Foraging in the ant Camponotus mus: nectar-intake rate and crop filling depend on colony starvation

The effects of colony starvation on the dynamics of nectar collection were studied in individual workers of the ant Camponotus mus. A laboratory colon y was first deprived of carbohydrates for 15 days, and thereafter fed daily ad libitum with diluted honey until satiation. During these two successive experimental phases, the probability of feeding, crop filling and fluid-in take rates were recorded daily for individual foragers collecting a 10% (w/ w) sucrose solution. The feeding responses of individuals varied with the n utritional state of the colony. When the colony was deprived of sugar, acce ptance of the sucrose solution was higher than under satiation. Feeding tim e increased with increasing starvation. During deprivation workers fed near ly continuously on the solution, whereas a number of feeding interruptions occurred under satiation. Crop filling also increased with increasing starv ation, and showed a marked decrease when the colony was satiated. Fluid-int ake rate during the deprivation phase was roughly twice that during the sat iation phase. This matched well with the difference in sucking frequency re corded during ingestion in satiated and starved workers, which was also hig her during starvation. Results indicate that the responsiveness of foragers , determined by the nutritional state of the colony, influenced both foragi ng decisions and the dynamics of fluid intake. (C) 2000 Elsevier Science Lt d. All rights reserved.