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Large predators limit herbivore densities in northern forest ecosystems
Abstract
There is a lack of scientific consensus about how top-down and bottom-up forces interact to structure terrestrial ecosystems. This is especially true for systems with large carnivore and herbivore species where the effects of predation versus food limitation on herbivores are controversial. Uncertainty exists whether top-down forces driven by large carnivores are common, and if so, how their influences vary with predator guild composition and primary productivity. Based on data and information in 42 published studies from over a 50-year time span, we analyzed the composition of large predator guilds and prey densities across a productivity gradient in boreal and temperate forests of North America and Eurasia. We found that predation by large mammalian carnivores, especially sympatric gray wolves (Canis lupus) and bears (Ursus spp.), apparently limits densities of large mammalian herbivores. We found that cervid densities, measured in deer equivalents, averaged nearly six times greater in areas without wolves compared to areas with wolves. In areas with wolves, herbivore density increased only slightly with increasing productivity. These predator effects are consistent with the exploitation ecosystems hypothesis and appear to occur across a broad range of net primary productivities. Results are also consistent with theory on trophic cascades, suggesting widespread and top-down forcing by large carnivores on large herbivores in forest biomes across the northern hemisphere. These findings have important conservation implications involving not only the management of large carnivores but also that of large herbivores and plant communities.
... This economic burden can create negative attitudes towards carnivores, further escalating the conflict. Moreover, the depletion of carnivore populations disrupts the delicate balance within ecosystems, leading to cascading effects on prey populations, vegetation dynamics, and overall biodiversity (Prugh et al., 2009;Creel et al., 2011;Ripple & Beschta, 2012). The loss of carnivores can result in an overabundance of herbivores, leading to habitat degradation and altered ecosystem functioning (Beschta & Ripple, 2012;Ripple & Beschta, 2012). ...
... Moreover, the depletion of carnivore populations disrupts the delicate balance within ecosystems, leading to cascading effects on prey populations, vegetation dynamics, and overall biodiversity (Prugh et al., 2009;Creel et al., 2011;Ripple & Beschta, 2012). The loss of carnivores can result in an overabundance of herbivores, leading to habitat degradation and altered ecosystem functioning (Beschta & Ripple, 2012;Ripple & Beschta, 2012). Therefore, addressing human-wildlife conflict and finding sustainable solutions is crucial for the conservation of both carnivores and the ecosystems they inhabit. ...
... Moreover, the depletion of carnivore populations disrupts the delicate balance within ecosystems, leading to cascading effects on prey populations, vegetation dynamics, and overall biodiversity (Prugh et al., 2009;Creel et al., 2011;Ripple & Beschta, 2012). The loss of carnivores can result in an overabundance of herbivores, leading to habitat degradation and altered ecosystem functioning (Beschta & Ripple, 2012;Ripple & Beschta, 2012). Therefore, addressing human-wildlife conflict and finding sustainable solutions is crucial for the conservation of both carnivores and the ecosystems they inhabit. ...
Human-wildlife coexistence in rural coastal areas of southern Chile is analyzed, emphasizing the variable nature of interactions and the negative impacts of human-wildlife conflict on both human well-being and wildlife populations. The objectives of the study include exploring local perceptions of carnivores, investigating the social factors that influence these perceptions, and collecting data through structured surveys to obtain information for specific conservation interventions. To investigate the conflict between humans and carnivores in rural areas of southern Chile, structured surveys were carried out using questionnaires. The questionnaire addressed various topics, including demographic and socioeconomic information, management techniques used, predation history, and perceptions of carnivores in the area. A total of forty-three surveys were collected, revealing the deep vulnerability of rural dwellers to conflict and the high impact of livestock losses on their livelihoods. The most valued and commonly used handling techniques turned out to be confinement and the use of guard dogs. Respondents reported attacks by both native species (mainly pumas and foxes) and exotic species (dogs and introduced American minks) in roughly equal measures. The losses suffered by these ranchers were quantified as substantial, especially considering their reliance on subsistence economies.
... Apex predators are an important component of ecosystem function. They shape the population size, behavior, spatial distribution, and physiological condition of prey (Okarma, 1995;Ripple and Beschta, 2012;Wikenros et al., 2015;Mattisson et al., 2016;Klich et al., 2020), and directly affect ecosystems by exerting top-down control on lower trophic levels (Ripple and Beschta, 2012). At the same time, predator populations are often challenging to manage, as they commonly come into conflict with humans, including depredating economically and culturally important livestock (Woodroffe et al., 2005;Aryal et al., 2014;McManus et al., 2015). ...
... Apex predators are an important component of ecosystem function. They shape the population size, behavior, spatial distribution, and physiological condition of prey (Okarma, 1995;Ripple and Beschta, 2012;Wikenros et al., 2015;Mattisson et al., 2016;Klich et al., 2020), and directly affect ecosystems by exerting top-down control on lower trophic levels (Ripple and Beschta, 2012). At the same time, predator populations are often challenging to manage, as they commonly come into conflict with humans, including depredating economically and culturally important livestock (Woodroffe et al., 2005;Aryal et al., 2014;McManus et al., 2015). ...
... The gray wolf (Canis lupus) is an important apex predator that affects both their prey populations as well as ecosystem function (Ripple and Beschta, 2012). After a period of long-term population decline in central Europe, wolf populations have increased, and their range expanded, over the last 20 years (Chapron et al., 2014). ...
The gray wolf (Canis lupus) is one of the most conflictual mammals in Europe. Wild boar (Sus scrofa) are an essential part of gray wolf diet in central Europe, but after the emergence of African swine fever (ASF) in Europe, a sharp decline of the wild boar occurred. We examined how the wild boar population decline, due to African swine fever outbreak and mitigation efforts, affected the number of livestock killed by wolves in Poland using long-term data on wild ungulate and livestock population sizes and wolf-induced mortality between 2013 and 2019. We examined the influence of multiple factors on livestock kill rate, and the influence of wild boar population declines on the number of Cervidae killed by wolves using linear mixed models. We also explored the possibility of predicting a dramatic decrease in the wild boar population based on livestock depredation patterns. The number of livestock killed by wolves decreased with wild boar and roe deer (Capreolus capreolus) population size, and increased with red deer (Cervus elaphus) population size. A decline in the wild boar population was significantly correlated with an increase in the number of both red and roe deer killed by wolves. A drastic decline of wild boar population (over 30%) could be predicted by the numbers of livestock killed by wolves. Our study confirms that large changes in the number of naturl prey can increase livestock depredation, although these changes may be difficult to detect when the fluctuations in the numbers of natural prey are smaller. In our opinion, this indicates that the assessment of factors influencing livestock depredation should consider historical changes in prey dynamics. We suggest managers and conservationists use the predator population as a 'first alert system' for indirect monitoring of prey species. In this system, a sudden increase in wolf attacks on livestock across a large area of should trigger an alarm and prompt verification of the number of natural prey in the environment.
... Restoring predator-prey interactions is another complementary yet controversial measure to reduce the impacts of overabundant ungulates (Apollonio et al. 2017;Marrotte et al. 2022;Nilsen et al. 2007). Large carnivores predate on large ungulates (Jedrzejewska and Jedrzejewski 1998;Jedrzejewski et al. 2002;Ripple and Beschta 2012;van Beeck Calkoen et al. 2023) and modulate prey behaviour through landscapes of fear (Epperly et al. 2021;Gaynor et al. 2019). The grey wolf (Canis lupus) -the apex predator with the largest distribution in Europe (Chapron et al. 2014) -can reduce the risk of disease transmission from wild boars to livestock by removing diseased individuals (Tanner et al. 2019) and the incidence of deer-vehicle collisions by keeping ungulates away from roads (Raynor et al. 2021). ...
... Despite the lack of scientific consensus on the relative extent to which predation limits large herbivore abundance (Kuijper 2011;Melis et al. 2009;Ripple and Beschta 2012), lethal management of predators might collide with the goal of controlling overabundant ungulates by limiting predation impact. Wolf harvest can reduce the mortality rate of wild herbivores due to lower wolf numbers, destabilized wolf packs (Fernández-Gil et al. 2016), or lower interactions with ungulates due to altered activity patterns of wolves (Frey et al. 2022). ...
Increasing abundance of large ungulates is raising human-wildlife impacts and the effectiveness of recreational hunting to reduce their population growth is increasingly questioned. We report on long-term trends (> 15 years) in wildlife-vehicle collisions (WVC) and hunting bags, and on associations between the annual growth rate of WVC and that of hunting bags for three ungulates – the wild boar, the red deer, and the roe deer – and the grey wolf in northwest Spain to evaluate the regulating capacity of recreational hunting at large spatial scale. Wildlife-vehicle collisions increased by 332% in 16 years and 91% of all traffic accidents were caused by collisions with these three ungulates. All ungulate species showed significant positive trends in WVC and hunting bags, but we did not observe a negative association between annual growth rate of hunting bags and that of WVC except for the wild boar. Results suggest that recreational hunting was unable to reduce ungulate population growth at the regional scale. There was no upward trend of vehicle collisions with wolves over the study period, possibly reflecting stable wolf populations. Natural mortality due to predation could be promoted through the protection of apex predators, but the lethal management of apex predators, often based on sociopolitical pressures rather than damage levels, can conflict with the strategy for mitigating ungulate impacts. Ungulate management needs to be reconsidered from an ecological perspective that integrates human management measures, including recreational hunting, based on the population dynamics and the recovery of predator–prey interactions by favoring the expansion of apex predators.
... Anthropogenic linear features 41 produce long, cleared sections across a landscape (Knight and Kawashima, 1993) and are the 42 cause of much habitat loss and fragmentation (Luque et al., 2013). For wildlife, landscape 43 changes create a tension between resource acquisition and avoidance of areas associated with 44 humans (Ripple and Beschta, 2012). This trade-off between risk and reward for animals shapes 45 animal behaviour including movement patterns and resource selection (Coulson et al., 2011;Frid 46 and Dill, 2002; Sih et al., 2011). ...
... Predator species are particularly susceptible to anthropogenic environmental change, as 75 they are wide-ranging and have high metabolic requirements, two traits that result in high rates 76 of human-wildlife conflict, and conflict-related wildlife mortality (Ripple and Beschta, 2012). 77 ...
Anthropogenic linear features are often linked to alterations in wildlife behaviour and movement. Landscape features such as habitat can have important mediating effects on wildlife response to disturbance and yet is rarely explicitly considered in how it interacts with other features. This study tests the effects of habitat variation on the space-use responses of GPS-collared wolves to linear features in eastern Manitoba. We simultaneously model wolf movement and selection within a conditional logistic regression framework (integrated Step Selection Analysis) with explicit consideration for how habitat alters these responses through either added cover or friction to movement. Classifying linear features based on the selection and movement response of wolves revealed that pairing transmission lines and primary roads increased the avoidance response to be greater than either feature on their own and provided evidence of a semi-permeable barrier to movement. In contrast, features with reduced human activity, including secondary and tertiary roads were highly selected for and provided access to movement corridors. Explicit parameterization of habitat provides evidence that where a linear feature is routed and which habitats it interacts with will have the greatest implications for wolf behavioural responses. Reduction of avoidance behavioural in highly risky environments signifies the importance of habitat for maintaining landscape connectivity, particularly when routing multiple features together. Natural regrowth along these features reduced movement advantages by increasing friction, indicating that actively decommissioning other features such as secondary roads would have important implications for reducing wolf encounters with prey. Knowing the influence of adjacent habitats on the likelihood of wolves selecting for a given linear feature creates context to minimize the impact of new anthropogenic features on behaviour.
... Equivalently, from a top-down perspective, herbivore prey abundance should decrease with predator abundance, but only where productivity is high; otherwise, both prey and predators should be limited to low abundance by low productivity (Oksanen et al., 1981;Richards and Coley, 2007;Wilkinson and Sherratt, 2016). Indeed, vertebrate herbivore abundance increases with primary productivity across continents, but only where canid predators are rare (Letnic and Ripple, 2017;Ripple and Beschta, 2012), and insect herbivore biomass increased with plant biomass in temperate grasslands, but only where spider abundance was low (Welti et al., 2020). However, it is unclear whether this effect generalizes across trophic levels (e.g. ...
... The Exploitation Ecosystems Hypothesis predicts that increases in herbivore abundance with plant productivity should weaken with increasing predator abundance due to direct consumption of prey surplus and/or foraging costs of predator avoidance (Oksanen, 1992;Oksanen et al., 1981;Zanette and Clinchy, 2019). This has been supported for both vertebrate (Letnic and Ripple, 2017;Ripple and Beschta, 2012) and invertebrate herbivores (Richards and Coley, 2007;Welti et al., 2020). Furthermore, similar patterns have been reported across trophic levels: herbivores weakened the increase of plant biomass with primary productivity at higher latitudes (Oksanen and Oksanen, 2000), and parasitoids appeared to weaken the increase of spider density with insect prey density in desert islands (Polis et al., 1998). ...
Community trophic structure is shaped by concurrent bottom-up (resources) and top-down effects (predators), but the extent to which they interact remains uncertain. The Exploitation Ecosystems Hypothesis predicts that predators should offset increases in herbivore abundance with plant productivity, which is supported by data. However, the extent to which interactions within trophic levels (e.g. competition, intraguild predation) have similar effects is less clear. Ants and spiders are abundant in vegetation and consume similar arthropod prey (occasionally each other) and plant exudates, with ants generally showing competitive dominance over spiders. We tested whether ants could shape the trophic structure of tree-dwelling macroarthropod communities by offsetting increases in spider abundance with insect prey. We performed three surveys of the macroarthropod community of 97 trees from two sites in the savanna of Northern Amazonia. Together, ants and spiders represented 74% of the sampled individuals per tree. Insect prey abundance increased with tree crown volume and crown flower cover, consistent with bottom-up limitation. Likewise, both ants and spiders increased with insect prey abundance, with ant abundance also varying with tree species, suggesting reliance on both animal and plant resources. However, as predicted, the positive relationship between spider abundance and insect prey abundance disappeared as ant abundance increased. Our results suggest that agonistic interactions within trophic levels can strongly shape community structure and size by modifying bottom-up effects as much as interactions across trophic levels.
