So close and yet so different: The importance of considering temporal dynamics to understand habitat selection

Behavioural responses of brown bears to roads and hunting disturbance

Harvest regulations commonly attenuate the consequences of hunting on specific segments of a population. However, regulations may not protect individuals from non-lethal effects of hunting and their consequences remain poorly understood. In this study, we compared the movement rates of Scandinavian brown bears (Ursus arctos, n = 47) across spatiotemporal variations in risk in relation to the onset of bear hunting. We tested two alternative hypotheses based on whether behavioural responses to hunting involve hiding or escaping. If bears try to reduce risk exposure by avoiding being detected by hunters, we expect individuals from all demographic groups to reduce their movement rate during the hunting season. On the other hand, if bears avoid hunters by escaping, we expect them to increase their movement rate in order to leave high-risk areas faster. We found an increased movement rate in females accompanied by dependent offspring during the morning hours of the bear hunting season, a general decrease in movement rate in adult lone females, and no changes in males and subadult females. The increased movement rate that we observed in females with dependant offspring during the hunting season was likely an antipredator response because it only occurred in areas located closer to roads, whereas the decreased movement rate in lone females could be either part of seasonal activity patterns or be associated with an increased selection for better concealment. Our study suggests that female brown bears accompanied by offspring likely move faster in high-risk areas to minimize risk exposure as well as the costly trade-offs (i.e. time spent foraging vs. time spent hiding) typically associated with anti-predator tactics that involve changes in resource selection. Our study also highlights the importance of modelling fine-scale spatiotemporal variations in risk to adequately capture the complexity in behavioural responses caused by human activities in wildlife.

Time-varying habitat selection analysis: A model and applications for studying diel, seasonal, and post-release changes

Resource selection functions are commonly used to evaluate animals' habitat selection, for example, the disproportionate use of habitats relative to their availability. While environmental conditions or animal motivations may vary over time, sometimes in an unknown manner, studying changes in habitat selection usually requires an a priori segmentation of time in distinct periods. This limits our ability to precisely answer the question "When is an animal's habitat selection changing?" Here, we present a straightforward and flexible alternative approach based on fitting dynamic logistic models to used/available data. First, using simulated datasets, we demonstrate that dynamic logistic models perform well in recovering temporal variations in habitat selection. We then show real-world applications for studying diel, seasonal, and post-release changes in the habitat selection of the blue wildebeest (Connochaetes taurinus). Dynamic logistic models allow the study of temporal changes in habitat selection in a framework consistent with resource selection functions but without the need to segment time in distinct periods, which can be a difficult task when little is known about the process studied or may obscure interindividual variability in timing of change. These models should undoubtedly find their place in the movement ecology toolbox. We provide R scripts to facilitate their adoption. We also encourage future research to focus on how to account for temporal autocorrelation in location data, as this would allow statistical inference from location data collected at a high frequency, an increasingly common situation.

Effects of temperature heterogeneity on freshwater turtle habitat selection at their northern range limit

Environmental temperature is a crucial resource for ectotherms, affecting their physiology, behaviour and fitness. To maintain body temperatures within a suitable performance range, ectotherms select thermally-favourable locations, but this selection may be challenging in environments with high spatio-temporal heterogeneity. We assessed thermal habitat selection in two freshwater turtles (Emydoidea blandingii; Chrysemys picta) within a thermally heterogeneous environment at two spatial scales (selection of home ranges within the landscape, selection of locations within home ranges) and across seasons, by comparing temperatures at turtle locations vs. those available in the environment. Turtles selected warmer locations compared to those available in aquatic and terrestrial habitats only within home ranges, but did not show any temperature preferences when selecting home ranges at the larger scale. Turtles selected locations that were less thermally-variable than their surroundings, both at the home range scale and within home ranges. Thermal habitat selection was strongest during colder and more thermally-variable pre-nesting season compared to later periods. Despite differences in thermal mass between species, both species responded similarly to temperature variation. We conclude that freshwater turtles at their northern range margin select suitable microclimates within the suite of conditions that are naturally available.

