Movement Ecology最新文献

Background: Many animals must adapt their movements to different conditions encountered during different life phases, such as when exploring extraterritorial areas for dispersal, foraging or breeding. To better understand how animals move in different movement phases, we asked whether movement patterns differ between one way directed movements, such as during the transient phase of dispersal or two way exploratory-like movements such as during extraterritorial excursions or stationary movements.

Methods: We GPS collared red foxes in a rural area in southern Germany between 2020 and 2023. Using a random forest model, we analyzed different movement parameters, habitat features-for example landclasses and distances to linear structures-and time variables (season and time of day) within red fox exploratory, transient and stationary movement phases to characterize phase specific movement patterns and to investigate the influence of different variables on classifying the movement phases.

Results: According to the classification model, the movement patterns in the different phases were characterized most strongly by the variables persistence velocity, season, step length and distance to linear structures. In extraterritorial areas, red foxes either moved straight with high persistence velocity, close to anthropogenic linear structures during transient movements, or more tortuously containing a higher variance in turning angles and a decrease in persistence velocity during exploratory-like movements. Transient movements mainly took place during autumn, whereas exploratory-like movements were mainly conducted during winter and spring.

Conclusion: Movement patterns of red foxes differ between transient, exploratory and stationary phases, reflecting displacement, searching and resident movement strategies. Our results signify the importance of the combined effect of using movement, habitat and time variables together in analyzing movement phases. High movement variability may allow red foxes to navigate in extraterritorial areas efficiently and to adapt to different environmental and behavioral conditions.

Background: Many species are exhibiting range shifts associated with anthropogenic change. For migratory species, colonisation of new areas can require novel migratory programmes that facilitate navigation between independently-shifting seasonal ranges. Therefore, in some cases range-shifts may be limited by the capacity for novel migratory programmes to be transferred between generations, which can be genetically and socially mediated.

Methods: Here we used 50 years of North American Breeding Bird Survey and Audubon Christmas Bird Count data to test the prediction that breeding and/or non-breeding range-shifts are more prevalent among flocking migrants, which possess a capacity for rapid social transmission of novel migration routes.

Results: Across 122 North American bird species, social migration was a significant positive predictor for the magnitude of non-breeding centre of abundance (COA) shift within our study region (conterminous United States and Southern Canada). Across a subset of 81 species where age-structured flocking was determined, migrating in mixed-age flocks produced the greatest shifts and solo migrants the lowest. Flocking was not a significant predictor of breeding COA shifts, which were better explained by absolute population trends and migration distance.

Conclusions: Our results suggest that social grouping may play an important role in facilitating non-breeding distributional responses to climate change in migratory species. We highlight the need to gain a better understanding of migratory programme inheritance, and how this influences spatiotemporal population dynamics under environmental change.

Grey mullets (family Mugilidae) are widespread across coastal, brackish, and freshwater habitats, and have supported fisheries for millennia. Despite their global distribution and commercial value, little is known about their movement ecology and its role in the co-existence of sympatric mullet species. Gaps in knowledge about migratory behaviour, seasonal occurrence, and movement scales have also impeded effective management, highlighting the need for further research. This study aimed to identify key habitats and timing of grey mullet presence across the Dutch Wadden Sea, North Sea, and freshwater areas, and to explore potential behavioral differences between two grey mullet species: thicklip mullet (Chelon labrosus) and thinlip mullet (Chelon ramada). Using acoustic telemetry, we tracked 86 tagged grey mullet over three years (thicklip mullet, N = 74; thinlip mullet, N = 12), combining data from 100 local acoustic receivers and the European Tracking Network. Both species were detected in the Wadden Sea from April to November, however, thinlip mullet arrived in the Wadden Sea earlier than thicklip mullet (median date = May 16 vs. June 7). Individual residency in the Wadden Sea lasted a median 97 days for thicklip mullet and 94 days for thinlip mullet. Thinlip mullet were also detected by more receivers and over a larger area than thicklip mullet, indicating differences in movement behaviour. Both species showed an affinity for receivers near major harbours, with thinlip mullet more often detected near fresh water outflows. Seasonal migrations between coastal and offshore waters were also observed, with one thinlip mullet returning to freshwater across consecutive years. North Sea detections spanned ten months, with a gap during the presumed spawning period (Jan-Feb). Our data suggest that thinlip mullet show a preference for deeper gullies while thicklip mullet may spend more time in shallow areas and flooded tidal flats. These findings highlight the importance of the Wadden Sea as a seasonal foraging ground and provide insights into the migratory patterns of grey mullets.

