Summary1. Most studies of intraspecific variation in home range size have investigated only a single or a few factors and often at one specific scale. However, considering multiple spatial and temporal scales when defining a home range is important as mechanisms that affect variation in home range size may differ depending on the scale under investigation. 2. We aim to quantify the relative effect of various individual, forage and climatic determinants of variation in home range size across multiple spatiotemporal scales in a large browsing herbivore, the moose (Alces alces), living at the southern limit of its distribution in Norway. 3. Total home range size and core home range areas were estimated for daily to monthly scales in summer and winter using both local convex hull (LoCoH) and fixed kernel home range methods. Variance in home range size was analysed using linear mixed-effects models for repeated measurements. 4. Reproductive status was the most influential individual-level factor explaining variance in moose home range size, with females accompanied by a calf having smaller summer ranges across all scales. Variation in home range size was strongly correlated with spatiotemporal changes in quantity and quality of natural food resources. Home range size decreased with increasing browse density at daily scales, but the relationship changed to positive at longer temporal scales. In contrast, browse quality was consistently negatively correlated with home range size except at the monthly scale during winter when depletion of high-quality forage occurs. Local climate affected total home range size more than core areas. Temperature, precipitation and snow depth influenced home range size directly at short temporal scales. 5. The relative effects of intrinsic and extrinsic determinants of variation in home range size differed with spatiotemporal scale, providing clear evidence that home range size is scale dependent in this large browser. Insight into the behavioural responses of populations to climatic stochasticity and forage variability is essential in view of current and future climate change, especially for populations with thermoregulatory restrictions living at the southern limit of their distribution.
Summary1. Mechanisms that affect the spatial distribution of animals are typically scale-dependent and may involve forage distribution. Forage quality and quantity are often inversely correlated and a much discussed trade-off is whether or not to select for high-quality forage at the expense of forage abundance. This discussion has rarely involved scale-dependence or been applied to Northern browsing herbivores. At small spatial scales, browsers are assumed to select for the best quality forage. But, as high-quality forage resources are often scarce and may become depleted, coarse-scale habitat selection is assumed to be driven by forage availability. 2. To evaluate if moose selection for forage quantity and quality is scale-dependent we modelled summer and winter habitat selection of 32 GPS-marked female moose (Alces alces) at two spatial scales (landscape-scale vs. within-home range-scale). We used mixed-effects resource selection functions (RSFs) and landscape-scale forage availability models of six tree species of varying quality for moose. We considered silver birch (Betula pendula), downy birch (Betula pubescens.), Scots pine (Pinus sylvestris) as low quality browse species and rowan (Sorbus aucuparia), aspen (Populus tremula), willow (Salix spp.) as high-quality species. 3. As expected, the overall selection patterns for available browse biomass and quality varied across spatiotemporal scales. At the landscape-scale, moose selected for habitat with high available browse biomass of low quality species while at the within-home range-scale moose selected for sites with the highest quality browse species available. Furthermore, selection patterns during summer remained fairly stable, while during winter, selection at the within-home range-scale switched from sites with high quality to sites with lower quality browse species which suggests depletion of highquality species. Consistent with expectations from seasonal resource depletion, site fidelity (bimonthly home range overlap) was much lower in winter than in summer. 4. Coarse-scale habitat selection by moose as a function of forage variability revealed a scaledependent trade-off between available browse quantity and browse quality. Moreover, resource depletion changed the winter selection criteria of free-ranging moose and we demonstrate how the behavioural response to such a dynamic process can be inferred from RSFs.
Summary1. Density is a fundamental driver of many ecological processes including habitat selection. Theory on density-dependent habitat selection predicts that animals should be distributed relative to profitability of habitat, resulting in reduced specialization in selection (i.e. generalization) as density increases and competition intensifies. 2. Despite mounting empirical support for density-dependent habitat selection using isodars to describe coarse-grained (interhabitat) animal movements, we know little of how density affects fine-grained resource selection of animals within habitats [e.g. using resource selection functions (RSFs)]. 3. Using isodars and RSFs, we tested whether density simultaneously modified habitat selection and within-habitat resource selection in a rapidly growing population of feral horses (Equus ferus caballus Linnaeus; Sable Island, Nova Scotia, Canada; 42% increase in population size from 2008 to 2012). 4. Among three heterogeneous habitat zones on Sable Island describing population clusters distributed along a west-east resource gradient (west-central-east), isodars revealed that horses used available habitat in a density-dependent manner. Intercepts and slopes of isodars demonstrated a pattern of habitat selection that first favoured the west, which generalized to include central and east habitats with increasing population size consistent with our understanding of habitat quality on Sable Island. 5. Resource selection functions revealed that horses selected for vegetation associations similarly at two scales of extent (total island and within-habitat zone). When densities were locally low, horses were able to select for sites of the most productive forage (grasslands) relative to those of poorer quality. However, as local carrying capacity was approached, selection for the best of available forage types weakened while selection for lower-quality vegetation increased (and eventually exceeded that of grasslands). 6. Isodars can effectively describe coarse-grained habitat selection in large mammals. Our study also shows that the main predictions of density-dependent habitat selection are highly relevant to our interpretation of RSFs in space and time. At low but not necessarily high population size, density will be a leading indicator of habitat quality. Fitness maximization from specialist vs. generalist strategies of habitat and resource selection may well be apparent at multiple spatial extents and grains of resolution.
