Magnetic maps in animal navigation

Abstract

In addition to providing animals with a source of directional or ‘compass’ information, Earth’s magnetic field also provides a potential source of positional or ‘map’ information that animals might exploit to assess location. In less than a generation, the idea that animals use Earth’s magnetic field as a kind of map has gone from a contentious hypothesis to a well-established tenet of animal navigation. Diverse animals ranging from lobsters to birds are now known to use magnetic positional information for a variety of purposes, including staying on track along migratory pathways, adjusting food intake at appropriate points in a migration, remaining within a suitable oceanic region, and navigating toward specific goals. Recent findings also indicate that sea turtles, salmon, and at least some birds imprint on the magnetic field of their natal area when young and use this information to facilitate return as adults, a process that may underlie long-distance natal homing (a.k.a. natal philopatry) in many species. Despite recent progress, much remains to be learned about the organization of magnetic maps, how they develop, and how animals use them in navigation.

Direct Interaction of Avian Cryptochrome 4 with a Cone Specific G-Protein

“…Sensing the Earth s magnetic field is a widespread ability in the animal kingdom. Behavioral experiments and analyses of data from wild animals have shown that nightmigratory songbirds, fish, amphibians, reptiles and insects orientate and navigate using magnetic sensing [1][2][3][4][5]. Birds sense the inclination of the magnetic field by a process that involves the absorbance of blue light, indicating the involvement of a photoreceptor protein [2,[6][7][8].…”

Gauge-and-compass migration: inherited magnetic headings and signposts can adapt to changing geomagnetic landscapes

“…As an alternative to a clock-and-compass migratory orientation program, it has been proposed that naïve migrants might be able to perform navigation by following gradients in the geomagnetic field (4,28). However, this would result either tend to produce nearly N-S routes following large-scale inclination or intensity gradients, or else involve interpolation between often nearly-parallel inclination and intensity gradients (27,86).…”

“…Many airborne migration routes can be largely explained by one or more compass courses (9,10), contingent upon possessing sufficient compass precision (11)(12)(13) and ability to negotiate currents (14,15). However, many migration routes require distinct direction changes (often termed "Zugknicks" for bird migration), e.g., to avoid regions with unfavourable habitats (16)(17)(18), or to exploit favourable habitat (19,20) or supportive current systems (4,21). Mediating such direction changes solely according to a circannual clock is likely unreliable given unpredictable variation in migratory schedules (22,23).…”

“…Myriads of migrating animals undertake seasonal journeys across regional to cross-continental-scales (1,2). Experienced migrants can make use of a developed map-sense based on experienced geophysical (solar, stellar and geomagnetic) and olfactory cues (3,4). In particular, both first-spring bird migrants (5,6) and subadult oceanic migrants (4) apparently identify natal locations using geomagnetic signatures imprinted at the natal site.…”

“…Experienced migrants can make use of a developed map-sense based on experienced geophysical (solar, stellar and geomagnetic) and olfactory cues (3,4). In particular, both first-spring bird migrants (5,6) and subadult oceanic migrants (4) apparently identify natal locations using geomagnetic signatures imprinted at the natal site. Contrastingly, many inexperienced (naïve) migrants on their first journey are thought to reach remote destinations independently in migratory steps based on inherited headings, often termed clock-and-compass migration (3,7).…”