Movement Ecology最新文献

Background: Studies on movement behaviour and habitat use are central to understanding the ecology of migratory animals and play an important role in the conservation and management of these species. However, individuals' spatial ecology can vary substantially, and failing to understand differences within or between populations may be problematic. In British Columbia, Canada, where Western Rattlesnakes reach their northern range limit, individuals undertake seasonal migrations between communal hibernacula and summer hunting grounds. Western Rattlesnakes commonly are associated with low-elevation grasslands and open Ponderosa pine habitats; however, recent work has shown that some animals undertake longer-distance migrations into higher-elevation Douglas-fir forests.

Methods: To further investigate multi-phenotypic migratory tactics and habitat use, we compiled all available raw data from radio-telemetry studies conducted on adult males (n = 139) between 2005 and 2019 from nine study sites across the Canadian range of Western Rattlesnakes. We quantify variation in migration distance, timing, altitudinal migration, home range sizes, and destination habitats used across our sample, and we use a linear mixed-modelling approach to assess potential drivers of long-distance migration.

Results: On average, snakes migrated 1364 ± 781 m (ranging from 105 m to 3832 m) from their overwintering dens. Migratory distance differed significantly between sites and was higher among individuals using forests as their migratory destination, yet within-habitat variation was high, suggesting a continuum of migratory phenotypes. Migratory distance was best predicted by two top models: terrain and combined effects (including terrain, physiology, and vegetation factors). Even these top-performing models, however, left much of the variation in migratory distance unexplained (r_s = 0.65 and 0.64 respectively based on k-fold cross-validation where k = 10), suggesting other factors not measured here, such as genetics and prey quality, may also be contributing.

Conclusions: Overall, this study provides critical knowledge on the movement ecology of a far-ranging reptile with implications for the conservation and management of the species in the far north where seasonal movements are commonplace. Our results shed light on some drivers of multi-phenotypic migration in a taxonomic group where this phenomenon has largely been unstudied, while contributing more broadly to a growing body of literature on migratory variation in animals.

Knowledge about habitat selection is crucial for ungulate management and conservation to handle competing land use. Thermal tolerance and access to food are two important drivers of habitat selection. Thus, moving into thermal shelter when temperatures increase may result in reduced energy intake e.g. mature forests providing thermal shelters through high canopy cover, but lower amounts of forage than more open habitats. Body size affects heat sensitivity, with larger animals being more sensitive. In this study, we investigated ambient temperature mediated habitat selection in three differently-sized, sympatric, deer species (moose, red deer and roe deer) during spring and summer in Sweden. We also assessed the trade-off between thermal shelter and forage availability. We used data from GPS-collared animals with a combination of land cover and airborne LIDAR data to quantify canopy cover as a proxy for thermal refuge and shrub cover as a proxy for forage availability. We found that temperature influenced habitat selection in all three deer species however with divergent patterns. During warmer daily temperatures, moose and red deer selected areas with more canopy cover for thermal shelter, however showing opposite patterns during warmer nights, suggesting patterns of thermoregulatory behaviour. Roe deer showed no influence of high temperatures on canopy cover selection however,, selected more strongly for areas with high canopy cover during colder temperatures i.e. showing contrasting patterns compared to moose and red deer, suggesting that canopy cover may be relatively less important for roe deer as temperature increase. All three species selected for shrub cover during warmer temperatures, which can provide both high forage availability and shade over bed sites for smaller deer species. Our findings indicate that canopy cover and shrub cover habitats appear to be important as temperatures increase, but their significance varies among species. Furthermore, our study highlights the complexity behind habitat selection in sympatric ungulate species, food intake and predation risk.

Background: Migration is a critical behavioural strategy across many taxa, allowing individuals to respond to seasonal shifts in environmental conditions and resource availability. Understanding animal movements, their plasticity, and their variation within-and among-individuals, is essential for assessing species resilience to environmental changes and developing effective conservation strategies. This study investigates the individual variation in migration patterns of the little bustard (Tetrax tetrax), one of Europe's most threatened birds, using tracking data from 66 individuals from Southwest Iberia.

Methods: We applied an innovative, yet straightforward approach, combining cluster analysis on net displacement values with boosted regression trees, to classify migration patterns of 105 year-round tracks and explore among-and within-individual variation in migratory behaviour. This approached was then complemented with traditional linear mixed models on the daily ND values throughout the year.

