Movement Ecology最新文献

Background: Pelagic seabirds forage over vast areas, and their movements and diet provide valuable insights into environmental conditions that are otherwise difficult to observe. Snow petrels Pagodroma nivea forage largely on sea-ice-associated prey, rendering the energy-rich lipids into stomach oil, some of which is spat defensively at nest sites where it accumulates over tens of millennia. These deposits contain chemical signatures of the foraging environment, providing a unique biological archive of sea-ice conditions in the pre-satellite era. Accurate interpretation of these proxies, however, requires detailed knowledge of foraging ranges-how far the petrels travel, the habitats they target, and how these behaviours vary with season, colony location, and sex.

Methods: To estimate foraging ranges at three colonies located 180-200 km inland in Dronning Maud Land, we tracked 94 snow petrels (34 with light-based geolocators and 60 with GPS loggers). We tested whether foraging latitude is associated with the latitude of the ice edge, estimated via satellite remote sensing. We then projected potential foraging ranges for all known colonies in the study area to reexamine assumptions made in paleoclimate studies.

Results: During most breeding stages, and across breeding seasons, core foraging areas were centred approximately 2° south of the outer sea-ice edge and tracked this habitat as it receded during the spring melt. Female snow petrels were approximately 7% lighter than males but foraged at similar distances and in similar areas. Foraging ranges differed little between colonies but substantially between breeding stages. For example, average median range was ~1400 km (95% CI 1340-1470 km) during the pre-laying exodus vs. ~530 (430-660) km during brood-guard.

Conclusions: Snow petrel stomach-oil deposits potentially integrate environmental conditions over greater and more seasonally variable areas than previously assumed, probably with a bias towards conditions in the marginal ice zone (outer pack ice) during the early summer when stomach oil deposition due to nest competition is likely greatest. Our results are consistent with the hypothesis that snow petrel breeding range in the western Weddell Sea is limited by access to foraging habitat, such as coastal polynyas. Although tracking data from other colonies would be useful to confirm the generality of our foraging range estimates, we hypothesise that as sea ice fluctuated over previous glacial-interglacial cycles, this regulated breeding distribution across the region.

Background: Individual foraging site fidelity is a common mechanism for dealing with environmental variability across marine predator species. However, there has been little research on long-term individual repeatability to date, especially over time periods where significant environmental and ecological change has occurred. The grey seal is a long-lived pinniped species that forages on the Scotian Shelf and in the Gulf of St. Lawrence, two ecosystems which are characterized by spatio-temporal variability in oceanographic conditions and have also undergone dramatic changes to ecological structuring and functioning in recent decades.

Methods: Between 1995 and 2018, 22 adult grey seals (17 females, 5 males) were repeatedly instrumented with tracking devices in two or three different years. We fitted continuous-time correlated random walk state-space models to estimate grey seal locations and move persistence along tracks. We then calculated the kernel utilization distribution overlap for home ranges (99%) and core areas (50%) within and between individuals as well as for areas (95%) associated with apparent foraging behaviour (move persistence < 0.5).

Results: Here, we show that grey seals demonstrated long-term moderate to high levels of fidelity in home ranges between years. By contrast, there was little between-year overlap in core areas used. Nevertheless, areas associated with low move persistence, inferred as area-restricted search and hence where foraging maybe more likely, were highly consistent between years. Habitat overlap between individuals was low across years.

Conclusions: Home range fidelity appears to persist over the life of grey seals, despite significant environmental and ecological change occurring within their habitat during our study period. These findings contribute to understanding the potential consequences of projected environmental change for this and other central place foraging species.

Background: Site fidelity, the tendency to return to previously visited locations, is common across a wide range of taxa and ecosystems. Site fidelity can benefit animals by improving foraging efficiency, reducing movement costs, and increasing reproductive success. Nevertheless, considerable variation exists within and among species in the nature and magnitude of site fidelity, and the mechanisms underpinning this variation are poorly understood. One hypothesis for explaining variation in site fidelity suggests that in predictable resource landscapes, fidelity should be conditional on prior reproductive success (win-stay, lose-switch). Alternatively, animals occupying less predictable resource landscapes should make greater use of cues from their current environment and site fidelity should scale inversely with the magnitude of environmental heterogeneity.

