Effect of Magnetic Field on the Foraging Rhythm and Behavior of the Swarm-founding Paper Wasp Polybia paulista Ihering (hymenoptera: vespidae)

The geomagnetic field can be used by insects for navigation and orientation, through different magnetoreception mechanisms. Magnetic sensitivity is very well documented in honeybees, ants and termites, but few studies have examined this capability in social wasps. The present study analyzed the magnetic sensitivity of the paper wasp Polybia paulista. The wasps' behavior was analyzed in the normal geomagnetic field and in the presence of external magnetic fields generated by permanent magnets or by Helmholtz coils. The frequency of foraging flights was measured in both conditions, and also the behavior of the individuals on the nest surface was analyzed. The magnetic field from the permanent magnet produced an increase in the frequency of departing foraging flights, and also the wasps grouped together on the nest surface in front of the magnet. The electromagnetic field created by the Helmholtz coils also increased foraging flights, but individuals did not show grouping behavior. This Helmholtz electromagnetic field induced wasp workers to perform “learning flights”. These results show for the first time that Polybia paulista wasps are sensitive to magnetic fields, including it in the list of animal models to study magnetoreception and magnetic sensitivity

Novelty detection and context dependent processing of sky-compass cues in the brain of the desert locust Schistocerca gregaria

NERVOUS SYSTEMS facilitate purposeful interactions between animals and their environment, based on the perceptual powers, cognition and higher motor control. Through goal-directed behavior, the animal aims to increase its advantage and minimize risk. For instance, the migratory desert locust should profit from being fast in finding a fresh habitat, thus minimizing the investment of bodily resources in locomotion as well as the risk of starvation or capture by a predator en route. Efficient solutions to this and similar tasks – be it finding your way to work, the daily foraging of worker bees or the seasonal long-range migration of monarch butterflies - strongly depend on spatial orientation in local or global frames of reference. Local settings may include visual landmarks at stable positions that can be mapped onto egocentric space and learned for orientation, e.g. to remember a short route to a source of benefit (e.g. food) that is distant or visually less salient than the landmarks. Compass signals can mediate orientation to a global reference-frame (allothetic orienation), e.g. for locomotion in a particular compass direction or to merely ensure motion along a straight line. Whilst spatial orientation is a prerequisite of doing the planned in such tasks, animal survival in general depends on the ability to adequately respond to the unexpected, i.e. to unpredicted events such as the approach of a predator or mate. The process of identifying relevant events in the outside world that are not predictable from preceding events is termed novelty detection. Yet, the definition of ‘novelty’ is highly contextual: depending on the current situation and goal, some changes may be irrelevant and remain ´undetected´. The present thesis describes neuronal representations of a compass stimulus, correlates of novelty detection and interactions between the two in the minute brain of an insect, the migratory desert locust Schistocerca gregaria. Experiments were carried out in tethered locusts with legs and wings removed. More precisely, adult male subjects in the gregarious phase (see phase theory, Uvarov 1966) that migrates in swarms across territories in North Africa and the Middle East were used. The author performed electrophysiological recordings from single neurons in the locust brain, while either the compass stimulus (Chapter I) or events in the visual scenery (Chapter II) or combinations of both (Chapter III) were being presented to the animal. Injections of a tracer through the recording electrode, visualized by means of fluorescent-dye coupling, allowed the allocation of cellular morphologies to previously described types of neuron or the characterization of novel cell types, respectively. Recordings were focused on cells of the central complex, a higher integration area in the insect brain that was shown to be involved in the visually mediated control of goal-directed locomotion. Experiments delivered insights into how representations of the compass cue are modulated in a manner suited for their integration in the control of goal-directed locomotion. In particular, an interaction between compass-signaling and novelty detection was found, corresponding to a process in which input in one sensory domain (object vision) modulates the processing of concurrent input to a different exteroceptive sensory system (compass sense). In addition to deepening the understanding of the compass network in the locust brain, the results reveal fundamental parallels to higher context-dependent processing of sensory information by the vertebrate cortex, both with respect to spatial cues and novelty detection

Magnetic orientation and navigation behavior of loggerhead sea turtle hatchlings (Caretta caretta) during their transoceanic migration

