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Eye movements in the natural world reflect the information needs of the momentary behavioral goals, the rewards and costs associated with those goals, and uncertainty about the state of the world. We examine how these factors trade off in the context of walking outdoors in terrains of varying difficulty, a situation where little is known about how visual and locomotor systems work together to achieve efficient and stable behavior. We developed a novel system to simultaneously record gaze and full-body kinematics during locomotion. Walkers tune their gaze behavior to the specific information needed for paths of varying complexity and modulate the energetically optimal preferred gait to balance between the competing demands of efficiency and stability as terrain complexity increases. They do this while maintaining a constant temporal look-ahead window across all terrains. Thus gaze and locomotion are intimately linked and, revealing the varying information demands of the natural world.