The future role of large carnivores in terrestrial trophic interactions: the northern temperate view (original) (raw)
Habitat differentiation within the large‐carnivore community of Norway's multiple‐use landscapes
Journal of Applied …, 2008
The re-establishment of large carnivores in Norway has led to increased conflicts and the adoption of regional zoning for these predators. When planning the future distribution of large carnivores, it is important to consider details of their potential habitat tolerances and strength of inter-specific differentiation. We studied differentiation in habitat and kill sites within the large-carnivore community of south-eastern Norway.We compared habitat selection of the brown bear Ursus arctos L., Eurasian lynx Lynx lynx L., wolf Canis lupus L. and wolverine Gulo gulo L., based on radio-tracking data. Differences in kill site locations were explored using locations of documented predator-killed sheep Ovis aries L. We modelled each species’ selection for, and differentiation in, habitat and kill sites on a landscape scale using resource selection functions and multinomial logistic regression. Based on projected probability of occurrence maps, we estimated continuous patches of habitat within the study area.Although bears, lynx, wolves and wolverines had overlapping distributions, we found a clear differentiation for all four species in both habitat and kill sites. The presence of bears, wolves and lynx was generally associated with rugged, forested areas at lower elevations, whereas wolverines selected rugged terrain at higher elevations. Some degree of sympatry was possible in over 40% of the study area, although only 1·5% could hold all four large carnivores together.Synthesis and applications. A geographically differentiated management policy has been adopted in Norway, aimed at conserving viable populations of large carnivores while minimizing the potential for conflicts. Sympatry of all four carnivores will be most successful if regional zones are established of adequate size spanning an elevational gradient. High prey densities, low carnivore densities, low dietary overlap and scavenging opportunities have most probably led to reduced competitive exclusion. Although regional sympatry enhances the conservation of an intact guild of large carnivores, it may well increase conflict levels and resistance to carnivore conservation locally.
Frontiers in Ecology and Evolution
Carnivores act as top-down regulators in terrestrial ecosystems, and their occurrence and relative abundance is a result of complex interactions between food and habitat availability, human pressure (e.g., trapping, hunting, roadkill), and intraguild interactions (competition, predation). Eastern United States has a long history of human impact, which resulted in an altered carnivore community. Specifically, Ohio presents an interesting case for evaluating the relative roles of interspecific relations and habitat characteristics for shaping the carnivore community, as its carnivore community has a unique dynamics and composition: invasive coyote and red fox (Vulpes vulpes), and native bobcat (Lynx rufus), currently recovering and expanding its range, gray fox (Urocyon cinereoargenteus) declining at a fast pace, and the generalist raccoon (Procyon lotor) and Virginian opossum (Didelphis virginiana). We used 50 camera traps to collect presence/absence data in southeastern Ohio, USA. We hypothesized potential interactions between the six carnivores, and used land cover variables, as well as occupancy probabilities of interacting species, to parameterize to single-species occupancy models. We found that landscape composition at three different scales (500 and 1000 m buffer around camera locations, and 3 × 3 km grid cell) had little effect on species occurrence. We identified strong negative interspecific relations between carnivores, with bobcat occurrence being influenced by presence of coyotes, red fox occurrence by gray foxes, and raccoon occurrence by Virginia possums. While these findings cannot discriminate between habitat partitioning (spatial or temporal) and competition (direct or interference), they lend support to complex dynamics between invasive coyotes and red foxes and recovering (bobcat) and declining (gray fox) native carnivore species. In particular, the negative relation between the apex predator in our system, C. latrans, and L. rufus, raise further questions on whether direct competition from coyotes has the potential to slow bobcat population recovery. In the context of regulated trapping (ongoing for gray fox and potential season for bobcat), a better understanding of the carnivore intraguild relations can inform management and conservation actions targeted at minimizing the impact of competition on at-risk native species from non-native species.
