  Animals chain movements into long-lived motor strategies, exhibiting
variability across scales that reflects the interplay between internal states
and environmental cues. To reveal structure in such variability, we build
Markov models of movement sequences that bridges across time scales and enables
a quantitative comparison of behavioral phenotypes among individuals. Applied
to larval zebrafish responding to diverse sensory cues, we uncover a hierarchy
of long-lived motor strategies, dominated by changes in orientation
distinguishing cruising versus wandering strategies. Environmental cues induce
preferences along these modes at the population level: while fish cruise in the
light, they wander in response to aversive stimuli, or in search for appetitive
prey. As our method encodes the behavioral dynamics of each individual fish in
the transitions among coarse-grained motor strategies, we use it to uncover a
hierarchical structure in the phenotypic variability that reflects
exploration-exploitation trade-offs. Across a wide range of sensory cues, a
major source of variation among fish is driven by prior and/or immediate
exposure to prey that induces exploitation phenotypes. A large degree of
variability that is not explained by environmental cues unravels motivational
states that override the sensory context to induce contrasting
exploration-exploitation phenotypes. Altogether, by extracting the timescales
of motor strategies deployed during navigation, our approach exposes structure
among individuals and reveals internal states tuned by prior experience.
