FORAGING BY A GENERALIST GRASSHOPPER - THE DISTANCE BETWEEN FOOD RESOURCES INFLUENCES DIET MIXING AND GROWTH-RATE (ORTHOPTERA, ACRIDIDAE)

The grasshopper, Schistocerca americana, grew better on a mixture of c otton and kale than on either alone. When the two foods were placed in close proximity, growth rates were similar among individuals, but whe n they were 20 cm apart growth rates were extremely variable among ind ividuals. Behavioral analyses showed that distance influenced the diet ary mixing behavior of individuals. Foods close together were sampled more often and there were more meals that included both food types. Wh en foods were distant, individuals tended to stay for relatively long periods at one or the other; when on cotton, this resulted in more fee ding on cotton, which was an inferior food. Individuals varied in the extent to which they were constrained by the distance between the two foods. Those that moved between the foods less and therefore mixed les s seemed to grow less well, suggesting the possibility of a trade-off- between active foraging and behavior associated with predator avoidanc e.