The impact of human land use and landscape productivity on population dynamics of red fox in southeastern Norway

Hair analysis as a non-invasive method for assessing the exposure of wildlife to per- and poly-fluoroalkyl substances (PFAS)

In mammals, exposure to PFAS is usually assessed by measuring burdens in internal organs (i.e., liver and brain) or plasma, while less emphasis is devoted to non-invasive and non-destructive methods. We assess the suitability of hair as a non-invasive matrix for monitoring the exposure of mammals to 33 PFAS, including perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkane sulfonic acids (PFSAs), perfluoroalkylether carboxylic acids (PFECAs), perfluoroalkylether sulfonic acids (PFESAs), perfluoroalkane sulfonyl fluoride-based substances (PASFs), and fluorotelomers (FTs). The Red fox is chosen as the target species due to its apical position in the terrestrial food web of the study area, the Cavallino-Treporti peninsula in North-East Italy. All analysed samples (n = 24) are positive for PFAS, with eight compounds quantified in all samples, including PFHxA, PFOA, PFDA, PFUnDA, PFDoDA, PFTriDA, PFTeDA, and PFOS. The highest mean concentration in hair samples is measured for PFOS (1.40 ± 0.48 ng g-1 dw) followed by PFDoDA (0.31 ± 0.05 ng g-1 dw), and PFOA (0.31 ± 0.19 ng g-1 dw), while the mean ∑33PFAS was 3.41 ± 0.93 ng g-1 dw. The dominance of PFOS and long-chain PFAS in the PFAS profile and the occurrence of compounds with even-numbered carbon chains at higher concentrations than the odd-numbered compounds with a one-carbon longer chain (i.e., PFOA > PFNA, PFDA > PFUnDA, PFDoDA > PFTriDA) suggest the trophic transfer along the terrestrial food web as the primary exposure pathway in the study area. The data suggest hair analysis as a reliable, non-invasive method for assessing the possible exposure of mammals to PFAS and suggested that the Red fox can be used as a sentinel of the environment, embracing the One Health perspective.

Correlation between mammal track abundance and Forest Landscape Integrity Index validates actual forest ecological integrity

Human disturbance compromises the ecological integrity of forests, negatively affecting associated species. Assessing the impact of forest integrity on biodiversity is complex due to the interplay of various human activities, ecological factors, and their interactions. Current large-scale indices assess forest integrity but often lack a direct connection to the biotic environment. We tested the effectiveness of the global Forest Landscape Integrity Index (FLII) in evaluating aspects of anthropogenic forest degradation on the biotic community. We analyzed the relationship between changes in the ecological integrity of Finnish forests and variations in mammal species abundance, using the number of tracks from 17 different species collected during the winter seasons between 2016 and 2020 in south-central Finland. Beyond the FLII, we analyzed forest and canopy cover to enhance the accuracy of habitat preference assessments. We found that the FLII captures the varying degrees of forest integrity, as reflected by the correlation between the abundance of winter tracks and the FLII for most mammals. Species that were positively associated with forest integrity were all native to the boreal forest, while mammals that adapt well to human-disturbed environments including two invasive species were more common in lower FLII forests. Significant differences in habitat preferences were also observed in relation to forest and canopy cover, revealing additional nuances that the FLII alone did not capture. This study demonstrates that the FLII, when combined with a comprehensive dataset and supplemented with region-specific factors, can assess species' adaptability to human-modified forests, aiding in the development of conservation strategies.

How do microtine rodent abundance, snow and landscape parameters influence pine marten Martes martes population dynamics?

The pine marten (Martes martes) occupies the northernmost extent of its distribution in Norway, where microtine rodents are an important food item. The relationship between microtine rodent abundance and pine marten population dynamics is not well understood. In this paper, we examined this relationship and tested if environmental factors (e.g. snow depth, elevation, mature spruce forest density and agricultural land density) modulate pine marten population dynamics. We calculated pine marten abundance indices using data collected from 593 unique snow transects surveyed between 2003 and 2014 in Hedmark, Norway. We employed a Partial Rate Correlation Function to identify potential cyclicity in pine marten populations. We did not observe any cyclical patterns in pine marten populations within our short time series. Instead, their population appeared to be directly density-dependent. Although the population growth rate of pine marten tended to increase with increasing elevation, it was not affected by individual variables including a microtine rodent abundance index and snow depth. However, the annual growth rate of pine marten populations was positively affected by the interaction between the microtine rodent abundance index and increasing elevation. Pine marten abundance increased with microtine rodent abundance, elevation, snow depth and density of mature spruce forest, but decreased with increasing agricultural land density. Pine martens are opportunistic diet generalists that can switch between prey and cache food for later consumption. They are also strongly territorial with delayed implantation and are slow to respond to environmental changes due to their relatively low reproductive potential. These life-history traits may mitigate the effects of fluctuating microtine rodent abundance on pine marten reproduction and survival. Nevertheless, our findings suggest that microtine rodents still serve as important prey which can influence the population dynamics of pine martens in higher elevation habitats where alternative prey may be less available.

