Can tongue flicks be used to measure niche sizes?

Abstract

Competition between animal species is often inferred from a demonstration of niche 'shift' in one or both species. In snakes, potential niches along the food-type dimension may be measurable in terms of responses of naive young snakes to chemical stimuli of various prey types. If responses differ markedly from actual food habits in the wild, diet shift due to competition may be implied. This approach was used on naive young of three species of garter snakes (Thamnophis) that coexist on Vancouver Island. Responses to stimuli, measured as numbers of tongue flicks per minute, were generally strong to prey normally eaten in the field, but strong responses to unusual prey items were also noted. No two species responded identically to all the stimuli used. The diets of two of the species are possibly determined in part by competition between them. Various weaknesses of this method and other interpretations of results are discussed.