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Sheep grazing

Livestock grazing is common throughout the world especially in areas with arid to semi-arid grasslands where more intensive forms of agricultural are impractical. The steppe and grassland habitats of eastern Montana, where I work, had been grazed by bison for thousands of years and are relatively resistant to grazing. Today, livestock have replaced bison. In eastern Montana, properly managed livestock help maintain sustainable natural habitats and ecosystems while also producing important agricultural products.

This sequence shows sheep grazing experimental plots at the USDA-ARS Fort Keogh Livestock & Range Research Laboratory in Miles City, Montana. The purpose was to incorporate grazing into an experimental design. Plots receive different levels of grazing (e.g. 0%, 50% or 70% of standing biomass utilized by livestock) and potentially other treatments. In this example, the researchers alter the numbers of sheep per plot and the duration they are in the plot in order for the sheep to consume relatively fixed amounts of vegetation. These sheep were in the plots for approximately 4 hours. A common belief is that livestock will graze selectively when at low densities (or low intensity grazing) and will be less selective during high intensity grazing. The video reveals that the sheep clearly exhibit some interesting group foraging behaviors. Also, the researchers reported some selectivity.

This video is made up of two sequences of images taken using a Canon Digital Rebel controlled by a TC-80N3. The sequences were shot over approximately 30 minutes (first part) and 4 hours (second part) at an interval of one frame every 5 and 20 seconds, respectively.