Numerous animals embark on long-distance migrations, during which some of these animals can use the Earth’s magnetic field as a cue in orientation and navigation. Here, I study how loggerhead sea turtle hatchlings (Caretta caretta) use geomagnetic cues to guide themselves during their migration around the north Atlantic gyre, a current system that encircles the Sargasso Sea. My results suggest that hatchling turtles can use regional magnetic fields from numerous locations along the northern segment of their migratory pathway as open ocean guideposts. Exceptions may exist, however, in cases where regional fields have changed significantly in the recent past because of secular variation. My results also suggest that the magnetic field in which sea turtle eggs incubate influences the hatchlings’ subsequent ability to use regional fields for navigation. This finding has important implications for sea turtle conservation, as anthropogenic magnetic anomalies encountered by developing hatchlings at nesting beaches might disrupt their magnetic navigation abilities later in life

From Perception to Cognition: Multisensory object recognition and navigation in the weakly electric fish <em>Gnathonemus petersii</em>

Within a multisensory system, individual senses can interact in several beneficial ways increasing the reliability and flexibility of the multisensory percept. Such a multisensory system is found in the African weakly electric fish Gnathonemus petersii , which uses active electrolocation and a specialised visual system for the perception of its environment. Additionally, these fish possess a mechanosensory lateral line system, which, however, has been scarcely investigated. In this thesis I used two behavioural paradigms, object recognition and navigation, as well as anatomical methods to investigate how the sensory systems of G. petersii operate together and how multisensory information is processed. The results during object recognition show that G. petersii is capable of spontaneous cross-modal object recognition, a highly cognitive ability previously known only in a few mammalian species, during which object related information can be transferred between senses and used for object recognition in a flexible manner. Furthermore, I found that these fish process multisensory information similarly to mammals, by using dynamic weighting of sensory inputs. The anatomical studies of the mechanosensory lateral line system additionally show a reduction of the peripheral lateral line system, explaining why the lateral line system was not involved in object recognition during my experiments. In the second part of my thesis the results of the navigational experiments show that G. petersii uses an egocentric strategy aided by visual landmarks for navigation in a familiar environment and is able to use cross-modal landmark recognition to fulfil the task. In conclusion, the results of my thesis show that the multisensory system of G. petersii optimally exploits the advantages of possessing multiple senses, which provide similar information on different spatial scales and provide new insights into the mechanisms underlying multisensory processing in non-mammalian vertebrates

Variation in habitat preference and distribution of harbour porpoises west of Scotland

The waters off the west coast of Scotland have one of the highest densities of harbour porpoise (Phocoena phocoena) in Europe. Harbour porpoise are listed under Annex II of the EU Habitats Directive, requiring the designation of Special Areas of Conservation (SACs) for the species’ protection and conservation. The main aim of this thesis is to identify habitat preferences for harbour porpoise, and key regions that embody these preferences, which could therefore be suitable as SACs; and to determine how harbour porpoise use these regions over time and space. Designed visual and acoustic line-transect surveys were conducted between 2003 and 2008. Generalised Estimating Equations (GEEs) were used to determine relationships between the relative density of harbour porpoise and temporally and spatially variable oceanographic covariates. Predictive models showed that depth, slope, distance to land and spring tidal range were all important in explaining porpoise distribution. There were also significant temporal variations in habitat use. However, whilst some variation was observed among years and months, consistent preferences for water depths between 50 and 150 m and highly sloped regions were observed across the temporal models. Predicted surfaces revealed a consistent inshore distribution for the species throughout the west coast of Scotland. Regional models revealed similar habitat preferences to the full-extent models, and indicated that the Small Isles and Sound of Jura were the most consistently important regions for harbour porpoise, and that these regions could be suitable as SACs. The impacts of seal scarers on distribution and habitat use were also investigated, and there were indications that these devices have the potential to displace harbour porpoise. These results should be considered in the assessment of sites for SAC designation, and in implementing appropriate conservation measures for harbour porpoise

