ABSTRACT
Navigation by smell is perhaps the most fundamental form of perceptual control of locomotion. Even the simplest species such as bacteria use chemical substances and associated gradient fields for navigation. Although navigation by smell seems to be simpler than similar tasks based on other perceptual modalities, search patterns in navigation towards a source of a chemical diffusion field are still not fully understood. Chemotaxis can, in principle, be used in a stable smooth diffusion field, but it cannot fully account for meandering search patterns in intrinsic instable and naturally weak diffusion fields. Chemotaxis seems unreliable when chemical gradients are weak and easily disturbed by other processes.
