Effects of grazing on the demography and growth of the Texas tortoise

Published source details Kazmaier R.T., Hellgren E.C., , & Synatzske D.R. (2001) Effects of grazing on the demography and growth of the Texas tortoise. Conservation Biology, 15, 1091-1101.
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This study is summarised as evidence for the following.

	Action	Category
	Cease livestock grazing: Grassland & shrubland Action Link

Cease livestock grazing: Grassland & shrubland

A replicated, controlled study in 1994–1997 in four pastures in chaparral shrubland in Texas, USA (Kazmaier et al. 2001) found that excluding grazing from pastures resulted in similar abundance, survival and size of Texas tortoises Gopherus berlandieri compared to pastures with rotational grazing. The abundance of tortoises was similar in ungrazed (4 tortoises/100 km and 3 tortoises/10 hours) and grazed pastures (5 tortoises/100 km and 4 tortoises/10 hours). Annual survival of radio tracked individuals was similar in ungrazed (70–83%) and grazed pastures (73–84%), and size and growth were also similar (see paper for details). Two pastures each were ungrazed and grazed. Grazing was rotational (October–May) and stocking densities varied (0.2–0.6 animal units/ha; animal unit = 2 steers), though impacts on herbaceous vegetation were similar. Tortoises were counted by driving along tracks (recording the distance and time travelled) throughout the pastures between 7 April 1994 and 12 October 1997. Search effort was equal across months and time of day, and between grazed and ungrazed pastures. Forty-seven tortoises were also radiotracked.

(Summarised by: William Morgan)