Submitted to: Metaleptea
Publication Type: Abstract Only
Publication Acceptance Date: June 9, 2001
Publication Date: August 19, 2001
Citation: BRANSON, D.H., HAFERKAMP, M.R. EFFECTS OF THE TIMING AND INTENSITY OF LIVESTOCK GRAZING ON GRASSHOPPER POPULATION DYNAMICS DURING A GRASSHOPPER OUTBREAK. METALEPTEA. V.21, P. 96. 2001. Technical Abstract: Grasshopper outbreaks can cause major depletions of range vegetation. Grazing management appears able to reduce grasshopper outbreaks in some grassland ecosystems and has received little attention. The timing and intensity of livestock grazing can impact grasshopper population dynamics in a number of ways by changing host plant quantity and quality, habitat structure, or microclimate conditions for grasshoppers. An experiment was conducted in eastern Montana to determine how the timing and intensity of livestock grazing (season long, early summer, late summer, no livestock grazing) affects grasshopper population dynamics and vegetation characteristics; and, to determine if there are interactions between grazing treatments and grasshopper densities. Screen cages were stocked at 33% and 100% of field density in a factorial design. Field densities of grasshoppers at stocking were 120 grasshoppers per square meter. The dominant grasshopper species at the site were Melanoplus sanguinipes and Phoetaliotes nebrascensis. Although livestock grazing significantly affected both vegetation biomass and grasshopper desities over time, the specific grazing treatments did not differ in their effects. In addition, there were no significant interactions between livestock grazing and grasshopper density. Both high cage grasshopper densities and livestock grazing appeared to increase grasshopper food limitation. Since grasshopper stocking densities were high in all treatments, it appears grazing management may not have large effects when initiated during periods of high grasshopper densities. The results indicate that experimental approaches can be used to provide insights on interactions between livestock grazing and grasshopper population dynamics. Similar experiments are needed with lower grasshopper densities and varying climate conditions to more fully examine the interactions between grazing and grasshopper population dynamics.