Moving in the Anthropocene : Global reductions in terrestrial mammalian movements
2018-01-26, Tucker, Marlee A., Böhning-Gaese, Katrin, Blake, Stephen, Davidson, Sarah C., Fiedler, Wolfgang, Kranstauber, Bart, LaPoint, Scott, Safi, Kamran, Wikelski, Martin, Mueller, Thomas
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.
Wind estimation based on thermal soaring of birds
2016, Weinzierl, Rolf, Bohrer, Gil, Kranstauber, Bart, Fiedler, Wolfgang, Wikelski, Martin, Flack, Andrea
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.
Here today, gone tomorrow : saving migratory animals
2011, Kays, Roland, Blake, Stephen, Cruz, Sebastian, Fiedler, Wolfgang, Kranstauber, Bart, Proanio, Carolina, Weinzierl, Rolf, Wikelski, Martin
Extinct might be a word you associate with animals that lived long ago, like the dinosaurs, but did you know that over 18,000 species are classified as "threatened" (susceptible to extinction) today? Scientists involved in wildlife conservation have a tough job; they're in charge of determining what needs to be done to prevent a species from becoming extinct. Habitat, food supply, and impacts of local human populations are just a few of the factors these scientists take into account. It's a lot to keep track of for a single location, but the job becomes even harder when it's a migratory animal. In this science project, you'll get a firsthand look at their job. You'll access real data about migratory birds and use satellite images to analyze their habitats, then come up with a conservation plan to protect the species from extinction.