New insights from an eight-year study on per- and polyfluoroalkyl substances in an urban terrestrial ecosystem

Per- and polyfluoroalkyl substances (PFAS) were analysed in a high number of terrestrial samples of soil, earthworm, bird eggs and liver from red fox and brown rat in an urban area in Norway from 2013 to 2020. PFOS and the long chain PFCAs were the most dominating compounds in all samples, proving their ubiquitous distribution. Other less studied compounds such as 6:2 FTS were first and foremost detected in earthworm. 8:2 FTS was found in many samples of fieldfare egg, sparrowhawk egg and earthworm, where the eggs had highest concentrations. Highest concentrations for both 6:2 FTS and 8:2 FTS were detected at present and former industry areas. FOSA was detected in many samples of the species with highest concentrations in red fox liver and brown rat liver of 3.3 and 5.5 ng/g ww. PFAS concentrations from the urban area were significantly higher than from background areas indicating that some of the species can be suitable as markers for PFAS emissions in an urban environment. Fieldfare eggs had surprisingly high concentrations of PFOS and PFCA concentrations from areas known to be or have been influenced by industry. Biota-soil-accumulation factor and magnification calculations indicate accumulation and magnification potential for several PFAS. Earthworm and fieldfare egg had average concentrations above the Canadian and European thresholds in diet for avian wildlife and predators. For earthworms, 18 % of the samples exceeded the European threshold (33 ng/g ww) of PFOS in prey for predators, and for fieldfare eggs, 35 % of the samples were above the same threshold. None of the soil samples exceeded a proposed PNEC of PFOS for soil living organisms of 373 ng/g dw.

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.

Environmental filtering drives the assembly of mammal communities in a heterogeneous Mediterranean region

Agricultural expansion and intensification are major drivers of global change. Quantifying the importance of different processes governing the assembly of local communities in agroecosystems is essential to guide the conservation effort allocated to enhancing habitat connectivity, improving habitat quality or managing species interactions. We used multiple detection methods to record the occurrence of medium-sized and large-sized mammals in three managed landscapes of a heterogeneous Mediterranean region. Then we used a joint species distribution model to evaluate the relative influence of dispersal limitation, environmental filtering, and interspecific interactions on the local assembly of mammal communities in 4-km² plots. The partitioning of the explained variation in species occurrence was attributed on average 99% to environmental filters and 1% to dispersal filters. No role was attributed to biotic filters, in agreement with the scarce support for strong competition or other negative interactions found after a literature review. Four principal environmental factors explained on average 63% of variance in species occurrence and operated mainly at the landscape scale. The amount of shrub cover in the neighboring landscape was the most influential factor favoring mammal occurrence and accounted for nearly one-third of the total variance. The proportion of intensively managed croplands and proxies of human activity within landscape samples limited mammal presence. At the microhabitat scale (~80 m² plots) the mean percentage area deprived of woody vegetation also had a negative effect. Functional traits such as body mass or social behavior accounted for a substantial fraction of the variation attributed to environmental factors. We concluded that multiscale environmental filtering governed local community assembly, whereas the role of dispersal limitation and interspecific interactions was negligible. Our results suggest that further removal of shrubland, the expansion of intensive agriculture, and the increase of human activity are expected to result in species losses. The fact that community integrity responds to a single type of ecological process simplifies practical recommendations. Management strategies should focus on the conservation and restoration of shrubland, adopting alternatives to intensive schemes of agricultural production, and minimizing recreational and other human activities in remnant natural habitats within agroecosystems or mosaic landscapes.

