Animal-habitat Relationships Research Articles

Rethinking Habitat Occupancy Modeling and the Role of Diel Activity in an Anthropogenic World

AbstractCurrent methods to model species habitat use through space and diel time are limited. Development of such models is critical when considering rapidly changing habitats where species are forced to adapt to anthropogenic change, often by shifting their diel activity across space. We use an occupancy modeling framework to specify the multistate diel occupancy model (MSDOM), which can evaluate species diel activity against continuous response variables that may impact diel activity within and across seasons or years. We used two case studies, fosas in Madagascar and coyotes in Chicago, Illinois, to conceptualize the application of this model and to quantify the impacts of human activity on species spatial use in diel time. We found support that both species varied their habitat use by diel states-in and across years and by human disturbance. Our results exemplify the importance of understanding animal diel activity patterns and how human disturbance can lead to temporal habitat loss. The MSDOM will allow more focused attention in ecology and evolution studies on the importance of the short temporal scale of diel time in animal-habitat relationships and lead to improved habitat conservation and management.

Spaceborne LiDAR and animal-environment relationships: An assessment for forest carnivores and their prey in the Greater Yellowstone Ecosystem

Animal conservation requires understanding animal-habitat relationships. The integration of novel remote sensing platforms such as Light Detection and Ranging (LiDAR) technology has dramatically improved the resolution of insight when evaluating animal-habitat relationships by characterizing forest structure. However, conventional LiDAR collection (e.g., airborne or terrestrial laser scanning) may be limited by small spatial extents and logistical constraints (e.g., budget) associated with sampling. NASA’s Global Ecosystem Dynamics Investigation (GEDI) mission provides an alternative and complement to conventional LiDAR sampling with globally available waveform LiDAR, which is being collected to characterize vertical and horizontal structure of Earth’s forests. Forest carnivores are wide-ranging species occupying forested ecosystems, and are generally associated with vertical and horizontal forest structure for their survival and reproduction. We evaluated patterns in occurrence and habitat use of forest carnivores, which included Pacific martens (Martes caurina), Rocky Mountain red foxes (Vulpes vulpes macroura), and coyotes (Canis latrans) and patterns in occurrence of their prey; American red squirrels (Tamiasciurus hudsonicus) and snowshoe hares (Lepus americanus). Camera trap data were collected during the 2014–2017 winters in the Greater Yellowstone Ecosystem in Wyoming, USA. Our objectives were to (1) combine GEDI samples with multispectral satellite imagery from Landsat 8 to upscale vertical forest structure metrics; (2) assess the relative importance of environmental characteristics influencing occurrence and habitat use of forest-associated predators and prey; and (3) determine if GEDI-derived variables aided our efforts in characterizing animal-environment relationships. We used Random Forest regression models to upscale GEDI samples across our study area and implemented a multi-tiered approach using generalized linear mixed effect models to simultaneously evaluate animal-environment relationships and how GEDI-derived metrics improved the animal-habitat models. GEDI-derived metrics of relative height and foliage height diversity improved our animal-environment models and were among the strongest covariates (effect sizes were 1.3–1.8 times larger than the next closest) in the coyote, red squirrel, and snowshoe hare models. All five species were influenced to some degree by the frequency of rebaiting a camera trap and varying conditions of snow depth. Collectively, our work indicates forest canopy height and complexity variables significantly improved our ability to assess the importance of forest characteristics on forest carnivores and their prey. Indeed, there is an untapped opportunity to enhance animal ecology and conservation planning with continued integration of GEDI information with freely available satellite data to characterize attributes of forest structure across expansive areas.

