Naguib / Barrett Advances in the Study of Behavior

1. Auflage 2014
ISBN: 978-0-12-800316-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 46, 444 Seiten

Reihe: Advances in the Study of Behavior

Advances in the Study of Behavior was initiated over 40 years ago to serve the increasing number of scientists engaged in the study of animal behavior. That number is still expanding. This volume makes another important 'contribution to the development of the field' by presenting theoretical ideas and research to those studying animal behavior and to their colleagues in neighboring fields. - Initiated over 40 years ago to serve the increasing number of scientists engaged in the study of animal behavior - Makes another important contribution to the development of the field - Presents theoretical ideas and research to those studying animal behavior and to their colleagues in neighboring fields

Autoren/Hrsg.

Naguib, Marc

Barrett, Louise

Leseproben

Chapter Two Magnetoreception in Mammals
Sabine Begall*,1; Hynek Burda*,†; Erich Pascal Malkemper*    * Faculty of Biology, Department of General Zoology, University of Duisburg-Essen, Essen, Germany
† Faculty of Forestry and Wood Sciences, Department of Game Management and Wildlife Biology, Czech University of Life Sciences, Praha, Czech Republic
1 Corresponding author email address: [e-mail] Abstract
In comparison to birds, magnetoreception in mammals has been understudied. This negligence has historical and methodological causes. We summarize the paradigms that have been applied in the study of magnetoreception in mammals. We also provide an overview of mammalian taxa in which magnetoreception has been studied and indicate potential receptor mechanisms. We discuss the biological significance of the magnetic sense with respect to sensory ecology and putative sensory mechanisms and show that magnetic field cues are used not only for navigation (in the context of homing or migration) but also in the context of “everyday life” in many species that are generally considered to be nonmigratory. We review current knowledge of magnetoreception in humans and finish with a synopsis of issues relating to anthropogenic magnetic pollution. Keywords Anthropogenic magnetic noise Conditioning Homing Human navigation Magnetite Magnetic alignment Migration Navigation Radical-pair mechanism Spatial orientation 1 Biological Significance of Magnetoreception
Magnets and magnetism have nowadays very wide technological application (e.g., storage of information on magnetic tape such as on audiocassettes, on magnetic strips on credit cards, in loudspeakers to convert electric energy into mechanical energy, in medicine for magnetic resonance imaging, and many more), however, most people associate those terms mainly with items which attract iron and with a compass. And although it appears that magnetic fields have also wider range of biological significance than previously thought (e.g., pain reception and circadian clocks to name just a few), researchers traditionally considered the compass principle as the major use of magnetism in animals. The ability to sense the geomagnetic field, in short magnetoreception, has fascinated (not only) researchers for almost half a century, starting when Wolfgang Wiltschko first provided evidence for its existence in a migratory bird (Wiltschko, 1968). Up to now, a number of species of most classes of vertebrates has been shown to possess a magnetic sense (Wiltschko & Wiltschko, 1995) but, contrary to general trends in biology, studies on mammals are still underrepresented in this field of research. Among vertebrates, not only birds but also teleosts, sea turtles, and amphibians have managed to attract more attention of researchers studying magnetoreception than mammals. Why particularly birds became the researchers’ favorite study subjects has historical and methodological reasons. Homing and navigation abilities of pigeons and migratory bird species have fascinated people for centuries, and research (including model species, experimental designs, etc.) on orientation and navigation in birds was established in many laboratories well before the role of magnetoreception was recognized and first proved. A comparable useful pool of study designs to draw on in magnetic research was not available for mammal species at that point. Although in mammals also long-distance migrations are known (whales, bison, caribou, East African gnus, etc.) and the homing abilities of dogs, cats, and horses are well (albeit only anecdotally) documented, experimental paradigms, such as the Emlen funnel and migratory restlessness (Zugunruhe) in birds, were not available for mammals. Displacement experiments with big mammals and homing experiments with cats, dogs, and horses are—for ethical and technical reasons—also not practicable. It was only until very recently that new methods and insights have emerged that enable us to study the distribution and nature of the magnetic sense on a broader scale. Humans find technical compass and GPS navigation