92 research outputs found
Effects of Trophy Hunting Leftovers on the Ranging Behaviour of Large Carnivores: A Case Study on Spotted Hyenas
Get PDFHuman-related food resources such as garbage dumps and feeding sites have been shown to significantly influence space use, breeding success and population dynamics in a variety of animal species. In contrast, relatively little is known on the effects of unpredictable sources of food, such as carcasses discarded by hunters, on carnivore species. We evaluated the effect of elephant carcasses, mainly deriving from trophy hunting, on the ranging and feeding behavior of spotted hyenas (Crocuta crocuta) in the Okavango Delta, Botswana. Using data from hyenas monitored before and during carcass availability via GPS radio-collars and camera traps, we investigated changes in ranging and feeding behavior over time. Carcass availability influenced hyenas’ ranging behavior for an average of 10–12 days, after which their movements returned to patterns observed before carcass availability. In particular, we observed an increased spatial clustering of locations and reduced speeds (up to 15% less) between successive locations with carcass availability. Consistent feeding at carcasses during the first two weeks was typical, and some individuals fed from elephant carcasses for as long as 50 days. The impact and conservation value of hunting are often assessed based solely on the effects on the hunted species. Our results show that hunting remains can influence other species and suggest that such extra food could have important effects on critical life history processes and ultimately population dynamics. We recommend conservationists and wildlife managers evaluate management strategies and hunting practices regarding carcass disposal in order to incorporate the potential collateral impacts of hunting on non-hunted species in the same community
Dynamic Range Size Analysis of Territorial Animals: An Optimality Approach
Get PDFHome range sizes of territorial animals are often observed to vary periodically in response to sea-sonal changes in foraging opportunities. Here we develop the first mechanistic model focusedon the temporal dynamics of home range expansion and contraction in territorial animals. Wedemonstrate how simple movement principles can lead to a rich suite of range size dynamics, bybalancing foraging activity with defensive requirements and incorporating optimal behavioral rulesinto mechanistic home range analysis. Our heuristic model predicts three general temporal patternsthat have been observed in empirical studies across multiple taxa. First, a positive correlation be-tween age and territory quality promotes shrinking home ranges over an individual’s lifetime, withmaximal range size variability shortly before the adult stage. Second, poor sensory information,low population density, and large resource heterogeneity may all independently facilitate range sizeinstability. Finally, aggregation behavior towards forage-rich areas helps produce divergent homerange responses between individuals from different age classes. This model has broad applica-tions for addressing important unknowns in animal space use, with potential applications also inconservation and health management strategies
Functional diversity enhances the resistance of ecosystem multifunctionality to aridity in Mediterranean drylands
Get PDF1. We used a functional trait-based approach to assess the impacts of aridity and shrub encroachment on the functional structure of Mediterranean dryland communities (functional diversity (FD) and community-weighted mean trait values (CWM)), and to evaluate how these functional attributes ultimately affect multifunctionality (i.e. the provision of several ecosystem functions simultaneously).2. Shrub encroachment (the increase in the abundance/cover of shrubs) is a major land cover change that is taking place in grasslands worldwide. Studies conducted on drylands have reported positive or negative impacts of shrub encroachment depending on the functions and the traits of the sprouting or nonsprouting shrub species considered.3. FD and CWM were equally important as drivers of multifunctionality responses to both aridity and shrub encroachment. Size traits (e.g. vegetative height or lateral spread) and leaf traits (e.g. specific leaf area and leaf dry matter content) captured the effect of shrub encroachment on multifunctionality with a relative high accuracy (r2 = 0.63). FD also improved the resistance of multifunctionality along the aridity gradient studied.4. Maintaining and enhancing FD in plant communities may help to buffer negative effects of ongoing global environmental change on dryland multifunctionality
Contrasting movement strategies among juvenile albatrosses and petrels
Get PDFAnimal movement is a fundamental eco-evolutionary process yet the behaviour of juvenile animals is largely unknown for many species, especially for soaring seabirds which can range widely over the oceans at low cost. We present an unprecedented dataset of 98 juvenilealbatrosses and petrels (nine species), tracked for the first three months after independence. There was a startling diversity within and among species in the type and scale of post-natal movement strategies, ranging from area-restricted to nomadic patterns. Spatial scales were clustered in three groups that ranged from 6000km from the natal nest. In seven of the nine species, the orientation of flight paths and other movement statistics showed strong similarities between juveniles and adults, providing evidence for innate orientation abilities. Our results have implications for understanding the development of foraging behaviour in naïve individuals and the evolution of life history traits such as survival, lifespan and breeding strategy