... In tri-trophic systems (i.e. plants, herbivores and carnivores), the relationships become less clear because herbivore densities may be influenced by both top-down and bottom-up effects (Oksanen et al., 1981;Ripple & Beschta, 2012). In such systems, carnivore densities may show a positive relationship with plant productivity while herbivore densities are relatively stable across productivity gradients (Oksanen et al., 1981, Ripple & Beschta, 2012. ...
... plants, herbivores and carnivores), the relationships become less clear because herbivore densities may be influenced by both top-down and bottom-up effects (Oksanen et al., 1981;Ripple & Beschta, 2012). In such systems, carnivore densities may show a positive relationship with plant productivity while herbivore densities are relatively stable across productivity gradients (Oksanen et al., 1981, Ripple & Beschta, 2012. Remotely sensed estimates of plant productivity, especially the suite of MODIS vegetation products, provide great opportunities to explore such relationships. ...
Aim
Predicting biodiversity responses to global changes requires good models of species' distributions. Both environmental conditions and human activities determine population density patterns. However, quantifying the relationship between wildlife population densities and their underlying environmental conditions across large geographical scales has remained challenging. Our goal was to explain the abundances of mammal species based on their response to several remotely sensed indices including the Dynamic Habitat Indices (DHIs) and the novel Winter Habitat Indices (WHIs).
Location
Russia, the majority of regions.
Taxon
Eight mammal species.
Methods
We estimated average population densities for each species across Russia from 1981 to 2010 from winter track counts. The DHIs measure vegetative productivity, a proxy for food availability. Our WHIs included the duration of snow‐free ground, duration of snow‐covered ground and the start, end and length of frozen season. In models, we included elevation, climate conditions, human footprint index. We parameterized multiple linear regression and applied best‐subset model selection to determine the main factors influencing population density.
Results
The DHIs were included in some of the top‐twelve models of every species, and in the top model for moose, wild boar, red fox and wolf, so they were important for species at all trophic levels. The WHIs were included in top models for all species except roe deer, demonstrating the importance of winter conditions. The duration of frozen ground without snow and the end of frozen season were particularly important. Our top models performed well for all the species ( R ² adj 0.43–0.87).
Main Conclusions
The combination of the DHIs and the WHIs with climate and human‐related variables resulted in high explanatory power. We show that vegetation productivity and winter conditions are key drivers of variation in population density of eight species across Russia.
... Brown bear predation patterns are strongly seasonal, especially in coastal populations, as brown bears switch from ungulate calves in the spring to more readily available salmon and berries during summer [84]. Though winter severity and predation may have additive effects on ungulate survival [21], we did not find that the long-term decline in elk recruitment translated to a decline in abundance, indicating that high juvenile and adult survival in mild winters may be supporting compensatory brown bear predation, even in a low-density population [7,72,85,86]. The strong influence of brown bear abundance on elk recruitment indicates that ungulate populations that are small or declining may experience accelerated declines where brown bear populations are increasing [87], especially where other predator species occur, or where winter conditions are more severe [21,86]. ...
... Though winter severity and predation may have additive effects on ungulate survival [21], we did not find that the long-term decline in elk recruitment translated to a decline in abundance, indicating that high juvenile and adult survival in mild winters may be supporting compensatory brown bear predation, even in a low-density population [7,72,85,86]. The strong influence of brown bear abundance on elk recruitment indicates that ungulate populations that are small or declining may experience accelerated declines where brown bear populations are increasing [87], especially where other predator species occur, or where winter conditions are more severe [21,86]. ...
Ungulates are key components of ecosystems due to their effects on lower trophic levels, role as prey, and value for recreational and subsistence harvests. Understanding factors that drive ungulate population dynamics can inform protection of important habitat and successful management of populations. To ascertain correlates of ungulate population dynamics, we evaluated the effects of five non-exclusive hypotheses on ungulate abundance and recruitment: winter severity, spring nutritional limitation (spring bottleneck), summer-autumn maternal condition carryover, predation, and timber harvest. We used weather, reconstructed brown bear (Ursus arctos) abundance, and timber harvest data to estimate support for these hypotheses on early calf recruitment (calves per 100 adult females in July–August) and population counts of Roosevelt elk (Cervus canadensis roosevelti) on Afognak and Raspberry islands, Alaska, USA, 1958–2020. Increasing winter temperatures positively affected elk abundance, supporting the winter severity hypothesis, while a later first fall freeze had a positive effect on elk recruitment, supporting the maternal carry-over hypothesis. Increased brown bear abundance was negatively associated with elk recruitment, supporting the predation hypothesis. Recruitment was unaffected by spring climate conditions or timber harvest. Severe winter weather likely increased elk energy deficits, reducing elk survival and subsequent abundance in the following year. Colder and shorter falls likely reduced late-season forage, resulting in poor maternal condition which limited elk recruitment more than winter severity or late-winter nutritional bottlenecks. Our results additionally demonstrated potential negative effects of brown bears on elk recruitment. The apparent long-term decline in elk recruitment did not result in a decline of abundance, which suggests that less severe winters may increase elk survival and counteract the potential effects of predation on elk abundance.
... Species belonging to this body size category usually require large areas of suitable habitats used for territorial behavior and hunting needs (Ewer, 1998), posing high current and future conservation challenges in Mexico (Munguía et al., 2016). If species from this group increase their risk, resulting in decreasing local population abundance, we can expect important disruptions in predator-prey interactions in large areas of Mexico, with profound ecological implications (Erlinge et al., 1984;Estes, 1996;Ripple & Beschta, 2012). Further studies must also focus on species-by-species cases, where species belonging to several functional groups at risk deserve conservation attention. ...
... If rainfed agricultural areas expand, then there is a strong need to move forward with the implementation of agroecological practices, including integrated pest management(Ha, 2014). Furthermore, herbivores play a fundamental role as a primary consumer of vegetation in many ecosystems, preserving a balance between vegetation communities and this group of terrestrial mammals(Lacher et al., 2019;Ripple & Beschta, 2012; ...
There is a need to revise the framework used to project species risks under climate change (CC) and land‐use/cover change (LUCC) scenarios. We built a climate change risk index using the latest IPCC framework, where risk is a function of vulnerability (sensitivity and adaptive capacity), exposure, and hazard. We incorporated future LUCC scenarios as part of the exposure component. We combined a trait‐based approach based on biological characteristics of species with a correlative approach based on ecological niche modeling, assigning risk scores to species, taxonomic (orders), and functional (trophic, body size, and locomotion) groups of terrestrial mammals occurring in Mexico. We identified 15 species projected to lose their climatic suitability. Of the 11 taxonomic orders, Eulipotyphla, Didelphimorphia, Artiodactyla, and Lagomorpha had the highest risk scores. Of the 19 trophic groups, piscivores, insectivores under canopy, frugivores‐granivores, herbivores browser, and myrmecophagous had the highest risk scores. Of the 5 body‐sized groups, large‐sized species (> 15 kg) had highest risk scores. Of the 7 locomotion groups, arboreal and semi‐aquatics had highest risk scores. CC and LUCC scenarios reduced suitable areas of species potential distributions by 37.5% (with CC), and 51% (with CC and LUCC) under a limited full‐dispersal assumption. Reductions in suitable areas of species potential distributions increased to 50.2% (with CC), and 52.4% (with CC and LUCC) under a non‐dispersal assumption. Species‐rich areas (> 75% species) projected 36% (with CC) and 57% (with CC and LUCC) reductions in suitability for 2070. Shifts in climatic suitability projections of species‐rich areas increased in number of species in northeast and southeast Mexico and decreased in northwest and southern Mexico, suggesting important species turnover. High risk projections under future CC and LUCC scenarios for species, taxonomic and functional group diversities, and species‐rich areas of terrestrial mammals highlight trends in different impacts on biodiversity and ecosystem function.
... Currently, approximately 40% of all wild terrestrial mammal biomass is concentrated in only 10 species, including five deer species (family Cervidae) and two kangaroo species from the family Macropodidae (Greenspoon et al. 2023). Sympatric gray wolves and bears ( Ursus spp.) apparently limit the densities of northern hemisphere cervids, which were found to be nearly six times greater in areas without wolves than in areas with wolves (Ripple and Beschta 2012 ). White-tailed deer ( Odocoileus virginianus ) have the greatest biomass among terrestrial wild mammals, and it is well documented that their populations can irrupt and cause significant browsing impacts following wolf extirpation and land-use change (Rooney and Waller 2003 ). ...
... Different mechanisms can induce these ecological effects of large carnivores on their prey. Historically, studies on predator-prey interactions mainly focused on consumptive effects, where predators affect population densities by killing their prey (Messier 1991, Ripple andBeschta 2012). In addition to such 'lethal' or 'consumptive' effects on the population dynamics of prey, the presence of predators can also induce antipredator responses in behaviour or physiology (Lima and Dill 1990, Boonstra et al. 1998, Creel et al. 2005. ...
Predators can affect ecosystems through non‐consumptive effects (NCE) on their prey, which can lead to cascading effects on the vegetation. In mammalian communities, such cascading effects on whole ecosystems have mainly been demonstrated in protected areas, but the extent to which such effects may occur in more human‐dominated landscapes remains disputable. With the recolonisation of wolves Canis lupus in Europe, understanding the potential for such cascading processes becomes crucial for understanding the ecological consequences of wolf recovery and making appropriate management recommendations. Here, we investigate the evidence for non‐consumptive effects of wolves on their wild ungulate prey and cascading effects on the vegetation in European landscapes. We reviewed empirical studies reporting wild ungulate responses to wolves involving spatio‐temporal behaviour at large and fine spatial scales, activity patterns, vigilance, grouping, physiological effects, and effects on the vegetation. We reveal that non‐consumptive effects of wolves in Europe have been studied in few regions and with focus on regions with low human impact, are highly context‐dependent, and might often be overruled by human‐related factors. Hence, we highlight the need for a description of human influence in NCE studies. We discuss challenges in NCE research and the potential for advances in future research on NCE of wolves in a human‐dominated landscape. We emphasise the need for wildlife management to restore ecosystem complexity and processes, to allow non‐consumptive predator effects to occur.
... The wolf (Canis lupus Linnaeus, 1758) is one of the most important carnivores and keystone species, both in Europe and in many other parts of the world (Beschta & Ripple, 2016;Mech & Boitani, 2003). This predator shapes the population size, behaviour, spatial distribution, and physiological state of its prey (Klich et al., 2020;Kuijper et al., 2015;Mattisson et al., 2016;Okarma, 1995;Ripple & Beschta, 2012). In general, although many species and taxa may shape the wolf food spectrum the ungulates, mainly the wild boar Sus scrofa, red deer Cervus elaphus and roe deer Capreolus capreolus, are its primary prey (Newsome et al., 2016;Okarma, 1995;Sidorovich et al., 2017;Zlatanova et al., 2014). ...
In 2021 in northwestern Bulgaria, on the territory of State Forestry "Midzhur", West Stara Planina Mtn, we analysed the temporal and spatial activity of the roe deer (Capreolus capreolus) in an area with scarce other large ungulates. In the locations where both wolf and roe deer were recorded a significant (75%) temporal overlap between the two species was found (Δ = 0 75, range 0.62-0.96 at CI 95). Although the overlap between the activity of the roe deer in locations with and without wolf registrations was high (Δ = 0.72, range 0.58-0.92 at CI 95), the activity had two clearly different main peaks-around 18:00 in locations without wolves and around 05:00 h in locations with wolves. The results of the time-spacing analysis showed that the average time for a roe deer to appear after the presence of a wolf (min = 8:17 h) was greater than the time needed for the wolf to appear after a roe deer (min = 1:35 h). The difference in the spatial distribution of roe deer in areas with and without wolf presence was not statistically significant; yet the highest detection rate of roe deer was recorded in locations with wolf registrations. This allowed us to conclude that the roe deer as a potential main prey species of the wolf in the region was not avoiding the predator spatially but temporarily while the wolf the strategy of the wolf was to synchronize its circadian activity with that of the roe deer.
... Governments have for a century or more justified killing grey wolves to increase hunting opportunity for ungulates, such as elk (Cervus canadensis) and deer (Leopold 1933(Leopold reprinted 19861949;Harbo and Dean 1983;Theberge and Gauthier 1985). Grey wolves are capable of reducing wild ungulate populations (Ripple and Beschta 2012); however the effect of grey wolves on ungulate abundances depends on other factors, such as ungulate vulnerability driven by winter severity (Vucetich and Peterson 2009;Peterson et al. 2014), local primary productivity (Melis et al. 2009), the abundance of ungulates relative to their carrying capacity (Ballard et al. 2001), the diversity of the local carnivore guild and potential for multiple ungulate predators (Griffin et al. 2011), and the abundance of alternative prey (i.e., apparent competition, Wittmer et al. 2005). A recent meta-analysis of the outcomes of carnivore removal on geographically diverse ungulate populations estimated that predator removals resulted in increased juvenile survival and recruitment on average, but equivocal effects on average adult ungulate abundance, which should be the metric that determines if efforts to increase huntable population size or hunting opportunity succeeded (Clark and Hebblewhite 2021). ...
... Different mechanisms can induce these ecological effects of large carnivores on their prey. Historically, studies on predator-prey interactions mainly focused on consumptive effects, where predators affect population densities by killing their prey (Messier 1991, Ripple andBeschta 2012). In addition to such 'lethal' or 'consumptive' effects on the population dynamics of prey, the presence of predators can also induce antipredator responses in behaviour or physiology (Lima and Dill 1990, Boonstra et al. 1998, Creel et al. 2005. ...