Factors associated with co-occurrence of large carnivores in a human-dominated landscape
Biodiversity and Conservation
We investigated the factors facilitating co-occurrence of two large carnivores, tigers (Panthera tigris) and common leopards (Panthera pardus), within a human-dominated landscape. We estimated their density and population size using camera-trap photographs and examined spatial segregation of habitats, temporal activity pattern, and diets in Chitwan National Park, Nepal. A Bayesian spatially-explicit capture-recapture model estimated densities of 3.2-4.6 (3.94 ± 0.37) tigers and 2.6-4.1 (3.31 ± 0.4) leopards per 100 km 2 with abundance of 70-102 tigers and 66-105 leopards. Tigers occupied the prime habitats (grasslands and riverine forests) in alluvial floodplains of the Park whereas leopards appeared in Sal forests and marginal areas where livestock are present. Both tigers and leopards showed crepuscular activity patterns with a high overlap but tigers were less active during the day compared to leopards. Leopards' activity in the day increased in the presence of tigers. Tiger and leopard diet overlapped considerably (90%). Compared to leopards, tigers consumed a higher proportion of the large prey and a smaller proportion of livestock. Our study demonstrates that sympatric large carnivores can coexist in high densities in prey rich areas that contain a mosaics of habitats. To increase the resilience and size of the Chitwan carnivore population, strategies are needed to increase prey biomass and prevent livestock depredation in adjacent forests. Long-term monitoring is also required to obtain a detailed understanding of the interaction between the large carnivores and their effects on local communities living in forest fringes within the landscape.
Frontiers in Ecology and Evolution, 2022
Ecological studies investigating niche breadth and overlap often have limited spatial and temporal scale, preventing generalizations across varying environments and communities. For example, it is not clear whether species having restricted diets maintain such patterns relative to closely related species and across their geographic range of co-occurrence. We used stable isotope analysis of hair and fur samples collected from four regions of sympatry for Canada lynx (Lynx canadensis) and bobcat (Lynx rufus) spanning southern Canada and the northern United States, to test the prediction that the more generalist species (bobcat) exhibits a wider dietary niche than the more specialist species (Canada lynx) and that this pattern is consistent across different regions. We further predicted that Canada lynx diet would consistently exhibit greater overlap with that of bobcat compared to overlap of bobcat diet with Canada lynx. We found that Canada lynx had a narrower dietary niche than bobcat, with a high probability of overlap (85-95%) with bobcat, whereas the bobcat dietary niche had up to a 50% probability of overlap with Canada lynx. These patterns of dietary niche breadth and overlap were consistent across geographic regions despite some regional variation in diet breadth and position, for both species. Such consistent patterns could reflect a lack of plasticity in species dietary niches. Given the increasingly recognized importance of understanding dietary niche breadth and overlap across large spatial scales, further research is needed to investigate the mechanisms by which broad-scale patterns are maintained across species and systems.
The Role of Top Carnivores in Regulating Terrestrial Ecosystems
1999
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 herbivores 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, short-sighted management strategies to reduce carnivores might cause extensive and long-term changes in ecosystem structure and function.
Use of winter habitat by roe deer at a northern latitude where Eurasian lynx are present
Journal of Zoology, 2007
Winter climate at northern latitudes is a challenge to small-bodied ungulates, and they modify behaviour to save energy and to increase the likelihood of survival. Also, the ongoing expansion of large carnivores in several European countries can lead to the recovery of (potentially energetically costly) anti-predator behaviours.
Prey density, environmental productivity and home-range size in the Eurasian lynx (Lynx lynx
Journal of Zoology, 2005
Variation in size of home range is among the most important parameters required for effective conservation and management of a species. However, the fact that home ranges can vary widely within a species makes data transfer between study areas difficult. Home ranges of Eurasian lynx Lynx lynx vary by a factor of 10 between different study areas in Europe. This study aims to try and explain this variation in terms of readily available indices of prey density and environmental productivity. On an individual scale we related the sizes of 52 home ranges, derived from 23 (9:14 male:female) individual resident lynx obtained from south-eastern Norway, with an index of density of roe deer Capreolus capreolus. This index was obtained from the density of harvested roe deer within the municipalities covered by the lynx home ranges. We found a significant negative relationship between harvest density and homerange size for both sexes. On a European level we related the sizes of 111 lynx (48:63 male: female) from 10 study sites to estimates derived from remote sensing of environmental productivity and seasonality. A multiple linear regression model indicated that productivity of the study site had a clear negative relationship with home-range size. At both scales, sex emerged as a significant explanatory variable with males having larger home ranges than females. In addition, the size of male home-ranges increased faster with decreasing prey density than for females. These analyses support widely held predictions that variation in home-range size is due to variation in prey density.