Spatiotemporal Patterns of Wolves, and Sympatric Predators and Prey Relative to Human Disturbance in Northwestern Greece

In an era of increasing human pressure on nature, understanding the spatiotemporal patterns of wildlife relative to human disturbance can inform conservation efforts, especially for large carnivores. We examined the temporal activity and spatial patterns of wolves and eight sympatric mammals at 71 camera trap stations in Greece. Grey wolves temporally overlapped the most with wild boars (Δ = 0.84) and medium-sized mammals (Δ > 0.75), moderately with brown bears (Δ = 0.70), and least with roe deer (Δ = 0.46). All wild mammals were mainly nocturnal and exhibited low temporal overlap with human disturbance (humans, vehicles, livestock, and dogs; Δ = 0.18–0.36), apart from roe deer, which were more diurnal (Δ = 0.80). Six out of nine species increased their nocturnality at sites of high human disturbance, particularly roe deer and wolves. The detection of wolves was negatively associated with paved roads, the detection of roe deer was negatively associated with human disturbance, and the detection of wild boars was negatively associated with dogs. The detection of bears, boars, and foxes increased closer to settlements. Our study has applied implications for wolf conservation and human–wildlife coexistence.

Food habits of the Red Fox Vulpes vulpes (Mammalia: Carnivora: Canidae) in Dachigam National Park of the Kashmir Himalaya, India

Food habits of the Red Fox Vulpes vulpes were studied in Dachigam National Park of the Kashmir Himalaya from December 2017 to November 2018 by scat analysis. A total of 246 scats were collected across seasons from different habitat types of the park. The diet of the Red Fox was characterized by a wider prey spectrum with small rodents, plants, and Himalayan Grey Langur Semnopithecus ajax as the major food items. The dietary behaviour showed slight seasonal variation with more invertebrates and plant material (fruits, berries, & grasses) during spring and summer. The food niche of the canid was wider in the warm season than in the cold season. Diet analysis revealed substantial use of anthropogenic food sources (human refuse and livestock carrion) by the Red Fox. The frequency of occurrence of human refuse and livestock carrion in the scats of the canid species varied seasonally. The results show that the Red Fox is an opportunistic feeder, and capable of adapting to a variety of dietary items.

Understanding the distribution and fine-scale habitat selection of mesocarnivores along a habitat quality gradient in western Himalaya

Background: Human activities have resulted in a rapid increase of modified habitats in proximity to wildlife habitats in the Himalaya. However, it is crucial to understand the extent to which human habitat modification affects wildlife. Mesocarnivores generally possess broader niches than large carnivores and adapt quickly to human activities. Here, we use a case study in the western Himalaya to test the hypothesis that human disturbance influenced mesocarnivore habitat use. Methods: We used camera trapping and mitochondrial DNA-based species identification from faecal samples to obtain mesocarnivore detections. We then compared the responses of mesocarnivores between an anthropogenic site and a less disturbed park along a contiguous gradient in habitat quality. The non-linear pattern in species-specific habitat selection and factors responsible for space usage around villages was captured using hierarchical generalized additive modelling (HGAM) and non-metric multidimensional scaling (NMDS) ordination. Results: Wildlife occurrences along the gradient varied by species. Leopard cat and red fox were the only terrestrial mesocarnivores that occurred in both anthropogenic site and park. We found a shift in habitat selection from less disturbed habitat in the park to disturbed habitat in anthropogenic site for the species detected in both the habitat types. For instance, red fox showed habitat selection towards high terrain ruggedness (0.5 to 0.7 TRI) and low NDVI (-0.05 to 0.2) in the park but no such specific selection in anthropogenic site. Further, leopard cat showed habitat selection towards moderate slope (20°) and medium NDVI (0.5) in park but no prominent habitat selections in anthropogenic site. The results revealed their constrained behaviour which was further supported by the intensive site usage close to houses, agricultural fields and human trails in villages. Conclusions: Our results indicate shifts in habitat selection and intensive site usage by mesocarnivores in the human-modified habitat. In future, this suggests the possibility of conflict and disease spread affecting both the people and wildlife. Therefore, this study highlights the requisite to test the wildlife responses to rapidly growing human expansions in modified habitats to understand the extent of impact. The management strategies need to have an integrated focus for further expansions of modified habitat and garbage disposal strategies, especially in the human-wildlife interface area.