Methods: We investigated the causes (e.g., prior reproductive success, foodscape heterogeneity) and consequences (e.g., nutritional condition, neonate survival) of intraspecific variation in site fidelity during spring and summer among three bighorn sheep (Ovis canadensis) populations occupying a low-elevation grassland and two alpine ecosystems. We used distance-based metrics to quantify site fidelity at inter-annual, inter-month and inter-week scales to better understand the behavioral strategies employed by bighorn sheep to mitigate environmental variation and optimize foraging opportunities.

Results: Site fidelity varied considerably among study areas and across temporal scales. Prior reproductive success was not an important predictor of site fidelity by bighorn sheep, and instead, site fidelity appeared to be influenced by quality and predictability of forage resources within individual home ranges. Despite consistency of this effect, however, we found little evidence that site fidelity improved nutritional condition of female sheep or neonate survival to 120 days.

Conclusions: Our results generally support the notion that environmental conditions shaped the strength of site fidelity across temporal scales. Yet, the benefits of site fidelity were limited, at least based on the performance metrics we measured. Continuing to parse the complex mechanisms underpinning variation in site fidelity will shed important light on the capacity of animals to adjust to an unpredictable and changing environment.

1. Effective conservation planning and conflict mitigation can hinge on accurately modelling wildlife movement paths (WMPs), yet progress is hindered by both a shortage of reliable methods and limited data. The critical challenge, therefore, is to devise limited-data models that faithfully reproduce elusive species' movements and deliver actionable insights for human-wildlife conflict management. 2. We introduce the Enhanced Resource Selection Function-Vector-network Iterative Pathfinding Algorithm (ERSF-VIPA), a novel framework for simulating WMPs with limited data. Drawing on historical occurrence records of Asian elephants (Elephas maximus), we assume individuals make rational, goal-driven decisions based on local environmental knowledge. The ERSF employs a random forest on a hexagonal grid to estimate nonlinear resource-selection probabilities, while VIPA conducts an iterative, node-to-node search across that hexagonal vector network-scoring each candidate by combining selection probability with cubic distance coefficients to ensure ecological validity and energetic efficiency. 3. The model demonstrates high accuracy, with 90.3% of the 68 simulated paths approximating the observed paths with an average maximum deviation of 418 m. These findings underscore the model's robustness and its capacity to translate limited tracking data into actionable insights for conservation. 4. ERSF-VIPA operates using only coarse, non-continuous historical data that lack precise timestamps or spatial accuracy. By operating with minimal data requirements, ERSF-VIPA demonstrates exceptional extensibility and broad applicability for reconstructing movement paths of elusive wildlife species. Its proven accuracy in simulating Asian elephant paths further positions it as a potentially powerful decision-support framework for real-time animal monitoring and proactive human-wildlife conflict mitigation.

Background: Understanding the movement of organisms is critical for species conservation in the context of changing landscapes and climate. As climatic extremes impact the United States Great Basin, quantifying the movements of native fishes like Lahontan cutthroat trout (Oncorhynchus clarkii henshawi) is vital for facilitating their persistence. These climatic extremes are projected to alter flow regimes, specifically, reducing hydrologic connectivity needed to maintain populations. By studying fish movement patterns during streamflow recession and baseflow conditions, we can identify the factors responsible for movement and habitat selection to better manage these factors in a changing world.

Methods: We radio tagged 57 stream-resident Lahontan cutthroat trout from early summer to fall in 2021 and 2022 in the Summit Lake watershed (NV, USA). The location of each fish was associated with local hydraulic, physical habitat, invertebrate drift concentration, and water quality data to assess which factors impact habitat selection, abandonment, and overall movement. Linear mixed effects models were used to assess which factors were associated with trout movement. Density estimates from electrofishing were used as a proxy to assess habitat selection using multiple linear regression modeling.

