Diet, nutrition, and reproductive success of Roosevelt elk in managed forests of the Olympic Peninsula, Washington

The relationship between reproductive success, vegetation types in the home range, and diet composition and nutritional quality was examined in female Roosevelt elk on the Olympic Peninsula, Washington. Nine elk herds were radio-tracked during 2001 to quantify reproductive success (as calf:cow ratio), home range size and location, and vegetation types used. I measured diet composition from fecal samples, and collected plant samples of forages found in the diet. I analyzed plant samples for nutritional quality (protein content, digestibility, and energy). Herds were grouped into highly productive (December calf:cow ratio 0.30) and less productive (December calf:cow ratio 0.30). Highly productive herds had more 2 – 9 year old timber (P = 0.03) and less 11 – 24 year old timber (P = 0.03) available in the home range than less productive herds. Highly productive herds consumed more grasses (P = 0.008) and less shrubs (P = 0.02) and ferns (P = 0.02) than less productive herds. In addition, I found negative correlations between percentage grass or forb in the diet and percentage shrub or fern in the diet. Percentage shrub in the diet was positively correlated to percentage 20 – 24 year old timber, and negatively correlated to percentage 2 – 9 year old timber available in the home range.