How to scale up from animal movement decisions to spatiotemporal patterns: An approach via step selection
Get PDFUncovering the mechanisms behind animal space use patterns is of vital importance for predictive ecology, thus conservation and management of ecosystems. Movement is a core driver of those patterns so understanding how movement mechanisms give rise to space use patterns has become an increasingly active area of research.This study focuses on a particular strand of research in this area, based around step selection analysis (SSA). SSA is a popular way of inferring drivers of movement decisions, but, perhaps less well appreciated, it also parametrises a model of animal movement. Of key interest is that this model can be propagated forwards in time to predict the space use patterns over broader spatial and temporal scales than those that pertain to the proximate movement decisions of animals.Here, we provide a guide for understanding and using the various existing techniques for scaling up step selection models to predict broad-scale space use patterns. We give practical guidance on when to use which technique, as well as specific examples together with code in R and Python.By pulling together various disparate techniques into one place, and providing code and instructions in simple examples, we hope to highlight the importance of these techniques and make them accessible to a wider range of ecologists, ultimately helping expand the usefulness of SSA
Crop succession and habitat preferences drive the distribution and abundance of carabid beetles in an agricultural landscape
Get PDFThis study investigated how crop type and crop succession influence the distribution and the dynamics of abundance of two dominant carabid beetle species (Poecilus cupreus and Brachinus sclopeta) at two critical stages of their life cycle: the spring reproductive and overwintering periods. The study was conducted over 9 years in an agricultural landscape of western France using both pitfall and emergence traps located within and in the margins of fields of the five dominant crops in the study area. The two carabid species used crop and non-crop habitat types differently during the reproductive period and while overwintering, suggesting two different strategies of habitat use. Both species used within-field areas during the spring reproductive period. However, B. sclopeta was only active in oilseed rape while P. cupreus was also active in the other crops. Overall, data suggested a beneficial role of oilseed rape for both species. B. sclopeta emergence from overwintering occurred predominantly in the margins of fields cropped with oilseed rape the previous year. P. cupreus used both margins and within field areas as overwintering habitats. Results suggest that inter-field movements and active selection rather than differences in survival rates may explain distribution and abundance dynamics of these two carabid species in agricultural landscapes
Fire, humans, and climate: modeling distribution dynamics of boreal forest waterbirds
Get PDFUnderstanding the effects of landscape change and environmental variability on ecological processes is important for evaluating resource management policies, such as the emulation of natural forest disturbances. We analyzed time-series of detection/nondetection data using hierarchical models in a Bayesian multi-model inference framework to decompose the dynamics of species distributions into responses to environmental variability, spatial variation in habitat conditions, and population dynamics and interspecific interactions, while correcting for observation errors and variation in sampling regimes. We modeled distribution dynamics of 14 waterbird species (broadly defined, including wetland and riparian species) using data from two different breeding bird surveys collected in the Boreal Shield ecozone within Ontario, Canada. Temporal variation in species occupancy (2000 - 2006) was primarily driven by climatic variability. Only two species showed evidence of consistent temporal trends in distribution: ring-necked duck (Aythya collaris) decreased and red-winged blackbird (Agelaius phoeniceus) increased. The models had good predictive ability on independent data over time (1997 - 1999). Spatial variation in species occupancy was strongly related to the distribution of specific land cover types and habitat disturbance: fire and forest harvesting influenced occupancy more than did roads, settlements or mines. Bioclimatic and habitat heterogeneity indices and geographic coordinates exerted negligible influence on most species distributions. Estimated habitat suitability indices had good predictive ability on spatially independent data (Hudson Bay Lowlands ecozone). Additionally, we detected effects of interspecific interactions. Species responses to fire and forest harvesting were similar for 13 of 14 species; thus, forest harvesting practices in Ontario generally appeared to emulate the effects of fire for waterbirds over time scales of 10-20 years. Extrapolating to all 84 waterbird species breeding on the Ontario shield, however, suggested that up to 30 species may instead have altered (short-term) distribution dynamics due to forestry practices. Hence, natural disturbances are critical components of the ecology of the boreal forest and forest practices which aim to approximate them may succeed in allowing the maintenance of the associated species, but improved monitoring and modeling of large-scale boreal forest bird distribution dynamics is necessary to resolve existing uncertainties, especially on less-common species