Better together? Assessing different remote sensing products for predicting habitat suitability of wetland birds

AbstractAimThe increasing availability of remote sensing (RS) products from airborne laser scanning (ALS) surveys, synthetic aperture radar acquisitions and multispectral satellite imagery provides unprecedented opportunities for describing the physical structure and seasonal changes of vegetation. However, the added value of these RS products for predicting species distributions and animal habitats beyond land cover maps remains little explored. Here, we aim to assess how metrics derived from different types of high‐resolution (10 m) RS products predict the habitat suitability of wetland birds.LocationNorth‐eastern part of the Netherlands.MethodsWe built species distribution models (SDMs) with occurrence observations from territory mapping of two selected wetland bird species (great reed warbler and Savi's warbler) and metrics from a Dutch land cover map, country‐wide ALS and Sentinel‐1 and Sentinel‐2 RS products. We then compared model performance, relative variable importance and response curves of the SDMs to assess the contribution and ecological relevance of each RS product and metric.ResultsOur results showed that ALS and Sentinel metrics improve SDMs with only land cover metrics by 11% and 10% of the Area Under Curve (AUC) for the great reed warbler and the Savi's warbler respectively. Assessments of feature importance revealed that all types of RS products contributed substantially to predicting the habitat suitability of these wetland birds, but that the most important variables vary among species.Main conclusionsOur study demonstrates that metrics from different high‐resolution RS products capture complementary ecological information on animal habitats, including aspects such as the proportional cover of habitat types, vegetation density and the horizontal variability of vegetation height. Land cover maps with detailed spatial and thematic information can already achieve high model accuracies, but adding metrics derived from ALS point clouds and Sentinel imagery further improve model accuracy and enhance the understanding of animal–habitat relationships.

Disentangling the direct and indirect effects of canopy and understory vegetation on the foraging habitat selection of the brown bear Ursus arctos

Elucidating the factors affecting the foraging habitat selection of wildlife can further our understanding of the animal–habitat relationships and inform wildlife conservation and management. Canopy and understory vegetation may directly or indirectly affect the foraging habitat selection of carnivores through changes in habitat structure and prey availability, respectively; however, the relative importance of these two effects remains largely unknown. Dwarf bamboo Sasa kurilensis is a predominant understory plant that suppresses regeneration in the forests of northern Japan. The purpose of this study was to disentangle the direct and indirect effects of canopy forest type Larix kaempferi plantation versus natural mixed forest) and dwarf bamboo on foraging habitat selection of a large carnivore, the brown bear Ursus arctos. In the Shiretoko World Heritage, brown bears dig for cicada nymphs during summer. We evaluated the frequency of brown bear foraging on cicadas by investigating traces of digging for cicada nymphs. A structural equation model was used to statistically disentangle the direct and indirect effects of vegetation. Our results demonstrated that canopy and understory vegetation directly and indirectly affected foraging habitat selection of brown bears. Dwarf bamboo negatively affected cicada nymph density, which positively affected brown bear digging. This suggests that dwarf bamboo also had indirect negative effects on brown bears. Forest type had significant direct and indirect effects via change in cicada nymph density on foraging behavior in brown bears. Forestry managers in northern Japan, including the study site, try to remove dwarf bamboo for assisting natural regeneration. Removal of dwarf bamboo by scarification might not only promote natural regeneration, but also provide a beneficial foraging habitat for bears.

Context Dependence: A Conceptual Approach for Understanding the Habitat Relationships of Coastal Marine Fauna

Abstract Coastal habitats, such as seagrasses, mangroves, rocky and coral reefs, salt marshes, and kelp forests, sustain many key fish and invertebrate populations around the globe. Our understanding of how animals use these broadly defined habitat types is typically derived from a few well-studied regions and is often extrapolated to similar habitats elsewhere. As a result, a working understanding of their habitat importance is often based on information derived from other regions and environmental contexts. Contexts such as tidal range, rainfall, and local geomorphology may fundamentally alter animal–habitat relationships, and there is growing evidence that broadly defined habitat types such as “mangroves” or “salt marsh” may show predictable spatial and temporal variation in habitat function in relation to these environmental drivers. In the present article, we develop a framework for systematically examining contextual predictability to define the geographic transferability of animal–habitat relationships, to guide ongoing research, conservation, and management actions in these systems.

