A movement ecology paradigm for unifying organismal movement research

Abstract

Movement of individual organisms is fundamental to life, quilting our planet in a rich tapestry of phenomena with diverse implications for ecosystems and humans. Movement research is both plentiful and insightful, and recent methodological advances facilitate obtaining a detailed view of individual movement. Yet, we lack a general unifying paradigm, derived from first principles, which can place movement studies within a common context and advance the development of a mature scientific discipline. This introductory article to the Movement Ecology Special Feature proposes a paradigm that integrates conceptual, theoretical, methodological, and empirical frameworks for studying movement of all organisms, from microbes to trees to elephants. We introduce a conceptual framework depicting the interplay among four basic mechanistic components of organismal movement: the internal state (why move?), motion (how to move?), and navigation (when and where to move?) capacities of the individual and the external factors affecting movement. We demonstrate how the proposed framework aids the study of various taxa and movement types; promotes the formulation of hypotheses about movement; and complements existing biomechanical, cognitive, random, and optimality paradigms of movement. The proposed framework integrates eclectic research on movement into a structured paradigm and aims at providing a basis for hypothesis generation and a vehicle facilitating the understanding of the causes, mechanisms, and spatiotemporal patterns of movement and their role in various ecological and evolutionary processes. "Now we must consider in general the common reason for moving with any movement whatever." (Aristotle, De Motu Animalium, 4th century B.C.).

Fig. 1.

Fundamental spatiotemporal scaling of movement of an individual organism. A short movement path representing five steps and one stop (A); a longer path representing three movement phases (B); a lifetime track (C). The concept of movement phase, as defined here, provides the essential link between movement patterns and their underlying processes. Glossary: Movement, a change in the spatial location of the whole individual over time; Movement step (or simply “step”), a displacement between two successive positional records of the organism; Movement phase, a sequence of steps and stops associated with the fulfillment of a particular goal or a set of goals; Goal, a proximate cause of movement, combining ultimate internal drivers (e.g., to gain energy, seek safety, learn, or reproduce) and external stimuli; Lifetime track, the complete sequence of steps and stops of an individual from birth to death; Movement path, a general term for a sequential collection of steps and stops, applied flexibly to various step/stop definitions and overall length or duration.

Fig. 2.

A general conceptual framework for movement ecology, composed of three basic components (yellow background) related to the focal individual (internal state, motion capacity, and navigation capacity) and a fourth basic component (turquoise background) referring to external factors affecting its movement. Relationships among components related to the processes by which they affect each other, with arrows indicating the direction of impact. The resulting movement path (defined in Fig. 1) feeds back to the internal and external components. Glossary: Internal state, the multidimensional state (e.g., physiological and neurological) of the focal individual that affects its motivation and readiness to move; Motion capacity, the set of traits (e.g., biomechanical or morphological machineries) that enables the focal individual to execute or facilitate movement; Navigation capacity, the set of traits (e.g., cognitive or sensory machineries to obtain and use information) that enables the focal individual to orient its movement in space and/or time; External factors, the set of biotic and abiotic environmental factors that affect the movement of the focal individual; Motion process, the realized motion capacity given the impact of the current location, internal state, and external factors on the fundamental motion capacity of the focal individual; Navigation process, the realized navigation capacity given the impact of the current location, internal state, and external factors on the fundamental navigation capacity of the focal individual; Movement propagation process, the realized movement produced by the motion process and (optionally affected by the navigation process).

Fig. 3.

The relationships among the proposed movement ecology paradigm (Fig. 2) and four existing paradigms representing different scientific disciplines in which the movement of organism is being studied. Elements in the gray background are components of the movement ecology framework.