A behavioral mechanism for incorporating an unpalatable food in the diet of a generalist herbivore (Orthoptera: Acrididae)

We investigated mechanisms that could lead to incorporation of unpalatable foods into the diet of a generalist grasshopper, Schistocerca americana: nutritional stress, habituation, learning, and attraction to novelty. The model sl stein involved mesquite, a palatable but inferior food, and mulberry, an unpalatable but adequate food. Nutritional stress, due to prolonged intake of the inferior food, mesquite, did not increase the acceptability of mulberry. Habituation to the deterrent compounds in mulberry and associative learning of the nutritional benefits of mulberry also did not occur. However, mulberry became more acceptable after a day of restriction to a single food type other than mulberry, and even deterrent and nutritionally worthless alternatives such as filter paper became acceptable after a day on any one food type. A tendency to feed on novel food types may be a proximate mechanism for the incorporation of relatively unpalatable, but nutritionally valuable foods into the diet. Novelty and the apparent need for diversity of foods are discussed in the context of exploratory foraging behavior by generalist herbivores.