Determinants of the nursery role of seagrass meadows in the sub-tropical Gulf of Mexico: inshore-offshore connectivity for snapper and grouper

Quantifying the nursery role of habitats or locations in supporting fisheries is central to understanding population-scale animal-habitat relationships, and in guiding ecosystem-based management. We assessed the nursery role of northern Gulf of Mexico seagrass meadows for gray snapper, lane snapper, and gag recruiting to Alabama’s extensive offshore reef complex. We accomplished this using broadscale juvenile trawl surveys and geochemical tags—indicative of past habitat use—stored in the otoliths of >2200 fishes. These natural tags revealed that 47-61% of snapper and gag recruits to Alabama reefs originated in Florida panhandle seagrass nurseries. Seagrass meadows in Alabama and Mississippi were also important nurseries for snappers and gag, contributing 26-46% of recruits. Despite high juvenile snapper and gag catches along the extensive Chandeleur Islands, Louisiana, relatively few of those fishes recruited to Alabama’s reefs (<13% of total recruits, across species), although they may have recruited to populations outside our sampling domain. Beyond the applied value of these data for resource management (i.e. interstate connectivity), our findings highlight broadscale drivers of the nursery role of juvenile habitats for coastal marine populations. These factors include: (1) juvenile habitat extent (i.e. extensive Florida panhandle meadows sourced the most recruits for Alabama fisheries); (2) proximity between juvenile and adult habitats (i.e. highest unit-area contribution from Alabama-Mississippi meadows); and (3) unidirectional, alongshore migration of egressing juveniles (i.e. primarily east-to-west movement, enhancing connectivity with Florida panhandle nurseries, and dampening connectivity with Chandeleur nurseries).

Functional responses in habitat use explain changes in animal–habitat interactions during forest succession

The growing rate of resource extraction forces increasing numbers of late-seral species to occupy habitats that are in early stages of succession. Sustainable management must maintain habitat features that are required for recovery of these species, which may be challenging because their response to those features can vary following nonsystematic trends during stages of succession. We investigated whether simple movement rules could explain such variations by assessing how movements of a late-seral species, the red-backed vole (Myodes gapperi (Vigors, 1830)), vary during postlogging forest succession using the spool and line technique in recent cuts, mid-successional forests, and old-growth forests. We found that voles moved selectively along coarse woody material (CWM), and this selection was weaker in mid-successional forests. This change was best explained by a simple functional response, whereby voles selected CWM more strongly in stands where canopy cover availability was moderately high. Likewise, voles more rapidly left patches that had high canopy cover when it was less available in stands and tended to spend more time in patches with high CWM volumes. Our study demonstrates that the highly dynamic nature of animal–habitat relationships observed during forest succession can be summarized by a few simple functional responses in movement and habitat selection.

Evaluating the individuality of animal-habitat relationships.

Examining the ways in which animals use habitat and select resources to satisfy their life history requirements has important implications for ecology, evolution, and conservation. The advent of radio‐tracking in the mid‐20th century greatly expanded the scope of animal‐habitat modeling. Thereafter, it became common practice to aggregate telemetry data collected on a number of tagged individuals and fit one model describing resource selection at the population level. This convention, however, runs the risk of masking important individuality in the nature of associations between animals and their environment. Here, we investigated the importance of individual variation in animal‐habitat relationships via the study of a highly gregarious species. We modeled elk (Cervus elaphus) location data, collected from Global Positioning System (GPS) collars, using Bayesian discrete choice resource selection function (RSF) models. Using a high‐performance computing cluster, we batch‐processed these models at the level of each individual elk (n = 88) and evaluated the output with respect to: (a) the composition of parameters in the most supported models, (b) the estimates of the parameters featured in the global models, and (c) spatial maps of the predicted relative probabilities of use. We detected considerable individual variation across all three metrics. For instance, the most supported models varied with respect to parameter composition with a range of seven to 17 and an average of 14.4 parameters per individual elk. The estimates of the parameters featured in the global models also varied greatly across individual elk with little conformity detected across age or sex classes. Finally, spatial mapping illustrated stark differences in the predicted relative probabilities of use across individual elk. Our analysis identifies that animal‐habitat relationships, even among the most gregarious of species, can be highly variable. We discuss the implications of our results for ecology and present some guiding principles for the development of RSF models at the individual‐animal level.

