Database Reference
In-Depth Information
Commuting
: Recently, an intermediate use of space between residence and
migration has been described as “commuting behavior,” that is, displacement
of individual animals between resources that are set apart in space, but not in
time.
Migration
: Migratory movement defines the shift of an organism between two
nonoverlapping home ranges. Typically, migration is a seasonal process, but
it can span also an individual life cycle, or even several generations. Vertical
migrations represent the special case where organisms shift up and down
a fluid column. Altitudinal migration indicates a shift between lowland and
elevations. It must be noted that migrationmay refer to the population or to the
individuals. Partial migration indicates that only a segment of the population
migrates, while facultative migration indicates that an individual may, or may
not, migrate. Differential migration means that two segments (typically males
and females) of a population have different migratory schedules. Proterandric
(proteroginic) migration indicates that males (females) migrate before the
other sex.
Dispersal
: At the individual level, dispersal indicates spreading with respect
to a reference point or area. The dispersal from the origin of the movement is
given by itsmean squared displacement,
MSD
=
x
0
)
2
, where
x
t
denotes
the coordinates at time
t
and
x
0
at time 0, respectively. The more common
types of dispersal are natal dispersal, when an organism leaves forever the
range where it was born, and mating dispersal, when the home range is left
only for breeding purposes. The adaptive consequence of this behavior is to
reduce inbreeding.
Nomadism
: Nomadic behavior refers to an opportunistic use of space, which
is continuously searched for resources from one spot to the following.
(
x
t
−
Migrations
represent one of the most surprising patterns observable in nature;
animals canmove for thousands of kilometers and finally recover their wintering,
or breeding, grounds. Indeed much effort has been dedicated to the study of long-
range migrations, which are quite impressive examples of animal movement.
The Artic stern,
Sterna paradisea
, for instance, migrates from the North to
the South Pole, flying about 80,000 km per year. Both marine and terrestrial
mammals perform long range migrations. Grey whales (
Eschrichtius spp.
)in
the Pacific Ocean move from the Baja California, where they reproduce, to
the Arctic Ocean to forage; wildebeests (
Connochaetes taurinus
) and other
ungulates move hundreds of kilometers to attain favorable foraging habitats.
Another very impressive example is the migration of the European eel (
Anguilla
anguilla
) from Europe to the Sargassum sea, 5,000 km.
Migrations are outstandingmovements that allow animals to exploit resources
(food, breeding territories, or refuges) that are separated in space and time. By
migrating, animals reach the most suitable conditions to their survival, and
