Foraging behavior of ants: Experiments with two species of myrmecine ants

Summary

• 1. Experiments presented in this paper for two species of ants confirm the predictions of models based upon the hypothesis that the animals maximize the net rate of energy intake while foraging.

• 2. Solenopsis geminata in the laboratory recruited at higher rates to patches of sugar solution when the distance to a patch decreased, the diameter of a patch increased, or the sugar concentration increased.

• 3. Pogonomyrmex occidentalis in its natural setting recruited at higher rates to patches of seeds mixed with pebbles when the distance to a patch was decreased, the size of the patch was increased (when recruitment was already at a high level), the density of seeds was increased, or seed size was increased. When presented with a uniform distribution of seed sizes within a patch, this species tended to choose intermediate-sized seeds, but there was no tendency to choose a narrower range of seed sizes as the distance to the patch increased. This last finding was the only one inconsistent with a model based on maximization of net rate of energy intake.

• 4. The tendency for Solenopsis to respond to sugar concentration and for Pogonomyrmex to respond to seed size refutes the predictions of models based on minimization of the average time required to obtain each food item.

• 5. Increased temperature increases running speed. Thus, when the temperature increased during an experimental session for Pogonomyrmex, a particular rate of recruitment to a patch was maintained by a decrease in the total number of recruits on the trail to the patch.

• 6. Further analysis of the Pogonomyrmex results reveals that different levels of response to variable changes in the various experiments can be explained in terms of the model. This indicates that interference among recruits to a patch is always important to the level of response.