Brain Mechanisms of Visual Localization by Frogs and Toads

Abstract

Classical ethology provides two fundamental themes which remain at the heart of current research in neuroethology. First, is the assumption that events in the sensory “Umwelt” activate behavior via narrowly-tuned stimulus filters — i.e., that relatively few distinctive features determine the recognition of food, mate, parent or enemy. The term “innate releasing mechanisms” is probably too narrow to characterize the complexity of sensory recognition schema for birds and mammals, but it still seems to apply to many behaviors of fishes, amphibians and reptiles. As an example, the feeding behavior in newly metamorphosed froglets (Ingle, unpubl. data) seems to emerge fullblown: with no prior experience as tadpoles in pursuing visual objects, they accurately turn and snap at small moving prey. These movement sequences also fit the original notion of a “fixed action pattern”, which is the second main inheritance from classical ethology. During prey-catching the frog’s coordination of head, mouth, tongue and leg movements is highly stereotyped. The patterns predictable from knowing the radial location, height and distance of the prey. Although the behavior appears rigid, it is fast and accurate: well-adapted for the rigorous competition for food and survival among a large population with limited resources.