Predators can affect ecosystems through non-consumptive effects on their prey, which can lead to cascading effects on the vegetation. In mammalian communities, such cascading effects on whole ecosystems have mainly been demonstrated in protected areas, but the extent to which such effects may occur in more human-dominated landscapes remains disputable. With the recolonisation of wolves (Canis lupus) in Europe, understanding the potential for such cascading processes becomes crucial for understanding the ecological consequences of wolf recovery and making appropriate management recommendations. Here, we investigate the evidence for non-consumptive effects of wolves on their wild ungulate prey and cascading effects on the vegetation in European landscapes. We reviewed empirical studies reporting wild ungulate responses to wolves involving spatio-temporal behaviour at large and fine spatial scales, activity patterns, vigilance, grouping, physiological effects, and effects on the vegetation. We reveal that non-consumptive effects of wolves in Europe have been studied in few regions and with focus on regions with low human impact and are highly context-dependent and might often be overruled by human-related factors. Further, we highlight the need for a description of human influence in NCE studies. We discuss challenges in NCE research and the potential for advances in future research on NCE of wolves in a human dominated landscape. Further, we emphasise the need for wildlife management to restore ecosystem complexity and processes, to allow non-consumptive predator effects to occur.
... As Homo sapiens populations expanded out of Africa in successive waves and arrived in new environments, they were added to the secondary consumer guild. Following trophic cascade postulates, it has been proposed that H. sapiens increased the trophic pressure on herbivores and triggered the disappearance of some of their predators (4,5). However, the pace and extent of these extinctions were spatially and temporally diverse. ...
It has been proposed that climate change and the arrival of modern humans in Europe affected the disappearance of Neanderthals due to their impact on trophic resources; however, it has remained challenging to quantify the effect of these factors. By using Bayesian age models to derive the chronology of the European Middle to Upper Paleolithic transition, followed by a dynamic vegetation model that provides the Net Primary Productivity, and a macroecological model to compute herbivore abundance, we show that in continental regions where the ecosystem productivity was low or unstable, Neanderthals disappeared before or just after the arrival of Homo sapiens . In contrast, regions with high and stable productivity witnessed a prolonged coexistence between both species. The temporal overlap between Neanderthals and H. sapiens is significantly correlated with the carrying capacity of small- and medium-sized herbivores. These results suggest that herbivore abundance released the trophic pressure of the secondary consumers guild, which affected the coexistence likelihood between both human species.
... They directly shape the landscape by trampling, dispersing seeds, fertilizing the soil, and reducing the growth and resource uptake of plants by grazing, browsing, stripping, and fraying [1]. Due to a lack of predators and to active protection and promotion of certain ungulate species, the population of wild ungulates in Western Europe has increased over the last few decades [2][3][4]. ...
The browsing of wild ungulates can have profound effects on the structure and composition of forests. In the Swiss National Park, the density of wild ungulates, including red deer (Cervus elaphus), ibex (Capra ibex), and chamois (Rupicapra rupicapra), is exceptionally high due to strict protection and the absence of large predators. We examined count data of larch (Larix decidua), cembra pine (Pinus cembra), spruce (Picea abies), upright mountain pine (Pinus mugo subsp. uncinata), and mountain ash (Sorbus aucuparia) of four sampling years between 1991 and 2021, and modelled how topographic and location factors affected the probability of browsing on saplings of larch, cembra pine, and spruce. Despite the high density of wild ungulates, the number of saplings and young trees has increased over the past 30 years. The probability of browsing on saplings was highest for larch at a height of 10–40 cm and increased with increasing elevation. In our study area, open grasslands are mainly located above the tree line, which might explain the positive correlation between elevation and the probability of browsing. Further, the probability of browsing was related to exposition and slope, diversity of tree species, and disturbance by humans. It appears that in the investigated part of the Swiss National Park, the potential of the forest to regenerate has increased despite the high densities of wild ungulates.
... Moreover, Tasker and Dickman (2004) found a small number of pookila in a forested area with an open grassy understorey maintained by low-intensity cattle grazing and moderately frequent low-intensity burns, while finding none in un-grazed forests where there was a dense shrubby mid-storey. Aside from (or complementary to) lethal control, the management of grazing pressure may include applying patchy low-intensity burns (Fuhlendorf and Engle, 2004;Tuft et al., 2012), restoring native top predators (Pople et al., 2000;Ripple and Beschta, 2012), considered management of invasive predators (Bergstrom et al., 2009;Dexter et al., 2013), adding coarse woody debris (Barton et al., 2011;Stapleton et al., 2017), fertility manipulation (Raiho et al., 2015;Wimpenny et al., 2021), and exclusion fencing Shorthouse et al., 2012;Morgan et al., 2018;Smith et al., 2023b). ...
Wildlife translocations to human-modified and inferred formerly occupied habitats can be controversial when they involve a high degree of perceived risk of failure, often stemming from a large number of unknowns or misconceptions regarding the focal species' ecology. However, it is increasingly recognised that such trans-locations are necessary to guide effective conservation strategies, particularly for species that persist in a subset of the habitats they formerly occupied. As a step towards alleviating some of the perceived risks around these translocations, we suggest the focal species' microhabitat use in the recipient locality of a trial translocation be compared with that where they still persist. Using a case study of a threatened Australian rodent, the pookila (Pseudomys novaehollandiae, New Holland mouse), we demonstrate how such an assessment can shed light on ecological misconceptions that may need to be addressed, and bring about the revision of species-specific recommendations for restoration works and release tactics. Feeding this knowledge back into the decision-making process, practitioners may more confidently direct future conservation activities (including further trial trans-locations) across a broader diversity of habitats within the species' indigenous range. Widespread and systematic implementation of this approach may help to reverse the impacts of shifting baseline syndrome, and should ultimately aid the resilience of species to future environmental change.
... In terrestrial ecosystems, however, increasing primary productivity appears only to result in increased density of predators (Crête 1999, Ripple and Beschta 2012, Letnic and Ripple 2017. The observed pattern thus corroborates the predictions of simple, 'laissez-faire' food chain models (Oksanen et al. 1981(Oksanen et al. , 2020, where both predator-predator interference and evolutionary responses of herbivores are ignored. ...
The searching efficiency of predators depends on the balance between the adaptations of the predator and the counter‐adaptations of the prey. In this evolutionary race, the prey should normally have the upper hand, as it can perform tradeoffs between efficiency in resource use and ability to avoid predators. In terrestrial predator–herbivore systems, however, the huge difference in food quality between prey and predators seems to give predators an advantage. In productive terrestrial ecosystems, predators thus chronically overexploit herbivores, i.e. regulate them at densities far below the point of maximum sustainable yield. Assuming type II functional response, this should result in violent limit cycle dynamics. In reality, however, such cycles are only common at high latitudes, whereas the herbivory‐based food webs of species‐rich ecosystems at middle and low latitudes are characterized by asymptotic dynamics, where numerical changes only occur in response to external forcing. One way or another, diversity thus seems to beget stability in terrestrial grazing webs. We propose that strong, donor‐controlled energy flows from the detritus web and directly from plants to predators are the key for the prevalence of asymptotic dynamics at middle and low latitudes. These flows support generalists with type III functional response and, therefore, a capacity to curb budding outbreaks at an early stage. The ongoing extinction wave could critically weaken these stabilizing interactions, which could destabilize currently stable food webs. and result in violent limit cycle dynamics in ecosystems, where the dominating species have evolved under asymptotic dynamics. This could cause secondary extinctions and inflict large economic losses.
Keywords: extinction, food webs, limit cycles, overexploitation, searching efficiency, stability
... They directly shape the landscape by trampling, dispersing seeds, fertilizing the soil and by reducing the growth and resource uptake of plants by grazing, browsing, stripping, and fraying [1]. Due to a lack of predators and to active protection and promotion of certain ungulate species, the population of wild ungulates in Western Europe has increased over the last few decades [2][3][4]. ...
Browsing of wild ungulates can have profound effects on the structure and composition of forests. In the Swiss National Park, the density of wild ungulates including red deer (Cervus elaphus), ibex (Capra ibex), and chamois (Rupicapra rupicapra) is exceptionally high due to strict protection and the absence of large predators. We examined count data of larch (Larix decidua), cembra pine (Pinus cembra), spruce (Picea abies), upright mountain pine (Pinus mugo subsp. uncinata), and mountain ash (Sorbus aucuparia) of four sampling years between 1991 and 2021 and modelled how different topographic and location factors affected the probability of browsing on saplings of larch, cembra pine, and spruce. Despite the high density of wild ungulates, the numbers of saplings and young trees increased over the past 30 years. The probability of browsing on saplings was highest for larch at a height of 10 – 40 cm and increased with increasing elevation. In our study area, open grasslands are mainly located above the tree line, which might explain the positive correlation between elevation and the probability of browsing. Other factors like exposition and slope, available food resources and disturbance by humans did not have clear effects on the probability of browsing.
... Tamaraws may already be experiencing a food resource shortage, which could make the population more prone to parasitism (Stien et al., 2002) or epizootics (Davidson & Doster, 1997). More generally, density-dependence should be of concerned and investigated for large herbivores living in protected environments lacking apex predators, which contributes to limit abundance and reduces annual growth of prey species (Sinclair, Mduma, & Brashares, 2003;Ripple & Beschta, 2012). ...
Endangered species, despite often living at low population densities, may undergo unexpected density‐dependent feedbacks in the case of successful recovery or marked reduction in range. Because density‐dependence dynamics can increase risk of extinction, these effects can hamper conservation efforts. In this study, we analyze the dynamics of the largest population of the tamaraw Bubalus mindorensis, a critically endangered ungulate species endemic to Mindoro island, Philippines. The population is located within a <3000 ha area in Mounts Iglit‐Baco Natural Park, with limited expansion possibilities. We took advantage of a 22 year time series of tamaraw counts to estimate annual population growth rate and possible density‐dependence, accounting for sampling errors in the counts. The tamaraw population has been increasing at an average rate of +5% per year, as would be expected given its protected status by law. Population growth showed strong spatial structuring, with a population growth close to +10% in the core area of protection, and a reduction of abundance of −5% at the periphery of its range, inside the protected area. This range constriction is concerning because our best population dynamics model suggests significant negative density‐dependence (Bayes factor = 0.9). The contraction of tamaraw range is likely caused by anthropogenic pressures forcing the species to live at relatively high densities in the core zone where protection is most effective, creating source‐sink dynamics. Our study highlights the fact that, despite the continuous population growth over the last two decades, the long‐term viability of the Mounts Iglit‐Baco Natural Park tamaraw population remains uncertain.
... It is necessary to continue working on mitigating the gap between the sectors that have direct contact with the wolf and may suffer damage caused by the wolf through the economic compensation of damages. It is also necessary to continue training and raising awareness of this species, which plays a fundamental role in the configuration of ecosystems [48]. The results presented here coincide with those obtained in other studies, for example, in Skogen and Thrane [49] in Norway found that cultural patterns such as education, place of residence (urban/rural), and cultural capital could influence how people see wolves. ...
Surveys have been used to study the current perception towards wolves by different stakeholders such as ranchers, landowners, hunters, experts in the field, and employees of the environmental administration in the provinces of Pontevedra and A Coruña, in the northwest of Spain. The main objective of this study is the evaluation and further discussion of the compensation offered to affected people for damages caused by wolf attacks and whether such compensations represent an improvement in the degree of tolerance towards these animals. Significant differences (p < 0.05) were found among the different sectors interviewed, with the hunters being the least tolerant sector, followed by ranchers. The number of attacks in the area was proven to influence their perspective toward wolves and the need for preventive measures. There was unanimity among hunters, ranchers, and locals, who do not consider the tools provided by the Galician administration sufficient to palliate the damages produced by wolves. However, 53.8% of ranchers, the group whose livelihood will most likely be affected by wolf attacks, and 60% of the wolf experts believe that compensation does not help to reduce tolerance towards wolves. Losing an animal makes people more likely to agree to the use of lethal and non-lethal methods.
... Carnivore communities are important for maintaining the structure and function of terrestrial ecosystems. Living at the top of the food web, large carnivores maintain the populations of large herbivores at a stable level by exerting strong top-down control on prey (Perilli et al., 2016;Schmitz et al., 2000), consequently stabilizing an ecosystem (Ripple & Beschta, 2012;Roemer et al., 2009). However, over the past two centuries, the global population of large carnivores has been seriously endangered because of habitat degradation, fragmentation, or shrinkage of prey populations (Ceballos & Ehrlich, 2002), making efforts for their research and conservation essential (Ripple et al., 2014). ...
Abstract Carnivores, especially top predators, are important because they maintain the structure and function of ecosystems by top‐down control. Exploring the coexistence between carnivores belonging to different ecological guilds can provide the data needed for the development of effective conservation strategies of endangered species. We used scats and camera traps to molecularly analyze the dietary composition of four predators that inhabit the Everest region and assess their activity patterns. Dietary analysis revealed 22 food Molecular Operational Taxonomic Units (MOTUs) of 7 orders and 2 classes. Snow leopard (Panthera uncia) and wolf (Canis lupus) had high dietary overlap (Pianka's index = 0.95), as they both mainly preyed on ungulates (%PR = 61%, 50%), while lynx (Lynx lynx) and red fox (Vulpes vulpes) mainly consumed small mammals (%PR = 62%, 76%). We observed lower dietary overlaps (Pianka's index = 0.53–0.70) between predators with large body size difference (snow leopard versus lynx, snow leopard versus red fox, wolf versus lynx, wolf versus fox), and dietary difference was significant (p
... Defoliation reduces plant growth, vigor, competitive ability, and fitness, which are issues exacerbated by environmental stressors such as drought or nutrient scarcity (Gottschalk, 1989;Jedlicka et al., 2004;McGraw et al., 1990;Rieske & Dillaway, 2008;Wargo, 1996;Wright et al., 1989). Thus, by reducing defoliation, predators contribute to the structure and composition of ecosystems, and, consequently, the loss of predators leads to community reorganization and the decline of diversity within those systems (Ripple & Beschta, 2012;Terborgh, 2015;Terborgh et al., 2006). ...
