Determining the impacts of forage consumption by Aleutian cackling geese on livestock production from north coastal pasture lands in Humboldt County, California

Private pasture lands managed with rotational grazing practices for beef cattle production are being utilized by Aleutian cackling geese (Branta hutchinsii leucopareia) during their annual migration through northern California. Continued growth in the population size of this species has led to increased reports of forage depredation in pastures used by geese. To quantify reports of forage losses, research was conducted to determine effects different grazing conditions have on pasture regrowth. Field work was completed during the Aleutian goose spring staging periods in late winter/early spring in 2008/2009 and 2009/2010 on three ranches each season. Responses in pasture regrowth were studied under three different grazing conditions utilizing multiple study pastures on each ranch: 1) no grazing; 2) grazing by cattle only; and 3) grazing by cattle and Aleutian geese. Results from analyses showed that different grazing conditions led to statistically significant differences in pasture regrowth. Across all ranches over both seasons, regrowth in pastures with no grazing was 62% higher than cattle only grazing, and 280% higher than cattle and Aleutian goose grazing. Regrowth with cattle only grazing was nearly 140% higher than cattle and Aleutian goose grazing. This study confirmed that grazing by Aleutian geese impacted pasture regrowth that would have been otherwise available for cattle grazing and production. An economic analysis using results from this study was also performed. The difference between mean regrowth with cattle only grazing and cattle and Aleutian goose grazing was approximately 572.0 lbs/acre. Using the 2010 cost of grass hay of $150.00/ ton, the estimated cost of lost forage was $42.90 per acre. With the continued growth in the population of Aleutian geese, it is likely that forage losses from geese grazing on private pasture lands will also increase. Options to help offset losses to production should be investigated.