Habitat structure modifies microclimate: An approach for mapping fine‐scale thermal refuge

Abstract Contemporary techniques predicting habitat suitability under climate change projections often underestimate availability of thermal refuges. Habitat structure contributes to thermal heterogeneity at a variety of spatial scales, but quantifying microclimates at organism‐relevant resolutions remains a challenge. Landscapes that appear homogeneous at large scales may offer patchily distributed thermal refuges at finer scales. We quantified the relationship between vegetation structure and the thermal environment at a scale relevant to small, terrestrial animals using a new approach for mapping fine‐scale thermal heterogeneity. We expected that vegetation would create attenuated microclimates and that the influence of vegetation structure would vary seasonally. We measured shrub volume, horizontal cover and operative temperature (Te) in a sagebrush‐steppe habitat in Idaho, USA, at 534 microsites across two study sites of c. 1 km2 each. We modelled relationships between habitat structure and both mean daily maximum temperature () and mean diurnal temperature range () for each study site during summer and winter. Aerial imagery from unmanned aerial systems was used to estimate shrub volume and canopy cover at 1‐m resolution, and we applied the best fit model to map thermal heterogeneity across broader extents. Increasing shrub volume and cover was associated with lower and , but strengths of the relationships differed between study sites. There was considerable heterogeneity in availability of thermal refuges across sagebrush‐steppe rangelands that have traditionally been considered relatively homogeneous. This technique can help ecologists and land managers identify critical thermal refuges that large‐scale climate modelling can overlook and thus contribute to an understanding of animal–habitat relationships under changing climates and land uses.

Functional responses in animal movement explain spatial heterogeneity in animal-habitat relationships.

Understanding why heterogeneity exists in animal-habitat spatial relationships is critical for identifying the drivers of animal distributions. Functional responses in habitat selection - whereby animals adjust their habitat selection depending on habitat availability - are useful for describing animal-habitat spatial heterogeneity. However, they could be yielded by different movement tactics, involving contrasting interspecific interactions. Identifying functional responses in animal movement, rather than in emergent spatial patterns like habitat selection, could disentangle the effects of different movement behaviours on spatial heterogeneity in animal-habitat relationships. This would clarify how functional responses in habitat selection emerge and provide a general tool for understanding the mechanistic drivers of animal distributions. We tested this approach using data from GPS-collared woodland caribou (Rangifer tarandus), a prey species under top-down control. We tested how caribou selected and moved with respect to a key resource (lichen-conifer stands) as a function of the availability of surrounding refuge land-cover (closed-conifer stands), using step selection functions. Caribou selected resource patches more strongly in areas richer in refuge land-cover - a functional response in habitat selection. However, adjustments in multiple movement behaviours could have generated this pattern: stronger directed movement towards resource patches and/or longer residency within resource patches, in areas richer in refuges. Different contributions of these behaviours would produce contrasting forager spatial dynamics. We identified functional responses in both movement behaviours: caribou were more likely to move towards resource patches in areas richer in refuge land-cover, and to remain in these patches during movement steps. This tactic enables caribou to forage for longer in safer areas where they can rapidly seek refuge in dense cover when predators are detected. Our study shows that functional responses in movement can expose the context-dependent movement decisions that generate heterogeneity in animal-habitat spatial relationships. We used these functional responses to characterise anti-predator movement tactics employed by a large herbivore, but they could be applied in many different scenarios. The movement rules from functional responses in movement are well-suited to integration in spatial explicit individual-based models for forecasting animal distributions in landscapes undergoing environmental change.

