Skip to main content

Research

The Cognition and Animal Navigation Laboratory

My research group focuses on the cognitive processes and sensory mechanisms by which animals navigate and migrate. While my principle focus is at the level of the whole organism I also incorporate aspects of neurobiology, molecular biology, and physics to identify the  environmental cues, sensory pathways and mechanisms used by animals to decide how, when and where to move. My work also operates in a comparative framework as I compare and contrast across species, taxa, age class, spatial scale and sensory mechanisms to reveal how natural selection has acted to shape navigation behaviour in different animal groups.

Image of Lesser Black backed gull
    Lesser Black backed gull tracked from Europe to Africa

The navigation map of migratory birds

The answer to the question of how migratory birds return to the same nest every year after journeys of thousands of miles continues to elude scientists. So far, because it is difficult to study migration in the field, most work has been done in laboratory settings using directed migratory restlessness in Emlen funnels as a proxy for migratory behaviour. Our lab addresses this challenge directly however, and we have developed methods to successfully study aspects of migration in the wild. This has resulted in significant breakthroughs in bridging the gap between field and laboratory. We use a range of tracking methods to study behaviour in response to sensory manipulations; from global satellite tracking of complete migration, to radio tracking the departure directions of small songbirds at stop over sites, in addition to calling on the “controlled” environment of the Emlen funnel. We have established model systems for work on migratory passerines at field sites across Europe and have demonstrated a crucial role for olfactory cues in the migration of adult songbirds, as well as age and location specific reliance on magnetic cues. Additionally, we have demonstrated that juvenile songbirds, previously thought to navigate based purely on an inherited compass direction, are capable of correcting for displacements in some circumstances. Collaboration with an Italian Neurobiologist, Dr Anna Gagliardo, of Pisa University, to investigate the mechanisms of magnetoreception in homing pigeons is on-going.


Big brown bat, tracked for 20km using hand held and aircraft based radio telmetry

Orientation and Navigation in bats

Bats are remarkably under studied with regard to orientation, navigation and spatial memory, but I have re-launched the study of long distance navigation in this taxa. I have established several model homing systems (in the USA and Bulgaria) in colony roosting bats. Using this my lab has demonstrated that bats use the Earth’s magnetic field as a compass, and that this magnetic compass sense is calibrated through an interaction with the sunset. We are now investigating the sensory basis of magnetoreception in these animals. Whilst in birds, it is know that magnetoreception is visually dependent; in bats no such mechanism has been demonstrated, but we have produced evidence of a mechanism based on magnetite: magnetic iron particles in sensory cells. With funding recently obtained from a NERC new investigator grant a postdoctoral researcher, Stefan Greif, will investigate the sensory physiology of magnetoreception in sensory physiology of magnetoreception in bats. This will provide a comparative framework for magnetoreception across two taxa that navigate long distances, bats and birds. We will perform field based tests of the orientation and navigation behaviour of bats to test the sensory physiology of their magnetoreception. Additionally, we will explore the possibility that bats use polarized light cues as part of their compass system to calibrate the magnetic compass. The recent demonstration that short wavelength opsin genes (UV) are conserved across a number of bat species provides the possibility that this sensory pathway may be able to detect the e-vector of polarization, a cue that has been demonstrated to be important in the navigation systems of insects, reptiles and birds. Understanding the sensory mechanisms of orientation and navigation in bats has direct relevance to conservation. All bats are protected across Europe and they are vulnerable to collisions at wind farms. Given that the value of bats to ecosystem services and human health has been highlighted, understanding the mechanisms of their movement behaviour provides invaluable information for mitigating their decline.

Evolutionary aspects of migration

Understanding the mechanisms of migration is critical to studying the evolution of migration and has been my main focus until recently.  However, as mechanistic advances are made I am able to direct an increasing proportion of my work to address evolutionary questions.  The expansion of my work from the "classic" navigation model of birds, to bats, introduced a comparative element to my research.  Further to this, my 2009 paper on the evolution of migration in bats, using phylogenetic methods, was the first to quantitatively analyse the ecological factors that are common among migrating bats.  Now I have identified model systems for, and am developing a collaboration to work on, the genetics of migration.  Juvenile migratory passerine birds are thought to orient based on a genetically programmed distance and direction.  In recent (as yet unpublished) work on the Faroe Islands I have tested the orientation of "vagrant" juvenile migratory birds which arrived there despite it being in the opposite direction from their normal migration.  This may indicate faulty genetic programming.  Comparative work on satellite tracked migrating raptors is helping to indicate how migratory directions and distances may be selected depending on geographical constraints.

Image of Orchid bee
  Orchid bee, tracked for 9km using hand held radio   telemetry

Movement Ecology

Movement Ecology is an emerging field, recently defined as a unifying conceptual framework to allow us to understand the causes, mechanisms and patterns of movement across taxa (Nathan, R. 2008, PNAS 105, 19050-19051).  Much of my work falls within the Movement Ecology field, and I use state of the art tracking technology at a number of scales.  Current projects with collaborators involve linking migratory behaviour with immunology and disease in migrating gulls, seed dispersal in tropical frugivorous birds, and foraging ranges of bees.  Future work will investigate the role of environmental factors in the phenology of migration, as well as how environmental factors influence the migratory journey.  Studying migration with respect to environmental factors will bring a greater understanding of the way in which global environmental change will affect the billions of animals that migrate thousands of miles each year.

Image of Weakly electric fish
        Weakly electric fish Gnathonemus petersii

Sensory systems and spatial memory

In contrast to navigation from unfamiliar areas, in a familiar place, animals learn and remember spatial locations by constructing a “cognitive map” of the relationship between landmarks in their environment.  The theory of the cognitive map has been studied extensively by testing rats in mazes and by observing brain scans of humans, but has focused almost exclusively on the visual sense. There are sensory systems other than vision that can tell the animal the location of landmarks in space, for example, electro-location in weakly electric fish. My lab has started to investigate the way these fish build up a picture of their environment using their electric sense, and how this compares and contrasts with the way they learn about space using vision. This has implications for understanding the way the brain integrates information from different sensory modalities. A DEL funded PhD student will start in October, working on this system. A wider focus of this research path is to understand how age influences spatial memory. Spatial memory tasks have been used in animals to investigate ageing and understanding the interaction between ageing, sensory systems and memory has the potential to advance our understanding of mental health and wellbeing. A DEL funded PhD student, Claire McAroe is starting a project working on annual killifish of the genus Nothobranchius, a new model for ageing research, to investigate the impact of age on spatial memory