Bats suppress insect populations in agricultural ecosystems, yet the question of whether bats initiate trophic cascades in forests is mainly unexplored. We used a field experiment to test the hypothesis that insectivorous bats reduce defoliation through the top‐down suppression of forest‐defoliating insects. We excluded bats from 20 large, subcanopy forest plots (opened daily to allow birds access), each paired with an experimental control plot, during three summers between 2018 and 2020 in the central hardwood region of the United States. We monitored leaf area changes and insect density for nine to 10 oak or hickory seedlings per plot. Insect density was three times greater on seedlings in bat‐excluded versus control plots. Additionally, seedling defoliation was five times greater with bats excluded, and bats' impact on defoliation was three times greater for oaks than for hickories. We show that insectivorous bats drive top‐down trophic cascades, play an integral role in forest ecosystems, and may ultimately influence forest health, structure, and composition. This work demonstrates insectivorous bats' ecological and economic value and the importance of conserving this highly imperiled group of predators.
... Operating as a top-down force, they can affect the ecology of competitors and prey (Beschta and Ripple 2009), with the potential to shape the dynamics of communities (Paine 1969). Besides their potential direct effects on prey population size through increased mortality (Ripple et al. 2014), large predators may influence density (Ripple and Beschta 2012), distribution (Weterings et al. 2022), and habitat selection through effects on prey behavior, e.g., by affecting their movement patterns, selection of foraging and resting sites or grouping behavior (Fortin et al. 2005;Lima and Dill 1990;Schmitz et al. 1997). ...
Prey adjust their antipredator behavioral tactics to minimize the risk of an encounter with predators. Spatio-temporal responses of prey to predators have been reported, but antipredator response is not ubiquitous, and it is the object of increasing interest, especially considering the recent recovery of large carnivores in Europe, and the potential for behavioral antipredator responses to elicit consequences at the ecosystem level. We have tested multiple antipredator responses by fallow deer Dama dama to wolf Canis lupus, in a Mediterranean protected area recently recolonized by this apex predator. Through intensive camera trapping, we tested for temporal and spatial association between predator and prey, and we have also studied deer vigilance in forest habitats where focal observations are usually impossible. Wolf detection rates were spatially associated with those of fallow deer. Accordingly, no evidence was found for fallow deer avoiding sites with higher predator detection rates. Temporal activity patterns were significantly different between the two species, with the wolf being mainly nocturnal whereas fallow deer was active especially during daylight. A comparison with a preliminary study strongly suggests an increase in diurnal activity of fallow deer along with the stabilization of wolf presence in the area. Both the rate and the duration of vigilance of female fallow deer increased with the local frequency of wolf activity. We suggest an antipredator response based on temporal – rather than spatial – avoidance, as well as increased vigilance.
... However, at higher productivity, populations of secondary consumers will be high enough to suppress primary consumers, so only secondary consumers will appear to respond positively to productivity increases [8]. For example, herbivore density responds only weakly to increasing productivity in the presence of wolves [11]. ...
Under the Ecosystem Exploitation Hypothesis ecosystem productivity predicts trophic complexity, but it is unclear if spatial and temporal drivers of productivity have similar impacts. Long-term studies are necessary to capture temporal impacts on trophic structure in variable ecosystems such as deserts. We sampled ants and measured plant resources in the Simpson Desert, central Australia over a 22-year period, during which rainfall varied 10-fold. We sampled dune swales (higher nutrient) and crests (lower nutrient) to account for spatial variation in productivity. We asked how temporal and spatial variation in productivity affects the abundance of ant trophic guilds. Precipitation increased vegetation cover, with the difference more pronounced on dune crests; seeding and flowering also increased with precipitation. Generalist activity increased over time, irrespective of productivity. Predators were more active in more productive (swale) habitat, i.e. spatial impacts of productivity were greatest at the highest trophic level. By contrast, herbivores (seed harvesters and sugar feeders) increased with long-term rainfall; seed harvesters also increased as seeding increased. Temporal impacts of productivity were therefore greatest for low trophic levels. Whether productivity variation leads to top-down or bottom-up structured ecosystems thus depends on the scale and dimension (spatial or temporal) of productivity.
... A large scale of conservation strategy is focused on large mammalian carnivores as these species often play an important role in ecosystems and serve as umbrella and flagship species for an ecosystem (Ray et al., 2013). Large carnivores are apex carnivores in their habitat and they can exhibit direct and indirect downstream effect on subordinate carnivores and herbivores (Ripple and Beschta, 2012;Le Roux et al., 2019). In previous studies, it has been claimed that the loss of large carnivores has benefited the subordinates and small carnivores to the extent that the rapid growth and expansion of these species have adversely impacted the function of ecosystem (Prugh et al., 2009;Ritchie and Johnson, 2009;Brashares et al., 2010). ...
Small mammalian carnivores are playing various important roles in ecosystems by influencing the structure of ecosystem and also providing various ecosystem services. In the present study, the major categories of threats faced by small carnivores were reviewed. This study revealed that biological resource use and land use change are the leading threats for small carnivores. These species need great concern globally, particularly in Southeast Asia and Madagascar. This review has encouraged research and constant monitoring of current status which will be helpful in conservation of small carnivores in future.
... Their effects can be produced by consumption or by behavior [13]. The consumption function is also called lethal and can directly regulate prey population size [8,14] and mesopredators (in the case of apex predators) [15,16]; or indirectly by providing carrion [17,18], promoting higher biodiversity levels [19], or even influencing soil composition [20]. Their effects by behavior can be direct and indirect as well: Directly by influencing prey behavior and habitat use [21,22], prey pack size [23], reproductive physiology [24], and natural selection [25]. ...
The two mammalian carnivores, puma (Puma concolor) and South American grey fox
(Lycalopex griseus) were studied, in a remote area located in the humid temperate forest of the coastal range of southern Chile. A total of six locations were selected in three landscapes: pre-mountain range, mountain range, and coast. The chosen study locations are relevant because they correspond to threatened areas with different levels of human intervention., so they offer the ideal setting for
studying how different species of carnivores respond to both human presence and activities. A dataset was collected for 24 months during 2016–2018 through photo-trapping (13 camera traps placed along 50 photo-trap stations). Wes estimated the apparent occurrence and relative abundance index (RAI) of the fauna registered, by means of generalized linear models to contrast those of an apex predator, such as the puma and a sympatric mesopredator, the South American grey fox, across the three landscapes. The ecological variables assessed were the RAI of the other carnivore considered, exotic carnivores such as dogs and cats, human intervention, farmland effect, prey availability, and habitat
quality. The primary hypothesis was that the apparent occurrence and RAI of puma and fox would be positively associated with the RAI of prey and livestock and negatively with human intervention. On the other hand, the secondary hypothesis dealt with the interactions between puma and fox faced with different degrees of human intervention. The results showed that the apparent occurrence of the puma was statistically explained by location only, and it was highest at the mountain range. The apparent occurrence of foxes was explained by both puma apparent occurrence and relative integrated anthropization index (INRA), being highest in the pre-mountain range. Concerning the RAI of pumas, high values were yielded by location and fox RAI. For the RAI of foxes, they were location, puma RAI, and INRA. It can be suggested that eucalyptus plantations from the pre-mountain
range could offer an adequate habitat for the puma and the fox, but not the coastal range, as the mountain range could be acting as a biological barrier. Due to the nature of the data, it was not possible to detect any relevant effect between the two carnivores’ considered, between their respective preys, or the very abundant presence of dogs.
... Regarding rabbits, predators such as foxes may contribute to suppress rabbit densities in some circumstances but may not be enough in rabbit-rich years and areas with high availability of resources for rabbits (Newsome et al. 1989;Pech et al. 1992;Delibes-Mateos et al. 2008b;Norbury and Jones 2015;Fernandez-de-Simon et al. 2015). In this regard, ungulate/ large carnivore dynamics are probably as likely, or unlikely, to impose a regulatory function as rabbit/fox dynamics (Ripple and Beschta 2012). ...
Many game species are prey species and evolved to cope with significant mortality by natural predators. In the absence of predation or hunting, these game populations will be limited by resource depletion or disease. Both situations may fall within the overabundance definition. We review drivers of game species overabundance, considering if recreational hunting can effectively manage this challenge. We show examples of overabundance management in European rabbits (Oryctolagus cuniculus), deer (red deer Cervus elaphus and white-tailed deer Odocoileus virginianus), and wild boar (Sus scrofa) or its relative, the feral pig. We also consider available alternatives for managing overabundant wildlife such as habitat management, predator restoration, pathogen introductions, professional culling, immunocontraception, and poisoning. Most alternatives can be included in integrated wildlife management strategies but are unsuitable alone for large-scale overabundance control. We conclude that, when available, it is advisable to use recreational hunting as one tool in the box. Recreational hunting will perform best as a means of population control within integrated wildlife management strategies, combining hunting with habitat management. To maintain the contribution of recreational hunting for managing overabundance, hunters need to survey demographics of game populations to adequately plan harvest quotas. They should continue developing their commitment with biodiversity conservation, monitoring programs, and animal/public health. Agencies could set acceptable targets and facilitate hunting, educating the public about recreational hunting as socio-ecological service. Hunting and conservation should go hand in hand, with special caution regarding native endangered species that locally become pests needing sustainable management including adaptive hunting.
... Nonetheless, trophic cascades can also occur by non-lethal interactions through a behavioural change in response to a perceived predation risk (Schmitz et al., 2004) and the subsequent antipredatory behaviour modifies the ecosystem functioning (Ripple & Beschta, 2004). The most evident cascading effects on plants are mediated by herbivores (Ripple & Beschta, 2012a, 2012b, but little is known about the potential top-down effects of apex predators on plant-carnivore mutualisms. ...
Apex predators play key roles in food webs and their recovery can trigger trophic cascades in some ecosystems. Intra‐guild competition can reduce the abundances of smaller predators and perceived predation risk can alter their foraging behaviour thereby limiting seed dispersal by frugivorous carnivores. However, little is known about how plant–frugivore mutualisms could be disturbed in the presence of larger predators.
We evaluated the top‐down effect of the regional superpredator, the Iberian lynx Lynx pardinus , on the number of visits and fruits consumed by medium‐sized frugivorous carnivores, as well as the foraging behaviour of identified individuals, by examining the consumption likelihood and the foraging time.
We carried out a field experiment in which we placed Iberian pear Pyrus bourgaeana fruits beneath fruiting trees and monitored pear removal by frugivorous carnivores, both inside and outside lynx ranges. Using camera traps, we recorded the presence of the red fox Vulpes vulpes , the Eurasian badger Meles meles and the stone marten Martes foina , as well as the number of fruits they consumed and their time spent foraging.
Red fox was the most frequent fruit consumer carnivore. We found there were fewer visits and less fruit consumed by foxes inside lynx ranges, but lynx presence did not seem to affect badgers. We did not observe any stone marten visits inside lynx territories. The foraging behaviour of red foxes was also altered inside lynx ranges whereby foxes were less efficient, consuming less fruit per unit of time and having shorter visits. Local availability of fruit resources, forest coverage and individual personality also were important variables to understand visitation and foraging in a landscape of fear.
Our results show a potential trophic cascade from apex predators to primary producers. The presence of lynx can reduce frugivorous carnivore numbers and induce shifts in their feeding behaviour that may modify the seed dispersal patterns with likely consequences for the demography of many fleshy‐fruited plant species. We conclude that knowledge of the ecological interactions making up trophic webs is an asset to design effective conservation strategies, particularly in rewilding programs.
... Such analyses offer a mechanistic approach for evaluating wolf travel patterns and resource requirements. As northern latitudes continue to rapidly warm and change, the application of these methods to future studies would enable researchers to track how fluctuations in parameters including snowfall patterns and plant phenology and growth cascade up to impact the spatial ecology and energetics of predators [113,114]. In lower latitudes, recovering gray wolf populations in the USA have recently been delisted from protection under the Endangered Species Act of 1973 [115]. ...
Background
Environmental conditions can influence animal movements, determining when and how much animals move. Yet few studies have quantified how abiotic environmental factors (e.g., ambient temperature, snow depth, precipitation) may affect the activity patterns and metabolic demands of wide-ranging large predators. We demonstrate the utility of accelerometers in combination with more traditional GPS telemetry to measure energy expenditure, ranging patterns, and movement ecology of 5 gray wolves ( Canis lupus ), a wide-ranging social carnivore, from spring through autumn 2015 in interior Alaska, USA.
Results
Wolves exhibited substantial variability in home range size (range 500–8300 km ² ) that was not correlated with daily energy expenditure. Mean daily energy expenditure and travel distance were 22 MJ and 18 km day ⁻¹ , respectively. Wolves spent 20% and 17% more energy during the summer pup rearing and autumn recruitment seasons than the spring breeding season, respectively, regardless of pack reproductive status. Wolves were predominantly crepuscular but during the night spent 2.4 × more time engaged in high energy activities (such as running) during the pup rearing season than the breeding season.
Conclusion
Integrating accelerometry with GPS telemetry can reveal detailed insights into the activity and energetics of wide-ranging predators. Heavy precipitation, deep snow, and high ambient temperatures each reduced wolf mobility, suggesting that abiotic conditions can impact wolf movement decisions. Identifying such patterns is an important step toward evaluating the influence of environmental factors on the space use and energy allocation in carnivores with ecosystem-wide cascading effects, particularly under changing climatic conditions.
... Their effects can be produced by consumption or by behavior [13]. The consumption function is also called lethal and can directly regulate prey population size [8,14] and mesopredators (in the case of apex predators) [15,16]; or indirectly by providing carrion [17,18], promoting higher biodiversity levels [19], or even influencing soil composition [20]. Their effects by behavior can be direct and indirect as well: Directly by influencing prey behavior and habitat use [21,22], prey pack size [23], reproductive physiology [24], and natural selection [25]. ...