Microrefuges and the occurrence of thermal specialists: implications for wildlife persistence amidst changing temperatures

Contemporary climate change is affecting nearly all biomes, causing shifts in animal distributions, phenology, and persistence. Favorable microclimates may buffer organisms against rapid changes in climate, thereby allowing time for populations to adapt. The degree to which microclimates facilitate the local persistence of climate-sensitive species, however, is largely an open question. We addressed the importance of microrefuges in mammalian thermal specialists, using the American pika (Ochotona princeps) as a model organism. Pikas are sensitive to ambient temperatures, and are active year-round in the alpine where conditions are highly variable. We tested four hypotheses about the relationship between microrefuges and pika occurrence: 1) Local-habitat Hypothesis (local-habitat conditions are paramount, regardless of microrefuge); 2) Surface-temperature Hypothesis (surrounding temperatures, unmoderated by microrefuge, best predict occurrence); 3) Interstitial-temperature Hypothesis (temperatures within microrefuges best predict occurrence), and 4) Microrefuge Hypothesis (the degree to which microrefuges moderate the surrounding temperature facilitates occurrence, regardless of other habitat characteristics). We examined pika occurrence at 146 sites across an elevational gradient. We quantified pika presence, physiographic habitat characteristics and forage availability at each site, and deployed paired temperature loggers at a subset of sites to measure surface and subterranean temperatures. We found strong support for the Microrefuge Hypothesis. Pikas were more likely to occur at sites where the subsurface environment substantially moderated surface temperatures, especially during the warm season. Microrefugium was the strongest predictor of pika occurrence, independent of other critical habitat characteristics, such as forage availability. By modulating surface temperatures, microrefuges may strongly influence where temperature-limited animals persist in rapidly warming environments. As climate change continues to manifest, efforts to understand the changing dynamics of animal-habitat relationships will be enhanced by considering the quality of microrefuges.

Long-term trends in invertebrate–habitat relationships under protected and fished conditions

Few studies examine the long-term effects of changing predator size and abundance on the habitat associations of resident organisms despite that this knowledge is critical to understand the ecosystem effects of fishing. Marine reserves offer the opportunity to determine ecosystem-level effects of manipulated predator densities, while parallel monitoring of adjacent fished areas allows separating these effects from regional-scale change. Relationships between two measures of benthic habitat structure (reef architecture and topographic complexity) and key invertebrate species were followed over 17 years at fished and protected subtidal rocky reefs associated with two southern Australian marine reserves. Two commercially harvested species, the southern rock lobster (Jasus edwardsii) and blacklip abalone (Haliotis rubra) were initially weakly associated with habitat structure across all fished and protected sites. The strength of association with habitat for both species increased markedly at protected sites 2 years after marine reserve declaration, and then gradually weakened over subsequent years. The increasing size of rock lobster within reserves apparently reduced their dependency on reef shelters as refuges from predation. Rising predation by fish and rock lobster in the reserves corresponded with weakening invertebrate–habitat relationships for H. rubra and sea urchins (Heliocidaris erythrogramma). These results emphasise that animal–habitat relationships are not necessarily stable through time and highlight the value of marine reserves as reference sites. Our work shows that fishery closures to enhance populations of commercially important and keystone species should be in areas with a range of habitat features to accommodate shifting ecological requirements with ontogenesis.