Background: Globally, temperate lakes are experiencing increases in surface water temperatures, extended periods of summer stratification, and decreases of both surface and deep water dissolved oxygen (DO). The distribution of fish is influenced by a variety of factors, but water temperature and dissolved oxygen are known to be particularly constraining such that with climate change, fish will likely feel the "squeeze" from above and below.

Methods: This study used acoustic telemetry to explore the effects of both thermal stratification and the deoxygenation of the hypolimnion on walleye (Sander vitreus) movements in a coastal embayment in Lake Ontario. Using historical water quality monitoring data, we documented seasonal and annual fluctuations in availability of both 'suitable' (all temperatures, DO > 3 mg/L) and 'optimum' (temperatures 18-23 °C, DO > 5mg/L) abiotic habitat for walleye and determined how these changes influenced walleye movements over a three-year period.

Results: Hypoxia (< 3 mg/L DO) was present in Hamilton Harbour every summer that data were available (32 of the 42 years between 1976 and 2018), with a maximum of 68.4% of the harbour volume in 1990. We found that thermal stratification and a hypoxic hypolimnion greatly reduced the volume of suitable habitat during our telemetry study. The reduction of suitable habitat significantly reduced walleye movement distances, however as the summer progressed, this remaining suitable habitat warmed into their thermal optimum range which was found to increase walleye movement distances. Despite the seemingly poor conditions, tagged walleye remained in the harbour for most of the year, and were the fastest growing individuals compared to other sampled coastal subpopulations in Lake Ontario.

Conclusions: Although we documented a reduction in the quantity of non-hypoxic habitat available to walleye, the water temperature of the remaining habitat increased throughout the summer into the physiologically optimum range for walleye and increased in metabolic quality. Many abiotic factors influence how, where, and what habitat fish choose to use, and this study reveals the importance of considering both habitat quality (temperature and dissolved oxygen) and quantity when evaluating fish habitat use and behaviour.

Background: The distribution of hosts and parasitoids across patches is a key factor determining the dynamics of host-parasitoid populations. To connect behavioral rules with population dynamics, it is essential to comprehend how individual-level dispersal behavior influences the distribution of individuals. Typically, a simple deterministic model has been used to describe this connection. This study explicitly derived the relationship between individual-level dispersal behavior and the distribution of individuals across patches, contrasting it with the conventional deterministic model.

Methods: A stochastic individual-based model was developed from a widely used deterministic host-parasitoid population model. Individual-level dispersal rules were simulated in the stochastic model without assuming the resulting distributions. The models assume that the dispersal of hosts and parasitoids is independent of conspecific density. The deterministic model can be seen as an approximation of the stochastic model, describing the outcomes of stochastic processes as their expected patterns. In addition to describing the relationship between dispersal behavior and distribution across patches, its consequences for population dynamics were also examined.

Results: The stochastic model revealed that the distribution of individuals among patches varies with the number of dispersing conspecifics, whereas the deterministic model assumes independence from conspecific density, indicating that the deterministic model fails to capture the outcomes of stochastic dispersal. The resulting density-dependent distributions of hosts and parasitoids lead to other density-dependent interactions between them, such as density-dependent parasitism risk for hosts and density-dependent searching efficiency for parasitoids, ultimately affecting population dynamics. For instance, while aggregation of parasitoids is stabilizing in the deterministic model, it can be both stabilizing and destabilizing in the stochastic model.

Conclusions: The stochastic model revealed that density-dependent distributions of hosts and parasitoids emerge when individuals disperse in a density-independent manner, significantly impacting existing host-parasitoid theory, which assumes density-independent distributions. To address this, the implications of emerging density dependencies for well-known results, such as the pseudointerference of parasitoids and the CV² > 1 rule, were discussed. Explicitly considering individual-level dispersal behavior is essential for understanding host-parasitoid interactions and population dynamics.