Magnetoreception in mammals

Für Tiere ist es oft unerlässlich aus diversen Gründen ihr Territorium zumindest zeitweise zu verlassen. Die Fähigkeit zur Orientierung stellt dabei eine Notwendigkeit dar; die Tiere müssen geeignete Futterquellen, Sexualpartner oder Schutz vor Prädatoren finden und anschließend den Heimweg bestreiten. Eine erfolgreiche Orientierung setzt nicht nur Kenntnisse von der Richtung voraus, in der sich das Ziel befindet, sondern auch eine Bestimmung der Position. Die Orientierungshinweise, die dabei zu Hilfe gezogen werden, können z. B. visueller oder auditiver Natur sein, auf Landmarken oder eben auf der Wahrnehmung von magnetischen Parametern beruhen. Das Magnetfeld der Erde weist durch Inklination und Magnetfeldstärke räumliche Gradienten auf und gibt Auskunft über horizontale Richtungen. Das Erdmagnetfeld (EMF) ist jedoch auch unter Tage stabil und verlässlich und so orientieren sie sich beim Bau ihrer Nester an der Polarität des EMF. Die vorliegende Dissertation beschäftigte sich nun mit der Frage, ob die Tiere neben der Richtung des magnetischen Feldes auch die Feldstärke bzw. Schwankungen der Intensität wahrnehmen können und Präferenzen für einen bestimmten Intensitätsbereich zeigen. Leider habe ich keinen gesicherten Beweis dafür erbringen können. Sollten die Tiere jedoch in der Lage gewesen sein, die durch eine magnetische Anomalie beeinflussten Intensitäten wahrzunehmen, kann davon ausgegangen werden, dass diese nicht als störend empfunden worden sind. Möglicherweise funktioniert ihr Magnetkompass nur innerhalb eines festgelegten Intensitätsbereiches oder wird, neben dem Nestbau, nur bei Aufgaben genutzt, bei denen eine Orientierung über größere Distanzen notwendig ist. Des Weiteren sollte untersucht werden, ob Coruros (Spalacopus cyanus) zur Orientierung ebenfalls einen Magnetkompass nutzen, da sie auch den größten Teil ihres Lebens unter der Erde in Tunnel- und Gangsystemen verbringen. Ich habe untersucht, ob die Tiere, ähnlich den Graumullen, eine gemeinsame Richtungspräferenz beim Nestbau zeigen oder ob die Tiere eine Vorliebe für eine bestimmte Richtung haben, die sich von Individuum zu Individuum, von Coruro-Familie zu Coruro-Familie oder zwischen Männchen und Weibchen unterscheidet. Bis zum jetzigen Zeitpunkt konnte nicht nachgewiesen werden, dass Coruros beim Bau ihrer Nester eine bestimmte Richtung bevorzugen und auch meine Ergebnisse konnten leider nicht dazu beitragen eine solche Präferenz aufzuzeigen. Möglicherweise ist der magnetische Sinn innerhalb der Rodentia nur auf einige Familien beschränkt. Bislang war es schwierig, wenn nicht gar unmöglich, das spontane Verhalten größerer Säugetiere mit einer ausreichenden Stichprobenzahl in einem Labor zu studieren, doch jetzt ist es uns bei Rindern (Bos primigenius taurus), Rehwild (Capreolus capreolus) und Rotwild (Cervus elaphus) erstmalig mit einfachen, nicht-invasiven Methoden (Freilandbeobachtung, Messen von Betten im Schnee, Analyse von Satelliten- und Luftbildaufnahmen (Google Earth)) gelungen. Die Google Earth-Methode gestattet eine Analyse von Rindern weltweit und daher mit enormer Stichprobengröße; sie ist schnell, objektiv, erlaubt Vergleichbarkeit und zeigt Tiere, die sich vom Betrachter nicht gestört fühlen. So konnten wir ein neues und faszinierendes Phänomen entdecken und den ersten gesicherten Beweis dafür liefern, dass auch in größeren Säugetieren ein magnetischer Sinn präsent ist: Während Rinder, Reh- und Rotwild unter normalen Bedingungen des EMF eine Ausrichtung ihres Körpers zeigen, die in etwa einer nord-südlichen Richtung entspricht, ist diese Orientierung unter oder in der unmittelbaren Nähe von Hochspannungsleitungen gestört.For animals, it is often indispensable to at least temporarily leave their territory for various reasons. In doing so, the ability to orientate represents a necessity; animals have to find adequate food resources, sexual partners, and shelter from predators and to subsequently find their way back home. Successful orientation not only implies knowledge of the goal’s direction, but also position determination. Helpful orientation cues may be of e. g. visual or auditory nature, based upon landmarks or on the perception of magnetic parameters. Through both inclination and intensity, the magnetic field for instance exhibits regional gradients and provides information of horizontal directions. Especially for subterranean mole-rats (Fukomys sp.), access to many of such orientation cues and signals being used by aboveground living animals, is limited. However, the earth’s magnetic field (EMF) is stable and reliable even in the underground habitat; thus, these animals use the EMF’s polarity to build their nests. This thesis deals with the question whether, in addition to using polarity information, mole-rats are able to perceive the intensity of the EMF or intensity fluctuations, respectively, and also whether they show preferences for certain intensity ranges. Unfortunately, the data recovered and presented here does not adduce appropriate evidence. However, if the animals were indeed able to perceive the intensities influenced by magnetic anomalies, one can assume that they simply do not perceive them as disturbing. Possibly, their magnetic compass entirely works within a specific intensity range or is, in addition to the observed nest building behavior, used in tasks requiring orientation over larger distances only. A second part of this thesis aims at analyzing whether coruros (Spalacopus cyanus) also use a magnetic compass for orientation, a theory deduced from their lifetime mostly spent in underground burrow systems. I have here investigated whether the animals, just like mole-rats, show a common direction preference when building their nests and if so, whether such a preference differs from individual to individual, from family to family or between males and females. Up to now, a directional preference during nest building activity has not been demonstrated, and my study could neither fill this gap. The magnetic sense might be limited to just a few families within the Rodentia. The third part of this thesis deals with a topic that has been, until now, difficult or maybe impossible to study: spontaneous behavior of large animals with sufficient sample size. This study presents data from studies of domestic cattle (Bos primigenius taurus), roe deer (Capreolus capreolus), and red deer (Cervus elaphus) by means of simple, noninvasive methods (i.e. field observations, measuring deer beds in the snow and analysis of satellite images and aerial images). The Google Earth method enables the analysis of large mammals on the global scale and with an adequate sample size; this method is fast, objective, allows comparability, and shows animals which are undisturbed by the observer. We could detect a new and fascinating phenomenon and provide significant evidence for the existence of a magnetic sense in large mammals: Whereas domestic cattle, roe deer and red deer show a roughly north-south alignment of their body axes in the normal magnetic field, their orientation is disturbed under or in the vicinity of power lines and pylons