Variogram models reveal habitat gradients predicting patterns of territory occupancy and nest survival among vesper sparrows

Characterizing landscapes as gradients may help illuminate animal—habitat relationships that are either 1) masked by or 2) impractical to investigate using a purely patch‐based perspective. Among other methods, variogram models may reveal these gradients in the environment by quantifying spatial dependence among point samples, yet few analyses of animal habitat relationships employing variograms have been undertaken. Using vegetation volume measurements from 4‐m2plots within breeding vesper sparrowPooecetes gramineusterritories, we calculated four territory‐scale gradients: 1) mean volume, 2) standard deviation of volume, 3) nugget (a measure of fine‐scale variation), and 4) range (an index of patch size). The first two gradients are more commonly employed in animal ecology while the second two were derived using variogram models and are infrequently employed. We next used these gradients in generalized linear models predicting territory occupancy and daily nest survival. We found overwhelming support for employing the range parameter and models indicated 1) birds selected areas with lower average vegetation volume and smaller patch sizes and 2) had lower rates of nest predation in areas with larger patch sizes. While these results indicate a pattern of non‐ideal habitat selection, there was no indication that territories which experienced nest predation were selected disproportionately. Our results underscore the utility of 1) variograms among other methods for quantifying gradients in animal habitat and 2) variogram model parameters in investigating the habitat ecology of animals.

Temporal consistency in fine-scale habitat relationships of woodland birds during a period of habitat deterioration

Temporal consistency of models of animal-habitat relationships is important because it is widely assumed that such models have long-term relevance for conservation management. Habitat associations can potentially shift over time due to changes in factors such as habitat quality, predation risk and intra-specific competition. Relationships between vegetation attributes and bird distribution were examined in rotationally harvested woodland in two breeding seasons separated by 16years. Over this period habitat suitability deteriorated for understory bird species as a result of increased browsing pressure by deer. Generalised additive models were constructed for eight species and three groups of songbirds (all species, migrants, hole-nesters), with choice of predictors and the assumed form of underlying relationships informed by cross-validation deviance. Three species differed strongly between years in their responses to age of vegetation regrowth following harvesting; in two of these cases the differences were probably a consequence of deer browsing altering relationships between age of regrowth and vegetation structure. Canopy height was generally the single best predictor and for six of the 11 response variables, height was the best predictor in both years. Density of shrub layer foliage was frequently the second best predictor in both years. Multi-variable models in most cases selected canopy height as the first variable. Floristic variables (i.e. ones measuring aspects of tree or shrub species composition) featured in 64% of the multi-variable models and 27% of the selected variables were floristic rather than structural. Overall, there was a high level of temporal consistency in the bird-habitat models with most species apparently keying into very similar vegetation structures irrespective of browsing pressure. Canopy height is considered to be a surrogate for a complex of micro-habitat elements associated with resource provision for many birds. However, the understory micro-structures that are important determinants of habitat quality for many forest species are difficult to measure in ecologically meaningful ways. New technologies potentially offer better ways of measuring these habitat attributes and of assessing how they are affected by forest management.

Identifying unidirectional and dynamic habitat filters to faunal recolonisation in restored mine‐pits

Summary1. There is increasing evidence that passive faunal recolonisation of restored areas can take decades or even centuries, reducing benefits to biodiversity from restoration. Thus, there is a need to develop restoration and management strategies that facilitate and accelerate faunal recolonisation. This requires identification of habitat features that act as filters to slow or prevent recolonisation and whether those filters are temporally unidirectional or dynamic.2. We investigated successional patterns of reptiles and mammals in restored mine‐pits in south‐western Australia to identify potential filters to faunal recolonisation. We sampled reptiles and small mammals using 30 trapping grids across each of four restoration ages (4, 8, 12 and 17‐years old) and unmined forest and assessed vegetation structure to identify animal–habitat relationships.3. Mammal communities in restored areas converged on unmined forest communities as restoration matured, and all species recolonised rapidly, indicating there were no filters to mammal recolonisation. In contrast, reptile communities did not converge in the same way, indicating there were filters that slowed or prevented reptile recolonisation. We identified three reptile species that were slow, or failed, to recolonise restored areas and a fourth species that rapidly recolonised but disappeared as restoration matured. We identified low coarse woody debris (CWD) volumes and high overstorey stem densities as likely filters; the former is a unidirectional filter that will decrease gradually over long time frames, possibly centuries, while the latter is a dynamic filter that fluctuates in its intensity over short time frames of years.4. Synthesis and applications. Our study adds to growing evidence that filters to faunal recolonisation may be widespread in restored areas, with important implications for restoration practices. Firstly, examining individual species may more effectively identify filters than examining community successional patterns. Secondly, filters can persist over long time frames, possibly centuries, so management, such as the provision and accelerated development of CWD, may need to occur over similar time frames. Lastly, filters can be dynamic and repeated management interventions, such as thinning, may be required to overcome these filters. The growing evidence for filters suggests that facilitating faunal recolonisation is more complex than simply returning vegetation to restoration sites.

