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      Orientation and navigation in Bufo bufo: a quest for repeatability of arena experiments

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      Herpetozoa

      Pensoft Publishers

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          Abstract

          Research on navigation in animals is hampered by conflicting results and failed replications. In order to assess the generality of previous results, male Bufo bufo were collected during their breeding migration and translocated to two testing sites, 2.4 and 2.9 km away, respectively, from their breeding pond in the north of Vienna (Austria). There each toad was tested twice for orientation responses in a circular arena, on the night of collection and four days later. On the first test day, the toads showed significant axial orientation along their individual former migration direction. On the second test day, no significant homeward orientation was detected. Both results accord with findings of previous experiments with toads from another population. We analysed the potential influence of environmental factors (temperature, cloud cover and lunar cycle) on toad orientations using a MANOVA approach. Although cloud cover and lunar cycle had small effects on the second test day, they could not explain the absence of homeward orientation. The absence of homing responses in these tests may be either caused by the absence of navigational capabilities of toads beyond their home ranges, or by inadequacies of the applied method. To resolve this question, tracking of freely moving toads should have greater potential than the use of arena experiments.

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          Most cited references 51

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          Chemical magnetoreception in birds: the radical pair mechanism.

          Migratory birds travel vast distances each year, finding their way by various means, including a remarkable ability to perceive the Earth's magnetic field. Although it has been known for 40 years that birds possess a magnetic compass, avian magnetoreception is poorly understood at all levels from the primary biophysical detection events, signal transduction pathways and neurophysiology, to the processing of information in the brain. It has been proposed that the primary detector is a specialized ocular photoreceptor that plays host to magnetically sensitive photochemical reactions having radical pairs as fleeting intermediates. Here, we present a physical chemist's perspective on the "radical pair mechanism" of compass magnetoreception in birds. We outline the essential chemical requirements for detecting the direction of an Earth-strength approximately 50 microT magnetic field and comment on the likelihood that these might be satisfied in a biologically plausible receptor. Our survey concludes with a discussion of cryptochrome, the photoactive protein that has been put forward as the magnetoreceptor molecule.
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            Magnetite-based magnetoreception.

             J. Kirschvink (2001)
            Orientation, navigation, and homing are critical traits expressed by organisms ranging from bacteria through higher vertebrates. Sensory systems that aid such behavior have provided key selective advantages to these groups over the past 4 billion years, and are highly evolved; magnetoreception is no exception. Across many species and groups of organisms, compelling evidence exists that the physical basis of this response is tiny crystals of single-domain magnetite (Fe3O4). It is the opinion of the authors that all magnetic field sensitivity in living organisms, including elasmobranch fishes, is the result of a highly evolved, finely-tuned sensory system based on single-domain, ferromagnetic crystals.
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              Forty years of olfactory navigation in birds.

              Forty years ago, Papi and colleagues discovered that anosmic pigeons cannot find their way home when released at unfamiliar locations. They explained this phenomenon by developing the olfactory navigation hypothesis: pigeons at the home loft learn the odours carried by the winds in association with wind direction; once at the release site, they determine the direction of displacement on the basis of the odours perceived locally and orient homeward. In addition to the old classical experiments, new GPS tracking data and observations on the activation of the olfactory system in displaced pigeons have provided further evidence for the specific role of olfactory cues in pigeon navigation. Although it is not known which odours the birds might rely on for navigation, it has been shown that volatile organic compounds in the atmosphere are distributed as fairly stable gradients to allow environmental odour-based navigation. The investigation of the potential role of olfactory cues for navigation in wild birds is still at an early stage; however, the evidence collected so far suggests that olfactory navigation might be a widespread mechanism in avian species.
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                Author and article information

                Contributors
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                Journal
                Herpetozoa
                Herpetozoa
                Pensoft Publishers
                2682-955X
                1013-4425
                August 14 2020
                August 14 2020
                : 33
                : 139-147
                Article
                10.3897/herpetozoa.33.e52854
                © 2020

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