Results: Our analysis identified four main migration patterns: residents (63.8%), short-distance summer migrants (22.9%), medium-distance summer-winter migrants (6.7%), and long-distance summer migrants (5.7%). Different strategies were found in the same years and breeding areas, suggesting a high among-individual variation in migratory behaviour. Most individuals tracked for multiple years maintained consistent strategies (76%), suggesting a low intra-individual variation in migratory behaviour. This high among-and low within-individual variation was supported when using linear mixed models. While migratory polymorphism (resident vs. migrant) can provide populations with adaptability to environmental changes, the predominance of resident little bustards in Southwest Iberia may become maladaptive due to accelerating environmental changes in the region, particularly as a result of agriculture intensification and rising temperatures. Nevertheless, almost a quarter of all tracked individuals (24%) changed strategies between years, indicating some capacity to adapt to shifting conditions.

Conclusion: The framework presented here for little bustards can be easily applied to other tracking data, guiding conservation strategies and offering a practical tool for classifying movement patterns and exploring individual variation or plasticity.

Background: Behavioral responses of prey to predation risk have ecological impacts that can be as great as direct mortality. Risk response involves either behavioral changes or spatial avoidance, but it is not clear how prey decide between these strategies. Theory often suggests that prey pair responses to risks based on the hunting mode of the prey (hunting mode hypothesis), but prey may ignore hunting mode to prioritize responding to the most lethal predators (lethality hypothesis). Furthermore, prey may respond to the spatial distribution of these risks (risky places hypothesis) or respond only during the periods of highest risk (risky times hypothesis).

Methods: To test these hypotheses, we evaluated the behavioral responses of white-tailed deer (Odocoileus virginianus) to risks from two natural mesopredators and human sources of mortality. Specifically, we determined, for each source of risk, whether deer responded with behavioral state changes or spatial avoidance and whether this behavior changed with time (diurnally and annually). We collared and tracked 40 female and 29 male deer. To determine the response of deer to risk, we collected data on the distribution of coyotes (Canis latrans), bobcats (Lynx rufus), human modification, hunters, and roads. We used hidden Markov models to determine whether each covariate impacted the probability of transitioning between behavioral states and selection functions to determine whether deer spatially avoided each covariate.

Results: Generally, deer changed behavioral state in response to both mesopredators but avoided human modification. In response to mesopredators, deer consistently shifted to slower movement behavioral states. Spatial responses to human modification varied depending on the time of day. During daylight hours, deer selected for human modification, but during the crepuscular and nighttime period, deer avoided human modification.

Conclusions: Space use was most strongly related to more lethal humans, providing support for the lethality hypothesis. Despite prioritizing humans, mesopredators impacted behavioral state, suggesting that mesopredators still have important impacts on prey behavior. Finally, temporal patterns of avoidance align with other studies that indicate avoidance of predators is time-dependent, but further highlight the complex push-pull relationship of human modified areas on wildlife.

Background: The migration behavior of an organism is supposedly shaped by selection to best utilize favorable environmental conditions and unevenly distributed resources to maximize survival and reproductive success. Repeated migration tracks of individual birds allow us to estimate individual consistency in the spatio-temporal patterns of migration, and thereby better understand the potential constraints or drivers of migratory strategies.

Methods: We caught 48 long-billed dowitchers (Limnodromus scolopaceus) on their nest in Alaska in 2019 and equipped them with a 2 g Solar Argos PTT-100 satellite transmitter. We obtained repeat migration data from 19 individuals (11 males, 8 females) for up to four years. First, we quantified the within-individual repeatability in migratory route and migratory timing during both southward and northward migration. Second, we defined the home ranges for breeding, staging and non-breeding sites for each individual, and assessed their spatio-temporal overlap across consecutive years.

Results: Dowitchers were significantly more faithful to their wintering areas compared to any other stage of their annual cycle. Within their breeding range, individuals showed exploratory behavior and dispersed on average 159 [Formula: see text] 208 km (N = 42 bird-years) between breeding sites in consecutive years. The timing of migratory movements showed the highest individual repeatability when birds were at or near the wintering area.

Conclusion: Our study demonstrates that the within-individual repeatability in spatio-temporal patterns of migration and site use in dowitchers varies across different stages of the annual cycle. The birds' high fidelity to their wintering area contrasts sharply with a lack of fidelity to their breeding area. We suggest that the long-distance breeding dispersal - atypical for socially monogamous Scolopacids - is an adaptive response to unpredictable year-to-year variation in the physical and/or social environment during the breeding season.

Background: Information on reproductive success is crucial to understanding population dynamics but can be difficult to obtain, particularly for species that birth while denning. For grizzly (Ursus arctos) and polar bears (U. maritimus), den visits are impractical because of safety and logistical considerations. Reproduction is typically documented through direct observation, which can be difficult, costly, and often occurs long after den departure. Reproduction could be documented remotely, however, from post-denning movement data if discernable differences exist between females with and without cubs.