Prediction of National Vegetation Classification communities in the British uplands using environmental data at multiple spatial scales, aerial images and the classifier random forest

Summary 1. High-resolution vegetation maps are a valuable resource for conservation, land management and research. In Great Britain, the National Vegetation Classification (NVC) is widely used to describe vegetation communities. NVC maps are typically produced from ground surveys which are prohibitively expensive for large areas. An approach to produce NVC maps more cost-effectively for large areas would be valuable. 2. Creation of vegetation community maps from aerial or satellite images has often had limited success as the clusters separable by spectral reflectance frequently do not correspond well to vegetation community classes. Such maps have also been produced by exploring correlations between community occurrence and environmental variables. The latter approach can have limitations where anthropogenic activities have altered the distribution of vegetation communities. We combined these two approaches and classified 24 common NVC classes of the Yorkshire Dales and an additional class ‘wood’ consisting of trees and bushes at a resolution of 5 m from mostly remotely sensed variables with the algorithm random forest. 3. Classification accuracy was highest when environmental variables at low and high resolution (50 and 5–10 m, respectively) were added to aerial image information aggregated to a resolution of 5 m. Low-resolution environmental variables are likely to be correlated with the dominant vegetation surrounding a location and thus could represent critical area requirements or local species pool effects, while high-resolution environmental variables represent the environmental conditions at the location. 4. Overall classification accuracy was 87–92%. The median producer’s and user’s class accuracies were 95% (58–100%) and 92% (67–100%), respectively. 5. Synthesis and applications. The classification accuracies achieved in this study, the number of classes differentiated, their level of detail and the resolution were high compared with those of other studies. This approach could allow the production of good-quality NVC maps for large areas. In contrast to existing maps of broad land cover types, such maps would provide more detailed vegetation community data for applications like the monitoring of vegetation in a changing climate, the study of animal–habitat relationships, conservation management or land use planning.

The interpretation of habitat preference metrics under use–availability designs

Models of habitat preference are widely used to quantify animal-habitat relationships, to describe and predict differential space use by animals, and to identify habitat that is important to an animal (i.e. that is assumed to influence fitness). Quantifying habitat preference involves the statistical comparison of samples of habitat use and availability. Preference is therefore contingent upon both of these samples. The inferences that can be made from use versus availability designs are influenced by subjectivity in defining what is available to the animal, the problem of quantifying the accessibility of available resources and the framework in which preference is modelled. Here, we describe these issues, document the conditional nature of preference and establish the limits of inferences that can be drawn from these analyses. We argue that preference is not interpretable as reflecting the intrinsic behavioural motivations of the animal, that estimates of preference are not directly comparable among different samples of availability and that preference is not necessarily correlated with the value of habitat to the animal. We also suggest that preference is context-dependent and that functional responses in preference resulting from changing availability are expected. We conclude by describing advances in analytical methods that begin to resolve these issues.

