food [3–8]. As a result, many wildlife have adapted their foraging behaviour to capitalize on these resources [9,10], leading to subsidized populations that are often larger, more aggregated and better fed than their naturally foraging counterparts [11–13]. Importantly, novel assemblages of species can form around anthropogenic resources [14,15], which could facilitate the cross-species transmission of pathogens among wildlife, humans and domestic animals [16]. For example, bird feeders have been implicated in the emergence of virulent pathogens such as Mycoplasma gallisepticum and Trichomonas gallinae in songbirds [17,18]. The 2014 Ebola outbreak in West Africa and 1998 emergence of Nipah virus in Malaysia also underscore the importance of understanding how anthropogenic resources can bring wildlife reservoirs of zoonotic pathogens into close proximity with humans and domesticated species [19–21]. Predicting how anthropogenic resources will impact host–parasite interactions is challenging owing to multiple underlying mechanisms with potentially opposing effects [22,23]. Although energy and nutrients from supplemental food can support robust immune function needed to resist and recover from infections [24], anthropogenic food containing toxins or lacking nutrients could reduce host immunity and increase susceptibility to infection and pathogen shedding [25–27]. Moreover, aggregation around food sources can increase contact rates and facilitate pathogen transmission [28–30]. These individual-scale effects and local interactions are …

Feeder density enhances house finch disease transmission in experimental epidemics.

Anthropogenic food provisioning of wildlife can alter the frequency of contacts among hosts and between hosts and environmental sources of pathogens. Despite the popularity of garden bird feeding, few studies have addressed how feeders influence host contact rates and disease dynamics. We experimentally manipulated feeder density in replicate aviaries containing captive, pathogen-naive, groups of house finches (Haemorhous mexicanus) and continuously tracked behaviours at feeders using radio-frequency identification devices. We then inoculated one bird per group with Mycoplasma gallisepticum (Mg), a common bacterial pathogen for which feeders are fomites of transmission, and assessed effects of feeder density on house finch behaviour and pathogen transmission. We found that pathogen transmission was significantly higher in groups with the highest density of bird feeders, despite a significantly lower rate of intraspecific aggressive interactions relative to the low feeder density groups. Conversely, among naive group members that never showed signs of disease, we saw significantly higher concentrations of Mg-specific antibodies in low feeder density groups, suggesting that birds in low feeder density treatments had exposure to subclinical doses of Mg. We discuss ways in which the density of garden bird feeders could play an important role in mediating the intensity of Mg epidemics.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

Livestock abundance predicts vampire bat demography, immune profiles and bacterial infection risk.

Human activities create novel food resources that can alter wildlife–pathogen interactions. If resources amplify or dampen, pathogen transmission probably depends on both host ecology and pathogen biology, but studies that measure responses to provisioning across both scales are rare. We tested these relationships with a 4-year study of 369 common vampire bats across 10 sites in Peru and Belize that differ in the abundance of livestock, an important anthropogenic food source. We quantified innate and adaptive immunity from bats and assessed infection with two common bacteria. We predicted that abundant livestock could reduce starvation and foraging effort, allowing for greater investments in immunity. Bats from high-livestock sites had higher microbicidal activity and proportions of neutrophils but lower immunoglobulin G and proportions of lymphocytes, suggesting more investment in innate relative to adaptive immunity and either greater chronic stress or pathogen exposure. This relationship was most pronounced in reproductive bats, which were also more common in high-livestock sites, suggesting feedbacks between demographic correlates of provisioning and immunity. Infection with both Bartonella and haemoplasmas were correlated with similar immune profiles, and both pathogens tended to be less prevalent in high-livestock sites, although effects were weaker for haemoplasmas. These differing responses to provisioning might therefore reflect distinct transmission processes. Predicting how provisioning alters host–pathogen interactions requires considering how both within-host processes and transmission modes respond to resource shifts.This article is part of the theme issue ‘Anthropogenic resource subsidies and host–parasite dynamics in wildlife’.

Resource-driven changes to host population stability alter the evolution of virulence and transmission

What drives the evolution of parasite life-history traits? Recent studies suggest that linking within- and between-host processes can provide key insight into both disease dynamics and parasite evolution. Still, it remains difficult to understand how to pinpoint the critical factors connecting these cross-scale feedbacks, particularly under non-equilibrium conditions; many natural host populations inherently fluctuate and parasites themselves can strongly alter the stability of host populations. Here, we develop a general model framework that mechanistically links resources to parasite evolution across a gradient of stable and unstable conditions. First, we dynamically link resources and between-host processes (host density, stability, transmission) to virulence evolution, using a 'non-nested' model. Then, we consider a 'nested' model where population-level processes (transmission and virulence) depend on resource-driven changes to individual-level (within-host) processes (energetics, immune function, parasite production). Contrary to 'non-nested' model predictions, the 'nested' model reveals complex effects of host population dynamics on parasite evolution, including regions of evolutionary bistability; evolution can push parasites towards strongly or weakly stabilizing strategies. This bistability results from dynamic feedbacks between resource-driven changes to host density, host immune function and parasite production. Together, these results highlight how cross-scale feedbacks can provide key insights into the structuring role of parasites and parasite evolution.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

Food for contagion: synthesis and future directions for studying host–parasite responses to resource shifts in anthropogenic environments

