search strategies

each card contains: what it means, movement pattern, when its useful, key limitations

simple random walk

move in random directions with random step lengths

no correlation between steps

useful when resources are uniformly distributed

very inefficient in patchy landscapes

correlated random walk

keep moving in same direction

steps correlated = smoother paths

useful when animals have inertia or directional persistence

inefficient if resources are rare

biased random walk

movement is biased towards a target (e.g. smell or gradient)

direction of movement is influenced by the external cue

useful when animals can direct a gradient (e.g. odor, sound)

requires detectable cue

biased correlated random walk

combination of persistence and bias towards a target

smooth directed paths

useful when animals both sense a target and can maintain a direction

hard to distinguish from memory based movement

centrally biased random walk

movement biased toward a home/centre

turns oriented back to centre

useful for territorial species or homing

doesn’t explore far

systematic search

structured scanning of space

regular geometric patterns

useful when perceptual range is small and the environment is open

costly, rarely used by large animals

area restricted search

switch to small movements when resources are found

short steps and many turns in ‘good’ patches

useful for patchy resources (such as classic foraging)

requires feedback, resources must be detected

lévy walk

many short steps and occasional very long steps

heavy tailed step length distribution

useful when resources are sparse and unpredictable

often over claimed

brownian walk

mix of short and long step distributions

two modes of movement

useful when animals switch between searching and travelling

hard to detect without good data

correlated velocity models

movement modelled in continuous time

velocity autocorrelation

useful for high resolution tracking

requires advanced modelling