The two mammalian carnivores, puma (Puma concolor) and South American grey fox (Lycalopex griseus) were studied, in a remote area located in the humid temperate forest of the coastal range of southern Chile. A total of six locations were selected in three landscapes: pre-mountain range, mountain range, and coast. The chosen study locations are relevant because they correspond to threatened areas with different levels of human intervention., so they offer the ideal setting for studying how different species of carnivores respond to both human presence and activities. A dataset was collected for 24 months during 2016–2018 through photo-trapping (13 camera traps placed along 50 photo-trap stations). Wes estimated the apparent occurrence and relative abundance index (RAI) of the fauna registered, by means of generalized linear models to contrast those of an apex predator, such as the puma and a sympatric mesopredator, the South American grey fox, across the three landscapes. The ecological variables assessed were the RAI of the other carnivore considered, exotic carnivores such as dogs and cats, human intervention, farmland effect, prey availability, and habitat quality. The primary hypothesis was that the apparent occurrence and RAI of puma and fox would be positively associated with the RAI of prey and livestock and negatively with human intervention. On the other hand, the secondary hypothesis dealt with the interactions between puma and fox faced with different degrees of human intervention. The results showed that the apparent occurrence of the puma was statistically explained by location only, and it was highest at the mountain range. The apparent occurrence of foxes was explained by both puma apparent occurrence and relative integrated anthropization index (INRA), being highest in the pre-mountain range. Concerning the RAI of pumas, high values were yielded by location and fox RAI. For the RAI of foxes, they were location, puma RAI, and INRA. It can be suggested that eucalyptus plantations from the pre-mountain range could offer an adequate habitat for the puma and the fox, but not the coastal range, as the mountain range could be acting as a biological barrier. Due to the nature of the data, it was not possible to detect any relevant effect between the two carnivores’ considered, between their respective preys, or the very abundant presence of dogs.
... Among animals heavily impacted by illegal killing, wolves in particular, are often illegally shot, snared and poisoned across their whole range (Chapron and Treves, 2016;Suutarinen and Kojola, 2017;Treves et al., 2017a;Liberg et al., 2020;Musto et al., 2021). There is a growing understanding of the numerous positive roles wolves play in ecosystems, including: subsidizing carrion to scavengers which increases their survival and densities (Selva et al., 2005;Selva and Fortuna, 2007), reducing mesopredator populations (Krofel et al., 2017), limiting wild ungulate densities (Creel and Winnie, 2005;Ripple and Beschta, 2012b), changing deer feeding behaviour, structuring ecosystems and creating a landscape of fear (Ripple and Beschta, 2012a), which in turn reduces tree browsing by ungulates (Kuijper et al., 2013). Furthermore, wolves may also mitigate disease dynamics in wild ungulate populations (Tanner et al., 2019) and reduce the risk of disease transmission from wild ungulates to livestock (Stronen et al., 2007). ...
In central Europe, wolves Canis lupus prey on wild ungulates - main game species and occasionally kill livestock. The recovery of wolf population across the continent coincides with an increasing incidence of illegal killing, which level remains unknown. We analysed the illegal killing of wolves in Poland, where the species is strictly protected since 1998. We opportunistically collected data on wolves illegally shot and snared from 2002 to 2020, revealing their geographical extent and sex and age structure. Furthermore, we estimated their mortality rate due to illegal shooting on the basis of 16 GPS/GSM collared individuals between 2014 and 2020. We recorded 54 illegally shot and 37 snared wolves. The majority (63.7%) were killed between 2017 and 2020, mostly in Western Poland. The sex structure was similar between shot and snared individuals. In both groups, the wolves over one-year old prevailed, although there were 18 pups among shot wolves. We identified 6 shot and 3 snared breeders. Out of 16 GPS/GSM collared individuals, six were shot giving the mortality rate of 0.33 per year. Simulations revealed that the pooled number of wolves illegally shot in Poland annually, is between 147 and 1134 (99% highest density interval) or 216 and 1000 (95%). In six out of seven cases, in which the person who shot a wolf was eventually sentenced, hunters were responsible. We conclude that the present regulations concerning the prevention of illegal killing, pursuing and punishing the perpetrators of the illegal killing of wolves, require urgent improvements in order to effectively mitigate the problem.
There are two contrasting hypotheses regarding the drivers of biomass‐distribution among trophic levels within ecosystems. Energetic or bottom–up models propose control by supply of energy, either from autotrophy or from the underlying trophic level. Dynamical or top–down models propose control by predators in the overlying trophic level. Although multiple approaches have been used to reconcile these hypotheses, they have rarely considered the evolutionary pressures created by different distributions of biomass. Here, we study the effects of these evolutionary processes using an agent‐based, spatially‐explicit, eco‐evolutionary model. We demonstrate that, when ecosystems are simple and predator–prey relationships between species are fixed and do not evolve, primary productivity limits the number of trophic levels. In this case, the abundance in the top trophic level is always limited by productivity. However, productivity‐limited trophic levels subject those below them to limitation by predation, and predation‐limited trophic levels allow trophic levels below them to grow until limited by productivity. These results match the expectations of the exploitation ecosystems hypothesis (EEH), which predicts the same pattern of alternating top–down and bottom–up control on trophic levels. When species are able to evolve to adaptively adjust their trophic levels, however, selection is liable to lead to collapse of the trophic pyramid through prey switching. Under these conditions, all trophic levels experience bottom–up control. When the evolution of prey switching is restricted, higher trophic levels are evolutionarily stable and the predictions of the EEH are once again met; the stability of long food chains is thus dependent on the difficulty associated with prey switching. These results suggest that, at least under the combinations of model parameters explored in this study, evolutionary limitation is key to maintaining trophic structure.
In recent decades, ungulates have expanded in number and range in Europe. This review aims to analyze the impact of ungulate browsing in different forest ecosystems and identify the main driving factors and trends. In total, 155 studies were analyzed in preparing this review, across 19 European countries. In Europe, the main browsers are represented by roe deer (Capreolus capreolus L.), red deer (Cervus elaphus L.), moose (Alces alces L.), chamois (Rupicapra rupicapra L.), and fallow deer (Dama dama L.). Regarding browsing severity, they frequently exceeded 50%, meaning that over half of the saplings were browsed. Ungulate density was the main driving factor of browsing severity, with areas exhibiting high browsing pressure often having more than ten individuals per square kilometer. The type of silvicultural system used played a vital role in the severity of browsing, and trends in foraging for preferred tree species were identified. Fencing was the most common non-harmful protection method used, while hunting management was the most efficient method for controlling deer numbers and browsing intensity. Large carnivores were missing in most study areas, but in the areas where they were present, they played a significant role in creating a chain reaction of ecological impacts. Considering the significant impact of ungulate browsing on forest ecosystems, there is a pressing need for more research to comprehend and effectively mitigate the effects of deer presence comprehensively.
Diets of carnivores provide insights into predator-prey relationship and intra-guild competition, and contribute to drafting fruitful conservation strategies. However, few high-resolution dietary dataset of carnivores exist in Central Asia, hindering deep understanding of their coexistence in grazing landscape. Here, we present detailed trophic interaction among four carnivores in Tianshan Mountains of Northwest China deriving from 179 fecal samples.
Using DNA metabarcoding, we identified 20 prey items across 5 orders. High dietary overlap (Ojk = 0.995) was found between snow leopard (Panthera uncia) and wolf (Canis lupus), which mainly preyed on large mammals (%PR = 85%, 91%). Red fox (Vulpes vulpes) mainly consumed large and small mammals (%PR = 43%, 31%). Significant differences (P < 0.001, P < 0.05) and lower dietary overlaps (Ojk = 0.761, 0.756) were observed between red fox and snow leopard/wolf.
Wild animals such as ibex (Capra sibirica) were detected in the diet of dog (Canis lupus familiaris), indicating wildlife depredation. High dietary overlaps were observed between dog and snow leopard/wolf (Ojk = 0.989, 0.999). These results suggest that dog compete with wild predators for prey resources and underline the need to further study their potential disturbance to natural ecosystems. All carnivores consumed livestock (%PR = 14 ~ 27%). Corrals reinforcement and husbandry practice improvement are necessary to prevent potential economic losses and retaliatory killing.
Our results suggest that dietary partitioning and livestock subsidies facilitate carnivore coexistence in Tianshan and have implications for developing effective conservation intervention to promote human-carnivore coexistence in Central Asia.
Wraz ze wzrostem zasięgu występowania populacji wilka w Polsce wzrasta także prawdopodobieństwo napotkania tych drapieżników w lesie i na polach, a nawet na terenach zurbanizowanych. Wilki są zazwyczaj bardzo ostrożne, płochliwe i starają się nas unikać. To jednak bardzo inteligentne i plastyczne zwierzęta, umiejące szybko adaptować się do obecności ludzi i wykorzystywać możliwości, jakie stwarza nasza działalność, co prowadzi do wielu konfliktów. O tym, czy w środku zdominowanej przez człowieka Europy wilki pozostaną dzikie, decydujemy my, ludzie i nasze zachowania. Wszelkie pomocne rady i informacje o tym, jak unikać konfliktów z wilkami i jak z głową pomagać drapieżnikom, które wpadły tarapaty przez naszą działalność można znaleźć w naszej książce "Po sąsiedzku z wilkami".
The recovery and expansion of formerly isolated wolf populations in Europe raise questions about the nature of their interactions and future consequences for population viability and conservation. Will fragmented populations fuse or maintain a certain level of isolation with migration? Central Europe is suitable for obtaining empirical data in this field as it represents a ‘crossroad' with the potential for contact among several phylogeographic lineages. In this study, non‐invasive genetic samples obtained during population monitoring in the Bohemian and Bavarian Forest (BBF) mountain ranges in the Czech Republic and Germany (Bohemian Massif) were analysed at different neutral markers including mitochondrial sequence, nuclear autosomal microsatellites and gonosomal sex markers. Resultant genetic profiles were compared with reference data to study population ancestry. Both cluster analyses of microsatellite genotypes and syntopic occurrence of haplotypes HW01 and HW22 showed genetic admixture between Central European and Alpine populations. This represents secondary contact and interbreeding of formerly allopatric populations with different phylogeographic histories and distant expansion centres in different biomes in the Baltic region versus the Apennine peninsula and Alps. Moreover, the study describes the founding event and genealogy of this admixed deme, inhabiting intermediate environmental conditions compared to parental forms, and emphasises the role of protected areas as stepping stones in the range recolonization process in endangered large mammals.
Unmodified forests are increasingly rare worldwide, with forestry a major contributor to habitat modification. Extending conservation practices beyond protected areas is important to conserve forest ecosystems.
We investigate the response of native mammalian carnivores (both Order Carnivora and Family Dasyuridae) to production forests globally, including harvested native forest and timber plantations. We examine how carnivores recorded in production forests use these forests versus other land uses, particularly native and/or unharvested forest; how habitat use relates to threatened status, body size, diet and harvesting method; carnivore responses to habitat features within production forests; and carnivore denning, breeding and predation behaviour in production forests.
We review 294 studies recording 132 carnivore species in production forests. Carnivores generally show higher use of unharvested native forests and lower use of agricultural land than production forests. Threatened species and large carnivores respond more negatively to production forests than non‐threatened species and small carnivores respectively. Hypercarnivores respond more negatively than omnivores to plantations compared to native forest, with no difference in the use of harvested and unharvested native forest between these dietary groups.
Notably, a high proportion of carnivore species use clearfelled more than unharvested native forest. In forest with partial harvesting or reduced‐impact logging, most species show no difference in use between harvested and unharvested forest.
Carnivores generally respond positively to habitat features such as riparian areas and coarse woody debris. Several carnivores were recorded denning and breeding in production forests. Production forests often influence the prey availability, hunting success and diet of carnivores.
We show that many carnivores use production forests, and how they respond to production forestry varies with species traits and conservation status. We recommend that production forests are managed as valuable carnivore habitat, and highlight strategies to enhance the use of these forests by carnivores.
Terrestrial ecosystems are shaped by interacting top‐down and bottom‐up processes, with the magnitude of top‐down control by large carnivores largely depending on environmental productivity. While carnivore‐induced numerical effects on ungulate prey populations have been demonstrated in large, relatively undisturbed ecosystems, whether large carnivores can play a similar role in more human‐dominated systems is a clear knowledge gap. As humans influence both predator and prey in a variety of ways, the ecological impacts of large carnivores can be largely modified. We quantified the interactive effects of human activities and large carnivore presence on red deer (Cervus elaphus) population density and how their impacts interacted and varied with environmental productivity.
Data on red deer density were collected based on a literature survey encompassing 492 study sites across 28 European countries. Variation in density across study sites was analysed using a generalized additive model in which productivity, carnivore presence (grey wolf, European lynx, Brown bear), human activities (hunting, intensity of human land‐use activity), site protection status and climatic variables served as predictors.
The results showed that a reduction in deer density only occurred when wolf, lynx and bear co‐occurred within the same site. In the absence of large carnivores, red deer density varied along a productivity gradient without a clear pattern. Although a linear relationship with productivity in the presence of all three large carnivore species was found, this was not statistically significant. Moreover, hunting by humans had a stronger effect than the presence of all large carnivores in reducing red deer density and red deer density increased with increasing intensity of human land use, with stronger large carnivore effects (all three carnivore species present) at sites with low human land‐use activities.
Synthesis and applications. This study provides evidence for the dominant role played by humans (i.e. hunting, land‐use activities) relative to large carnivores in reducing red deer density across European human‐dominated landscapes. These findings suggest that when we would like large carnivores to exert numeric effects, we should focus on minimizing human impacts to allow the ecological impacts of large carnivores on ecosystem functioning.
North American mammals follow a well-established latitudinal diversity gradient in species richness. However, the degree to which species in different mammal clades follow the same latitudinal gradient—and to which each clade contributes to the pattern observed for all mammals remains unknown. Here, we separate the overall mammalian latitudinal diversity gradient by mammal orders and investigate the impact of climate and topography on the distribution of each major mammal clade. We joined an equal-area grid (100 × 100 km cells) of continental North America embedded with environmental variables (n = 10) with mammalian species ranges (n = 753). We used spatial regression models to quantify the relationship between species richness and latitude for all mammals, all mammals excluding select clades, and for each individual subordinate clade (n = 9). We used multiple linear regression and simultaneous autoregressive regression models to determine which environmental variables best explained patterns of species richness for each mammal order. Whereas North American mammals altogether exhibit a strong latitudinal diversity gradient in species richness, most orders deviate from the species richness pattern observed for all mammals and their gradients are weak or entirely absent. Bats (Chiroptera) exhibit the strongest latitudinal gradient—their removal from the pattern for all mammals substantially weakens the total mammalian gradient, more so than when rodents are removed. Environmental variables explain patterns of species richness well for some clades, but poorly for others. The gradient we observe for North American mammals today is likely a combined product of multiple diversification events, dispersals, and climatic and tectonic histories.