systems useful for orientation also on a small scale (e.g., in forests or in the city), yet people usually still ask why animals like red deer, cattle, or the red fox should be magnetoreceptive if they do not migrate over long distances like some birds. However, unless an animal species has been specifically studied by radiotelemetry or by other adequate methods, and unless animals are not constrained by natural or artificial barriers, we usually cannot be sure whether individuals of the given species or population are indeed sedentary, vagrant, or migratory. In any case, we should emancipate ourselves from considering magnetoreception an exotic sense only because we, humans, do not have conscious intimate experience with it. The magnetic sense may be of use not only for long-distance migration, and not only for providing spatial (directional/compass and topical/map) information, but also in diverse other contexts of everyday life. Most evidence for the use of a magnetic sense in mammals has been so far collected (and searched for) in the context of spatial orientation. A magnetic compass sense in combination with a reference map would be useful for spatial orientation in long-distance migrants, and/or in territories and home ranges without distinct landmarks. Local signs informing an animal about its actual position within its home range may be visual, olfactory, or acoustic—and they may provide the animal with a cognitive map, which could be used as a reference for the magnetic compass sense. But a magnetic compass sense alone (i.e., without a map) could also be very helpful in a great variety of contexts. A magnetic compass could be used, for instance, to keep the course of digging in subterranean mammals or the course of swimming in aquatic mammals. It could be also expedient for keeping a common direction of grazing in gregarious animals (such as large herbivores), which is of importance in order to synchronize movement, avoid collisions and keep a “common escape direction,” and thus maintain herd cohesion (cf. Section 2.5). Magnetoreception could theoretically also be utilized in chronobiology. The natural daily variation of the magnetic field follows a certain time pattern and might provide, at least theoretically, a Zeitgeber to animals living in a monotonous, stable, uniform sensory environment deprived of light cues (i.e., day-and night-cycles). Thus, it could be employed, for instance, by mammals living underground or in the deep-sea to synchronize their daily activities. The magnetic sense might also be used to estimate the distance to a given goal. This seems especially plausible for a mechanism proposed to underlie magnetoreception that involves a light-dependent process occurring in specialized photoreceptors which allows the animal to visualize information provided by the geomagnetic field (GMF) (cf. Section 3.2). This hypothesis was first proposed by John Phillips and colleagues who exemplified it in the everyday scanning and orientation of the surroundings by rodents (Phillips, Muheim, & Jorge, 2010). If true, it suggests new horizons for the biological significance of magnetoreception. Based on the model of Phillips et al., the range-finder-hypothesis has been suggested as a possible basis for hunting success in the red fox (cf. Section 2.5; Cervený, Begall, Koubek, Nováková, & Burda, 2011) and the estimation of flight distance and/or slope (inclination, cf. Hart, Malkemper, et al., 2013), and could be also useful for jumping or gliding mammals inhabiting trees, cliffs, or rocks. Here, we review the current state of knowledge of magnetoreception in mammals and discuss the approaches and findings of studies so far published. 2 How to Study Magnetoreception and Its Function in Mammals? Experimental Paradigms and Interpretation of Findings
2.1 Homing
Many mammals are able to return to their home range after being relocated, in some cases over hundreds of kilometers (Rogers, 1988; Schmidt-Koenig, 1965). The first evidence for a magnetic sense, however, stems from orientation experiments with small epigeic rodents. 2.1.1 Homing in Rodents The ability of some rodents to return to their home range after being experimentally displaced for up to hundreds of meters has puzzled researchers for a long time, but compass-map based navigation has mostly been rejected as an explanation in favor of simple landmark-based piloting strategies (reviewed in Joslin, 1977). The majority of these early studies used the simple approach of capture, displacement, and recapture (e.g., Gentry, 1964; Murie & Murie, 1931) or recording of vanishing directions after release (e.g., Bovet, 1971); but these did not yield insights into the sensory mechanisms involved and often ended in negative results since the animals simply aimed for the nearest shelter. A major breakthrough was achieved by a new study design that measured the directional preference in an arena after release at an unfamiliar site instead of measuring the homing success. Mather and Baker (1980) were the first to...