Targeted Grazing Medusahead for Rangeland Improvement

Medusahead (Elymus caput-medusae), an invasive annual grass, is a major problem on California's rangelands. It outcompetes desirable species, reducing both biodiversity and forage quality. Its high silica content makes it unpalatable to livestock and slows decomposition, allowing it to form dense thatch that blocks the growth of desirable grasses and increases fire risk (George 1992; Young 1992). Medusahead's dominance over large areas poses a significant threat to rangeland productivity (Kyser et. al. 2014). Grazing is a natural process in grasslands. Properly managed livestock grazing can help to remove litter, recycle nutrients, stimulate tillering of perennial grasses, and reduce seedbanks of invasive plants (DiTomaso and Smith 2012). Furthermore, proper livestock grazing can restore rangeland services and increase resistance to invasion (Krueger-Mangold et al. 2006).

Virtual fencing (VF) has potential to direct cattle to graze on areas infested with medusahead, which they typically avoid due to its unpalatability. In doing so, VF can be used as a tool by land managers to use livestock to target invasive grass and support the recovery of desirable and/or native forage.

In December 2022, we tested this on a pasture that had been ungrazed for nearly 20 years. Medusahead accounted for about 80% of the available forage. Using Vence VF collars, we concentrated 25 Black Angus cattle on a 3-acre infested area for 8 days, supplementing their diet with alfalfa hay. By the end of the trial, the cattle had reduced the medusahead thatch from 5,090 pounds of thatch per acre to 524 pounds per acre. The VF successfully contained the cattle 94.8% of the time. This trial was conducted during the birthing season, and some cows would temporarily leave the VF area to calve then return to the herd.

This trial effectively removed old medusahead thatch but did not address the existing seed bank. By May 2024, medusahead still comprised 22% of the living vegetation within the same area as the previous trial. It has been observed that medusahead is most palatable to cattle towards the end of spring, when other grasses have turned brown and the medusahead remains the only green grass. During this time, the seed heads are still immature and the silica content hasn’t yet fully built up. (Murphy and Turner 1959).

In May 2024, we employed Gallagher eShepherd collars to concentrate 25 steers and heifers on the same 3-acre area as the previous trial, aiming to target the medusahead before seed set. After 11 days of intense grazing, we compared the medusahead seedheads in the grazed area to those in an ungrazed site just outside the target zone. The grazed area had an average of 77 intact seedheads per square meter, while the ungrazed area had an average of 2,080 seedheads per square meter resulting in a 96% reduction in seedheads.