Diets structure of a common lizard Eremias argus and their effects on grasshoppers: Implications for a potential biological agent

Abstract

Outbreaks of grasshoppers (Orthoptera: Acrididae) often cause serious ecological damage. Recently, there has been interest in using natural enemies of grasshopper for their biological control. This study examined the biology and predation on grasshoppers by Eremias argus, a common lizard in Inner Mongolia. Its developmental duration and life history are consistent with adaptation to grasshopper phenology. The diet structure of E. argus included grasshoppers, beetles, ants, leafhoppers, moths, bees and spiders. A positive correlation between E. argus population numbers and grasshopper population numbers was highly significant. We built models describing the functional response and intraspecific competition for E. argus adults. The functional feeding response of E. argus on grasshopper was classed as Holling type III. The maximum number of grasshoppers consumed by female and male adults were 11.2 and 7.0 individuals per day, respectively. Predatory ability was strongest in female adults, with the second and third instars of Oedaleus asiaticus preferred. The predation ratios(E) of E. argus on grasshoppers declined with increasing lizard density, especially for female adult E. argus. E. argus could play an important role in grasshopper control and maintaining a population of E. argus in the grassland ecosystem could effectively control low-density grasshopper populations on grassland. Suggestions on how E. argus could fit into an IPM programme for biological control of grasshopper are discussed.