Impact of sagebrush nutrients and monoterpenes on greater sage-grouse vital rates

• Main Authors: Brian R. Wing, Terry A. Messmer
• Format: Article
• Language: English
• Published: Utah State University 2017-02-01
• Series: Human-Wildlife Interactions
• Subjects: artemisia spp.; centrocercus urophasianus; diet; greater sage-grouse; monoterpene; nest success; pre-nesting forage; sagebrush
• Online Access: https://digitalcommons.usu.edu/hwi/vol10/iss2/4
• ISSN: 2155-3874; 2155-3874

Greater sage-grouse (Centrocercus urophasianus; sage-grouse) depend on sagebrush (Artemisia spp.) to complete its annual life cycle. The winter diet for sage-grouse consists almost entirely of sagebrush leaves, and individual birds may gain weight while foraging on sagebrush. Previous studies have reported higher crude protein and lower monoterpene concentrations in the sagebrush species selected as winter forage by sagegrouse. However, no studies have attempted to link female sage-grouse vital rates (i.e., nest initiation and success, egg fertility, clutch size, and adult survival) to crude protein or monoterpene concentrations of sagebrush plants browsed during pre-nesting periods. From March to May 2013, we monitored pre-nesting diets for 29 radio-marked female sage-grouse in the Box Elder Sage-grouse Management Area in northwestern Utah to determine if a relationship existed between foraging patterns and vital rates. We randomly located radiomarked female sage-grouse ≥3 times during the study period and subsequently sampled 70 sagebrush communities where they were observed to determine which sagebrush species or subspecies were browsed and if samples collected of the browsed plants differed in nutritional quality (i.e., crude protein) and chemical composition (i.e., monoterpenes) from non-browsed plants in the areas sampled and non-browsed randomly selected plants in adjacent sagebrush communities. Seventy-three percent of these sites where radio-marked females were located consisted entirely of black sagebrush (A. nova) communities. Percent crude protein and total monoterpene concentration in black sagebrush and Wyoming big sagebrush (A. tridentata wyomingensis) did not diff er between browsed, non-browsed, and non-browsed random plants. Browsed black sagebrush plants were lower in average percent crude protein (P = 0.003) and higher in total monoterpene concentration (P ≤ 0.001) than browsed Wyoming big sagebrush. Apparent nest success, age of nesting females, egg fertility, clutch size (P > 0.05), and female monthly survival rates (CI = -0.21–0.49) for the radio-marked sagegrouse we monitored did not diff er based on sagebrush crude protein and total monoterpene content. However, all of the radio-marked female sage-grouse (n = 10) observed in black sagebrush communities where the collected plant samples exhibited higher concentrations of an unidentified monoterpene successfully hatched nests (P = 0.002). All of the nests of radiomarked female sage-grouse (n = 9) outside these areas failed. Our results lend additional support to previous published work regarding sage-grouse preferences for black sagebrush as pre-nesting forage and suggest a potential link to nest success.