Kranstauber, Bart
E-Mail-Adresse
ORCID
Geburtsdatum
Berufsbeschreibung
Nachname
Vorname
Name
Suchergebnisse Publikationen
Long-term movements and home-range changes : Rapid territory shifts in meerkats
1. Territoriality and stable home ranges are a common space-use pattern among animals. These ranges provide its inhabitants with important resources and thus favourable territories are associated with an increased fitness. While the role of territory quality and changes of territory ownership have often been investigated, the changes of territorial boundaries have been less studied.
2. Here, we investigated space-use changes in a social mammal species, applying a novel analytical approach, calculating long-term dissimilarity in space use using distancematrices based on periodic utilization distributions. This approach makes it possible to identify different space-use patterns, which cannot be distinguished by only considering changes between consecutive time periods.
3. We analysed meerkat (Suricata suricatta) movements of a total of 24 different groups over a 16-year period, resulting in 134 group years. We then correlated the identified home-range changes to life-history events and possible environmental drivers.
4. Groups had stable territories for several years before they abandoned their home range mostly to move quickly to new areas where they again remained for several years. Of 26 identified sudden shifts, 22 occurred in the summer months and often involved distances larger than the original home-range size. Home-range movements that were close together in time were often also spatially clustered and moved in a similar direction. These shifts were often preceded by more frequent interactions between groups, but did not seem to be a product of direct displacements by other groups. The normalized difference vegetation index as a measure of food production and social factors such as dominance changes did not correlate to changes.
5. Against our expectation space-use changes were not accumulations of small changes, but more often involved long-distance moves into unknown ranges. This means that the groups enter areas where they cannot profit from local knowledge. The methods used identify episodes of long stability alternated by sudden changes in meerkats and in general provides insight into long-term space use. Our methods can be used to analyse long-term space use, either within or across species.
Moving in the Anthropocene : Global reductions in terrestrial mammalian movements
Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission.
How Displaced Migratory Birds Could Use Volatile Atmospheric Compounds to Find Their Migratory Corridor : A Test Using a Particle Dispersion Model
Olfaction represents an important sensory modality for navigation of both homing pigeons and wild birds. Experimental evidence in homing pigeons showed that airborne volatile compounds carried by the winds at the home area are learned in association with wind directions. When displaced, pigeons obtain information on the direction of their displacement using local odors at the release site. Recently, the role of olfactory cues in navigation has been reported also for wild birds during migration. However, the question whether wild birds develop an olfactory navigational map similar to that described in homing pigeons or, alternatively, exploit the distribution of volatile compounds in different manner for reaching the goal is still an open question. Using an interdisciplinary approach, we evaluate the possibilities of reconstructing spatio-temporally explicit aerosol dispersion at large spatial scales using the particle dispersion model FLEXPART. By combining atmospheric information with particle dispersion models, atmospheric scientists predict the dispersion of pollutants for example, after nuclear fallouts or volcanic eruptions or wildfires, or in retrospect reconstruct the origin of emissions such as aerosols. Using simple assumptions, we reconstructed the putative origin of aerosols traveling to the location of migrating birds. We use the model to test whether the putative odor plume could have originated from an important stopover site. If the migrating birds knew this site and the associated plume from previous journeys, the odor could contribute to the reorientation towards the migratory corridor, as suggested for the model scenario in displaced Lesser black-backed gulls migrating from Northern Europe into Africa.
First three-dimensional tracks of bat migration reveal large amounts of individual behavioral flexibility
Animal migration has fascinated humans at least since Aristotle's time, but we only started to understand its details thanks to the famous "arrow storks" in the 19th century that returned to Europe with an arrow in their body, providing the first clues of African wintering sites. Bird migration has received a large amount of attention since then, but knowledge about migration of other organisms, even small passerine birds, remains rudimentary (Bowlin et al. 2010).
Integrating animal movement with habitat suitability for estimating dynamic migratory connectivity
High-resolution animal movement data are becoming increasingly available, yet having a multitude of empirical trajectories alone does not allow us to easily predict animal movement. To answer ecological and evolutionary questions at a population level, quantitative estimates of a species’ potential to link patches or populations are of importance.
