Movement Ecology最新文献

Understanding species responses to anthropogenic disturbance is fundamental to ecology and conservation. However, behaviour and inter-individual variation in habitat selection can complicate our understanding of population-level responses to human disturbance, and the initiatives we design to address them. We use a dataset of 601,000 locations from 42 GPS tracked individuals of three sympatric species - king (n = 32), turkey (n = 5) and black vultures (n = 5) - in Costa Rica to explore behaviour-specific habitat selection in a mixed forest-agriculture landscape. We separate the movement data into three key behaviours (flight, feeding and roosting), and then compare their habitat selection preferences using a species-specific generalised mixed modelling framework. We find that the disturbance sensitive king vultures typically prefer mature forest to anthropogenically modified habitats when flying or roosting, however, the difference in relative strength of selection disappears in relation to feeding. These patterns likely reflect king vultures selecting to feed in agricultural landscapes where dead livestock such as cattle are abundant. We find strong evidence for individual heterogeneity in the degree to which they select for livestock pasture as feeding sites, suggesting repeatable individual-variation in foraging tactics. We also found a strong reduction in habitat selection for all behaviours as the distance to contiguous high-quality habitat increases, showing the reliance on tracts of contiguous mature forest for this species. In comparison, the disturbance tolerant species showed idiosyncratic responses to modified habitats, whereby black vultures selected mature forests for flight, but disturbed forest and grassland margins for feeding and roosting, and turkey vultures selected disturbed forest over mature forest and grassland margins for all movement behaviours. These findings represent the first GPS derived habitat selection study of king vultures, the apex obligate scavengers in lowland neotropical habitats and the first multispecies, guild-level, habitat selection analysis of vultures in the lowland neotropics. As expected, we find that king vultures have a stronger affinity to mature forests than their disturbance tolerant counterparts, however cattle farming is likely strongly subsidising some individuals' diets. Despite this, the marked reduction in king vulture habitat use with increasing distances from contiguous mature forests suggests the existence of a disturbance threshold, whereby the carrying capacity of king vulture populations may be reduced in highly anthropogenically modified landscapes.

Background: Saltatory movement strategies in animal search are well known, but their role in pursuit and localization of targets is less so. There are multiple features of forager-target interactions that may generate saltatory forager movement during pursuit and/or localization of the target. Here, we explore how the reliability of the target's signal and the dependence of the forager's perception of that signal on the forager's own motion can generate a variety of different continuous and saltatory pursuit patterns in evolved model foragers with stationary targets.

Methods: We use dynamical analyses of evolved forager nervous systems to show the possible mechanisms through which saltatory movement was generated and how signals influence those movements in a foraging animal.

Results: Saltatory movement during pursuit independent of signal was routinely found when the forager's perception depended on its movement. Saltatory movement patterns could also be generated in otherwise cruise-like behaviors when target signal either excited or inhibited ongoing forager movement. Additionally, the magnitude of the signal's influence was found to depend on proximity to the target during pursuit.

Conclusions: These models present hypotheses for future empirical research and emphasize the importance of exploring variation in animal movement during different phases of foraging.

Background: Migratory birds often exhibit within-species variation in migration routes and non-breeding areas, yet the mechanisms shaping these patterns remain poorly understood, particularly in high-latitude breeding populations. Several hypotheses have been proposed to explain why birds follow particular routes: optimal migration theory proposes that routes minimizing time or energy expenditure are favored, whereas the historical contingency hypothesis posits that routes are shaped by past range expansion, sometimes resulting in "suboptimal" migrations. We investigated whether distance minimization or historical contingency more strongly influenced migration routes in high-latitude breeding myrtle warblers (Setophaga coronata coronata), which indirect evidence previously suggested follow a shorter route to the Pacific Coast rather than the core Gulf Coast nonbreeding area.

