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Browsing by Author "Hart, Vlastimil"

Now showing 1 - 3 of 3
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    Magnetic alignment enhances homing efficiency of hunting dogs
    Benediktova, Katerina; Adamkova, Jana; Svoboda, Jan; Painter, Michael Scott; Bartos, Ludek; Novakova, Petra; Vynikalova, Lucie; Hart, Vlastimil; Phillips, John; Burda, Hynek (2020-06-16)
    Despite anecdotal reports of the astonishing homing abilities in dogs, their homing strategies are not fully understood. We equipped 27 hunting dogs with GPS collars and action cams, let them freely roam in forested areas, and analyzed components of homing in over 600 trials. When returning to the owner (homewards), dogs either followed their outbound track ('tracking') or used a novel route ('scouting'). The inbound track during scouting started mostly with a short (about 20 m) run along the north-south geomagnetic axis, irrespective of the actual direction homewards. Performing such a 'compass run' significantly increased homing efficiency. We propose that this run is instrumental for bringing the mental map into register with the magnetic compass and to establish the heading of the animal.
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    Magnetoreception in the wood mouse (Apodemus sylvaticus): influence of weak frequency-modulated radio frequency fields
    Malkemper, E. Pascal; Eder, Stephan H. K.; Begall, Sobine; Phillips, John B.; Winklhofer, Michael; Hart, Vlastimil; Burda, Hynek (Nature Publishing Group, 2015-04-29)
    The mammalian magnetic sense is predominantly studied in species with reduced vision such as mole-rats and bats. Far less is known about surface-dwelling (epigeic) rodents with well-developed eyes. Here, we tested the wood mouse Apodemus sylvaticus for magnetoreception using a simple behavioural assay in which mice are allowed to build nests overnight in a visually symmetrical, circular arena. The tests were performed in the ambientmagnetic field or in a field rotated by 906.When plotted with respect tomagnetic north, the nests were bimodally clustered in the northern and southern sectors, clearly indicating that the animals used magnetic cues. Additionally,micewere tested in the ambientmagnetic field with a superimposed radio frequencymagnetic field of the order of 100 nT.Wood mice exposed to a 0.9 to 5 MHz frequency sweep changed their preference from north-south to east-west. In contrast tobirds, however, a constant frequency field tuned to the Larmor frequency (1.33 MHz) had no effect on mouse orientation. In sum, we demonstratedmagnetoreception in wood mice and provide first evidence for a radical-pair mechanism in a mammal.
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    Use of bio-loggers to characterize red fox behavior with implications for studies of magnetic alignment responses in free-roaming animals
    Phillips, John B.; Painter, Michael Scott; Blanco, Justin A.; Malkemper, E. Pascal; Anderson, Chris; Sweeney, Daniel C.; Hewgley, Charles W.; Cerveny, Jaroslav; Hart, Vlastimil; Burda, Hynek; Belotti, Elisa; Topinka, Vaclav (BMC, 2016-11-15)
    Background Spontaneous magnetic alignment (SMA), in which animals position their body axis in fixed alignments relative to magnetic field lines, has been shown in several classes of vertebrates and invertebrates. Although these responses appear to be widespread, the functional significance and sensory mechanism(s) underlying SMA remain unclear. An intriguing example comes from observations of wild red foxes (Vulpes vulpes) that show a ~fourfold increase in hunting success when predatory ‘mousing’ attacks are directed toward magnetic north-northeast. This form of SMA is proposed to receive input from a photoreceptor-based magnetoreception mechanism perceived as a ‘visual pattern’ and used as a targeting system to increase the accuracy of mousing attempts targeting hidden prey. However, similar to previous observational studies of magnetic orientation in vertebrates, direct evidence for the use of magnetic cues, and field-based experiments designed to characterize the biophysical mechanisms of SMA are lacking. Here, we develop a new approach for studies of SMA using triaxial accelerometer and magnetometer bio-loggers attached to semidomesticated red foxes. Results Accelerometer data were recorded from 415 ground-truth events of three behaviors exhibited by an adult red fox. A 5-nearest neighbor classifier was developed for behavioral analysis and performed with an accuracy of 95.7% across all three behaviors. To evaluate the generalizability of the classifier, data from a second fox were tested yielding an accuracy of 66.7%, suggesting the classifier can extract behaviors across multiple foxes. A similar classification approach was used to identify the fox’s magnetic alignment using two 8-way classifiers with differing underlying assumptions to distinguish magnetic headings in eight equally spaced 45° sectors. The magnetic heading classifiers performed with 90.0 and 74.2% accuracy, suggesting a realistic performance range for a classifier based on an independent set of training events equal in size to our sample. Conclusions We report the development of ‘magnetic ethograms’ in which the behavior and magnetic alignment of foxes can be accurately extracted from raw sensor data. These techniques provide the basis for future studies of SMA where direct observation is not necessary and may allow for more sophisticated experimental designs aimed to characterize the sensory mechanisms mediating SMA behavior.