Winter selection of landscapes by woodland caribou: behavioural response to geographical gradients in habitat attributes

Summary 1. Understanding animal-habitat relationships is central to the development of strategies for wildlife management and conservation. The availability of habitat attributes often changes along latitudinal and longitudinal axes, and animals may respond to those changes by adjusting their selection. We evaluated whether landscape selection by forest-dwelling woodland caribou Rangifer tarandus caribou varied along geographical gradients in habitat attributes. 2. Centroids {n = 422) of track networks made by caribou in winter were recorded during aerial surveys conducted over 161 920 km2 of boreal forest in Qu?bec, Canada. Autologistic models were estimated by comparing the characteristics of landscapes (201 km2) centred on each centroid to an equal number of randomly located landscapes, with an autocovariate controlling for the non independence among caribou locations. 3. The availability of habitat attributes varied along longitudinal and latitudinal gradients, and caribou altered their landscape selection with respect to those gradients. 4. Information Theory provided substantial support for only one model. The model revealed that the probability of occurrence of caribou increased with the abundance of conifer forests over most of the study region, but this positive response gradually became negative towards the southern portion of the region. The association between caribou and lichens changed from being negative west of the study region to being positive in the eastern part. Availability of landscapes dominated by lichen decreased from west to east. Finally, caribou generally displayed an aversion to areas with high road density, a negative association that became positive in the southern part of the study region. 5. Synthesis and applications. Under current legislation in Canada, the critical habitat of woodland caribou must be defined, and then protected. Our autoregressive models can help to identify landscapes to prioritize conservation efforts. The probability of occurrence of caribou was related to different landscape characteristics across their range, which implies that the typical habitat of woodland caribou differs spatially. Such behavioural plasticity could be problematic for defining critical habitat, but we showed that spatial variation in landscape selection was organized along geographical gradients. Our study illustrates how geographical trends in habitat selection can guide management and conservation decisions.

Lidar: shedding new light on habitat characterization and modeling

Ecologists need data on animal–habitat associations in terrestrial and aquatic environments to design and implement effective conservation strategies. Habitat characteristics used in models typically incorporate (1) field data of limited spatial extent and/or (2) remote sensing data that do not characterize the vertical habitat structure. Remote sensing tools that directly characterize three-dimensional (3-D) habitat structure and that provide data relevant to organism–habitat interactions across a hierarchy of scales promise to improve our understanding of animal–habitat relationships. Laser altimetry, commonly called light detection and ranging (lidar), is a source of geospatial data that can provide fine-grained information about the 3-D structure of ecosystems across broad spatial extents. In this review, we present a brief overview of lidar technology, discuss recent applications of lidar data in investigations of animal–habitat relationships, and propose future applications of this technology to issues of broad species-management and conservation interest.

Effects of Sampling Effort Based on GPS Telemetry on Home-Range Size Estimations

Home-range size is widely used in wildlife biology to assess animal-habitat relationships. But home-range size estimation largely depends on the estimator and sample size used. Using 3 different estimators (minimum convex polygons, fixed-kernels, clusters), we used data collected on moose (Alces alces), fitted with Global Positioning System (GPS) collars (which allow automatic recording of large data sets with fewer field constraints than VHF telemetry) to investigate to what extent increasing the number of locations affects home-range size estimations. Our results indicated that 100 to 300 locations per animal annually and 30 to 100 locations seasonally were needed to reach an asymptote. High biases occurred below this asymptotic value. Minimum convex polygons consistently underestimated home-range sizes, but fixed-kernel and cluster estimators followed variable trends that often overestimated home-range sizes. Low sampling efforts also affected the number of animals needed to ensure an adequate statistical power of analysis to compare space use between 2 groups. Despite the higher cost, our findings indicate that in most instances, GPS telemetry is better suited than conventional radiotelemetry to estimate home-range sizes precisely and accurately. Moreover, this tracking technique is not limited by meteorological constraints and allows for the collection of similar sample sizes for all tracked animals, which is of major importance for further comparisons of space use among individuals.