Methods: We tracked the migrations of six Alaskan myrtle warblers using geolocators measuring both light and atmospheric pressure and inferred nonbreeding areas using hydrogen isotopes for a larger sample of birds breeding in Alaska, British Columbia, and Alberta (n = 167). Additionally, we compared migration tracks derived from light-level data exclusively with those that incorporated atmospheric pressure.

Results: Contrary to expectations, all geolocator-tracked birds and most with stable isotope data migrated to the southeastern United States, with just 5% of individuals possibly wintering on the Pacific Coast. Using pressure data allowed us to resolve migration routes and timing more precisely than traditional light-level methods, while also elucidating flight altitude and fine-scale elevational movements.

Conclusions: We found that myrtle warblers breeding in northwestern North America migrate farther than previously thought, despite being generally regarded as a relatively short-distance migrant. Our findings contradict previous studies that suggested myrtle warblers breeding in Alaska and northern British Columbia typically follow a shorter migration route to the Pacific Coast. This seemingly suboptimal route-similar to routes followed by the few other songbirds tracked from the region-is consistent with the historical contingency hypothesis, which proposes that migration routes reflect past range expansions. We recommend that researchers conducting geolocation studies leverage tags with barometers, as the additional atmospheric pressure data greatly improved our ability to characterize migration at a fine scale over the full annual cycle.

Background: Radio telemetry offers new opportunities for studying the movement of insects. One important prerequisite for using radio tags to study butterfly movement ecology is that tag weight and attachment do not significantly affect butterfly flight performance. Despite recent applications of telemetry in butterflies, a systematic evaluation of tag-to-body-weight thresholds for successful tagging has been lacking.

Methods: We tested ultra-light radio tags (0.13 g) on 117 individuals of 18 butterfly species under greenhouse and field conditions. Tag-to-body-weight ratios ranged from 5.6% to 77.8%. We used generalized linear mixed-effects models to identify predictors of flight success and used ROC analysis to determine the critical tag-to-body-weight threshold. Tag retention was also compared between thoracic and abdominal attachment sites.

Results: We found that a threshold of approximately 20% of body weight marks a critical point beyond which flight performance declines significantly. Abdominal tag attachment proved more reliable and stable than thoracic attachment, with lower detachment rates.

Conclusions: This study presents the first comprehensive evaluation of tag-to-body-weight thresholds and attachment methods in butterfly telemetry. The results provide practical guidance for planning radio telemetry studies of butterflies and for conducting further methodological research, such as into the effects of tagging on butterfly behavior, body condition, survival, and reproduction.

Background: Quantification of locomotion is central to the study of animal movement ecology. Although technological advances have enabled researchers to acquire high-resolution kinematic data, the associated methods often require multiple cameras and complicate the analysis process. Quantifying complex animal locomotion in three-dimensional space lacks an accurate, user-friendly method.

Methods: By combining deep learning tools and the pinhole camera model, we develop a novel method for reconstructing three-dimensional animal motion trajectories from monocular videos and analyzing kinematic data. We tested spatial precision and occlusion robustness in both aerial-based and ground-based scenarios. Subsequently, the method was applied to a bat-predation biomechanics study to demonstrate its capabilities. The application is based on low-cost single camera and does not require multiple devices or precise calibration.

Results: Our method rapidly reconstructs 3D trajectories for various animal movements, including flight, walking, and preying. The estimated 3D coordinates have an average bias of 0.09 m for aerial motion and 0.044 m for ground motion. Moreover, our method is extremely robust in distance estimation when faced with foreground occlusion. We extracted kinematic parameters from the 3D trajectory and gait frequencies from pixel area changes. Applying these parameters to biomechanical analysis, the results show that the obtained parameters can accurately describe the animal's movement.

Conclusions: This lightweight and cost-effective approach allows the analysis of animal locomotion in the natural environment. It also allows researchers to flexibly adapt it to their specific needs, facilitating intelligent monitoring of the wild animals and enhancing the understanding of their locomotion data.