Methods: We trained support vector machines (SVMs) with eight variables derived from telemetry data of female grizzly (2000-2022) and polar bears (1985-2016) with or without cubs during seven periods with lengths ranging from 5 to 60 days starting at den departure. We assessed SVM classification accuracy by withholding two samples (one cub-present, one cub-absent), training SVMs with the remaining data, predicting classification of the withheld samples, and repeating this process for each sample combination. Additionally, we evaluated how classification accuracy for grizzly bears was influenced by sample size, length of the post-departure period, and frequency of standardized location estimates.

Results: Accuracy of predicting cub presence or absence was 87% for grizzly bears with only 5 days of post-departure data and increased to a maximum of 92% with 20 days of data. For polar bears, accuracy was 86% at 5 days post-departure and increased to a maximum of 93% at 50 days. Classification accuracy for grizzly bears increased from 76 to 90% when sample size increased from 10 to 30 bears while holding period length constant (30 days) but did not increase at larger sample sizes. When sample size was held constant, increasing the length of the post-departure period did not affect classification accuracy markedly.

Conclusion: Presence or absence of grizzly and polar bear cubs can be identified with high accuracy even when SVM models are trained with limited data. Detecting cub presence or absence remotely could improve estimates of reproductive success and litter survival, enhancing our understanding of factors affecting cub recruitment.

Animal groups come in diverse forms-from fish schools swimming in unison to crickets chirping in synchrony. Although these behaviors may seem considerably different to one another, they share a common mathematical core, and can therefore be considered in a unified manner. We discuss the commonalities and differences by synthesizing existing literature from both fields, encompassing both theoretical and empirical advances. We emphasize the crucial role of mixing, induced by individual movements, as a main differentiating factor. Along the way, we propose promising future directions for achieving a more comprehensive understanding of self-organized collective behavior.

Background: Dispersal includes three phases: emigration, transit, and immigration. The transit phase, which involves all movements between departure and arrival, is the least understood phase of dispersal. During the transit phase, individuals prospect their environment to gather information about potential breeding sites, thus enhancing their future reproductive success and survival. Studies have revealed a wide inter-individual variability in prospecting behaviours which may result from complex interactions between external and internal factors affecting the costs and benefits of prospecting. Age, sex, and season are expected to strongly influence prospecting behaviours, yet their effects are far from established.

Methodology: We investigated how age, sex, and season interact and influence prospecting movements throughout the transit phase. We analysed telemetry data from 106 immature Golden eagles (Aquila chrysaetos), whose natal dispersal involves a transit phase lasting several years. Using a trajectory segmentation method, we identified the areas sequentially prospected by each individual and we assessed the size, duration of use, and spacing between these areas to uncover spatio-temporal variations in prospecting behaviours.

Results: We confirmed our predictions, revealing strong influences of age, sex, and season, as well as their interactions, on prospecting movements. First, age had a significant effect on prospecting behaviours: individuals displayed a progressive spatial concentration of prospecting, consistent with patterns observed in colonial species. Second, seasonal variations were detected, with peaks of prospection in spring and autumn, likely resulting from the constraints imposed by territorial adult reproduction and weather-related flight conditions. Third we found sexual differences in movement patterns, with females prospecting over a larger spatial range than males, in line with the female-biased dispersal existing in most bird species. The level of inter-sexual differences and seasonal variations in prospecting behaviours differed depending on the age of the individuals.

Conclusions: Our work strongly supports that individuals adjust their prospecting behaviour in response to interacting intrinsic and extrinsic factors, in order to reduce prospecting movement costs while maximising the information gathered to inform their immigration decision.

Background: To navigate, animals balance nearby perceptual cues, random search, and memory. Isolating the role of memory, however, remains difficult.

Methods: Here, we use a mechanistic movement model to do so, simulating animals responding solely to local perceptual cues (i.e., lacking memory) and comparing their paths with actual routes taken. By comparing route efficiency, we evaluate whether actual routes incorporate knowledge beyond the perceptual range (i.e., spatial memory).

Results: We show that wolverines (Gulo gulo) employ spatial memory to plan routes through a rugged, mountainous landscape. Furthermore, we find that wolverines most commonly plan routes to destinations 5.3-9.8 km ahead. We estimate that route-planning saves wolverines, on average, 19.3 kcal per 135 min of movement.

Conclusions: Our findings provide a template for evaluating how free-living animals recall the world beyond their perceptual range, offer a window into the cognitive mechanics underpinning navigation for this species, and support adding wolverines to the primate-dominated list of species with complex spatial memory.