Background: Movement behavior strongly mediates species and environment interactions, yet our understanding is constrained by challenges tracking space use at fine spatiotemporal resolutions.

Methods: Using an automated telemetry array, we quantified variation in and drivers of space use for a nonbreeding population of migratory bird, the American redstart Setophaga ruticilla.

Results: We identified two distinct and common behaviors - territoriality and floating,- that were governed primarily by NDVI as a proxy of resource availability. Within seasons, declines in weekly resources increased the prevalence of forays and the area of space utilized. Floaters were less likely to maintain body condition throughout the nonbreeding season, which is expected to negatively influence fitness and survival.

Conclusions: Our study demonstrates that nonbreeding migratory birds exhibit a high degree of plasticity in space use that is driven primarily by resource availability but influenced by the dominance hierarchy within an individual's environment which are expected to have important implications on migratory populations.

Background: The habitat use of wild ungulates is determined by forage availability, but also the avoidance of predation and human disturbance. They should apply foraging strategies that provide the most energy at the lowest cost. However, due to data limitations at the scale of movement trajectories, it is not clear to what extent even well-studied species such as red deer (Cervus elaphus) trade-off between forage quality and quantity, especially in heterogeneous alpine habitats characterized by short vegetation periods.

Methods: We used remote sensing data to derive spatially continuous forage quality and quantity information. To predict relative nitrogen (i.e. forage quality) and biomass (i.e. forage quantity), we related field data to predictor variables derived from Sentinel-2 satellite data. In particular, our approach employed random forest regression algorithms, integrating various remote sensing variables such as reflectance values, vegetation indices and optical traits derived from a radiative transfer model. We combined these forage characteristics with variables representing human activity, and applied integrated step selection functions to estimate sex-specific summer habitat selection of red deer in open habitats within and around the Swiss National Park, an alpine Strict Nature Reserve.

Results: The combination of vegetation indices and optical traits greatly improved predictive power in both the biomass (R² = 0.60, Root mean square error (RMSE) = 88.55 g/m²) and relative nitrogen models (R² = 0.34, RMSE = 0.28%). Both female and male red deer selected more strongly for biomass (estimate = 0.672 ± 0.059 SE for normalised values for females, and 0.507 ± 0.061 for males) than relative nitrogen (estimate = 0.124 ± 0.062 for females, and 0.161 ± 0.061 for males, respectively). Females showed higher levels of use of the Swiss National Park.

Conclusions: Red deer in summer habitats select forage quantity over quality with little difference between sexes. Females respond more strongly to human activities and thus prefer the Swiss National Park. Our results demonstrate the capability of satellite data to estimate forage quality and quantity separately for movement ecology studies, going beyond the exclusive use of conventional vegetation indices.

Background: Animal-borne sensors ('bio-loggers') can record a suite of kinematic and environmental data, which are used to elucidate animal ecophysiology and improve conservation efforts. Machine learning techniques are used for interpreting the large amounts of data recorded by bio-loggers, but there exists no common framework for comparing the different machine learning techniques in this domain. This makes it difficult to, for example, identify patterns in what works well for machine learning-based analysis of bio-logger data. It also makes it difficult to evaluate the effectiveness of novel methods developed by the machine learning community.

Methods: To address this, we present the Bio-logger Ethogram Benchmark (BEBE), a collection of datasets with behavioral annotations, as well as a modeling task and evaluation metrics. BEBE is to date the largest, most taxonomically diverse, publicly available benchmark of this type, and includes 1654 h of data collected from 149 individuals across nine taxa. Using BEBE, we compare the performance of deep and classical machine learning methods for identifying animal behaviors based on bio-logger data. As an example usage of BEBE, we test an approach based on self-supervised learning. To apply this approach to animal behavior classification, we adapt a deep neural network pre-trained with 700,000 h of data collected from human wrist-worn accelerometers.

