Animal or Algal Materials: Food Toughness, Food Concentration, and Competitor Density Influence Food Choice in an Omnivorous Tadpole

摘要

Little is known about behavioral aspects of tadpole feeding ecology. Resource protein is by far the most studied factor assumed to govern food choice in tadpoles, whereas other factors such as resource toughness and competition have received less attention. Here, we tested the food choice of an omnivorous pond-dwelling tadpole when exposed to animal and algal materials at different toughnesses and concentrations (13 and 23 amount of food per volume), used as a proxy indicator of energy gain per bite. We subsequently tested how tadpole feeding behavior and food choice change with competitor density (when alone, in pairs, or in a group). We found that type, toughness, and concentration of the food influenced choice by the tadpoles; however, a three-way interaction among these variables was absent. The tadpoles did not feed randomly and preferred the algal materials when these were softer than, or as tough as, the animal materials. The tadpoles discriminated among foods of different concentrations and readily fed on the high-concentration food materials. Tadpole feeding behavior was density dependent. In a group, the tadpoles nearly doubled their feeding activities and increased their feeding on animal materials, here the less-preferred foods. Food toughness, energy gain per bite, and the presence of competitors influence tadpole feeding behavior, and could be factors used as proximate cues for determining food quality in tadpole foraging strategies.