Examining grasshopper herbivory and foraging strategies in a diverse grasshopper community from central New Mexico

Climate change has resulted in environmental stress on ecosystems worldwide, shifting the species composition of both plants and the insects that consume them. Studying plant-insect interactions can provide important insights into ecosystem health. Although grasshoppers are important herbivores in semi-arid desert grasslands of North America, species-specific diets are not well understood. Our research examines grasshopper herbivory in grassland and shrubland habitats at the Sevilleta National Wildlife Refuge in central New Mexico. We conducted an observational study on grasshopper diet selection from May–October 2014. Additionally, we collected 30 different grasshopper species for carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope and gut content analysis. Half of the grasshoppers were dissected and their crops removed for comparison against reference slides of common plant species’ tissues. The remaining grasshoppers were dissected to obtain muscle and chitin samples, from which δ¹³C and δ¹⁵N values were measured and compared to the values from the same plant tissue samples. Most grasshopper species were observed to eat only 5% of the time, and isotope data showed that some species (e.g., Melanoplus gladstonii) were foraging generalists, while others (e.g., Psoloessa delicatula) specialized on C₄ grasses. While most grasshopper species were found to consume young green leaves, Trimerotropis pallidipenis was only observed to consume detritus. The diet selections for different grasshopper species were consistent, regardless of sex, age, or month of collection. This research provides valuable information about how abundant primary consumers such as grasshoppers may affect plant species in arid grassland ecosystems.