Results: We find that deep neural networks out-perform the classical machine learning methods we tested across all nine datasets in BEBE. We additionally find that the approach based on self-supervised learning out-performs the alternatives we tested, especially in settings when there is a low amount of training data available.

Conclusions: In light of these results, we are able to make concrete suggestions for designing studies that rely on machine learning to infer behavior from bio-logger data. Therefore, we expect that BEBE will be useful for making similar suggestions in the future, as additional hypotheses about machine learning techniques are tested. Datasets, models, and evaluation code are made publicly available at https://github.com/earthspecies/BEBE , to enable community use of BEBE.

Background: Migratory bats perform seasonal movements between their summer and winter areas. When crossing ecological barriers, like the open sea, they are exposed to an increased mortality risk due to energetically demanding long-distance flights and unexpected inclement weather events. How such barriers affect bat migratory movements is still poorly known.

Methods: To study bat migration patterns in response to an ecological barrier, we tagged 44 Nathusius' pipistrelles Pipistrellus nathusii with radio-transmitters on the East coast of the United Kingdom (UK) in spring 2021 and 2022. Subsequently, we assessed their movements to continental Europe using the MOTUS Wildlife Tracking System. We investigated route selection, timing of migration, overall migration speed and the influence of wind on airspeed, groundspeed and flight altitude during migratory overseas flights.

Results: Barrier effects cause migratory movements along the coast, and crossings over sea are shortened by deviating from the general migration direction. Males depart from the UK later in the season compared to females. The overall migration speed of females was 61 km/day and 88 km/day after their last detection in the UK. Our estimated airspeeds during oversea flights correspond well with airspeeds measured in a wind tunnel. Bats use wind adaptively to reduce airspeed when flying under tailwind and increase airspeed when flying under crosswind conditions. Departures over sea coincidence with tailwinds, enabling bats to more than double their airspeed, reaching ground speeds of up to 16.8 m/s (60.5 km/h). Our analysis suggests that bats select altitudes with favourable wind conditions and that they seek altitudes of several hundred meters, possibly extending up to 2,500 m. Low-altitude migration occurs when wind conditions are less favourable.

Conclusions: Our study demonstrates that bat migratory movements are highly influenced by barrier effects, sex-biased timing of migration and the adaptive use of winds. The results of our study contribute to a more comprehensive understanding of the decision-making process and adaptations bats employ during their migration. Elucidating bat migration patterns will enable us to develop effective conservation measures, for example in relation to the development and operation of coastal and offshore wind farms.

Background: Population growth and management in cervid species is dependent on reproductive ecology and factors influencing juvenile survival. Aspects of the female's movement behavior likely affect juvenile survival and movement patterns of pregnant and lactating females differ from non-pregnant or non-lactating females. Explanations for these differing movement patterns include change in nutritional demands for the female, isolation during parturition, and predator avoidance. White-tailed deer (Odocoileus virginianus) are an important managed cervid and a better understanding of their reproductive ecology, including the relationships between resources, movement, and juvenile survival, can better inform management.

Methods: Our objective was to determine if biological factors, such as female age, fawn age, number of fawns, as well as characteristics of prepartum range affected the female's postpartum daily movement or overlap of space used pre- and postpartum in Sussex County, Delaware, USA (2,420 km²). We collected GPS locations 2 weeks pre- and postpartum on 22 individual females from 2016 to 2017. In total, we recorded data from 263 days of postpartum movement for an average of 12 days/individual. We used a hierarchical modeling process to test biological factors and prepartum home range characteristics on two aspects of postpartum movement behavior, mean hourly displacements and daily use of prepartum home range.

Results: Mean hourly displacement decreased with increased female age and increased with number of known fawns alive and the female's home range size prior to parturition. We found that as fawns aged the doe increased use of the prepartum home range.

Conclusions: Our results indicate that younger females are moving more than older females during lactation potentially to access higher quality habitat. This increased movement increases nutritional demand and may play a role in fawn survival. Females are more likely to use more of their prepartum home range as fawns age, a finding congruent with previous research. This differentiation in metric response (movement rate vs. space use) emphasizes the complexities of movement ecology and the importance of considering multiple dependent variables for complex behavior.