Results: Stream-resident trout displayed little movement during streamflow recession and baseflow conditions, with median daily movements of 0.3 m/day and a median home range of 10.2 m; these results suggest even less movement than those reported in previous studies. Declines in riffle crest thalweg (RCT) depth were the primary factor associated with increases in distance traveled, yet there were only four observed movements below RCT depths of 5 cm and no observations below 4 cm. Woody debris, mean maximum stream depth, and availability of mid-channel pool habitat were the strongest predictors of habitat selection.

Conclusions: The findings from this study suggest that stream-resident trout movement occurs when absolutely necessary, such as escaping drying reaches or avoiding risk of predation in shallow water. We suggest that watershed managers implement low-flow hydrologic monitoring to identify vulnerable stream reaches, with an emphasis on preserving streamflow connectivity for stream-rearing salmonids. Additionally, this emphasizes the importance of tracking movements for species of interest as a strategy to identify factors potentially reducing population fitness.

Large herbivores play a central role in dryland ecosystems, influencing vegetation dynamics, nutrient cycling, and trophic interactions. While they are adapted to cope with harsh climates, their persistence is increasingly threatened by anthropogenic pressures. However, the behavioural strategies they use to cope with these combined environmental challenges remain understudied. Using multi-year accelerometer data from springbok (Antidorcas marsupialis), greater kudu (Tragelaphus strepsiceros), and common eland (Taurotragus oryx) in northern Namibia, we examined diel and seasonal behaviour in relation to vegetation greenness (NDVI), temperature, lunar phase, and individual differences. While activity was mainly diurnal, nocturnal behaviour was closely linked to the lunar cycle: during moonlit nights, antelope, particularly springbok, increased feeding and walking while reducing rumination and resting. Seasonal patterns tracked plant phenology, with head-up feeding rising sharply during the woody flush at the onset of the green season, while head-down feeding followed grass growth but declined as the season progressed. Seasonal dynamics differed from studies in other regions, suggesting that prolonged dryness and mild winters favour energy conservation over compensatory feeding. Hierarchical partitioning showed that feeding behaviours were environmentally cued, driven by plant phenology and seasonality, whereas walking, rumination, and resting were shaped mainly by individuality. Ambient temperature added little explanatory power, indicating that long-term rhythms are governed more by vegetation cycles and photoperiod than by thermal conditions. Our findings reveal that external cues such as phenology and moonlight synchronise foraging across individuals, while intrinsic factors contribute most to the variation in walking, ruminating and resting, potentially buffering populations against environmental variability. Recognising the combined influence of environmental cues and individual variation is essential for predicting how dryland herbivores will respond to climate and land-use change.

Background: Characterizing the diversity of migration behaviors from the individual to the population level is essential for understanding how organisms respond to environmental variation and how these responses affect survival and habitat use. Lake sturgeon (Acipenser fulvescens) is a species of special concern in the Laurentian Great Lakes that are long-lived and generally classified as intermittent, adfluvial spawners. Observations of lake sturgeon movements at ecologically relevant spatiotemporal scales have shown that migration behavior often varies among individuals within the same population. However, studies on individual populations, particularly when focused only on a part of the life cycle (e.g., often spawning), provide just a partial understanding of the species' full migratory scope and processes underlying expression of different migratory behaviors. To better understand lake sturgeon migratory diversity, we characterized and compared migratory behaviors of six lake sturgeon populations occupying environments that varied in habitat availability and connectivity in different Laurentian Great Lakes.

Methods: Sequence analysis combined with agglomerative hierarchical clustering and visual inspection of daily location data were used to identify distinct lake sturgeon migratory behaviors present in each population.

Results: Seven distinct migratory behaviors were identified based on differential patterns of lake and river use that encompass spawning and other seasonal periods. Behaviors were categorized as annual spring river, intermittent spring river, intermittent two-step, annual summer river, annual winter river, and annual interlake migrants along with river residents. The presence and frequency of migratory behaviors varied substantially among populations.

Conclusions: Our study demonstrated that migratory diversity is a general feature of lake sturgeon life history that may be partially shaped by habitat availability and connectivity. Given these results, we propose a conceptual model that links habitat availability and connectivity to migratory diversity and predict a positive association between them. This updated framework provides a cohesive basis for understanding lake sturgeon migratory behavior across variable ecological contexts in the Laurentian Great Lakes and will help promote future research to refute or refine the model.