Objectives
We introduce an approach that combines movement-informed simulated trajectories with an environment-informed estimate of the trajectories’ plausibility to derive connectivity. Using the example of bar-headed geese we estimated migratory connectivity at a landscape level throughout the annual cycle in their native range.
Methods
We used tracking data of bar-headed geese to develop a multi-state movement model and to estimate temporally explicit habitat suitability within the species’ range. We simulated migratory movements between range fragments, and calculated a measure we called route viability. The results are compared to expectations derived from published literature.
Results
Simulated migrations matched empirical trajectories in key characteristics such as stopover duration. The viability of the simulated trajectories was similar to that of the empirical trajectories. We found that, overall, the migratory connectivity was higher within the breeding than in wintering areas, corroborating previous findings for this species.
Conclusions
We show how empirical tracking data and environmental information can be fused for meaningful predictions of animal movements throughout the year and even outside the spatial range of the available data. Beyond predicting migratory connectivity, our framework will prove useful for modelling ecological processes facilitated by animal movement, such as seed dispersal or disease ecology.
Wind estimation based on thermal soaring of birds
The flight performance of birds is strongly affected by the dynamic state of the atmosphere at the birds' locations. Studies of flight and its impact on the movement ecology of birds must consider the wind to help us understand aerodynamics and bird flight strategies. Here, we introduce a systematic approach to evaluate wind speed and direction from the high-frequency GPS recordings from bird-borne tags during thermalling flight. Our method assumes that a fixed horizontal mean wind speed during a short (18 seconds, 19 GPS fixes) flight segment with a constant turn angle along a closed loop, characteristic of thermalling flight, will generate a fixed drift for each consequent location. We use a maximum-likelihood approach to estimate that drift and to determine the wind and airspeeds at the birds' flight locations. We also provide error estimates for these GPS-derived wind speed estimates. We validate our approach by comparing its wind estimates with the mid-resolution weather reanalysis data from ECMWF, and by examining independent wind estimates from pairs of birds in a large dataset of GPS-tagged migrating storks that were flying in close proximity. Our approach provides accurate and unbiased observations of wind speed and additional detailed information on vertical winds and uplift structure. These precise measurements are otherwise rare and hard to obtain and will broaden our understanding of atmospheric conditions, flight aerodynamics, and bird flight strategies. With an increasing number of GPS-tracked animals, we may soon be able to use birds to inform us about the atmosphere they are flying through and thus improve future ecological and environmental studies.
Similarity in spatial utilization distributions measured by the earth mover's distance
Estimating the similarity in space use (spatio-temporal home range overlap) of animals is important for many questions regarding behavioural ecology, wildlife management and conservation. The current methods that calculate joint space use generally do not account for proximity in space use, as all of them rely on the differences between the exact spatial overlay of utilization distributions, while spatial distances between distributions should be considered to truly quantify similarity. We implemented the earth mover's distance (EMD), a spatially explicit method, that quantifies similarity between utilization distributions by calculating the effort it takes to shape one utilization distribution landscape into another, hence EMD. The EMD is a method commonly used in image retrieval applications, and we propose its use to calculate similarity in space use in the framework of movement ecology. We show that the EMD is a consistent and useful as well as versatile measure of overlap and provide an easy to use implementation in the r package move.
True navigation in migrating gulls requires intact olfactory nerves
During migratory journeys, birds may become displaced from their normal migratory route. Experimental evidence has shown that adult birds can correct for such displacements and return to their goal. However, the nature of the cues used by migratory birds to perform long distance navigation is still debated. In this experiment we subjected adult lesser black-backed gulls migrating from their Finnish/Russian breeding grounds (from >60°N) to Africa (to < 5°N) to sensory manipulation, to determine the sensory systems required for navigation. We translocated birds westward (1080 km) or eastward (885 km) to simulate natural navigational challenges. When translocated westwards and outside their migratory corridor birds with olfactory nerve section kept a clear directional preference (southerly) but were unable to compensate for the displacement, while intact birds and gulls with the ophthalmic branch of the trigeminal nerve sectioned oriented towards their population-specific migratory corridor. Thus, air-borne olfactory information seems to be important for migrating gulls to navigate successfully in some circumstances.