Accounting for behaviour in fine-scale habitat selection: A case study highlighting methodological intricacies

Animal habitat selection-central in both theoretical and applied ecology-may depend on behavioural motivations such as foraging, predator avoidance, and thermoregulation. Step-selection functions (SSFs) enable assessment of fine-scale habitat selection as a function of an animal's movement capacities and spatiotemporal variation in extrinsic conditions. If animal location data can be associated with behaviour, SSFs are an intuitive approach to quantify behaviour-specific habitat selection. Fitting SSFs separately for distinct behavioural states helped to uncover state-specific selection patterns. However, while the definition of the availability domain has been highlighted as the most critical aspect of SSFs, the influence of accounting for behaviour in the use-availability design has not been quantified yet. Using a predator-free population of high-arctic muskoxen Ovibos moschatus as a case study, we aimed to evaluate how (1) defining behaviour-specific availability domains, and/or (2) fitting separate behaviour-specific models impacts (a) model structure, (b) estimated selection coefficients and (c) model predictive performance as opposed to behaviour-unspecific approaches. To do so, we first applied hidden Markov models to infer different behavioural modes (resting, foraging, relocating) from hourly GPS positions (19 individuals, 153-1062 observation days/animal). Using SSFs, we then compared behaviour-specific versus behaviour-unspecific habitat selection in relation to terrain features, vegetation and snow conditions. Our results show that incorporating behaviour into the definition of the availability domain primarily impacts model structure (i.e. variable selection), whereas fitting separate behaviour-specific models mainly influences selection strength. Behaviour-specific availability domains improved predictive performance for foraging and relocating models (i.e. behaviours with medium to large spatial displacement), but decreased performance for resting models. Thus, even for a predator-free population subject to only negligible interspecific competition and human disturbance we found that accounting for behaviour in SSFs impacted model structure, selection coefficients and predictive performance. Our results indicate that for robust inference, both a behaviour-specific availability domain and behaviour-specific model fitting should be explored, especially for populations where strong spatiotemporal selection trade-offs are expected. This is particularly critical if wildlife habitat preferences are estimated to inform management and conservation initiatives.

Flexible hidden Markov models for behaviour-dependent habitat selection

BACKGROUND

There is strong incentive to model behaviour-dependent habitat selection, as this can help delineate critical habitats for important life processes and reduce bias in model parameters. For this purpose, a two-stage modelling approach is often taken: (i) classify behaviours with a hidden Markov model (HMM), and (ii) fit a step selection function (SSF) to each subset of data. However, this approach does not properly account for the uncertainty in behavioural classification, nor does it allow states to depend on habitat selection. An alternative approach is to estimate both state switching and habitat selection in a single, integrated model called an HMM-SSF.

METHODS

We build on this recent methodological work to make the HMM-SSF approach more efficient and general. We focus on writing the model as an HMM where the observation process is defined by an SSF, such that well-known inferential methods for HMMs can be used directly for parameter estimation and state classification. We extend the model to include covariates on the HMM transition probabilities, allowing for inferences into the temporal and individual-specific drivers of state switching. We demonstrate the method through an illustrative example of plains zebra (Equus quagga), including state estimation, and simulations to estimate a utilisation distribution.

RESULTS

In the zebra analysis, we identified two behavioural states, with clearly distinct patterns of movement and habitat selection ("encamped" and "exploratory"). In particular, although the zebra tended to prefer areas higher in grassland across both behavioural states, this selection was much stronger in the fast, directed exploratory state. We also found a clear diel cycle in behaviour, which indicated that zebras were more likely to be exploring in the morning and encamped in the evening.

CONCLUSIONS

This method can be used to analyse behaviour-specific habitat selection in a wide range of species and systems. A large suite of statistical extensions and tools developed for HMMs and SSFs can be applied directly to this integrated model, making it a very versatile framework to jointly learn about animal behaviour, habitat selection, and space use.

Settling Preference of Two Coexisting Aphid Species on the Adaxial and Abaxial Surfaces of Walnut Leaves

Walnut dusky-veined aphid Panaphis juglandis (Goeze) and walnut green aphid Chromaphis juglandicola (Kaltenbach) cause economic losses and co-occur on walnut trees, but they have separate niche. Panaphis juglandis feeds on the upper (adaxial) surface of leaves while C. juglandicola feeds on the lower (abaxial) surface. Field surveys and controlled experiments in the field and laboratory were conducted to determine microhabitat selection by P. juglandis and C. juglandicola and the factors associated with this behavior. In the field, the two aphid species colonized a leaflet as follows: P. juglandis only, 16.5%; C. juglandicola only, 44.5%; and both species on same leaflet, 39%. C. juglandicola settled on the abaxial surface earlier than P. juglandis settled on the adaxial surface. P. juglandis showed the highest reproduction rate when they were in the erect position on the adaxial surface. C. juglandicola exhibited the highest reproduction rate when they were inverted and on the abaxial surface. Under a light intensity of 50,000 lux, 60.5% of C. juglandicola remained on the illuminated surface, while P. juglandis did not move from the illuminated surface. Through field and laboratory experiments, we found that P. juglandis preferred to settle on the adaxial surface and C. juglandicola preferred to settle on the abaxial surface. Leaf surface, gravity, and light were three physical factors affecting microhabitat selection by the two aphid species but light intensity was the key factor. This information will help to better understand the habitats of two aphid species, which may be helpful for walnut aphids management strategies such as the usage of insecticides option and spraying.

