Independent effects of geometry and landmark in a spontaneous reorentation task: a study of two species of fish.

While disoriented humans and animals use both landmarks and environmental geometry to guide their navigation, it is not clear what kinds of mechanisms underlie these behaviors. Because traditional tests of trained navigation behavior in environments containing both landmarks and geometric information may cloud our insight into the nature of these processes, the present study tested the spontaneous use of landmarks and environmental shape by two species of fish - Redtail Splitfins (Xenotoca eiseni) and Zebrafish (Danio rerio). The results suggest that while geometry is spontaneously used by both species and both sexes to compute relative direction, the use of landmarks is limited to direct beaconing, complicated by attraction to features, and variable across species and sex. These findings support the view that while multiple cues may ultimately guide behavior, the computation of orientation and relative positions is specified by geometric input and is independent from other navigation processes as beaconing.