Oceanographic and Geomagnetic Influences on Sea Turtle Migrations

The research presented here explores the migratory behavior of sea turtles from behavioral, ecological, and evolutionary perspectives. Turtles display long-distance migratory movements at all stages of their lives; as hatchlings they migrate offshore from nesting beaches, as juveniles they navigate oceanic gyres, and as adults they move between foraging and reproductive grounds. For each of these migrations I examine how behavioral processes mediate large-scale biogeographic patterns. Analyses revealed a relationship between sea turtle nest abundance and offshore oceanic conditions. A disproportionate number of nests were deposited on beaches near ocean currents that facilitate the successful migration of hatchling turtles. This nesting pattern may persist through time because turtles return to nest near their natal beaches; thus, areas that produce the most surviving hatchlings and juveniles might also have the highest number of adults returning to nest. Laboratory experiments demonstrated that young turtles are capable of extracting latitudinal and longitudinal information from the earth's magnetic field to assess their position along their open ocean migration. Computer simulations indicated that even limited swimming in response to these magnetic cues exerts considerable influence on the open-ocean distribution of turtles. Specifically, magnetic navigation behavior appears to increase the number of turtles that encounter high-productivity foraging grounds and decrease the number that enter or remain in suboptimal oceanic regions. Additionally, the synthesis of results from a decade of behavioral assays on magnetic navigation in turtles, combined with geomagnetic and ocean circulation models, provided the first quantitative insight into how environmental conditions select for the evolution of this behavior. Finally, geomagnetic models were used to explore the long-standing mystery of how female turtles return to their natal beach after dispersing thousands of kilometers over a decade or more. Analyses indicate that a simple strategy of imprinting on the magnetic field of the natal site and using this information to return at maturity can account for the known homing precision of several different species of sea turtles. Moreover, the predictions from this hypothesis are consistent with the population structure for numerous sea turtle nesting assemblages across the world, as well as other spatiotemporal patterns in nest abundance.Doctor of Philosoph