Individual variability in habitat selection by aquatic insects is driven by taxonomy rather than specialisation

Habitat selection, the choice of a habitat based on its perceived quality, is a key mechanism structuring freshwater communities. To date, individual variability in habitat selection has been neglected, and specialisation has never been considered in this type of studies. We examined the individual differences in the habitat selection of backswimmers (Notonectidae) and diving beetles (Dytiscidae). From each family, we selected one habitat generalist able to coexist with fish (Notonecta glauca, Dytiscus marginalis), and one species specialised to fishless habitats (Notonecta obliqua, Acilius sulcatus). We performed a mesocosm experiment quantifying the consistency in individuals' decisions in response to fish and vegetation structure, in relation to sex and specialisation. Neither the overall pattern of preferences nor consistency in individuals' decisions differed between specialists and generalists or between the sexes, but both were consistent within families. At the population level, backswimmers preferred fishless pools with submersed and floating macrophytes, while diving beetles showed no clear preferences. Individual decisions of backswimmers were consistent and likely driven by conspecific/heterospecific attraction. In diving beetles, individual decisions were primarily density-dependent. Our results reinforce the significance of habitat selectivity for aquatic community assembly, while suggesting a range of mechanisms driving variability in individual behaviour.

Grazing by wild red deer can mitigate nutrient enrichment in protected semi-natural open habitats

Eutrophication through atmospheric nutrient deposition is threatening the biodiversity of semi-natural habitats characterized by low nutrient availability. Accordingly, local management measures aiming at open habitat conservation need to maintain habitat-specific nutrient conditions despite atmospheric inputs. Grazing by wild herbivores, such as red deer (Cervus elaphus), has been proposed as an alternative to mechanical or livestock-based measures for preserving open habitats. The role of red deer for nutrient dynamics in protected open habitat types, however, is yet unclear. Therefore, we collected data on vegetation productivity, forage removal, quantity of red deer dung and nutrient concentrations in vegetation and dung from permanent plots in heathlands and grasslands (eight plots à 225 m² per habitat type) on a military training area inhabited by a large population of free-ranging red deer over one year. The annual nutrient export of nitrogen (N) and phosphorus (P) by red deer grazing was higher than the nutrient import through red deer excreta, resulting in an average net nutrient removal of 14 and 30 kg N ha⁻¹ a⁻¹ and 1.1 and 3.3 kg P ha⁻¹ a⁻¹ in heathlands and grasslands, respectively. Even when considering approximate local atmospheric deposition values, net nutrient depletion due to red deer grazing seemed very likely, notably in grasslands. Demonstrating that grazing by wild red deer can mitigate the effects of atmospheric nutrient deposition in semi-natural open habitats similarly to extensive livestock grazing, our results support the idea that red deer are suitable grazing animals for open habitat conservation.

Are several small wildlife crossing structures better than a single large? Arguments from the perspective of large wildlife conservation

Crossing structures for large wildlife are increasingly being constructed at major roads and railways in many countries and current guidelines for wildlife mitigation at linear infrastructures tend to advocate for large crossing structures sited at major movement corridors for the target species. The concept of movement corridors has, however, been challenged and pinching animal movements into bottlenecks entails risks. In this paper, I address the SLOSS dilemma of road ecology, i.e. the discussion whether a Single Large Or Several Small crossing structures along a linear barrier would produce the most benefit for wildlife, using the case of crossing structures for large wildlife in Sweden. I point out risks, ecological as well as practical, with investing in one large crossing structure and list a number of situations where it may be more beneficial to distribute the conservation efforts in the landscape by constructing several smaller crossing structures; for example, when the ecological knowledge is insufficient, when animal interactions are expected to be significant, when the landscape changes over time or when future human development cannot be controlled. I argue that such situations are often what infrastructure planning faces and that the default strategy, therefore, should be to distribute, rather than to concentrate passage opportunities along major transport infrastructures. I suggest that distributing passage opportunities over several smaller crossing structures would convey a risk diversification and that this strategy could facilitate the planning of wildlife mitigation. What to choose would however depend on, inter alia, landscape composition and ecology and on relationships amongst target species. A single large structure should be selected where it is likely that it can serve a large proportion of target animals and where the long-term functionality of the crossing structure can be guaranteed. New research is needed to support trade-offs between size and number of crossing structures. Cost-effectiveness analyses of wildlife crossing structures are currently rare and need to be further explored. Camera trapping and video surveillance of crossing structures provide opportunities to analyse details concerning, for example, any individual biases according to sex, age, status and grouping and any antagonism between species and individuals. Wildlife ecology research needs to better address questions posed by road and railway planning regarding the importance of specific movement routes and movement distances.