1. Unmodified forests are increasingly rare worldwide, with forestry a major contributor to habitat modification. Extending conservation practices beyond protected areas is important to conserve forest ecosystems.
2. We investigate the response of native mammalian carnivores (both Order Carnivora and Family Dasyuridae) to production forests globally, including harvested native forest and timber plantations. We examine how carnivores recorded in production forests use these forests versus other land uses, particularly native and unharvested forest; how habitat use relates to threatened status, body size, diet, and harvesting method; carnivore responses to habitat features within production forests; and carnivore denning, breeding, and predation behaviour in production forests.
3. We review 294 studies recording 132 carnivore species in production forests. Carnivores generally show higher use of native and unharvested forests and lower use of agricultural land than production forests. Threatened species and large carnivores respond more negatively to production forests than non-threatened species and small carnivores respectively. Hypercarnivores respond more negatively than omnivores to plantations compared to native forest, but there was no difference in the use of harvested and unharvested native forest between these dietary groups.
4. Surprisingly, a high proportion of carnivore species use clearfelled more than unharvested native forest. In forest with partial harvesting or reduced-impact logging, most species show no difference in use between harvested and unharvested forest.
5. Carnivores generally respond positively to habitat features such as riparian areas and coarse woody debris. Several carnivores were recorded denning and breeding in production forests. Production forests often influence the prey availability, hunting success, and diet of carnivores.
6. We show that many carnivores use production forests, and how they respond to production forestry varies with species traits. We recommend that production forests are managed as valuable carnivore habitat, and highlight strategies to enhance the use of these forests by carnivores.
Mesopredators abundance is often limited by top‑order predators and also by key food resources. However, the contribution of these bidirectional forces to structure carnivore community is still unclear. Here, we studied how the presence and absence of an apex predator which is currently recovering its former distribution range, the Iberian lynx (Lynx pardinus), determined the absolute abundance and fine‑scale spatiotemporal avoidance mechanisms of two sympatric mesocarnivores (stone marten Martes foina and common genet Genetta genetta) with different dietary plasticity. We hypothesized that the lynx causes a mesopredator suppression and subordinate predators develop segregation strategies in respect to their trophic niche breadth. We placed 120 camera‑traps in Southern Spain for 8 months in two consecutive years to estimate mesocarnivore abundances by using SCR Bayesian models, prey availability and assess spatio‑temporal patterns. We found that the lynx reduced mesocarnivore abundance up to 10 times. Stone marten, a mesopredator with a broad food resources spectrum, showed a total spatial exclusion with the apex predator. Meanwhile, fine‑scale avoidance mechanisms allowed the genet to persist in low density inside lynx territories, probably taking advantage of high availability of its preferred prey. Thus, the strength of these top‑down and bottom‑up effects was rather species‑specific. Given the recent recovery of large carnivore populations worldwide, variation in suppression levels on different mesopredator species could modify ecosystem functions provided by the carnivore community in contrasting ways.
Nowadays, the grey wolf (Canis lupus) is spreading again in Hungary. The assessment of the species is controversial, as in addition to its beneficial ecological effects, it can also cause economic damage to the populations of wild game and grazing domestic ungulates. In our publication we give an overview of the scientific knowledge gained so far about the feeding habits of the wolf, on the basis of which we can make the nature conservation management of the species more effective and reduce the species-related conflicts. Literature information gathered from many countries on three continents suggests that for the wolf population expanding in the North Hungarian Mountains, wild ungulate populations are likely to be the primary source of prey, as has been observed in many parts of Europe or North America. Based on previous studies, red deer may be the most frequent food source, and killing of wild boar and roe deer, or even mouflon, may be common. Consumption of grazing domestic animals may increase if the density and diversity of wild ungulate communities decline significantly or if livestock farming occurs in large areas without adequate protection. The presence of the wolf as a top predator in the Hungarian fauna ensures important ecological regulatory roles, which e.g., can mitigate the strong local effects of large herbivorous species. However, the natural predatory behavior of the wolf can have a significant adverse economic effect on the populations of wild and domestic ungulates. Thus, it is important to explore these interactions in more detail in Hungary as well, so that the conflicts that arise at the same time as conserving the wolf population can be better managed.
The re-introduction of animal and plant species is intended, on the one hand, to support a population threatened with extinction in a certain area or on a restoration site (reinforcement), or to bring back a plant or animal species that has disappeared within its natural range due to anthropogenic impact (re-introduction). Examples of the re-introduction of plant and animal species from Central Europe are presented here, and the success of these measures is critically reflected upon.
It is vitally important to understand the ecological roles of medium and small carnivores in the context of the massive decline in the number of large carnivores around the world. Based on a spatial association network of terrestrial birds and mammals, this study analyzed the ecological roles of medium and small carnivores in the community in Liancheng National Nature Reserve. From October 2019 to June 2020, we obtained 3559 independent detections of 20 terrestrial birds and mammals from 112 camera traps. There are seven species that are medium and small carnivores present in the study area, including red fox (Vulpes vulpes), leopard cat (Prionailurus bengalensis), Chinese mountain cat (Felis bieti), stone marten (Martes foina), Asian badger (Meles leucurus), Siberian weasel (Mustela sibirica) and mountain weasel (Mustela altaica). By calculating the Phi coefficient of all species pairs, a spatial association network composed of twelve species was constructed. We analyzed the characterization of spatial associations by the Shannon–Wiener index and Lambda statistic. The results showed that: (1) the status of the network reflects the changes of community composition and structure after the decline in large carnivores and other species; (2) with the exception of the Chinese mountain cat and stone marten, the other five medium and small carnivores were located in the network, which played an important role in the complexity of the network and the maintenance of the community; (3) the medium and small carnivores could not take the place of the large carnivores in order to control the population of herbivores, such as Siberian roe deer (Capreolus pygargus) and Himalayan marmot (Marmota himalayana). The results of this study provide guidance for determining the direction and focus of conservation efforts.
Garry oak (Quercus garryana) and associated ecosystems (GOAE) are culturally and ecologically significant landscapes home to over 100 Species at Risk. With less than 5% of their original extent remaining in Canada, GOAE require urgent attention to guide management of remnant habitats and protect them from ongoing cumulative threats. The loss of top predators has played a large role in a trophic cascade where hyperabundant black-tailed deer (Odocoileus hemionus columbianus) are reshaping plant and animal communities, even within protected areas. The impacts of deer browsing on plant communities is well-documented; however, the impact on pollinators that are essential for the restoration and conservation of GOAEs is still unknown. We tested the hypothesis that deer browsing has an indirect impact on bumblebee populations through their direct negative impact on floral communities. We surveyed deer density, floral communities, and bumblebee abundances across ten islands with differing levels of deer presence in the Salish Sea. We found that deer had a negative effect on the abundance of flowering plants, with an even greater effect on native species that bumblebees rely on for foraging. Deer presence had an indirect negative impact on female bumblebee abundances through the depletion of floral resources. Deer also had a negative impact on male bumblebee abundances, potentially caused by lowered colony success over the season on islands with less floral resources. These findings highlight the importance of immediate deer management to prevent the loss of native pollinators and further, potentially irreversible, ecological degradation of GOAEs.
Because ungulates are important contributors to ecosystem function, understanding the "ecology of fear" could be important to the conservation of ecosystems. Although studying ungulate ecology of fear is common, knowledge from ungulate systems is highly contested among ecologists. Here, we review the available literature on the ecology of fear in ungulates to generalize our current knowledge and how we can leverage it for conservation. Four general focus areas emerged from the 275 papers included in our literature search (and some papers were included in multiple categories): behavioral responses to predation risk (79%), physiological responses to predation risk (15%), trophic cascades resulting from ungulate responses to predation risk (20%), and manipulation of predation risk (1%). Of papers focused on behavior, 75% were about movement and habitat selection. Studies were biased toward North America (53%), tended to be focused on elk (Cervus canadensis; 29%), and were dominated by gray wolves (40%) or humans (39%) as predators of interest. Emerging literature suggests that we can utilize predation risk for conservation with top-down (i.e., increasing predation risk) and bottom-up (i.e., manipulating landscape characteristics to increase risk or risk perception) approaches. It is less clear whether fear-related changes in physiology have population-level fitness consequences or cascading effects, which could be fruitful avenues for future research. Conflicting evidence of trait-mediated trophic cascades might be improved with better replication across systems and accounting for confounding effects of ungulate density. Improving our understanding of mechanisms modulating the nature of trophic cascades likely is most important to ensure desirable conservation outcomes. We recommend future work embrace the complexity of natural systems by attempting to link together the focal areas of study identified herein.
Predation, one of the most dramatic interactions in animals' lives, has long fascinated ecologists.
This volume presents carnivores, raptors and their prey in the complicated net of interrelationships, and shows them against the background of their biotic and abiotic settings. It is based on long-term research conducted in the best preserved woodland of Europe's temperate zone. The role of predation, whether limiting or regulating prey (ungulate, rodent, shrew, bird, and amphibian) populations, is quantified and compared to parts played by other factors: climate, food resources for prey, and availability of other potential resources for predators.
During September 1980-December 1986, 81 radio-collared wolves (Canis lupus) were monitored in and near the 839-km2 Bearville Study Area )BSA) in north-central Minnesota. Each year winter-territory size averaged 78-153 km2; no territories had road densities >0.72 km/km2. From zero to 30% of radiomarked pup, yearling, or adult wolves left their territories each month. Pups left natal packs during January-March and older wolves left frequently during September-April. Wolves temporarily leaving territories moved 5-105 km away and were absent 3-118 days; up to 6 exploratory moves were made prior to dispersal. Dispersing wolves traveled 5-100 km away during periods of 1-265 days. One disperser joined and established pack, but 16 others formed new packs. Annual dispersal rates were about 0.17 for adults, 0.49 for yearlings, and 0.10 for pups.
Each year mean pack size ranged from 5-9 in November/December to 4-6 in March. Annual wolf density (including 16% lone wolves) ranged from 39-59 wolves/1,000 km2 in November-December and 29-40 wolves/1,000 km2 in March. Annual immigration was 7%. The observed mean annual finite rate of increase was 1.02, and annual rates of increase were correlated with mean number of pups per pack in November. Litters averaged 6.6 pups at birth and 3.2 pups by mid-November, at which time pups made up 46% of pack members. Annual survival of radio-marked wolves >5 months old was 0.64. Despite legal protection, 80% of identified wolf mortality was human caused (30% shot, 12% snared, 11% hit by vehicles, 6% killed by government trappers, and 21% kill by humans in some undetermined manner); 10% of wolves that died were killed by other wolves.
During sample periods in 2 winters, wolves were located twice daily to estimate predation rates on white-tailed deer (Odocoileus virginianus). Estimated minimum kill rates during January-February (x = 21 days/kill/wolf) did not differ between winters with differing snow depths. Winter consumption averaged 2.0 kg deer/wolf/day (6% body wt/day). Scat analyses indicated deer were the primary prey in winter and spring, but beaver (Castor canadensis) were an important secondary prey (20-47% of items in scats) during April-May. Neonatal deer fawns occurred in 25-60% of scats during June-July whereas the occurrence of beaver declined markedly. Overall, deer provided 79-98% of biomass consumed each month. Adult wolves consumed an estimated 19/year, of which 11 were fawns.
A review of North American studies indicates that wolf numbers are directly related to ungulate biomass. Where deer are primary prey, territory size is related to deer density. Per capita biomass availability likely affects pup survival, the major factor in wolf population growth. Annual rates of increase of exploited populations vary directly with mortality rates, and harvest exceeding 28% of the winter population often result in declines. Management decisions concerning wolf and ungulate density and ungulate harvest by humans can be made using equations that incorporate estimate of wolf density, annual ungulated kill per wolf, ungulate densities, potential rate of increase for ungulates, and harvest.
Based on the assumption that each trophic level acts as a single exploitative population, a model relating the trophic structure of ecosystems to their potential primary productivity is developed. According to the model, herbivory pressure should be most severe in relatively unproductive environments. With increased potential productivity, the role of predation in herbivore regulation should become more important and the impact of herbivory upon plant communities should decrease. In very productive environments, increase in herbivory pressure is again probable, at least in aquatic ecosystems. The predicted pattern of phytomass and predicted results of manipulations are compared with available data. A reasonable fit between predictions and observations is found, although the sparsity of data and methodological uncertainties weaken the corroboration in several cases. In terrestrial ecosystems, the present version of the model seems best applicable to the vertebrate branch of the grazing chain, whereas the a...
