Determining whether generalist herbivores regulate lipid intake

All organisms perform best at a balanced point of intake where nutrients are ingested in specific amounts to confer optimal performance. However, when faced with limited nutrient availability, organisms are forced to make decisions which prioritize intake of certain macronutrients. While intake regulation has been more thoroughly studied in omnivores and carnivores, no research exists regarding lipid regulation in generalist herbivores. Traditionally, proteins and carbohydrates were thought to be the most important macronutrient for herbivore intake; however the large differences in lipid nutritional content between different plant species offers lots of potential for regulation of an important macronutrient. We studied whether generalist herbivores can regulate lipid intake, using the migratory locust (Locusta migratoria). Though herbivore protein and carbohydrate intake is well studied, less research studies regulation of lipid intake. We tested this by offering choice diets of varying carbohydrate and lipid content makeup and measuring consumption of each diet choice to determine overall carbohydrate and lipid intake. Four different lipid sources were used in order to control for taste or texture related confounds; canola oil, sunflower oil, grapeseed oil, and a lab designed synthetic oil based on the four most abundant fatty acids in common plant oils. On three out of four diet sources, groups evidences strong regulation of narrow intake target, with little disparity in overall intake of carbohydrate and lipid content between various choice diet treatments. Groups feeding on canola oil and sunflower oil based diets displayed the best regulation based on their having small disparities in intake between treatments, while those feeding on grapeseed oil based diets displayed wide variation in feeding behavior between treatments. Groups feeding on the synthetic oil based diet choice unexpectedly consumed much more carbohydrates than lipids when compared to all other groups. In conclusion, generalist herbivores are capable of regulating lipid intake.