Abstract
Little is known about how grasshopper species abundances shift during and following severe outbreaks, as sampling efforts usually end when outbreaks subside. Grasshopper densities, species composition and vegetation have infrequently been sampled during and after a severe outbreak in the western U.S., which is needed to better understand the cause of outbreaks and population declines. In this study, grasshopper densities, species composition and vegetation were monitored at a northern mixed rangeland site from 1999 to 2003 where densities reached 130 per m2 during a severe outbreak. Phoetaliotes nebrascensis (Acrididae: Melanoplinae) comprised 79% of the outbreak in 2000, but declined to 3% by 2003. The dramatic shifts in proportional and actual abundance of P. nebrascensis over a 5 year period illustrate that species dominance can change rapidly, even for a highly dominant outbreak species. The difficulty of fully understanding factors causing shifts in grasshopper populations is illustrated by population declines in all species observed in 2002 and 2003. The data can help predict the intensity and decline of outbreaks and points to the critical importance of long term simultaneous monitoring of grasshopper densities, species composition and vegetation for outbreak prediction.
Highlights
Grasshopper densities, species composition and vegetation were monitored at a northern mixed rangeland site from 1999 to 2003 where densities reached 130 per m2 during a severe outbreak
If any, data exist where grasshopper densities, species composition and vegetation were sampled during and after a severe outbreak, which is needed to better understand the cause of outbreaks and population declines in the western U.S (Branson et al 2006, Branson and Haferkamp 2014)
Grasshopper densities and species composition were sampled at a northern mixed prairie site during and after a severe outbreak
Summary
Grasshoppers are often the dominant herbivore in western U.S grasslands (Belovsky and Slade 2000, Branson et al 2006), with both cyclical regional grasshopper outbreaks and localized outbreaks of 30 to 90 per m2 in western North America (Nerney and Hamilton 1969, Hewitt and Onsager 1983, Belovsky 2000, Onsager 2000). Grasshopper densities, species composition and vegetation have infrequently been sampled during and after a severe outbreak in the western U.S, which is needed to better understand the cause of outbreaks and population declines.
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