Ants typically use path integration and vision for navigation when the environment precludes the use of pheromones for trails. Recent simulations have been able to accurately mimic the retinotopic navigation behaviour of these ants using simple models of movement and memory of unprocessed visual images. Naturally it is interesting to test these navigation algorithms in more realistic circumstances, particularly with actual route data from the ant, in an accurate facsimile of the ant world and with visual input that draws on the characteristics of the animal. While increasing the complexity of the visual processing to include skyline extraction, inhomogeneous sampling and motion processing was conjectured to improve the performance of the simulations, the reverse appears to be the case. Examining closely the assumptions about motion, analysis of ants in the field shows that they experience considerable displacement of the head which when applied to the simulation leads to significant degradation in performance. The family of simulations rely upon continuous visual monitoring of the scene to determine heading and it was decided to test whether the animals were similarly dependent on this input. A field study demonstrated that ants with only visual navigation cues can return the nest when largely facing away from the direction of travel (moving backwards) and so it appears that ant visual navigation is not a process of continuous retinotopic image matching. We conclude ants may use vision to determine an initial heading by image matching and then continue to follow this direction using their celestial compass, or they may use a rotationally invariant form of the visual world for continuous course correction.

A significant body of research has focused on tracking behaviors of predators responding to prey odor plumes, yet little is known about the specific mechanisms by which predators make decisions during tracking that lead them to a source. This dissertation advances the current knowledge of plume tracking behavior by examining blue crab tracking behavior over a large range of bed-roughnesses (thereby manipulating ambient levels of turbulence), and interpreting these results with respect to chemical signal structure derived from separate examinations of plume characteristics as determined by planar laser induced fluorescence (PLIF). Foraging success and the speed of blue crabs attempting to locate the odorant source both decline consistently with increasing bed roughness. In contrast, steering (path linearity) appears unaffected by bed roughness induced turbulence. The spatial arrangement of blue crab chemosensors combined with the three-dimensional structure of odorant plumes accounts for the differential effects of turbulence on the speed and success of crab tracking behavior. Separate examinations of tracking behavior and plume properties cannot directly examine hypotheses concerning the utility of specific chemical signal properties. In order to make a direct link between cue and behavior, three-dimensional laser induced fluorescence (3DLIF) was used to analyze three-dimensional plume structure and concentration of odor filaments that reach blue crab sensory structures. The corresponding tracking behavior was simultaneously recorded and then analyzed with a motion analysis system. These data provide the most comprehensive examination of odor signal input-behavioral output functions for animals in turbulent plumes. Crabs do not react differentially in response to the absolute concentration of antennule spikes above threshold at their antennules but do show a state-dependent acceleration response to antennule spikes. Signals arriving at the leg sensors of blue crabs help mediate upstream motion and signal change across a single set of leg sensors is sufficient to induce turning during upstream motion. Blue crabs decrease the height of their antennules in correspondence with changing plume properties as they approach the source and the timing of signals arriving at the antennules appears to affect upstream motion.