Conceptual and methodological advances in habitat-selection modeling: guidelines for ecology and evolution

Habitat selection is a fundamental animal behavior that shapes a wide range of ecological processes, including animal movement, nutrient transfer, trophic dynamics and population distribution. Although habitat selection has been a focus of ecological studies for decades, technological, conceptual and methodological advances over the last 20 yr have led to a surge in studies addressing this process. Despite the substantial literature focused on quantifying the habitat-selection patterns of animals, there is a marked lack of guidance on best analytical practices. The conceptual foundations of the most commonly applied modeling frameworks can be confusing even to those well versed in their application. Furthermore, there has yet to be a synthesis of the advances made over the last 20 yr. Therefore, there is a need for both synthesis of the current state of knowledge on habitat selection, and guidance for those seeking to study this process. Here, we provide an approachable overview and synthesis of the literature on habitat-selection analyses (HSAs) conducted using selection functions, which are by far the most applied modeling framework for understanding the habitat-selection process. This review is purposefully non-technical and focused on understanding without heavy mathematical and statistical notation, which can confuse many practitioners. We offer an overview and history of HSAs, describing the tortuous conceptual path to our current understanding. Through this overview, we also aim to address the areas of greatest confusion in the literature. We synthesize the literature outlining the most exciting conceptual advances in the field of habitat-selection modeling, discussing the substantial ecological and evolutionary inference that can be made using contemporary techniques. We aim for this paper to provide clarity for those navigating the complex literature on HSAs while acting as a reference and best practices guide for practitioners.

The spatial ecology of red deer under different land use and management scenarios: Protected areas, mixed farms and fenced hunting estates

The knowledge regarding the spatial ecology of red deer (Cervus elaphus) in different environments is crucial if effective management actions are to be designed. However, this knowledge continues to be scarce in the complex contexts of mixed land use and management circumstances. This study describes the spatial ecology of red deer monitored using GPS collars in Mediterranean ecosystems of South-Central Spain, considering the effect of individual and seasonal (food shortage period, rut, hunting season and food abundance period) factors on different land use and management scenarios, namely protected areas, mixed farms and fenced hunting estates. Our results showed less activity (ACT), a shorter daily range (DR) and a smaller home range (HR) during the food shortage period: ACT: 0.38 ± (SD) 0.12; DR: 3010.9 ± 727.3 m; and weekly HR: 122.2 ± 59.6 ha. With regard to land use, individuals were less ACT and had a smaller DR on fenced hunting estates (ACT: 0.24 ± 0.12; DR: 1946.3 ± 706.7 m) than in protected areas (ACT: 0.59 ± 0.12; DR: 4071.4 ± 1068.2 m) or on mixed farms (ACT: 0.57 ± 0.29; DR: 5431.1 ± 1939.5 m) in all the periods studied. Red deer selected land cover with forage and shelter when foraging and resting, respectively. When drive hunt events occurred (mixed farms and fenced hunting estates), the deer were more prone to select safer habitats (scrublands) and avoid open areas (crops or grasslands) than were their counterparts in protected areas. The patterns observed can be explained by sexual and seasonal differences as regards requirements, the response to disturbances and, interestingly, population management. Our results provide useful information with which to design scientifically-based species adaptive management in response to relevant and timely situations in Europe, such as the potential transmission of shared infections, vehicle collisions, and damage to crops and ecosystems.