Predator–Prey Movement Interactions: Jaguars and Peccaries in the Spotlight
Get PDFUnderstanding how landscape structure influences predator–prey dynamics is critical for conservation. This study analyzed jaguar‐peccary interactions, revealing uncommon close distances and prevalent 3–5 km ranges, especially away from grasslands. Low peccary densities increased interactions. Findings inform conservation strategies, highlighting landscape structure and prey density roles in maintaining Pantanal's balance
Priorities for translating goodwill between movement ecologists and conservation practitioners into effective collaboration
Get PDFAddressing ongoing biodiversity loss requires collaboration between conservation scientists and practitioners. However, such collaboration has proved challenging. Despite the potential importance of tracking animal movements for conservation, reviews of the tracking literature have identified a gap between the academic discipline of movement ecology and its application to biodiversity conservation. Through structured conversations with movement ecologists and conservation practitioners, we aimed to understand whether the identified gap is also perceived in practice, and if so, what factors hamper collaboration and how these factors can be remediated. We found that both groups are motivated and willing to collaborate. However, because their motivations differ, there is potential for misunderstandings and miscommunications. In addition, external factors such as funder requirements, academic metrics, and journal scopes may limit the applicability of scientific results in a conservation setting. Potential solutions we identified included improved communication and better presentation of results, acknowledging each other's motivations and desired outputs, and adjustment of funder priorities. Addressing gaps between science and implementation can enhance collaboration and support conservation action to address the global biodiversity crisis more effectively
Towards transient space-use dynamics: re-envisioning models of utilization distribution and their applications
Get PDFModels of utilization distribution in the form of partial differential equations have long contributed to our understanding of organismal space use patterns. In studies of infectious diseases, they are also being increasingly adopted in support of epidemic forecasting and scenario planning. However, as movement research shifts its focus towards large data collection and statistical modeling of movement trajectories, the development of such models has notably slowed. Here, we demonstrate the continued importance of modeling utilization distribution to predict variation in space-use patterns over time. We highlight the considerable, yet largely untapped, potential of such models, which have historically been limited by the steady-state assumption due to longstanding technical constraints. Now, by adapting existing computational tools primarily developed for material science and engineering, we can probe beyond the steady states and unlock from them a broad spectrum of complex, transient space-use dynamics. Our approach requires little experience in numerical analysis and is readily accessible to model practitioners in ecology and epidemiology across diverse systems where movement is a critical feature. We illustrated our approach using a mix of canonical and novel case studies, covering topics from wildlife translocation to vaccine deployment. First, we revisited a classical model of canid territorial formation driven by scent-mediated conspecific avoidance. Transient space-use analysis uncovered previously hidden spatial dynamics that are ecologically informative. Next, we applied our approach to long-distance movement on realistic landscapes. Habitat and land-use heterogeneities markedly affected the transient space-use dynamics and short-term forecasts, even when the steady state remained unchanged, with direct implications for conservation management. Finally, we modeled transient space-use dynamics as both a response to and a driver of transient population dynamics. The importance of this interdependence was shown in the context of epidemiology, in a scenario where the movement of healthcare personnel is influenced by local outbreak conditions that are stochastically evolving. By facilitating transient space-use analysis, our approach could lead to reevaluations of foundational ecological concepts such as home range and territory, replacing static with dynamic definitions that more accurately reflect biological realities. Furthermore, we contend that a growing interest in transient space-use dynamics, spurred by this work, could have transformative effects, stimulating new research avenues in ecology and epidemiology
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