Human-provided resource subsidies for wildlife are diverse, common and have profound consequences for wildlife-pathogen interactions, as demonstrated by papers in this themed issue spanning empirical, theoretical and management perspectives from a range of study systems. Contributions cut across scales of organization, from the within-host dynamics of immune function, to population-level impacts on parasite transmission, to landscape- and regional-scale patterns of infection. In this concluding paper, we identify common threads and key findings from author contributions, including the consequences of resource subsidies for (i) host immunity; (ii) animal aggregation and contact rates; (iii) host movement and landscape-level infection patterns; and (iv) interspecific contacts and cross-species transmission. Exciting avenues for future work include studies that integrate mechanistic modelling and empirical approaches to better explore cross-scale processes, and experimental manipulations of food resources to quantify host and pathogen responses. Work is also needed to examine evolutionary responses to provisioning, and ask how diet-altered changes to the host microbiome influence infection processes. Given the massive public health and conservation implications of anthropogenic resource shifts, we end by underscoring the need for practical recommendations to manage supplemental feeding practices, limit human-wildlife conflicts over shared food resources and reduce cross-species transmission risks, including to humans.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'.

Winter feeding of elk in the Greater Yellowstone Ecosystem and its effects on disease dynamics.

Providing food to wildlife during periods when natural food is limited results in aggregations that may facilitate disease transmission. This is exemplified in western Wyoming where institutional feeding over the past century has aimed to mitigate wildlife–livestock conflict and minimize winter mortality of elk (Cervus canadensis). Here we review research across 23 winter feedgrounds where the most studied disease is brucellosis, caused by the bacterium Brucella abortus. Traditional veterinary practices (vaccination, test-and-slaughter) have thus far been unable to control this disease in elk, which can spill over to cattle. Current disease-reduction efforts are being guided by ecological research on elk movement and density, reproduction, stress, co-infections and scavengers. Given the right tools, feedgrounds could provide opportunities for adaptive management of brucellosis through regular animal testing and population-level manipulations. Our analyses of several such manipulations highlight the value of a research–management partnership guided by hypothesis testing, despite the constraints of the sociopolitical environment. However, brucellosis is now spreading in unfed elk herds, while other diseases (e.g. chronic wasting disease) are of increasing concern at feedgrounds. Therefore experimental closures of feedgrounds, reduced feeding and lower elk populations merit consideration.This article is part of the theme issue ‘Anthropogenic resource subsidies and host–parasite dynamics in wildlife’.

Anthropogenic Resource Subsidies Determine Space Use by Australian Arid Zone Dingoes: An Improved Resource Selection Modelling Approach

Dingoes (Canis lupus dingo) were introduced to Australia and became feral at least 4,000 years ago. We hypothesized that dingoes, being of domestic origin, would be adaptable to anthropogenic resource subsidies and that their space use would be affected by the dispersion of those resources. We tested this by analyzing Resource Selection Functions (RSFs) developed from GPS fixes (locations) of dingoes in arid central Australia. Using Generalized Linear Mixed-effect Models (GLMMs), we investigated resource relationships for dingoes that had access to abundant food near mine facilities, and for those that did not. From these models, we predicted the probability of dingo occurrence in relation to anthropogenic resource subsidies and other habitat characteristics over ∼ 18,000 km2. Very small standard errors and subsequent pervasively high P-values of results will become more important as the size of data sets, such as our GPS tracking logs, increases. Therefore, we also investigated methods to minimize the effects of serial and spatio-temporal correlation among samples and unbalanced study designs. Using GLMMs, we accounted for some of the correlation structure of GPS animal tracking data; however, parameter standard errors remained very small and all predictors were highly significant. Consequently, we developed an alternative approach that allowed us to review effect sizes at different spatial scales and determine which predictors were sufficiently ecologically meaningful to include in final RSF models. We determined that the most important predictor for dingo occurrence around mine sites was distance to the refuse facility. Away from mine sites, close proximity to human-provided watering points was predictive of dingo dispersion as were other landscape factors including palaeochannels, rocky rises and elevated drainage depressions. Our models demonstrate that anthropogenically supplemented food and water can alter dingo-resource relationships. The spatial distribution of such resources is therefore critical for the conservation and management of dingoes and other top predators.

DRC-1339 Egg Baits: Preliminary Evaluation of Their Effectiveness in Removing Ravens

I measured the preliminary effects of chicken egg baits treated with DRC-1339 on removing common ravens for the purpose of reducing raven depredation of prairie grouse nests in northeastern Nevada. Greater sage grouse and Columbian sharp-tailed grouse are game species that are declining in distribution and abundance throughout their historic range. Reduced nest success due to egg depredation by ravens is thought to be an important cause of nest failure. Ravens are subsidized nest predators that have substantially increased in abundance throughout their range within the past 25 years. During 2002-2004, I removed ravens from a treatment site using chicken egg baits treated with DRC-1339 to protect sage grouse and a nascent population of reintroduced Columbian sharp-tailed grouse in northeastern Nevada. I performed raven surveys at the treatment site and 2 control sites, located 22 and 53 km northwest of the treatment site, to measure the effects of using DRC-1339. Preliminary analyses indicate chicken egg baits treated with DRC-1339 significantly reduced raven densities at the treatment site, and change in densities over time was different at the treatment site than the control sites (F = 10.212,59, P < 0.001). Also, anthropogenic resource subsidies (i.e., power-lines, roads, agricultural fields, and public landfills) appeared to influence raven abundance. If lethal removal of ravens is implemented as a short-term management action to protect areas from ecological or economical damage, the technique described here is valuable to managers.