Individual study: The effects of livestock on California ground squirrels (Spermophilus beecheyii)
Fehmi J.S., Russo S.E. & Bartolome J.W. (2005) The effects of livestock on California ground squirrels (Spermophilus beecheyii). Rangeland Ecology & Management, 58, 352-359
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Other biodiversity: Exclude grazers
A replicated, randomized, controlled study in 1991–1994 in grassland and blue oak Quercus douglasii savannas in central California, USA, found that live plant cover, native plant cover, and plant biomass were lower in areas with high numbers of ground squirrel burrows in grazed plots, but not in ungrazed plots. Mammals: The number of active ground squirrel burrows, relative to pre-experiment numbers, did not differ between ungrazed and grazed plots (60–100% vs 40–100% of pre-experiment numbers). The spatial distribution of burrows did not differ between ungrazed and grazed plots (2.6–3.4 vs 2.2–4.1 m between nearest burrows). Plants: Live plant cover, plant biomass, and native plant cover did not decrease with increasing numbers of ground squirrel burrows in ungrazed plots, but did decrease in grazed plots (3%, 60 g/m2, and 1.8% declines, respectively, for every additional burrow in a colony). Methods: Three sites, each with four plots, were established in 1991. Half of the plots were in grassland, and half were in savanna. Half had cattle excluded from them by a fence, and half were grazed from spring to summer. Three ground squirrel colonies were monitored in each plot, and vegetation was measured in a 625 cm2 plot near the centre of each, at the end of the 1992–1994 growing seasons.