Generalist bird exhibits site-dependent resource selection

Quantifying resource selection (an organism's disproportionate use of available resources) is essential to infer habitat requirements of a species, develop management recommendations, predict species responses to changing conditions, and improve our understanding of the processes that underlie ecological patterns. Because study sites, even within the same region, can differ in both the amount and the arrangement of cover types, our objective was to determine whether proximal sites can yield markedly different resource selection results for a generalist bird, northern bobwhite (Colinus virginianus). We used 5 years of telemetry locations and newly developed land cover data at two, geographically distinct but relatively close sites in the south-central semi-arid prairies of North America. We fit a series of generalized linear mixed models and used an information-theoretic model comparison approach to identify and compare resource selection patterns at each site. We determined that the importance of different cover types to northern bobwhite is site-dependent on relatively similar and nearby sites. Specifically, whether bobwhite selected for shrub cover and whether they strongly avoided trees, depended on the study site in focus. Additionally, the spatial scale of selection was nearly an order of magnitude different between the cover types. Our study demonstrates that-even for one of the most intensively studied species in the world-we may oversimplify resource selection by using a single study site approach. Managing the trade-offs between practical, generalized conclusions and precise but complex conclusions is one of the central challenges in applied ecology. However, we caution against setting recommendations for broad extents based on information gathered at small extents, even for a generalist species at adjacent sites. Before extrapolating information to areas beyond the data collected, managers should account for local differences in the availability, arrangement, and scaling of resources.

Size is not everything: differing activity and foraging patterns between the sexes in a monomorphic mammal

Abstract

Animals balance foraging with other activities, and activity patterns may differ between sexes due to differing physical requirements and reproductive investments. Sex-specific behavioural differences are common in sexually dimorphic mammals, but have received limited research attention in monomorphic mammals where the sexes are similar in body size. Eurasian beavers (Castor fiber) are obligate monogamous and monomorphic mammals and a good model species to study sex-specific differences. As females increase energy expenditure during reproduction, we hypothesized differing seasonal activity budgets, circadian activity rhythms and foraging patterns between male and reproducing female beavers. To test this hypothesis, we equipped adult beavers with VHF transmitters (N=41; 16 female, 25 male) and observed them throughout their active period at night from spring to late summer. Occurrence of their main activities (foraging, travelling and being in lodge) and use of food items (trees/shrubs, aquatic vegetation and herbs/grasses) were modelled to investigate sex-specific seasonal activity budgets and circadian activity rhythms. The sexes did not differ in time spent foraging across the season or night, but during spring, females resided more in the lodge and travelled less. Males and females both foraged on aquatic vegetation during spring, but females used this food source also during late summer, whereas males mostly foraged on trees/shrubs throughout the year. We conclude that seasonal activity budgets and foraging differ subtly between the sexes, which may relate to different energy budgets associated with reproduction and nutritional requirements. Such subtle seasonal behavioural adaptions may be vital for survival and reproduction of monomorphic species.

Significance statement

Activity budgets and foraging patterns of animals are key to their survival and may differ between males and females with different body sizes and physical requirements. In monomorphic species, where males and females have similar body sizes, fewer differences are expected, but may still be pronounced during certain times of the year. We modelled sex-specific seasonal activity budgets and circadian activity rhythms and use of food items in a monomorphic mammal, the Eurasian beaver. By treating season and time of day as a continuous variable rather than modelling differences within distinct predefined periods, we identified subtle sex-specific seasonal trends in activity budgets and use of food items.

Trading fear for food in the Anthropocene: How ungulates cope with human disturbance in a multi-use, suburban ecosystem

Resource distribution, predation risk and disturbance in space and time can affect how animals use their environment. To date few studies have assessed the spatiotemporal trade-off between resource acquisition and avoidance of risks and human disturbance in small protected areas embedded in an urban matrix. A better understanding of the forage-safety trade-off in urban protected areas (UPA) is key to the design of evidence-based approaches to deal with the ever-increasing human-wildlife impacts typical of UPA. Herein, we analyzed camera trap data to evaluate how two ungulate species trade fear for food in a 60 km² human-dominated UPA without natural predators. We found that wild boar (Sus scrofa) were predominantly active at night, while roe deer (Capreolus capreolus) showed a typical bimodal crepuscular activity pattern. Occupancy analysis indicated that deciduous forest and the presence of high seats for hunting played an important role in determining the space use of wild boar. For roe deer, we found indications that the presence of forest influenced space use, although the null model was retained among the top ranked models. Our results confirm that wild boar and roe deer are able to thrive in heavily human dominated landscapes characterized by intensive recreational use and hunting, such as protected areas embedded in an urban matrix.