Animal Movement - Mobility Data - page 270

is that movement of animals is constrained to boundaries. Another implication
of Burt's definition is that space use can arise from different behavioral activities
such as finding food, shelter, partners, and where they survive, reproduce, and
maximize their fitness, that is, the use of space is tightly connected to selective
pressures. Indeed, those are the same forces causative of much more impressive
movement bursts, that is, migrations. Forms of movement behavior intermediate
between migration and residence have been described; for example, nomadism
or commuting behavior. A reductionist approach was used by observing the
behavior of organisms (usually invertebrates) in a simple sensorial environment
in controlled experiments. This research showed how simple behavioral mecha-
nisms were adaptive for the animals, which were thus able to avoid stress factors
and exploit windows of opportunities to get significant resources. In other words,
these studies introduced the idea that appropriate responses of organisms to cues
present in the environment allowed them to attain simple forms of habitat selec-
tion, improving their fitness. The analysis of movement becomes hence fully
embedded in the evolutionary theory.
Past studies have led to important definitions still used in animal movement
studies:
A stimulus represents a cue in the external environment that produces pre-
dictable physiological modifications. Stimuli can be scalar if they do not
carry directional information (e.g., temperature, chemical concentration) or
vectorial if they carry directional information (electromagnetic field, light
beam).
When orientation occurs on the basis of a scalar stimulus the orientation
mechanism is called kinesis . The signal can induce a variation in the speed
of movement (ortho-kinesis) or in the turning frequency or turning angles
(klino-kinesis).
When the stimulus is vectorial, the orientation mechanism is called taxis .
According to the direction of the movement with respect to the direction of
the stimulus we speak of positive or negative taxis. According to the nature
of the stimulus we have photo-taxis, geo-taxis, chemio-taxis, and so on.
13.1.2 State of the Art
Animal movements can be categorized in different broad categories along a
continuum of sedentarism-nomadism.
Home range : Sedentary animals use a stable range. The definition excludes
occasional sallies or exploratory movements outside the home range. Usually
only the 95% of inner spatio-temporal positions are considered part of the
home range.