Marine ecosystems are increasingly exposed to anthropogenic disturbances that cause animals to change behavior and move away from potential foraging grounds. Here we present a process-based modeling framework for assessing population consequences of such sub-lethal behavioral effects. It builds directly on how disturbances influence animal movements, foraging and energetics, and is therefore applicable to a wide range of species. To demonstrate the model we assess the impact of wind farm construction noise on the North Sea harbor porpoise population. Subsequently, we demonstrate how the model can be used to minimize population impacts of disturbances through spatial planning. Population models that build on the fundamental processes that determine animal fitness have a high predictive power in novel environments, making them ideal for marine management. K E Y W O R D Sagent-based model, anthropogenic disturbances, cumulative effects, displacement, harbor porpoise, individual-based modeling, marine spatial planning, movement model, Phocoena phocoena
Storaas, T. (2014). To feed or not to feed? Evidence of the intended and unintended effects of feeding wild ungulates.Journal of Wildlife Management, 78(8) Large ungulates are keystone species in many ecosystems and are a highly valued natural 47 resource for social, cultural, and economic reasons (Gordon et al. 2004). Many populations have grown over recent decades, causing environmental and socio-economic 49 impacts on wider communities and conservation concerns, as well as density-dependent 50 changes in performance (Côté et al. 2004, Putman et al. 2011. Consequently, conflicts 51 arise between stakeholders who benefit economically from high ungulate numbers (e.g., 52hunters, outfitters, tourism operators) and those faced with the costs of their presence 53(e.g., land managers, conservationists, transport users and operators; Austin et al. 2010). 54Manipulating forage availability through the provision of additional food could 60Wildlife can be fed by humans in many different ways, intentionally (e.g., at 61 feeding stations) and unintentionally (e.g., unprotected agricultural crops and rubbish 62 dumps; Oro et al. 2013, Sorensen et al. 2014. In this review, we focus on the effects of 63 intentional feeding of ungulates, specifically considering supplementary feeding (often 64 called winter feeding) and diversionary, or intercept, feeding used to attract animals away 65 from vulnerable vegetation, livestock, or major traffic arteries (defined fully in 66 Supplemental Material). However, many of the issues raised also apply across a broad 67 range of unintentional but predictable anthropogenic food subsidies (Oro et al. 2013). 68Earlier reviews of the consequences of feeding large herbivores, published a decade or 77 METHODS 78We reviewed articles in the peer-reviewed and, to a lesser extent, grey literature that our search terms resulted in 232 articles. 86We identified 5 major management goals of supplementary and diversionary 87 feeding and considered the intended effects of feeding that would allow these goals to be 88 achieved (Table 1). We also identified commonly perceived unintended or secondary 89 consequences of feeding ( Table S1). 152Among adult females, an effect of feeding is complicated by the strong impact of 153 reproductive status on autumn mass (Cook et al. 2013 and higher neonatal growth rates (Jacobsen et al. 1981, Smith et al. 1997). 160The reproductive rate (number of offspring per adult female in summer or 161 autumn) of supplementally fed herbivores increased in 5/7 studies ( were used (Gundersen et al. 2004, Sahlsten et al. 2010 feeding site users and non-users (van Beest et al. 2010b). 282Of 16 controlled studies, 6 showed diversionary feeding to be effective in 283 reducing damage in the targeted areas, whereas 4 showed a significantly increased 284 impact, opposing the management goal ( we found no studies that formally addressed this ( 379In studies addressing the increased probability of browsing or grazing impacts in 380 response to feeding (4/4 studies; Table 2 and Supplem...
. 2016. Seasonal habitat-based density models for a marine top predator, the harbor porpoise, in a dynamic environment. Ecosphere 7(6):e01367. 10. 1002/ecs2.1367 Abstract. Effective species conservation and management requires information on species distribution patterns, which is challenging for highly mobile and cryptic species that may be subject to multiple anthropogenic stressors across international boundaries. Understanding species-habitat relationships can improve the assessment of trends and distribution by explicitly allowing high-resolution data on habitats to inform abundance estimation and the identification of protected areas. In this study, we aggregated an unprecedented set of survey data of a marine top predator, the harbor porpoise (Phocoena phocoena), collected in the UK (SCANS II, Dogger Bank), Belgium, the Netherlands, Germany, and Denmark, to develop seasonal habitat-based density models for the central and southern North Sea. Visual survey data were collected over 9 yr (2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013) by means of dedicated line-transect surveys, taking into account the proportion of missed sightings. Generalized additive models of porpoise density were fitted to 156,630 km of on-effort survey data with 14,356 sightings of porpoise groups. Selected predictors included static and dynamic variables, such as depth, distance to shore and to sandeel (Ammodytes spp.) grounds, sea surface temperature (SST), proxies for fronts, and day length. Day length and the spatial distribution of daily SST proved to be good proxies for "season," allowing predictions in both space and time. The density models captured seasonal distribution shifts of porpoises across international boundaries. By combining the large-scale international SCANS II survey with the more frequent, small-scale national surveys, it has been possible to provide seasonal maps that will be used to assist the EU Habitats and Marine Strategy Framework Directives in effectively assessing the conservation status of harbor porpoises. Moreover, our results can facilitate the identification of regions where human activities and disturbances are likely to impact the population and are especially relevant for marine spatial planning, which requires accurate fine-scale maps of species distribution to assess risks of increasing human activities at sea.
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