Animal Behavior/Orienting
From Wikibooks, the open-content textbooks collection
Contents |
[edit] Animal Movement
Predictable fluctuations in environmental conditions impact the behavior and movement patterns of many animals. When nothern temperate ponds freeze over in winter, bald eagles are cutoff from their prey, forced to travel in search of open water. Animals respond by travelling to such seasonal changes in carrying capacity by seeking out abundant resources in the summer and emmigrating from limited, harsh resource conditions in the winter. Migration refers to these regular, seasonal journeys of animals that alternate between breeding and non-breeding locations. Many species are able to move great distances and excell at an ability to find their way. A combination of cues and mechanisms are employed to complete some of the most amazing achievements.
[edit] Animal Movements and Tinbergen's Four Aims
A series of independent questions can be addressed to explore the causation of migratory movements in animals, such as song birds.
Proximate Causation: hormonal influences on timing (restlessness), cues for navigation, ...
Ultimate Causation: For functional explanations of songbird migration, migrants must exceed local residents in the number of offspring, despite making up for additional energy costs and dangers associated with migration.
Phylogeny: Many species of birds migrate. Fossil evidence suggests that early songbirds evolved in the tropics. Migration may have arisen when individuals moved north (or southward) in spring to exploit longer daylight hours, local resource abundance in temperate zones, and release from competition in the tropics during the breeding season with its high food demands. The precise course of current major flyways have probably evolved since the last glaciation.
Ontogeny: learning of migration paths and innate preference for migration direction (European warblers, Starlings)
[edit] Homing
Homing refers to an individual's ability to return from a distant location to the only place it is certain to know something about. Animals may utilize a variety of cues and mechanisms to determine the location of its home site.
Limpets fit their shell to one specific spot on a rock. A close fit is critical to withstand the impact of waves when submerged and prevent dessication when exposed. Scraping algae from the rock surface, they travel from their home site, leaving behind a chemical trail. By reversing direction on this trail they are able to return to the very site they came from.
The homing pigeon has been selectively bred to be able to return to its home over extremely long distances. As a pigeon generally returns to its own nest and its own mate, human handlers have selectively bred subsets of birds that were particularly good at this task. Homing flights from as far as 1000 kilometers have been recorded by exceptional birds at average flying speeds of around 50km/h. For thousands of years humans have used homing pigeons to return messages back to home base by attaching them to the birds legs.
[edit] Migration
Migration includes all movements made in response to changes in food availability, habitat or weather.
Nomadic Migration'
'Seasonal Migration': Travel between a summer area for breeding and an area for overwintering are driving the seasonal migration of many animals, such as song birds. The energetic advantages of breeding in a site of seasonally high food resources and extended daylight hours allow diurnal birds to produce larger clutches than related non-migratory species that remain in the tropics year-round. In autumn, as the days shorten and food sources dwindle, birds return to warmer regions where the available food supply varies little with the season. The success of migrants indicates that these advantages greatly offset the high stress, energetic costs, and other risks of the migration. Cardinals are common winter residents in northern latitudes. As members of a taxon with mostly tropical distribution, they may have reduced their winter return migration.
Return Migration
[edit] Mechanisms
[edit] Orienting
Many individuals show a distinct preference for departing in one particular direction. This applies to diurnal movements of plankton that feed at the surface during the veening and night, and sink to lower, darker regions to avoid falling prey to visual predators.
[edit]
Navigation refers to the ability of planning and controlling one's movement from one place to another. It requires knowing one's current location on earth, the location of the desired goal, and an ability to calculate travel directions to get from here to there.
[edit] Pilotage
[edit] Dead Reckoning
Many birds determine a particular flight direction based on environmental cues that serve as landmarks on the Earth's surface, including longitudinally magnetic lines, the lcoation and direction of the sun and other celestial objects, or prevailing wind direction and odors.
In vector navigation individuals arrive at a given destination by maintaining a compass direction (or directions) for a predetermined amount of time or distance. Dead reckoning is the process of estimating one’s present position by projecting course and speed from a known past position. Honey bees for instance communicate the location of profitable nectora sources to hive mates. Using a waggle dance they are able to transmit codes for direction and distance.
European Starlings from much of continental Europe overwinter on the channels coast of France and Britain. A group of banded individuals was moved from one part of Europe to a more western geographic location. This transfer would now require a ninety degree change in direction to reach their traditional wintering grounds. Adult starlings were admirably able to perform that course adjustment and returned at their normal wintering range. Newly-hatched juveniles, however, which had never made the trip before, continued to fly their traditional southwesterly direction and ended up on the coast of Spain.
Desert ants (Cataglyphis) are able to obtain an accurate, mean return vector that reverses the distances accumulate in a number of invidual outward movements.
[edit] Orientation Cues
Niko Tinbergen's work on Digger wasps illustrates the importance of local visual cues to pinpoint the exact location of the burrow.
Radar images show that migrating bird flocks drift off courses in a strong crosswind, except for flocks that travel along distinct landmarks, such as rivers, coast lines, or mountain ridges. Landmarks may also arise from specific atmospheric conditions and distinct geographic features, such as Point Pelee, which jutts into Lake Erie and serves as key staging ground for migrating hawks in search of updrafts.
Visual Orientation refers to the use of geographic landmarks (rivers, coastlines, ridges, etc.). Diurnal migrants often follow such landmarks, generally of lesser importance for nocturnal migrants, although there are documented cases of nocturnal migrants following rivers or coastlines. This may be particularly important for navigation to a precise breeding or wintering locality.
[edit] Cognitive Map
Is an internal representation of the spatial relationships between objects in an animal’s surroundings