ABSTRACT Conflicts between humans and large carnivores are one of the most visible examples of the challenges that arise when seeking to achieve coexistence between humans and wildlife. With their large spatial requirements and predatory behavior, large carnivores are among the most difficult species to preserve in our modern day landscapes. Although large carnivores are usually considered as the epitomes of wilderness, because of human population growth and habitat fragmentation they are inexorably and increasingly faced with the need to live in human- modified landscapes. As a direct consequence, conflicts over depredation on livestock, competition for game species and sometimes over human injury or death will only increase if clear management measures are not taken. This is particularly true in Europe, where, after many decades of absence, large carnivores are recolonizing areas where millions of people are present and where landscapes have been drastically modified. Two approaches to integrating wildlife into a human-dominated world have been proposed at an international scale. The first solution is called land sparing, in which wildlife lives exclusively in protected or wilderness areas where contact between animals and humans will be reduced to the minimum. The second solution, called land sharing, proposes to integrate human activities and wildlife in the same landscapes in non-protected interface zones in what is often called a coexistence approach. In a context of scarce true wilderness areas and a continuum of human-modified habitats, land sharing (i.e. the coexistence approach) is seen as the only possible approach valid for Europe. While a coexistence approach can be readily implemented with smaller species, it can represent a major challenge for species with large space requirements and with predatory behavior. To help manage these species in a long-term conservation vision and to predict where potential conflicts could arise between humans and carnivores, information on large carnivores and their habitat use in anthropogenic landscapes is a pre-requisite. With the return of Eurasian lynx Lynx lynx in Western Europe, _the most densely populated areas of the continent_ information on the species tolerance to human land use will help predict where it is likely to occur in anthropogenic landscapes. Data collected in Scandinavia over 15 years were used to assess the use of landscape by lynx. In this study, we explored the effect of anthropogenic and environmental factors on Eurasian lynx habitat use in Scandinavia. The work was developed along two main axes. The first axis aims to explore large scale potential patterns of lynx distribution through transferability of results obtained from habitat modelling to geographically different areas. Transferability of results was tested in two steps. Firstly, transferability success (i.e. predictive ability of the map) was tested at a regional scale using data on roe-deer, the main prey of lynx, to create a map of relative distribution and abundance of prey in southeastern Norway (Chapter 1). Secondly, transferability success was assessed at a larger extent and using data obtained from different sampling method (Chapter 2). A habitat suitability map for Eurasian lynx was produced to be used in management planning in geographically differentiated lynx management zones in Scandinavia. The results indicated that transferability of results from one region to an ecologically different region must be taken with caution. Nevertheless, the habitat suitability maps we constructed on the basis of extrapolation are a valuable asset to help management of the Scandinavian lynx population. The second axis deals with lynx habitat use in relation to anthropogenic and environmental predictors. Lynx tolerance to human presence was first explored by looking at the orientation of home range in the landscape, taking into account proxies of human presence (Chapter 3). Values of these proxies were compared both inside home ranges and within a buffer surrounding the home ranges for several lynx inhabiting an anthropogenic gradient going from near-wilderness to urban periphery. Results showed a high diversity in the extent to which individual lynx are exposed to human influence, indicating that lynx are highly adaptable in terms of living space. Lynx seemed to be able to orientate their home range in order to avoid highest human impacts and select for areas of medium human impacts. Building on these results, finer scale information on lynx habitat use in an anthropogenic landscape were obtained taking into consideration different types of behavior (day-beds, moving and killing) displayed by adult lynx, as well as the effect of cumulative anthropogenic pressures on habitat selection (Chapter 4). Our results showed that lynx select for areas with medium levels of human modification, avoiding both the areas with highest and least modification. Females in general appear to be less tolerant to human modification than males, especially for day-beds. Our study shows that Eurasian lynx can be considered as a species that is adaptable to human- induced changes in landscape even if its motivation to tolerate human presence is clearly linked to the presence and density level of its main prey, the roe deer. Our work shows that, contrary to much of the public and many conservation professionals’ opinions, land sharing with large carnivores in Europe may be possible – even in the immediate proximity to urban centers. However, it is important to bear in mind that these results were obtained from countries with a relatively low human population density; even though some individuals observed lived in the periphery of large cities, the level of habitat fragmentation is less severe than in most of Western Europe. In order to properly assess the capacity of Eurasian lynx to live in highly populated areas, such as the Benelux, more detailed information on lynx distribution from continental European will be needed. However, our results underline the value of combining both correlational and mechanistic studies, and the need for caution in extrapolating data too far from its original context. As large carnivore recovery continues to progress in Europe we may not yet have seen the limits of these species' abilities to adapt.