Invasive species control with apex predators: increasing presence of wolves is associated with reduced occurrence of the alien raccoon dog

The role of an alien predator in the community depends on its interaction with native predators. The absence of apex predators may facilitate outbreaks of invasive mesopredators, but the effect of apex predators may vary between species and environments. We analysed the occurrence of a common invasive mesopredator in Europe, the raccoon dog (Nyctereutes procyonoides), and native mesopredators, the red fox and the Eurasian badger, in camera-trap data from Finland. The observations in cameras were analysed in relation to the presence of apex predators in the landscape (grey wolf and Eurasian lynx), human density, and habitat. We observed negative effect of increasing presence of wolves and lynxes on the occurrence of raccoon dogs. This effect appeared clear compared to the effects of habitat and human density. The effect of lynxes on raccoon dogs was clearer in areas with short growth season. For the occurrence of badgers, the presence of wolves had a weak negative effect and the presence of lynxes had a positive effect. For the occurrence of red foxes, wolves had a positive effect when agricultural fields were sparse in the landscape and lynxes had no effect. We also observed that the invasive raccoon dog currently appears to be the most common mesopredator within the study area. We conclude that the effect of apex predators on mesopredators depends on the environment and, in our case, was more suppressive on the alien mesopredator than on the native mesopredators. Thus, apex predators can play an important role in controlling invasive mesopredators.

Estimating red fox density using non-invasive genetic sampling and spatial capture-recapture modelling

Spatial capture-recapture modelling (SCR) is a powerful tool for estimating density, population size, and space use of elusive animals. Here, we applied SCR modelling to non-invasive genetic sampling (NGS) data to estimate red fox (Vulpes vulpes) densities in two areas of boreal forest in central (2016-2018) and southern Norway (2017-2018). Estimated densities were overall lower in the central study area (mean = 0.04 foxes per km2 in 2016, 0.10 in 2017, and 0.06 in 2018) compared to the southern study area (0.16 in 2017 and 0.09 in 2018). We found a positive effect of forest cover on density in the central, but not the southern study area. The absence of an effect in the southern area may reflect a paucity of evidence caused by low variation in forest cover. Estimated mean home-range size in the central study area was 45 km2 [95%CI 34-60] for females and 88 km2 [69-113] for males. Mean home-range sizes were smaller in the southern study area (26 km2 [16-42] for females and 56 km2 [35-91] for males). In both study areas, detection probability was session-dependent and affected by sampling effort. This study highlights how SCR modelling in combination with NGS can be used to efficiently monitor red fox populations, and simultaneously incorporate ecological factors and estimate their effects on population density and space use.

Small rodent cycles influence interactions among predators in a boreal forest ecosystem

Cyclic fluctuations of prey have profound effects on the functioning of ecosystems, for example, by changing the dynamics, behavior, and intraguild interactions of predators. The aim of this study was to assess the effect of rodent cyclic fluctuations in the interspecific interactions of a guild of small- and medium-sized predators: red fox (Vulpes vulpes), pine marten (Martes martes), and weasels (Mustela erminea and Mustela nivalis) in the boreal ecosystem. We analyzed eight years (2007–2014) of snow tracking data from southeastern Norway using structural equation models to assess hypothesized networks of causal relationships. Our results show that fluctuations in rodent abundance alter the strength of predator’s interactions, as well as the effect of determinant environmental variables. Pine marten and weasel abundances were positively associated with rodent population growth rate, but not red fox abundance. All predators were positively associated with each other; however, the association between red fox and the other predators weakened when rodents increased. Rodent fluctuations had variable effects on the habitat use of the predators. The presence of agricultural land was important for all predators, but this importance weakened for the mustelids as rodent abundance increased. We discuss the shifting role of interference and exploitative competition as possible mechanisms behind these patterns. Overall, we highlight the importance of accounting for the dynamics of prey resources when studying interspecific interactions among predators. Additionally, we demonstrate the importance of monitoring the predator populations in order to anticipate undesirable outcomes such as increased generalist predator abundances to the detriment of specialists.

Effects on carrion consumption in a mammalian scavenger community when dominant species are excluded

Carrion is a valuable resource exploited not only by obligate scavengers but also by a wide variety of facultative scavengers. These species provide several important ecosystem services which can suffer if the scavenger community composition is altered, thus reducing the ecosystem provided. We studied the response of the Mediterranean facultative scavenger community to the exclusion of larger scavenger species (red fox Vulpes vulpes, European badger Meles meles, and wild boar Sus scrofa) using an exclusion fence permeable to small scavenger species (mainly Egyptian mongoose Herpestes ichneumon, common genet Genetta genetta, and stone marten Martes foina). The exclusion of dominant facultative scavengers led to a significant reduction in the amount of carrion consumed and an increase in carrion available for smaller species and decomposers, over a longer period of time. Although carrion consumption by the non-excluded species increased inside the exclusion area relative to the control area, it was insufficient to compensate for the carrion not eaten by the dominant scavengers. Of the small scavenger species, only the Egyptian mongoose significantly increased its carrion consumption in the exclusion area, and was the main beneficiary of the exclusion of dominant facultative scavengers. Therefore, altering the facultative scavenger community in Mediterranean woodlands can reduce the efficiency of small carcass removal and benefit other opportunistic species, such as the Egyptian mongoose, by increasing the carrion available to them. This interaction could have substantial implications for disease transmission, nutrient cycling, and ecosystem function.