The objective of this study was to simulate dynamically the response of a complex landscape, containing forests, savannas, and grasslands, to potential climate change. Thus, it was essential to simulate accurately the competition for light and water between trees and grasses. Accurate representation of water competition requires simulating the appropriate vertical root distribution and soil water content. The importance of different rooting depths in structuring savannas has long been debated. In simulating this complex landscape, we examined alternative hypotheses of tree and grass vertical root distribution and the importance of fire as a disturbance, as they influence savanna dynamics under historical and changing climates. MC1, a new dynamic vegetation model, was used to estimate the distribution of vegetation and associated carbon and nutrient fluxes for Wind Cave National Park, South Dakota, USA. MC1 consists of three linked modules simulating biogeography, biogeochemistry, and fire disturbance. This new tool allows us to document how changes in rooting patterns may affect production, fire frequency, and whether or not current vegetation types and life-form mixtures can be sustained at the same location or would be replaced by others. Because climate change may intensify resource deficiencies, it will probably affect allocation of resources to roots and their distribution through the soil profile. We manipulated the rooting depth of two life-forms, trees and grasses, that are competing for water. We then assessed the importance of variable rooting depth on eco- system processes and vegetation distribution by running MC1 for historical climate (1895- 1994) and a GCM-simulated future scenario (1995-2094). Deeply rooted trees caused higher tree productivity, lower grass productivity, and longer fire return intervals. When trees were shallowly rooted, grass productivity exceeded that of trees even if total grass biomass was only one-third to one-fourth that of trees. Deeply rooted grasses developed extensive root systems that increased N uptake and the input of litter into soil organic matter pools. Shallowly rooted grasses produced smaller soil carbon pools. Under the climate change scenario, NPP and live biomass increased for grasses and decreased for trees, and total soil organic matter decreased. Changes in the size of biogeochemical pools produced by the climate change scenario were overwhelmed by the range of responses across the four rooting configurations. Deeply rooted grasses grew larger than shallowly rooted ones, and deeply rooted trees outcompeted grasses for resources. In both historical and future scenarios, fire was required for the coexistence of trees and grasses when deep soil water was available to trees. Consistent changes in fire frequency and intensity were simulated during the climate change scenario: more fires occurred because higher temperatures resulted in decreased fuel moisture. Fire also increased in the deeply rooted grass configurations because grass biomass, which serves as a fine fuel source, was relatively high.
Population studies of wolves (Canis lupus) were carried out during October 1975-June 1978 on 2 study areas in northern Alberta; 13 wolves in 6 packs and 2 lone wolves were captured, radio-collared, and located 939 times. Telemetry data indicated a winter wolf density of 1/158 km2 near Fort McMurray. Numbers increased from 1975 to 1977 at a rate of about 21% annually. The winter wolf density of 1/90km2 on a study area in the Swan Hills, 300 km southwest, appeared lower than in past years. The difference in wolf density between the 2 areas reflected available food resources. Trapping and early pup deaths were likely the major mortality factors. Wolves killed disproportionately more young, old, and probably debilitated moose (Alces alces), as well as more female calves and adult bulls. Most wolf kills in winter (88%) were made in lowland habitats despite an even distribution of moose in uplands and lowlands. Deeper snow and colder temperatures in 1978 resulted in decreased travel by 1 pack (straight-line distances between daily locations of 5.7 vs. 9.0 km/day). The mean kill rate of this pack was similar in both years (1 moose/4.7 days); per capita consumption decreased slightly in 1978 (0.12 vs. 0.15 kg prey/kg wolf/day) because of larger mean pack size (9.8 vs. 9.2). An equation was derived for calculating true kill rates when relocation flights were spaced more than 1 day apart. Summer food habits of wolves (1,723 scats analyzed) indicated that adult moose remained the staple food in all areas. Use of beaver (Castor canadensis) was related to availability. One wolf pack annually consumed about 15% of the yearling and older moose in their territory, close to the estimated 19% annual recruitment of new yearlings. Two lone wolves and 2 packs were partially dependent on dumps for food during winter; predation rates by these packs were much lower. Wolf densities near disturbed sites were higher than in surrounding areas.
We compared the historic and current geographical ranges of 43 North American carnivores and ungulates to identify large-scale
patterns in range contractions and expansions. Seventeen of the species had experienced range contractions over more than
20% of their historic range. In areas of higher human influence, species were more likely to contract and less likely to persist.
Species richness had also declined considerably since historic times. The temperate grasslands and temperate broadleaf–mixed
forest biomes lost the highest average number of species, while the boreal forest and tundra showed fewer numbers of species
lost. Species contractions were a result of Euro-American settlement and postsettlement development in North America. These
effects have been widespread and indicate a rapid collapse of species distributions over the course of only 1 to 2 centuries.
The results of this study can be used to improve scientists' knowledge of historical reference conditions and to provide input
for wildlife reintroductions and for the creation of wildlife reserves.
The elk or wapiti (Cervus elaphus) and bison (Bison bison) of Yellowstone National Park have lived in an environment free of wolves (Canis lupus) for the last 50 years. In the winter of 1994-1995, wolves were reintroduced into parts of Yellowstone National Park. Foraging theory predicts that elk and bison would respond to this threat by in - creasing their vigilance levels. We tested this prediction by comparing vigilance levels of elk and bison in areas with wolves with those of elk still in "wolf-free" zones of the Park. Male elk and bison showed no response to the reintro- duction of wolves, maintaining the lowest levels of vigilance throughout the study (≈12 and 7% of the time was spent vigilant, respectively). Female elk and bison showed significantly higher vigilance levels in areas with wolves than in areas without wolves. The highest vigilance level (47.5 ± 4.1%; mean ± SE) was seen by the second year for female elk with calves in the areas with wolves and was maintained during the subsequent 3 years of the study. As wolves ex- panded into non-wolf areas, female elk with and without calves in these areas gradually increased their vigilance levels from initially 20.1 ± 3.5 and 11.5 ± 0.9% to 43.0 ± 5.9 and 30.5 ± 2.8% by the fifth year of the study, respectively. We discuss the possible reasons for the differences seen among the social groups. We suggest that these behavioural re- sponses to the presence of wolves may have more far-reaching consequences for elk and bison ecology than the actual killing of individuals by wolves. 1409
Land managers often are responsible for the maintenance of species diversity and resilience. This requires knowledge of ecosystem dynamics over decades and centuries. Resource-driven (bottom-up) models have guided early thought on managing species and ecosystems. Under this paradigm, carnivores have little ecological value, and throughout the 20 th Century carnivore management strategies (often extirpation) have reflected that concept. An alternative hypothesis, however, states that herbivores reduce the biomass of plants, but in turn, the biomass of herbi- vores is checked by the presence of carnivores. As such, carnivores have great ecological value. Their predation activities create impacts that ripple downward through the trophic levels of an ecosystem. Here we discuss some potential pathways through which carnivores contribute to ecosystem processes and species diversity. The subtleties of these interactions have strong impli- cations for management strategies of carnivores. Without considering these indirect impacts, short-sighted management strategies to reduce carnivores might cause extensive and long-term changes in ecosystem structure and function.
Land managers often are responsible for the maintenance of species diversity and resilience. This requires knowledge of ecosystem dynamics over decades and centuries. Resource-driven (bottom-up) models have guided early thought on managing species and ecosystems. Under this paradigm, carnivores have little ecological value, and throughout the 20 th Century carnivore management strategies (often extirpation) have reflected that concept. An alternative hypothesis, however, states that herbivores reduce the biomass of plants, but in turn, the biomass of herbi-vores is checked by the presence of carnivores. As such, carnivores have great ecological value. Their predation activities create impacts that ripple downward through the trophic levels of an ecosystem. Here we discuss some potential pathways through which carnivores contribute to ecosystem processes and species diversity. The subtleties of these interactions have strong implications for management strategies of carnivores. Without considering these indirect impacts, shortsighted management strategies to reduce carnivores might cause extensive and long-term changes in ecosystem structure and function.
We review the ecological rationale behind the potential compatibility be-tween top predators and biodiversity conservation, and examine their ef-fectiveness as surrogate species. Evidence suggests that top predators pro-mote species richness or are spatio-temporally associated with it for six causative or noncausative reasons: resource facilitation, trophic cascades, dependence on ecosystem productivity, sensitivity to dysfunctions, selection of heterogeneous sites and links to multiple ecosystem components. There-fore, predator-centered conservation may deliver certain biodiversity goals. To this aim, predators have been employed in conservation as keystone, um-brella, sentinel, flagship, and indicator species. However, quantitative tests of their surrogate-efficacy have been astonishingly few. Evidence suggests they may function as structuring agents and biodiversity indicators in some ecosystems but not others, and that they perform poorly as umbrella species; more consensus exists for their efficacy as sentinel and flagship species. Con-servation biologists need to use apex predators more cautiously, as part of wider, context-dependent mixed strategies.
American black bears (Ursus americanus) and brown bears (U. arctos) can be important predators on neonatal ungulates. They prey less commonly on adult ungulates. Bear predation appears to be additive at low ungulate densities and may become compensatory as prey density approaches carrying capacity, K. As such, black and brown bear predation can limit, but generally does not regulate, ungulate populations. Maternal and neonatal physical condition, birth synchrony, and birth mass may predispose neonates to predation or other mortality factors. Though black and brown bear predation is an important proximate cause of ungulate neonatal mortality, habitat quality and quantity are important ultimate factors influencing this dynamic. Manipulating bear populations to enhance ungulate populations may be successful in the short-term if predation is additive, but long-term success has not been demonstrated.
Deer have expanded their range and increased dramatically in abundance worldwide in recent decades. They inflict major economic losses in forestry, agriculture, and transportation and contribute to the transmission of several animal and human diseases. Their impact on natural ecosystems is also dramatic but less quantified. By foraging selectively, deer affect the growth and survival of many herb, shrub, and tree species, modifying patterns of relative abundance and vegetation dynamics. Cascading effects on other species extend to insects, birds, and other mammals. In forests, sustained overbrowsing reduces plant cover and diversity, alters nutrient and carbon cycling, and redirects succession to shift future overstory composition. Many of these simplified alternative states appear to be stable and difficult to reverse. Given the influence of deer on other organisms and natural processes, ecologists should actively participate in efforts to understand, monitor, and reduce the impact of deer on ecosystems.
Moose Alces alces and caribou Rangifer tarandus populations increased following a wolf Canis lupus reduction program in the 1950's and reached peak abundance in the 1960's. Deep snow and heavy browsing caused an initial crash of moose in 1965-66. Moose continued to decline until 1976, primarily due to periodic deep snow, harvest by man, and wolf predation. The long-term effect of moose mortality from deep snow was to increase the impact of predation by lowering moose/wolf ratios. Hunting and wolf predation were the principal causes of moose mortality from 1971-75. Harvests removed 6-19% of the moose population annually; mean harvest rate equalled mean yearling recruitment. After 1974, harvest removed 2% of the moose. Predation by wolves removed 13-34% of moose during winters 1973-74 and 1974-75 and a high proportion of calves during summer. Mortality from predation during winter exceeded recruitment of calf moose. Hunting and wolf predation were also the primary proximate mortality causes in the decline of caribou, but calf recruitment was so low from 1971-75 that a significant decline would have occurred without hunting. After 1973 when hunting was stopped, predation limited the population. Following a 61% reduction in wolves in 1976, survival of calf and yearling moose increased 2- to 4-fold, adult mortality declined, and the moose population increased. Survival of caribou calves also increased significantly, and the population grew rapidly. -from Authors
Canis lupus recolonized the Kenai Peninsula in the 1960s following a 50-yr absence. Wolf density ranged from 11-20 wolves/1000 km². Wolves fed primarily on moose Alces alces (density 0.8/km²); predation rate in winter averaged 1 moose/pack/4.7 days. Food consumption in winter was 0.12 kg/kg wolf/day, but intake apparently declined in summer. Calves composed 20% of the moose population but 47% of wolf-killed moose examined; proportionately more calves were killed during a winter with deep snow. Wolf predation selectively removed the oldest moose in the population. All but 3 of 72 wolf-killed adult moose of which sex could be ascertained were females. Typically 1 litter of wolf pups was born annually to the dominant female in each pack. Pups born to a socially subordinate female were growth-retarded and apparently died. Extraterritorial movements were most commonly undertaken by subordinate adult wolves during the February breeding season. Survival of dispersing wolves was only half that of nondispersers; most dispersers were killed before they could reproduce successfully. Mortality was largely human-caused, averaging 33% annually. Harvest increased rapidly, reducing pack size and causing declines in pack territory size. Additional packs developed in vacated areas, and total wolf density was maintained until annual kill exceeded 30-40% of the early winter population.-from Authors
I review studies on the effects of mammalian herbivore grazing on plant species composition, biomass, productivity, and nitrogen cycling and the responses of ungulates to grazing perturbations at 2 sites in the northern United States. Vegetation studies involved use of permanent and moveable exclosures and comparison of vegetation attributes along natural grazing gradients. Animal responses to herbivore-induced vegetation changes were monitored by direct observation and by measurement of consumption at various sites. At Wind Cave National Park (WCNP), South Dakota, heavily grazed prairie dog (Cynomys ludovicianus) colonies typically had lower levels of plant biomass, were forb rather than grass dominated, and had plants with higher leaf nitrogen (N) concentrations than plants growing outside of the colonies. Soils in prairie dog colonies had greater rates of net N-mineralization than lightly grazed, uncolonized sites. Bison (Bison bison) grazed preferentially on prairie dog colonies, grassland patches mowed to simulate grazing, urine patches, and recently burned patches, presumably because of higher forage quality in each of these patch types than on unaltered grassland. Uncolonized grasslands used by bison and other ungulates at WCNP and areas used by wild horses (Equus caballus) at Bighorn Canyon National Recreation Area and the overlapping Pryor Mountain Wild Horse Range in Montana and Wyoming showed no consistent differences in plant species composition or in leaf N-concentrations compared to vegetation within exclosures. These data suggest that ungulates in these parks are managed at levels that are not presently degrading the vegetation. Although prairie dogs have had an impact on the vegetation in local areas, their colonies provide a significant portion of the food bison consume at WCNP. As long as their presence does not reduce forage availability for ungulates to a potentially critical level, further control of their populations does not appear to be warranted.
Moose (Alces alces) and gray wolf (Canis lupus) populations in Pukaskwa National Park, Ontario, were surveyed annually from 1975 to 1979. Annual population estimates were: 587, 679, 659, 460, and 387 moose and 28, 29, 22, 19, and 14 wolves. Wolf predation appeared to be limiting the increase of the Pukaskwa moose population. A model is presented to explain differences in the density of moose between areas based on the availability of escape habitats and the requisite space to increase the searching time for predators, and the escape tactics of moose, so that .
