Term
|
Definition
1. typically associated with a once in a lifetime event--movement to a new habitat
2. During the dispersal event, it is thought that animals might make a random movement, and then settle once suitable habitat is found.
3. Once the animal has settled in a suitable patch, it must move around its local universe and not get lost (i.e. orientation) |
|
|
Term
|
Definition
1. the use of external cues to move about the environment
2. can be achieved by fixing a position (landmark) and then using cues to determine the appropriate direction to move in (basically, a sense of where to go, direction) |
|
|
Term
| Adaptive Significance of Spatial Orientation |
|
Definition
| Acquire information about one's position and orientation relative to "fitness-enhancing" resources, such as food and mates |
|
|
Term
|
Definition
1. Rotational adjustments to stabilize the body axes relative to external stimuli
2. Goal orientation or movment toward a different place where the animal can find better conditions. For example: heading to nearby object in plain view, heading to an unseen feeding or nesting site within a familiar home range, or heading to home from a distant, unfamiliar location |
|
|
Term
Dispersal results in a tendency for animals that were once aggregated to become more widely distributed through movement away from aggregations. The most common aggregations found in nature are associated with the nest site.
Benefits: why disperse? |
|
Definition
1. Inbreeding avoidance
2. Colonization of new habitat |
|
|
Term
|
Definition
The term homing, as it is ordinarily understood, indicates a return to the place where an animal lives and has shelter.
However, homing must include consideration of any movement undertaken to reach a spatially restricted area that is known to an animal (i.e. a goal). |
|
|
Term
|
Definition
| Involves more sophistication in that a map sense (a sense of where, current location) in addition to a compass sense (a sense of the appropriate direction to move) are required for a complete navigational system. |
|
|
Term
| Animals are capable of true navigation IF... |
|
Definition
Animals are capable of true navigation if, after displacement to a location where they have never been, they can determine their position relative to a goal by exploiting cues of their new location (i.e. local cues) rather than by using info collected during the outward journey.
Ex: true navigation and magnetic maps by spiny lobster (able to orient themselves in the direction of their original site, and orientation takes place even when no clues are present during the relocation--they have magnetoreceptors and compare magnetic field to that of "home" to find their way back |
|
|
Term
|
Definition
1. Migration is usually a process of alternate episodes of fueling and transportation toward the goal destination, a cycle that is repeated many times on a long journey.
2. The movements are associated with a particular season and invariably tied into the reproductive cycle.
3. A key issue in migration is how animals navigate huge distances or orient to natal areas.
4. Underlying most migrations is a sense of time so that the appropriate season for migration is used.
5. Resource fluctuation plays a major EVOLUTIONARY role. |
|
|
Term
| The basic driving forces for migration are ecological and biogeographical factors such as: |
|
Definition
1. Seasonality
2. Spatiotemporal distribution of resources
3. Habitat distribution
4. Predation
5. Competition (intraspecific and interspecific) |
|
|
Term
|
Definition
Over evolutionary time, the benefits of increased resource availability will be balanced by costs associated with the migratory process in terms of time, energy, and mortality.
Currently the consensus is that long-distance migration evolved from short-distance migration, i.e. long-distance migrants are probably descended from species that moved far less on an annual basis.
Migratory behavior evolved three times in thrushes, with tropical birds giving rise to migratory lineages |
|
|
Term
| Fueling episodes are an important component of migration performance (if not the most important) because the rate of fuel accumulation determines the overall migration speed. |
|
Definition
| One of the problems that happens is that we're disrupting the migration patterns of birds by disrupting their refueling spots. They run low on gas causing birds to fly longer than they want, to lose energy, to lose fitness, or even to try a new route--making their migration route longer. |
|
|
Term
| Example of true navigators: big brown bats |
|
Definition
| The scientists released bats away from home and altered their magnetic field. After release, bats get the right cue and follow the natural magnetic field to home. |
|
|
Term
| Another example of navigation: wandering albatross |
|
Definition
| Do not rely on magnetic cues, and they forage pelagically in areas where there are no visual topographic landmarks. Instead they navigate using smell--able to detect concentrations in dimethyl sulfide, a compound produced by phytoplankton. |
|
|
Term
| Consequences of Geographical Barriers |
|
Definition
1. Put a stop to further migration (e.g. some species of birds will not disperse over water).
2. Lead to the evolution of detours, where the crossing of barriers is avoided or reduced (e.g. use land connection of Central America)
3. Requires that special instructions are incorporated into the migrants' endogenous spatiotemporal circannual program about increased fuel deposition and sometimes changes in the orientation at that barrier. |
|
|
Term
| Why do not all species migrate? |
|
Definition
For non-migratory species, there are a series of benefits in terms of reproductive success and physiological fitness associated with the quality of the habitat due to prior occupancy.
The benefit associated with prior occupancy as site fidelity is small or nonexistent in UNSTABLE or UNPREDICTABLE habitats, favoring the development of obligate migration in species of such habitat. (The tropics are very stable, and thus few species from there migrate.) |
|
|
Term
| Migration is in many cases primarily an adaptation for exploiting... |
|
Definition
seasonal peaks of resource abundance and avoiding seasonal resource depletion.
Example: the arctic tern takes advantage of patterns of solar energy reaching the earth at different latitudes and times of the years' spatiotemporal energy landscape. |
|
|
Term
| Differences in cognitive abilities can also play a role in migratory behavior, particularly in older birds after their first migration event. |
|
Definition
| Ex: Sardinian warbler (non-migratory) and garden warbler (migratory). Migratory birds remembered where the food bowls were much longer than non-migratory species--migratory species has a cognitive map of the area. For migratory species, cognitive maps of fueling areas would be selected for. |
|
|
Term
| Neuroanatomical differences between migratory and non-migratory birds |
|
Definition
Migratory: the relative size of the hippocampus increases between the first and second year of life (when they go for the first migration)
Non-migratory: such a pattern is NOT exhibited in the non-migratory species
*Hippocampus region is in charge of processing spatial information. |
|
|