Effects of human activity on the habitat utilization of Himalayan marmot (Marmota himalayana) in Zoige wetland

Human activity is increasingly and persistently disturbing nature and wild animals. Affected wildlife adopts multiple strategies to deal with different human influences. To explore the effect of human activity on habitat utilization of Himalayan marmot (Marmota himalayana), habitat utilization patterns of three neighboring marmot populations in habitats affected differently by human activities were recorded and compared. We found that (a) distance between reproductive burrows (a represent of reproductive pairs) becomes shorter under the influence of human activities, and more burrows were dug as temporary shelters, resulting in shorter distance between those shelters and shorter distance flee to those shelters and, consequently, shorter flight initiation distance when threatened. More burrows that are closer to the disturbed habitats improve the ability to escape from threats. (b) Reproductive burrow site selection of the species is determined by the availability of mounds in the habitat, and breeding pairs selectively build reproductive (also the hibernation) burrows on mounds, potentially to improve surveillance when basking and the drainage of burrows. Human activities generally drive breeding pairs away from the road to dig their reproductive burrows likely to reduce disturbance from vehicles. However, even heavy human activity exerts no pressure on the distance of reproductive burrows from the road or the mound volume of the high disturbance population, potentially because mounds are the best burrowing site to reproduce and hibernate in the habitat. Marmots deal with disturbance by digging more burrows in the habitat to flee more effectively and building reproductive burrows on mounds to gain better vigilance and drainage efficiency.

Spatiotemporal patterns of red fox scavenging in forest and tundra: the influence of prey fluctuations and winter conditions

Concern has been raised regarding red fox (Vulpes Vulpes) population increase and range expansion into alpine tundra, directly and indirectly enhanced by human activities, including carrion supply, and its negative impact on native fauna. In this study, we used cameras on bait stations and hunting remains to investigate how spatiotemporal patterns of red fox scavenging were influenced by abundance and accessibility of live prey, i.e., small rodent population cycles, snow depth, and primary productivity. We found contrasting patterns of scavenging between habitats during winter. In alpine areas, use of baits was highest post rodent peaks and when snow depth was low. This probably reflected relatively higher red fox abundance due to increased reproduction or migration of individuals from neighboring areas, possibly also enhanced by a diet shift. Contrastingly, red fox use of baits in the forest was highest during rodent low phase, and when snow was deep, indicating a higher dependency of carrion under these conditions. Scavenging patterns by red fox on the pulsed but predictable food resource from hunting remains in the autumn revealed no patterns throughout the rodent cycle. In this study, we showed that small rodent dynamics influenced red fox scavenging, at least in winter, but with contrasting patterns depending on environmental conditions. In marginal alpine areas, a numerical response to higher availability of rodents possible lead to the increase in bait visitation the proceeding winter, while in more productive forest areas, low availability of rodents induced a functional diet shift towards scavenging.

Evaluation of Spatio-Temporal Patterns of Predation Risk to Forest Grouse Nests in the Central European Mountain Regions

We evaluated the spatiotemporal patterns of predation risk on black grouse nests using artificial nests that were monitored by camera traps in mountain areas with a small extant (Ore Mts.) and already extinct (Jeseníky Mts.) black grouse population. The overall predation rate of artificial nests was 56% and we found significant differences in survival rate courses over time between both study areas (68% Ore Mts. vs. 41%, Jeseníky Mts.). Within the time required for successful egg incubation (25 days), nest survival probability was 0.32 in the Ore Mts. and 0.59 in Jeseníky Mts. The stone marten (Martes foina) was the primary nest predator in both study areas (39% in total), followed by common raven (Corvus corax, 25%) and red fox (Vulpes vulpes, 22%). The proportion of depredated nests did not differ between habitat types (i.e., open forest interior, clearing, forest edge), but we recorded the effect of interaction of study area and habitat. In Ore Mts., the main nest predator was common raven with seven records (37%). The Eurasian jay (Garrulus glandarius) was responsible for most predation attempts in Jeseníky Mts. (five records, i.e., 83%), while in the Ore Mts., most predation attempts were done by red fox (six records, i.e., 38%).