Winter food habits of gray wolves (Canis lupus) were studied in Riding Mountain National Park in 1978-79 by tracking radio-marked animals and checking kills on the ground. Elk (Cervus elaphus), moose (Alces alces), and white-tailed deer (Odocoileus virginianus) were the major prey species. Ungulate densities for the park were 1.4 elk, 0.94 moose, and 0.34 deer/km2. Elk outnumbered moose by 2.4:1 in the study area but, as prey, elk outranked moose by 15:1. Elk formed the main food base for the wolf population. In a mild winter with low snowfall, a pack of 3 wolves killed elk and deer but not moose. A pack of 5 wolves showed a strong preference for elk during a year with deep snow. The mid to late winter kill rate, under unusually deep snow conditions, was 1 elk or moose every 2.7 days. The calculated daily food consumption was 0.21 kg of prey/kg of wolf. Killing of prey in excess of needs occurred in late winter as carcass use was incomplete. Kill rate per wolf was 1 elk/14 days. Kill abandonment was not related to prey size, with the time spent at kills varying from 1.4 to 1.5 days for adults and calves, respectively. Mean straight-line distance between kills was 5.1 km. There was no clear pattern of elk distribution within wolf territories and kills were in a random pattern within territories. Wolves killed a larger proportion of young and old elk when compared to hunter kills adjacent to the Park. Length of discernible chases varied from 20 to 260 m. Predation on elk calves was greater in early to midwinter, whereas predation on cows increased in late winter. Condition of prey, based on femur fat, was good to excellent.
Relationships between large predators and their prey play an important part in maintaining the stability and diversity of ecological systems of nature reserves. Data obtained in 9 nature reserves in the European part of the RSFSR for the past 25-30 years permitted analysis of relations between ungulates (moose [Alces alces], roe deer [Capreolus capreolus], red deer [Cervus elaphus], sika deer [Cervus nippon], and reindeer [Rangifer tarandus]) and predators (wolf [Canis lupus], brown bear [Ursus arctos], lynx [Lynx lynx], wolverine [Gulo gulo], and stray or feral dogs). The intensity of predation by carnivore species, depending upon their numbers, fluctuated by 5-25 times, and the total natural mortality rate of prey, by 1.5 or 2 times. A rather stable mortality rate in ungulates was maintained by a system of compensating mechanisms. The functional substitution of mortality factors suggests that the weakening of one of the factors brings about the strengthening of another. Extirpation of large predators from nature reserves is not benefiical and therefore is not expedient.
Quantitative data on predation of white-tailed deer (Odocoileus virginianus) by wolves (Canis lupus) in east-central Ontario were obtained by following a pack of eight wolves from January 11 to March 20, 1969. Data on sex and age of deer killed during the winters of 1964 to 1969 and success of hunts by wolves in 1968 and 1969 have been included. During the main winter of study, the pack travelled a total of 327 km over a period of 46 days for an average daily travel rate of 7.1 km. The maximum range of the group during the period of surveillance encompassed 224 km2. The pack killed 29 deer during 63 days, or one deer per 2.2 days. Distances travelled between kills ranged from 0.3 to 43.4 km and averaged 14.7. The amount of food available per wolf per day was 3.67 kg. The calculated daily food consumption was 0.10 kg per kg of wolf per day. The average age (2.43) of deer killed by wolves was greater than the average age (2.02) of deer killed by hunters. The sex ratio of 42 adult deer killed by wolves was 250 males:100 females; in a sample of 290 hunter-killed deer the ratio was 92:100. In 1968, the hunting success of wolves was 25 percent compared with 63 percent in 1969. It was calculated that during the 5-month winter period, the wolves removed 9 to 11 percent of the 730 deer present when winter began.
Though composed of carbon, nitrogen and oxygen, like others, But still molecularly unique and different from my brothers, I have lately heard the first call of the inorganic To dissolve my special compounds, now so manic, Into simpler elements which nourish the cycling earth To infuse a fresh form into a new birth.
But will he be more lordly or more gay Than I who for his entry am programmed to fade away?
* John Zimmerman first raised the problem that this theory attempts to solve. Both he and Dick Marzolf provided the initial discussion that helped the theory to evolve. Sievert Rohwer, Dan Bowen, Bob Hirsch, and Lauri Oksanen helped to develop the arguments, and Chris Smith provided some contrasting viewpoints. The Summer 1972 environmental biology class at Kansas State University and Chip Taylor's organization for tropical ecology course in Costa Rica in Spring 1972 further helped to crystallize the theory. During some of the course of the study, I was supported by NSF GB-14293. Sharon Martin and Sue Hughes prepared the manuscript. I am grateful to all these persons for their help.
We determined the main factors that led to a decrease in the moose population of the Central Biosphere Reserve. The role and importance of the factors in this process were defined. The key role of predation by wolf in the moose population decline is emphasized. The predominant factor leading to the decrease in the moose population was wolf predation, which exerted a pronounced effect on the moose population number and on its age and sex composition. Review of the literature on ungulate– forest interactions shows some conflicting opinions that will require further detailed study. Nevertheless, there are data that allow estimation of the role of this group of animals in natural ecosystems. The ap-praisal of moose–forest interaction is com-plex and, to a certain degree, contradictory due to differing points of view of authors with respect to the forest as a whole and to moose in particular (Filonov 1983). Moose damage plant cover and thus cause changes not only in the structure and productivity of brush and woodland vegetation but also in the composition of leaf litter and properties of soils (Pastor et al. 1988). The extent of influence by moose on vegetation depends on moose population density (Gatikh 1980) and determines the characteristics of changes in natural forests. This is espe-cially important for the ecology of reserves. STUDY AREA Observations were performed in a 1,000 km 2 area in the Central Forest Biosphere Reserve, including a wildlife protection area and a sporting zone.
This survey was first undertaken for the purpose of compiling a country-wide map of deer problem areas for use in classes. There is no such map. When the job was half done, it was mentioned t o a meeting of deer men at the 1946 Wildlife Conference. This group asked that the &dings be pub-lished. We were told that the findings, however crude, were needed in other states. Apparently deer men everywhere have found it hard t o convince the aver-age citizen, and especially the average deer hunter, that (1) delay in reduction of overpopulated deer ranges means ultimate shrinkage of both the herd and the range; (2) reduction is the only remedy, nothing else works; (3) t o ac-complish a reduction, female deer must be killed. Our hope is that this imperfect his-tory of the recent behavior of deer populations may convey the lesson that in managing overlarge herds, "too little and too late" is the worst possible policy. Our data are gathered from the litera-ture and by correspondence. We tried t o find in each state someone posted on local deer. He was asked t o map, clas-sify, and date the areas of deer trouble. The problem areas (black in Figure 1) are plotted upon a deer distribution map published by Gabrielson in 1943 (Hearings, House Committee on Wildlife, p. SO (Dec. 9-10)), but modified in many states by more recent local maps published in cited papers. We are indebted to our Correspond-ents for their patient cooperation in this enterprise. ERRORS Appraisal of this technical problem by mail has undoubtedly led to errors both in our map, and in the later sum-mary and classification of cases. One error inheres in individual dif-ferences among our correspondents in viewpoint, knowledge, and freedom to talk. In some states the official policy is t o minimize deer troubles, and in a few to deny their existence. Another error inheres in seasonal shifts of deer. In the west, where the shift is usually altitudinal, only winter range is ordinarily mapped as in trouble. In the east, winter shift is so local that winter yards cannot be mapped separately except on very local maps. Thus Wisconsin alone has over 500 known yards. The result is that in a map like Figure 1, a given degree of overstocking "shows more black" in eastern than in western states. In order not to obscure the black problem areas, Figure 1 is hatched on the vacapt or near-vacant range, i.e., deer ranges are white. Boundaries of these white areas are very crude, and omit much fine detail because detailed distribution maps do not exist. The net result is that Figure 1 shows much more white area than is actually inhabited by deer. Some problem spots (black) ap-pear on hatched (uninhabited) range. This is because the inhabited range is too small t o map, and is coextensive with the problem area.
The 1995/1996 reintroduction of gray wolves (Canis lupus) into Yellowstone National Park after a 70 year absence has allowed for studies of tri-trophic cascades involving wolves, elk (Cervus elaphus), and plant species such as aspen (Populus tremuloides), cottonwoods (Populus spp.), and willows (Salix spp.). To investigate the status of this cascade, in September of 2010 we repeated an earlier survey of aspen and measured browsing and heights of young aspen in 97 stands along four streams in the Lamar River catchment of the park’s northern winter range. We found that browsing on the five tallest young aspen in each stand decreased from 100% of all measured leaders in 1998 to means of <25% in the uplands and <20% in riparian areas by 2010. Correspondingly, aspen recruitment (i.e., growth of seedlings/sprouts above the browse level of ungulates) increased as browsing decreased over time in these same stands. We repeated earlier inventories of cottonwoods and found that recruitment had also increased in recent years. We also synthesized studies on trophic cascades published during the first 15 years after wolf reintroduction. Synthesis results generally indicate that the reintroduction of wolves restored a trophic cascade with woody browse species growing taller and canopy cover increasing in some, but not all places. After wolf reintroduction, elk populations decreased, but both beaver (Caster canadensis) and bison (Bison bison) numbers increased, possibly due to the increase in available woody plants and herbaceous forage resulting from less competition with elk. Trophic cascades research during the first 15 years after wolf reintroduction indicated substantial initial effects on both plants and animals, but northern Yellowstone still appears to be in the early stages of ecosystem recovery. In ecosystems where wolves have been displaced or locally extirpated, their reintroduction may represent a particularly effective approach for passive restoration.
3 Centre d'études nordiques, Université Laval, Sainte-Foy, PQ, Canada G1K 7P4 ABSTRACT: Ungulates are both major consumers of vegetation and are themselves consumed by carnivores, so food web dynamics, both top-down (predation) and bottom-up (food and weather effects), are prominent in theoretical and applied research involving ungulates. The long generation time of ungulates induces long lags in population responses. Over broad geographic regions, ungulates commonly achieve high density only when predation is relatively low (< 2 species of predator), suggesting that predation provides a pervasive limitation of large herbivores. Ungulate stability is fundamentally a trophic-dynamics issue, usually a mix of top-down and bottom-up influences. The Isle Royale case history, spanning 4 decades, reveals a wolf-moose system fluctuating at 2-decade intervals with significant predation, food, and weather effects on ungulates. After a century, an equilibrium between moose and forest vegetation has not yet been reached, and a historical context seems necessary to understand trophic relationships. Components of predation compared at large spatial scales reveal different predator-prey patterns than the single system at Isle Royale, and analyses involving substitution of space for time also run counter to studies of single systems. Choice of spatial and temporal scales for field studies and meta-analyses appear to have a strong bearing on the results and their interpretation. Thus temporal and spatial scales enter influentially in the actual dynamics of carnivore-ungulate interaction as well problematically in our analyses of them. ALCES VOL. 39: 215-232 (2003)
Studies assessing the potential for large predators to affect, via trophic cascades, the dynamics of riparian plant communities and the morphology of river channels have been largely absent in the scientific literature. Herein, we consider the results of recent studies involving three national parks in the western United States: Yellowstone, Olympic, and Zion. Within each park, key large predators were extirpated or displaced in the early 1900s and subsequent browsing pressure by native ungulates initiated long-term declines in recruitment (i.e., growth of seedlings/sprouts into tall saplings and trees) of palatable woody species and impairment of other resources. Channel responses to browsing-suppressed riparian vegetation included increased widths of active channels via accelerated bank erosion, erosion of floodplains and erraces, increased area of unvegetated alluvium, channel incision, and increased braiding. A reduced frequency of overbank flows indicated these rivers have become increasingly disconnected from historical floodplains because of channel widening/incision. Results from Zion National Park also identified major biodiversity affects (e.g., reduced abundance of plant and animal species). Although these studies were conducted in national parks, results may have implications concerning riparian plant communities, biodiversity, and channel morphology for streams and rivers draining other public lands in the western US. It is on these lands that native and introduced ungulates have often heavily utilized riparian areas, largely in the absence of key predators, with significant consequences to plant communities and channels.
The relationship between native ungulates (mainly Roosevelt elk, Cervus elaphus L.) and the occurrence of three patch types in an old-growth (220- to 260-year-old) Sitka spruce (Picea sitchensis (Bong.) Carriere) - western hemlock (Tsuga heterophylla (Raf.) Sarg.) temperate coniferous rain forest was investigated on the South Fork Hoh River in Olympic National Park. The distribution, frequency, and size of two understory patches (grass, moss) and patches where shrubs had escaped herbivory (refugia) were sampled along transects. Vegetation standing crop, percent cover, species richness, and equitability along transects were compared with conditions in two 8-year-old 0.5-ha ungulate exclosures. Ungulate herbivory profoundly affected the distribution and abundance of understory patch types. Grass-dominated patches disappeared following 8 years of protection from ungulate herbivory. Ungulates maintained a reduced standing crop, increased forb species richness, and determined the distribution, morphology, and reproductive performance of several shrub species. There is clearly a dynamic relationship between patch type, tree fall, and ungulate herbivory in these old-growth forests. Our results show that ungulate herbivory is a driving force shaping vegetation patterns in coastal coniferous forests.
In 1998, Mexican gray wolves (Canis lupus baileyi) were introduced into the Blue Range Wolf Recovery Area (BRWRA) that spans adjacent portions of Arizona and New Mexico. In 2009 we selected three mixed-conifer sites on the Apache National Forest, within the BRWRA of east-central Arizona, to characterize long-term age structure of aspen (Populus tremuloides) and to check for the possible occurrence of a tri-trophic cascade involving Mexican wolves, Rocky Mountain elk (Cervus elaphus nelsoni), and aspen. These mixed-conifer sites included (a) a refugium site, (b) an old-growth site, and (c) a site thinned in 1991–1992. The refugium site was inaccessible to elk and cattle whereas the old-growth and thinned sites were accessible to elk, but not cattle. Age structure results indicated that aspen recruitment (i.e., the growth of sprouts/seedlings into tall saplings, poles, and eventually trees) at the refugium site had been ongoing over a period of many decades. In contrast, aspen recruitment at the old-growth and thinned sites decreased significantly (p